Published on EGEE 101: Energy and the Environment (https://www.e-education.psu.edu/egee101)

Home > Lessons > Lesson 1: You and the Plug: Electricity

Lesson 1: You and the Plug: Electricity

Overview

You are surrounded by items that use electricity: computers, cell phones, etc., all while sitting with task lighting, in a space that is air-conditioned or heated (perhaps with electricity). The many conveniences of modern life; flat-screen TVs, video game systems, fish tanks, smart phones, lamps, hairdryers, vacuum cleaners, electric toothbrushes, hot water for washing, heat (or cooling) for your room, the fridge, and the all-important coffee maker. Some of you will still have strands of Christmas lights up!

Considering that this is still only part of your individual energy use, imagine the energy supply needed just to serve the rest of your dorm, office, apartment building, neighborhood, or city. Add in all the businesses, schools, industries, etc. Imagine powering the entire state, or the entire country, and then imagine doing it every minute, of every hour, of every day. 

Please watch the following (5 min) introductory video:

Dr. Mathews shows welcomes you to his house and discusses energy use in the home. 
Click here for the Transcript

Hello. Today's lesson is all about energy use in the home. So let's go and look at my home. As you can see currently, it is a snowy day.

And so when we ask about what our energy-- large-scale energy use is in the home, and it is certainly a case of heating in central Pennsylvania. Obviously, in other locations, Central Florida, for example, it would be cooling. But you can see behind me the holes on the top of the roof. That's my air conditioning unit where the air jets come in, 1970 sort of fad.

But if we go and look at where I get my electricity from, my heating from, then it is from baseboard heating. And if you can see behind my right shoulder, that's an electric baseboard. Obviously, I've got electricity going on with lights and other things. Obviously a lot of day lighting as well, with the windows.

So back to heat. Obviously, the issue with heat is we have a variety of fuels we can use. 100 years ago, 50 years ago, there'd be a lot of coal use in Pennsylvania. That's mostly dwindling and only out now in the Anthracite Region, although, natural gas is heavily used as a heating fuel.

Propane, a little bit less, biomass, et cetera, et cetera. But the two big ones are natural gas and electricity. Newer homes, if they have access to electricity-- to natural gas will use natural gas.

Let's see, let's go take a look at some other big items. So the big items would be the water heater, which is in the basement. And that hot water, obviously, goes into the things like the dishwasher, the clothes washing, showers. And so the amount of energy utilized, again, depends on the fuel you use.

Again, you might use a natural gas hot water heater, or you could be using electricity. And depending on how many people, et cetera, and depending on the size of the house, these are the things that impact how much energy you're going to use and, of course, where you are and the particular seasonal transformations that occur. And so things like heating degree days and cooling degree days get covered later on.

The things that are going to impact how much energy we utilize is insulation in the house, air sealing, things like that. Obviously, things like a open fireplace would cause some issues. So in the kitchen, we've got the fridge. It's essentially a heat pump.

We've got a microwave. We've got an oven. We've got various other pieces that make utilization and my life a lot easier. So my microwave, my coffeemaker, et cetera, et cetera.

So we're going to learn about air infiltration. We're going to learn about day lighting, use of deciduous trees to stop the lights coming in-- the light coming in on a summer day. And this type of material is what's going to be covered.

So you can see that tree in front of my house doesn't have any leaves. It's deciduous, and that's helpful for shading. We want lots of light, but we don't want lots of heat in the summer.

A couple of things about lighting, I've got a variety of lights in the house. This would have been a fluorescent light until last year. Now, is an LED light. I do have some incandescents.

And if you take a look up here, I have a chandelier. It's a bit crappy. It's not very good task lighting for my puzzle that I'm doing. So I'm going to have to replace that with an LED.

And over here, I have got-- let's see-- I have got compact fluorescent and an LED light. They're a little difficult to see. I won't buy any more compact fluorescents. And a little LED sort of decorative tree.

So that's the lesson material today. It's about how we use energy in the house, could also be businesses. Of course, whenever we have the creation of energy that we utilize, Be it electronics, watching computers, TV, sound system, somewhere that electricity is being generated. And the way we generate electricity currently, there can be considerable pollution and emissions associated with your use of energy. So anyway, I will see you later.

Our Electricity Generation Mix is in Flux - Why?

The fuel or energy source for our electricity is generated by a variety of fossil fuels (natural gas and coal) along with increasingly more renewable sources (wind, hydro, and some solar) along with nuclear energy. The sources we use the most are the cheapest (this was traditionally fossil fuels: coal and natural gas, along with some nuclear and hydroelectric). It was traditionally more expensive to use more renewable energy (or to clean up more of the emissions from fossil fuels). Advances with wind and solar are occurring so cleaner electricity at competitive prices is available. Natural gas use has also increased dramatically due to a new domestic source (shale gas). So it is a time of dramatic change! If we are smarter about electricity use — through conservation and efficiency gains we can save money and protect the environment.

Lesson Objectives

Success in this lesson will be based on the following things;

  • articulate how electrical energy is used in the home
  • knowledge of energy conservation strategies
  • understanding how electricity is transformed and delivered
  • knowledge of how various light bulbs function
  • capture why electricity demand changes
  • recognize how electricity use improves the quality of life

Heat Transfer

pile of household electronics: stove, microwave, speaker, computer, TV, monitor, printer
Consumer electronics and appliances in the home. But it is missing the all-important coffee maker. One of the many devices in the kitchen that heats something.
Credit: Set of kitchen and household appliances [1] by alexlmx [2]/adobe.stock.com

As I stand in my kitchen, I realize that all of the various appliances only do a couple of functions: they either heat (the coffee machine, toaster oven, oven, microwave) or do work (the blender, extractor fan). For me, the absolute first thing I must have in the morning is my cup of tea! We’ll use my cup of tea to demonstrate the three modes of heat transfer; conduction, convection, and radiation. The key ingredients for a perfect cup of tea are tea and hot water. The hot water comes from a kettle which is a very simplistic boiler. I know when it has boiled — because as the steam escapes through a small hole in the spout, it whistles. Boiling water requires a great deal of energy to transform liquid water into a gas (steam).

Conduction

A  photograph of a red kettle sitting on an electric range. Steam is coming out of the spout.
Credit: Red Kettle [3] by
New Africa [4] / adobe.stock.com

In the case of my range, electric energy is supplying the heat. The electricity supplies a stream of electrons that whiz around in the coil at very high speed (close to the speed of light) until they encounter some resistance. Impeding the flow of electrons produces heat, and so the metal coil (on which the kettle sits) becomes hot. The first heat transfer mode to the kettle is conduction. The metal of the cool kettle is in contact with the metal of the hot heating element, and heat always “flows” from hot to cold, so there is heat transfer. The atoms in the heating element behave a little like slam dancers at a Green Day concert. They will pass on their energy to the surrounding people, making them more active, and in turn passing on their energy to another layer, and so on until the whole concert is full of crazed slam dancers.

Watch the following 1:33 minute video representation of conduction through a metal rod.

Click for a transcript of the conduction video.

Conduction is the transfer of heat energy by the kinetic motion of atoms in a substance. Remember that all atoms have motion of some sort. This is true even for atoms that make up a solid. In this animation, note that the atoms in the bar of metal are vibrating slowly due to their relatively low temperature (in real life, I might add, atoms are vibrating at tremendous speeds, so this is just a representation). Now watch what happens when I slide the bar of metal into a furnace.

Notice that as the metal heats up, the atoms at the end of the rod begin to vibrate faster. The faster-vibrating atoms transfer some of their energy to the slower adjacent atoms. Thus, the slower atoms also vibrate faster, giving them a higher temperature. This is conduction.

I should also mention that conduction works to cool an object as well. When a slower vibrating atom is next to a faster-vibrating one, we’ve seen that the slower atom takes some of the energy from the fast atom. This makes the slow atom vibrate faster BUT, it also slows down the faster-vibrating atom, cooling it. If there are MANY, MANY more “cooler” atoms than warmer ones, then the net effect of the energy transfer is to cool the warmer atoms back to a temperature equal to its surroundings.

Credit: David Babb

Some other examples of conduction include:

  • hot tea in a teacup transfers energy through a spoon to your hand as you stir in the honey

  • transfer of heat from a hot cookie sheet to the cooler cookie dough heats the dough and cooks the cookie

  • hot days heat is conducted into your home through the roof, walls, and windows

Convection

diagram of convection in a tea kettle as described below
Credit: Heidi Sporre © Penn State, CC BY-NC-SA 4.0 [5]

Convection is another way in which heat is transferred. It occurs when heat is transferred by the movement of fluids (liquids or gases). In our tea example, you’ll see that when a water molecule heats up, it has more energy, (occupies more volume) and is thus lighter and thermal gradients form where the warmer molecules rise to the top and the cooler molecules sink to the bottom. The cooler molecules are then closer to the heat source and become heated, repeating the cycle. Water molecules will also collide — passing along energy (heat).

Watch this 2:31 summary video about Convection from CentainTeed.

Click here for a transcript of the convection video.

Convection is the second mode of heat transfer. Heat transfer by convection occurs as a result of movement of liquid or gas over a surface. Wind blowing against the building is an example of a gas moving over a surface.

There are two types of convection: forced and natural.

Natural convection occurs when the movement of liquid or gas is caused by density differences. For example, we're all aware that warm air rises. That's because it has a lower density than the surrounding cool air and that's what causes a hot air balloon to rise. And of course, we know the opposite is true. Cool airdrops. In our wall example, the warm air inside the building comes in contact with the cool exterior wall. Some heat is lost to the wall, causing the interior air adjacent to the wall to cool. Since this air has a higher density, the airdrops. The warmer exterior surface of the wall heats the air next to it decreasing the air's density and causing it to rise. And as a result, the movement of the air along the surface of the wall increases the heat transfer. This type of heat transfer is called natural convection. This heating and cooling create convection loops adjacent to both the interior and exterior surfaces. Convection can also take place inside of empty cavities. One example is the movement of air in a double-pane window. In winter, air is heated on the inside surface of the window cavity causing the air to rise. The air adjacent to the outside surface cools and drops. What results is a convection loop inside the window cavity that transfers heat from the inside to the outside.

A second type of convection is forced convection. Here the movement of the liquid or gas is caused by outside forces. If the wind is blowing, the air movement across the outside of the wall will be higher increasing the rate of heat transfer. The rate of heat transfer by convection depends on the temperature difference, the velocity of the liquid or gas, and what kind of liquid or gas is involved. For example, heat transfers more quickly through water than through air.

Credit: CertainTeed [6]

Some other examples of convection include:

  • a lava lamp
  • the breeze on a windy day

Radiation

Radiation is how the “warmth” of the sun is transferred to you when you're out or how you warm your hands in front of the fire. It is electromagnetic radiation, and it does not need a medium or direct physical contact to propagate. Thus, it can travel through space. The red color from the heating element indicates that it is so hot that it is radiating energy, and these electromagnetic waves contribute to the heating of the kettle. Some of the more expensive models of stoves use this method of heat transfer primarily. Following is a nice video about how radiation works in a building.

Caption
Click here for a transcript of the Radiation video.

Radiation is the third type of heat transfer. Radiation heat transfer is by invisible electromagnetic waves from one object to another. Heat transfers from areas of higher temperature to areas of lower temperature. One common example of radiation heat transfer is from the sun. When you walk outside on a sunny day you immediately feel the warmth from the sun, even if the air is cold. Heat from the sun is being transferred through space by radiation, in order to warm you. Radiation also plays a role in heat transfer in a building. If you stand in front of a window on a cold day, your body radiates heat to the cold surface of the window and the result is, you feel colder. Likewise, if you stand in front of a window with the sun streaming in, you feel warm as a result of the incoming solar radiation. This type of energy--solar radiation is primarily shortwave radiation. Glass is nearly transparent to the shortwave radiant energy from the sun and as a result, once sunlight enters a room, the sun's energy is absorbed by the walls and the contents of the room and is converted to heat. At the same time, the warm objects in the room also emit radiant energy.

Credit: CertainTeed [6]

Some other examples of radiation include:

  • visible light from a candle
  • x-rays for an x-ray machine
  • microwaves from a microwave oven

Wake Up Your Brain

The Morning

 

We all have one of these! It is a splendid modern convenience and is an example of a heat pump— a device that moves heat, in this case, to ensure that my IPA is an acceptable cold temperature (being English I would also drink it warm). How does it work?

The case is simply an insulated box, so the heat cannot get in (remember that heat flows from hot to cold, so it would not be correct to say insulation keeps the cold in). At the back, there is a heat exchanger, a coil where the heat from inside the refrigerator can be dissipated—yes, this means that in the summer your refrigerator is pumping out heat which you are removing with the air conditioner (silly, isn't it!) But as heat flows from hot to cold, how did we manage to get it to flow the other way? We used a heat pump, to which we give energy so we can move heat; this is achieved because of the properties of the refrigerant (the liquid/gas that flows in the pipes) and the use of the compressor. The refrigerant will be a liquid with a low boiling point. Thus, we can easily convert refrigerant from the liquid phase into the gas phase.

To do this can require a great deal of energy, but, in this case, we already have the energy in place, the heat inside the refrigerator. Pumping in the liquid refrigerant and allowing it to expand and form a gas will cool the inside (this phase change can absorb a great deal of energy). Then, we can pump it through the coils and exchange the heat with the room. Unfortunately, the gas is not at a very high temperature, and so, the heat exchange does not work well, UNLESS we concentrate the heat in the gas, which we can do with the compressor. This will compress (pressurize) the gas so the heat is concentrated (the temperature is increased by the compression step), and thus the heat exchange will be more efficient. The coils at the back of the refrigerator will be enough to cool the gas down so it will turn back into a liquid, and the process can be repeated. The compressor operates only when it is needed.

Photograph of the cooling coils, compressor, and other replacement parts for a fridge
Replacement fridge parts showing the cooling coil and the compressor.
Source: Sears

Unfortunately, one of the best refrigerants was CFCs, (which stands for chlorofluorocarbons). This inert chemical managed to survive very long times in the atmosphere, reaching very high elevations where it reacted with the ozone layer (in the troposphere), causing the ozone hole(s). More on that in a later lesson, but if you cannot wait, The Ozone Layer Protection (EPA) [7] website will give you the rundown. To prevent the release of CFC's we have moved to other chemicals that are safer: hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). HCFCs also contribute to the destruction of stratospheric ozone, but to a much lesser extent than CFCs.

You'll learn more about this when we get to Geothermal heat pumps (see the helpful animations there where the heat exchange is with the outside/inside of a house rather than from the inside to the outside of the fridge).

Types of Lighting

On this page, we will discuss 5 types of electric lighting: incandescent, halogen, fluorescent, LED, and compact fluorescent. But to start, let's watch this 1:46 minute overview about lighting from the U.S. Department of Energy.

Video overview of Lighting
Click here for the transcript of the Energy 101: Lighting Choices video.

We light up dark spaces with the flip of a switch and we have been doing so since Thomas Edison invented the incandescent light bulb about 140 years ago. The same type is still used but there are more light bulb options. These bulbs will give you the light you want while using less energy (thus lower emissions and cost associated with that energy production). Initially, we moved to an energy-saving compact fluorescent bulb that uses about 25% less energy. But now it is LED bulbs Ithat often light up our homes and offices.  So, replace a traditional light bulb in your living room. Put an efficient LED bulb and you get the same light but with about 75% less energy and Energy Star bulbs last 10 to 25 times longer. Lighting your house used about 10% of your electricity use. So, when looking for a new bulb you'll find more energy-saving choices on store shelves giving you more options but save you money and that's a pretty bright idea.

Credit: U.S. Department of Energy [8]

In the “good old days,” when it was dark outside, people went to bed!  Around the American civil war, there were other sources of light, obviously. Candles had been used for a while, and lamps burning sperm whale oil were available. Poor old Moby Dick was a popular choice for this oil and was becoming quite scarce when, fortunately for the Sperm Whale, crude oil was found in Pennsylvania. Originally the crude oil was sold as rheumatism medicine before it was found that kerosene could be produced (separated out of the crude). Kerosene was a clean-burning light source (more about this in another lesson). Town gas has also been used to light towns (town gas tended to be the vapors of heated coal synthesis gas) or in some cases natural gas. However, the naked flame was always a fire risk, and when the incandescent light bulb was perfected, you could have light 24 hours a day, whenever it was needed (providing you could afford it, and there was an electricity supply!)

Incandescent

incandescent light bulb
Inside the incandescent light
bulb are two connections from
which a tungsten coil is
suspended. Shaking the bulb
produces a sound when the 
filament finally breaks.
Credit: Sergey Nivens /
adobe.stock.com

How many bulbs are visible from where you are sitting? How many are in your home? My guess is that you might have 30+ light bulbs. A decade ago these would probably be incandescent bulbs and it's still a good idea to know how they work. For these bulbs, electricity is used to heat a tungsten filament. This thin metal strand (the filament) gets so hot it becomes white-hot, producing bright white light. The bulb itself is simply an envelope in which we can put inert gases so the filament does not burn. The problem with this bulb is that it produces a lot of heat. This is fine if you are using your light bulb in an easy bake oven, but when you are lighting your house at night in the summer — you are heating the room — which you are probably cooling with an air conditioner! Thus the use of an incandescent light bulb is inefficient. We measure efficiency as the amount of useful energy that we get out of a system divided by the energy we put into a system, multiplied by 100 to obtain the %. While this low-efficiency bulb was acceptable for a long time, it is being phased out through legislation reducing production and use to help aid emission reductions. While this occurred under the George W. Bush presidency and was expanded under the Obama presidency. Some of the changes were reduced or eliminated under the Trump administration (you will see this as a common theme). There is obviously friction between emission reduction and cost (more on this later).

Efficiency = Useful energy out / energy in x 100

At about 5% efficiency, you can see that we are wasting a great deal of energy by using an incandescent light bulb. This is one of the basics of all our energy systems (one of the three laws), we don’t get out what we put in; there is always a reduction or an “energy tax.” We measure how much light intensity comes off a light bulb by either candle-power or lumens. By putting more electricity into a light bulb, we can, to a point, get more light. We measure the “flow” of electricity by the term Watt (W). You might purchase a 60 W light bulb, for example, that will produce 890 lumens of light and should last 1,000 hours of use. If you need more light, a higher wattage bulb will provide more light (and use more energy). Due to this inefficiency, these bulbs are being phased out and replaced by LED or compact fluorescent bulbs.

Fluorescent

classroom lit by fluorescent lighting
An office lit by fluorescent lighting.
Credit: sowanna / adobe.stock.com

This is a much better method of producing light as it is far more efficient (x 4 incandescent). That means it is about 20 % efficient which is still not an impressive number. How does fluorescent lighting work? Much of the energy required to "light" a fluorescent light is needed as soon as the light switch is turned on. The electrodes at either end of the lamp are the starting point for the electron to “flow” through the tube (from one electrode to the other). As they pass through the tube they excite the mercury vapor inside the tube; the excited mercury gives off ultraviolet radiation. Unfortunately, that is not very useful for us, as we cannot “see” that wavelength of light. However, we can use this ultraviolet radiation to excite a phosphor coating on the inside of the bulb which, when excited, gives off visible light. The lower rate of energy use (wattage) will however still produce as much light as an incandescent light because of the efficiency increase over the incandescent lighting (look at lumens levels to compare). Offices, universities, malls, supermarkets, apartment complexes will all use this type of lighting, as the light is on for long time periods, often 24 hours a day in some locations. Many of these bulbs are being replaced by LEDs.

Compact Fluorescent Lighting

compact fluorescent light bulb
CFL lightbulb
Credit: Dmytro Titov /
adobe.stock.com

As discussed above, an incandescent light bulb produces light by heating a tungsten wire to white-hot temperatures. No wonder it is not a very efficient form of lighting. Fluorescent is a lot better at about 20% efficient (converting electricity into light), but fluorescent lights were for a long time only long tubes. Now compact fluorescent light bulbs are available that simply screw into the same lamps that an incandescent light bulb did. The advantage is that your electricity bill will be less because for the same production of light (how many lumens), less electricity is used. The compact fluorescent bulbs also last much longer than the incandescent bulbs, so they don't need to be replaced as often. Yes, they will be more expensive to purchase but when you look at the lifecycle (how much money in total that you pay), compact fluorescent bulbs make a great deal of economic and environmental sense (electricity comes mostly from aging fossil fuel utilities that produce air pollution). An additional benefit is that less heat from the bulb provides less risk of fire or (they are safer). Now LED's are the better option.

Light Emitting Diode (LED)

LED flashlight
LED Flashlight
Credit: rottenman / adobe.stock.com

LEDs are small light sources that become illuminated by the movement of electrons through a semiconductor material [9]. LEDs have been around for a long time; the red, green, and blue lights were in various electronics such as my 1970s stereos (the things we used before iPods!) and now in cell phones and many other consumer electronics, from coffee machines to computers. Recently, they have become a lighting option for white light (often directional lighting for task lighting: reading lamps, countertops, etc.) Often there is an array of LEDs to provide enough light. They have a high efficiency (similar to fluorescent), don’t produce much heat, and can last a long time. They are increasingly common in general lighting and have a nicer color than compact fluorescent lighting. They are also being used in traffic lights, streetlights, Xmas tree lights, and other more common applications. They use less electricity, the light is closer to incandescent in color, and they last longer.

Lightbulbs and heat

We can "see" heat if we use an Infra-Red camera. In the image below, you can see two lamps, one with a Halogen lamp the other with a Compact Fluorescent lamp. The CFL has a higher efficiency because it does not produce as much heat. Replacing incandescent bulbs with compact fluorescent bulbs is a good way to lower your electricity bills. LEDs are however now the better choice commonly.

Photograph showing a collection of light bulbs in the visible and the infra-red spectra.

Look at the difference in the heat given off by the different bulbs. IR image.
Credit: Wired (Rhett Akkain)

Home Heating (what influences it and fuel choices)

In the northeast, we spend a great deal of our total energy (note this is not just electricity) on home heating (about 44% of the utility bill is heating & cooling). In other locations, home cooling is the major expense. In some locations, both heating and cooling are required to ensure our comfort. How much energy we will need is obviously weather dependent. The colder (or warmer) a location is, the more energy will be needed, and if the winter (or summer) is long and has many cold (hot) days, then more energy is needed. We can express this impact mathematically using heating degree days (HDD) for our heating needs and the summer equivalent cooling degree days (CDD).

HDD and CDD

How much energy is needed to heat (or cool) your home is dependent not only on how many days that heating (or cooling) is needed, but also how cold (or hot) it is outside. On a very cold day, you will need to use much more energy than on a slightly cool day. We can quantify this by examining the temperature difference and for how many hours it is needed (we need more heat in the evening/early morning or more cooling mid-day). Heating is needed < 65o F (<18o C), We use this information (HDD/CDD) to compare annual energy usage and to explain why heating/cooling costs will vary due to weather impacts or regional temperature differences (used in determining how much insulation is appropriate). For example in 2019 the Northeast had ~6000 heating degree days but Florida had ~ 2,500 heating degree days. Have a look at the regional map is here [10].

Insulation

 Picture of two houes, one with a full coating of snow on the roof and the other with only a partial covering.
These two houses are next to each other on the same side of the street. The images were taken 20 seconds apart on the same day after some light snowfall. Which house has the lower energy bill, and why?
Click here for the answer.

The house with more snow on the roof is more efficient and has a lower energy bill because there is less heat loss through the roof due to better insulation values!

Credit: JPM

Obviously, we can save energy if we capture it and don’t let the heat out (winter) or let the heat in (summer). We can achieve this with insulation. Our older houses often do not have the required insulation because when they were built energy was cheap, and so the economic incentive was not present (or, as we will see much later, the national energy security was not threatened—yet). Modern housing is required to have certain insulation levels to meet the building code. What these values are will vary by geographic region (related to HDD/CDD). We use R values to measure the insulating property of the material (the resistance of an area of material to heat flow over time). The units are:

h × f t 2 × F F t u

h= hours, ft2 is the area, F is degrees Fahrenheit, and Btu (British thermal units) is energy. So, as that is a mouthful, we just report the R-value as the unit.

As this is the resistance to heat flow, the higher the R-value the better the insulating ability. We can increase the R-value by adding more (thickness) insulation or by changing the insulating material to a higher R-value. Of course, if this is a wise investment or not depends on the climate (Heating degree days), how well the house is already insulated, along with the cost of insulation and the cost of heating. So, it makes sense to add insulation when the energy cost is high and the insulation costs are cheap. When energy is cheap, the payback period is too long. That is why old houses were poorly insulated. Now, however, the era of cheap energy is over.

 Picture of the sign on Burrows Road at the end of Hammond Building which talks about R-Value.
The R-value is a Penn State invention, now internationally adopted. This sign is at the Burrows Road end of Hammond Building on the University Park campus.
Credit: JPM

The map below shows the EPA insulation zones for houses across the country. Both cold and hot areas (those with high HDD AND CDD) are required to have higher levels of insulation (higher R-values).

United States map showing the recommended R-Values for different regions.
United States map showing the EPA insulation zones for different regions.
Credit: DOE

The chart below shows the EPA recommended R values for houses in (Zone 2), where Penn State's main campus is located. The highest R-values are required for the attic. R-values differ based on the area and location in the house (interior and exterior walls for example).

 Chart showing the EPA recommended R-Values for houses in our area.
EPA recommended R-Values for houses in Central Pennsylvania.
Credit: DOE

Air infiltration

Air infiltrates in and out of your home through every hole, nook, and cranny. About one-third of this air infiltrates through openings in your ceilings, walls, and floors. This provides a means for heat to escape or enter the home. Again this will differ due to area, location, and materials used in construction.

 Pie chart showing how air enters the home (31% Floors Walls and Ceiling, 14% Fireplace, 4% Vents, 11% Doors, 10% Windows, 13% Plumbing, 15% Ducts, 2% Outlets)
Percentage of air that infiltrates in and out of your home through various openings.
Credit: DOE
 Picture of a house which has been wrapped in white insulation to help prevent air infiltration.
This house has been wrapped to help reduce any air infiltration. I used to live in a rental where the wind would blow through the electric outlets. Not good for my heating or cooling bills!
Credit: Robert Pernel [11] / adobe.stock.com [12]

Home Heating

Although there are several different types of fuel available to heat our homes, about half of us use natural gas.
Credit: DOE

Natural gas is popular because of the (normally) low cost and ease of use (no cleaning up ashes, or arranging storage and delivery, etc). Not all of the houses have access to natural gas pipelines, so they tend to use electricity, or older houses (especially in the northeast) might use a fuel oil furnace. Had this course been taught in 1917, the local area would have been heated with coal. You may have heard the expression of getting coal for Christmas if you had been naughty. Coal was so abundant around the house for home heating, it had little value as far as children are concerned. Before the 1800s, biomass would have been the fuel of choice for home heating.

Biomass Combustion

 A log burning in a fire place
A fireplace crackles on a fall evening
Credit: Syda Productions [13] / adobe.stock.com [14]

Burning wood is still used in many nations and was, of course, the method of choice for the early settlers and Indigenous Americans. I still use wood furnaces to supplement my home heating as it is cheaper than using electricity. Cleanup is a pain and I often get yelled at for dropping bark on the floor or spilling ashes but it is nice and romantic on those cold winter evenings! Burning wood works because solar energy is stored in the plant in the form of chemical energy and then released as thermal energy during the combustion process.

Biomass is going to again contribute more to our energy mix. See the next lecture for why. Hint: Renewable Portfolio Standards!

Below you will find two videos from the US Department of Energy. They both provide a nice overview of home heating.

The first one, Energy 101: Home Energy Assessment (3:30 min.) discussed what a home energy assessor looks for when evaluating a home for efficiency, including insulation and air infiltration as described above.

Click here for the transcript of the US department of energy home energy assessment video.

In any season a leaky (high air infiltration) home costs money. How do you stop it? It starts with a comprehensive home energy checkup. That’s a series of tests and inspections to find out where your house could be more efficient. The end goal is to save energy, save money, and make your house more comfortable. Installing energy-efficient lighting and appliances will help. So will creating a sealed barrier around your house hence minimizing the leaks. Upgrading your home to save energy can put anywhere from 5 to 30% of your energy bill. To get a thorough home energy checkup, you’ll need some help from a professional. Look for a home energy technician, called an auditor, in your area. Now, in this cold-weather evaluation, the auditor starts on the outside, looking for problems around walls, joints and under the eaves. If there’s not a tight fit, you’re losing energy and money. Next the technician might head up to your attic to check for leaks in the top of your home barrier. That trap door could be a culprit, letting cold air pass into the house. A big part of the checkup is determining how well the insulation insulates. Insulation should be correctly installed in between all areas of the house frame. That means it needs to be evenly applied and not just jammed in spaces. And of course, if the insulation has fallen down, it’s not working. Your energy auditor will inspect the holes where electrical lines pass through. If they’re not sealed, they’re leaking. Then it’s down to the basement. Your furnace and water heater could be wasting energy. The auditor will check to see how energy efficient the furnace is. Furnaces generally lose efficiency as they get older, and it could cost you more to keep yours running than to replace it with a new one. Maybe all you need is a new filter. Some people haven’t changed their filter for months, even years. That gunk clogging the filter means your furnace has to work harder to heat your home. If the water heater is several years old, it may not be efficient, and if it isn’t insulated, it’s also losing energy. Now it’s on to the ductwork. The technician will inspect connections to make sure they make a tight fit. They have to be sealed to keep the warm air going where it’s supposed to go. If the screwdriver can go in the hole, it means one thing for sure: Money is going out. Now for the blower door test. The energy auditor will close all the windows and doors and anything else that let outside air in. This special fan will depressurize the home. The idea is to suck air out of the house, allowing outside air to rush into the home through all those openings you didn’t know about. OK, so with the windows and doors closed and the fan running, leaks are easy to spot with an infrared camera. In winter the auditor will scan the interior of the home looking for cold air rushing in. Here the darker the color, the worse it is. These black spots mean one big air leak. It’s an eye-opening experience. For this house, the recessed lighting fixtures are big problems. The auditor will also take a look at the kind of light bulbs in those fixtures. If they’re incandescents, they’re using a lot of energy. Warm compact fluorescents are an energy-saving alternative. So the home energy assessment reveals ways that energy escapes your home, costing you money. The good news is you’ll have a comprehensive home energy report showing which efficiency upgrades are right for you and where to stop those pesky leaks.

Credit: US Department of Energy

Now watch the 2:43 minute video about daylighting. 

Click here for a transcript of the Daylighting video.

Windows do more than provide a great view (or not).  When we maximize the use of windows to reduce lighting and heating needs It’s called daylighting. Daylighting combines lots of things – everything from the type of window, window placement. and interior design – to control how sunlight comes in. They all work to maximize benefits from natural sunlight. (Music.) Check this out. Windows that face south are best in the U.S. They let in the most light in the winter months, but little direct sun during the summer, keeping the inside cooler. North-facing windows are also good for daylighting. They let in even natural light with little glare and little summer heat. Windows that face east and west don’t work nearly as well for daylighting. They do provide lots of light in the morning and afternoon, but it often comes with lots of glare and excess heat during the summer months. (Music.) Have a look at this energy-efficient office building. The windows team up with skylights to provide most of the light you need. Notice the light color of the ceiling. It reflects and enhances the daylight so that it fills the room. And what about all the overhead lights? Most of the time, you don’t need them. To account for glare, this office building placed hoods outside around the windows. The hoods also cut down on summer heat, keeping the office cooler and more comfortable. On the inside, louvers or tinting reduce glare and also direct light to reflective surfaces inside, allowing plenty of natural light to come into work areas. One big help to daylighting is the window technologies available today. Windows are now way more energy efficient. They insulate while still letting the light you want in. And have a look at this. It’s an electrochromic window. This special window changes with the brightness of the sunlight outside. As the sun tracks across the sky, it darkens to keep excess heat out. It’s like giant polarized sunglasses. Daylighting can have a positive effect. Studies have shown that with good daylighting at the office, productivity goes up and absenteeism goes down, and that’s good for the bottom line. Natural lighting and heating means you use less electricity and lower your utility bill. And the more natural lighting, the more money you can save.

Credit: US Department of Energy

Home Heating and Cooling with a Heat Pump

The previous page explained what influences how much energy we need to heat or cool the home along with some of the traditional fuel choices. A modern approach however can also use a combination of electricity and geothermal (renewable energy) to heat and cool the home.

geothermal pipes going into the ground from a heat pump in a house.

Geothermal heat pump for residential home heating. Pipes need only go down about 8 feet before the earth is at a relatively constant temperature. Pumping a fluid through the pipes allows for heat exchange and hence heating and cooling.
Credit: A Students Guide to Global Climate Change, EPA [15]

This is perhaps one of the very best methods of both heating and cooling your home or office (and you also get cheap hot water in the summer). It works because unlike the air temperature which can vary greatly, the temperature of the earth is relatively constant (once you get deep enough). Here I am not talking about going very deep, only a few meters; once you start getting deeper, then the temperature of the earth increases as you get closer to the hot core. But at a few meters down, the temperature will be a constant value. It is called geothermal energy because it is energy from the ground, but it is actually mostly stored solar energy. 

Not only can this stored solar energy be used to heat your home, but it can also cool your home and provide hot water in the summer.

Watch this introduction to geothermal energy from the Department of Energy (2:31 minutes)

Click here for a transcript of the DOE Overview of Geothermal Heat Pumps.

We all want to save money heating or cooling our house or office, right?

The answer may be under your feet, literally. Much of the heating and cooling can come from the ground, below the surface, with something called a geothermal heat pump. You see, below the frost line about 10 feet down, the Earth maintains a nearly constant temperature of 54 degrees. We can tap into this energy to provide heating in the winter and cooling in the summer.

OK, now, here’s how it works. Bury a loop of pipes called a heat exchanger just below the surface, and fill them with water or a water and antifreeze solution. During the winter months, the air is usually cooler than the temperature below ground. The solution circulates in a loop underground and absorbs the Earth’s heat. This heat is brought to the surface and transferred to a heat pump. The heat pump warms the air, and then your regular heating system warms the air some more to a comfortable temperature. Finally,

ducts circulate the air to the various rooms. Now, a huge benefit is that the geothermal system doesn’t have to work as hard to make people inside comfortably warm, and you save lots of money on your heating bill. In the summertime, the system works in reverse. When it’s hot outside the temperature below the surface is cooler than the summer heat. So the fluid in the loop absorbs heat in the building and sends it underground. The ground’s lower temperature cools it, and it’s circulated again and again. Now you’re saving money on air conditioning.

Now, this church uses a large geothermal heat pump to heat and cool the building. It has a very big parking lot, which lets it spread out is loop horizontally. But if you don’t have all that space, you can go straight down and use a vertical loop system instead. Geothermal heat pumps can be used just about anywhere in the U.S. because all areas have nearly constant shallow-ground temperatures, although systems in different locations will have varying degrees of efficiency and cost savings.

The constant temperature of the Earth just below our feet is a sustainable resource literally in our own backyard. It’s a clean energy source ready for us to use to heat and cool our homes and buildings while

Credit: DOE

Heating

a hole in the ground with black pipes running into it.
Credit: JPM

So, it is a cold winter day, the outside air temperature is 30 °F, but the temperature of the ground 10 feet down is a balmy 50 °F. By putting pipes in the ground, we can exchange the heat from the ground to the house. A fluid is pumped through a closed loop of piping into the earth where it warms up. See more detailed information on the Geothermal heat pump [16] page of the Dept. of Energy website.

In the image to the right, pipes enter and exit the vertical hole in the ground. Most systems will be closed-loop systems like this, although you could take the water out of the ground in an open-loop system as the water temperature will remain constant. 

Cooling

So, it is a balmy 90 °F outside, but the ground is a cool 50 °F. We can now move heat from the house into the ground. All we need to pay for is the electricity to circulate the cooling fluid. You can also produce hot water via this method, more cheaply than using electricity, to heat cold water to hot water for your showers or clothes washer.

Geothermal heat pumps are sold by the weight of the cooling fluid. Some of the facilities require lots of pipes to provide enough heating and cooling for large buildings. This is the barrier to using a heat pump - the high initial cost (capital cost). After that, the cost of electricity is low and no fuel costs, thus producing cheap heating and cooling without air pollution (apart from the electricity needed to run the pumps).

How does it Work?

Okay, the above is a tad simplistic. We could, if we wanted to, flow the heating/cooling fluid around the house, but we tend not to. A cooling system works by turning a liquid into a gas. This liquid to gas process requires energy, and so it cools its surroundings (we actually lower the pressure surrounding the liquid). We use a compressor to compress the gas and turn it into a hot gas. We also need energy (electricity) to pump the fluid. This is how we would cool the house by expanding the liquid to a gas (absorbing heat) which cools the house. The gas is then compressed to produce a higher temperature gas (heat exchange here to get the hot water for the house) and then allow the hot gas to heat exchange with the earth, cooling the gas so it turns back into a liquid, so we can do the expansion again and cool the house.

To heat the house, we pump liquid into the pipes (which are in the ground). There, the liquid warms up and forms a gas. Unfortunately, the gas is not hot enough to directly warm the house, but if we increase the pressure, we can turn the gas into hotter gas (concentrate the heat). This process does require electrical energy. But, for a little energy, we are getting a great deal of free energy from the geothermal source —the earth. Now that the gas is much hotter than the air temperature, we have a heating cycle.

Cost

 Picture of a house which uses a geothermal heat pump.
This nice-looking house has a geothermal
heat pump system. 
Credit: Ursula Page [17] / adobe.stock.com [18]

The geothermal heat pump in this house provides all the heating, cooling, and hot water needs for the entire house. For a home of 1,500 square feet with a good building envelope (well-sealed so a low air-infiltration) and a geothermal heat pump, energy costs are about \$3 a day. This is much cheaper than the average energy cost but they are not cheap systems to install at about $7,500 in a new house, but they only use a small amount of energy (electricity), and they both cool and heat the house (and provide hot water). Payback time for this investment is about 6 years, so it is worth doing. However, the cost is more expensive if the house does not already have the ductwork in place for air handling. If you look back at the insulation page, you will see that the Department of Energy thinks that geothermal heat pumps can be used in PA. I only know of a few houses, however, that have an in-ground heat pump.

We will see that, in comparison to the other methods of heating and cooling the house, this will have a much lower environmental impact.

Note:

In lesson 2, we will also discover that the energy from the much deeper ground can also be used to generate electricity. Don't confuse the two types as it is a very common error:

  • Home heating and cooling use stored solar energy (warmth) in relatively shallow sites. Heat is moved around using a heat pump. Also, the system can cool when the air temperature is hotter than the ground.
  • Geothermal for electricity generation typically uses deep geothermal energy for electricity generation from very hot steam. 

Water Heater

This is another one of the big energy users (hence expenses) in your home. Generally, water heating will rank third after home heating and cooling. Many of our appliances are now much more efficient than they were 10-12 years ago. I think it might have something to do with efficiency limits mandated by the government for the area in which you live. One of the problems and advantages of the water heater is that she is a hard beast to kill and struggles on for years before the lingering death comes to a halt and your hot water heater fails.

The cheaper options are natural gas (assuming gas prices are not too high), oil, and propane, but since natural gas doesn't come to my house, I use an electric hot water heater which is more expensive.

Of course, the less hot water you use, the lower your electric and water bills will be. We use hot water for things like bathing, cleaning dishes, washing clothes, and, if you have an old house, perhaps even heating your home with a radiator.

The following are some ways to reduce your electric and water bills. Take a shower, rather than a bath. Showers use less hot water than baths. Cold showers are a bit extreme but would save both water and energy! (You could always shower with a friend to conserve.) Washing clothes in an efficient washer also helps. Aerators lower the water flow for washing hands, etc. Turn down the thermostats on your water heater. Water heaters have 2 thermostats, one each for the top and bottom element. Don't leave the tap running too long; insulate your pipes and keep the water heater in a heated part of the house rather than the deepest, darkest spot in the basement. Purchase a new water heater if you are still using an old model. These approaches will also lower your utility bills.

Water quality can also impact the cost of water heating. Hard water can add scale to the pipes and hinder the heat transfer from the element to the water.

Watch this (1:27) movie to see the effect of hard water.

Click Here for a Transcript of the Hard Water video

[Camera is zoomed in on a shower head.] Dr. Mathews: Hard water is certainly a problem in our area. And you can see pretty simply from the shower head that these hard water stains have affected it. One way I can clean it is by soaking it in a weak acid such as vinegar. [Camera shows the shower head in a glass bowl with a bottle of vinegar next to it] Dr. Mathews: By leaving this here for several hours it cleaned up the system quite nicely. Now if you have hard water whenever you are boiling water or say boiling a lot of water in a pan, kettle, or an electric kettle, [Camera zooms into the cleaned shower head.] you are going to start getting this coating in the metal. The hard water stains are going to impact the ability to do heat transfer and increase your heating costs. Now you can use vinegar to clean things like your coffee maker and things of small scale. You certainly wouldn't want to use it in a very large device like your water heater. So there your options are to replace the heating element if it is electric or one of the other things you can do is to prevent the problem from forming in the first place. And that is by taking your incoming street water, municipality water, and treating it to avoid the calcium and magnesium going into the system. There is a variety of techniques from adding salt, to magnetism, to osmosis, to all these other weird and wonderful things. But the bottom line is if you can do this you are going to have a much better heat transfer efficiencies and your hot water heating, which is a significant expense for most houses, will be considerably lowered. [Video ends]

Credit: JPM

Using Solar to Heat Water

 Picture of a pool.  The house behind the pool has solar panel on the roof.
Credit: JPM

This pool owner (one of my friends) uses active solar heat to keep her pool warm in Orlando. The solar panels on the roof warm the pool water which is pumped through the tubes when the thermostat indicates that the water from the solar heater is hotter than the pool (and the pool temperature is below the desired setting). The cage is to keep out the insects. Solar water heating (for pools or home hot water) is perhaps the most economic use of solar energy after passive solar heating.

The Microwave Oven

Before we can work out how a microwave oven works, we need to know what a microwave is. The electromagnetic spectrum consists of various wavelengths of visible light (colors) as well as radio waves, X-rays, etc. There are two simple parameters that change the utility and the behavior of these various waves: wavelength and frequency. The example below uses a frequency slider to adjust the frequency/wavelength of the wave.

Temperature and Wavelengths
Click Here for a transcript.

Let’s explore a simple model of how oscillation frequency is tied to the wavelength of electromagnetic radiation.

The frequency at which electrons oscillate is essentially set by the temperature of the matter in which the electron resides. Lower temperatures yield lower frequencies of oscillation. Here, we’ve set our temperature on the low side, and you can see the molecule oscillating fairly slowly, or in other words, at a low frequency. The wavelength of the emitted radiation is also relatively long.

But, when the temperature increases, the oscillations get faster, which makes for a higher oscillation frequency. This high frequency means that the emitted electromagnetic radiation has a relatively short wavelength. For comparison again, we can decrease our temperature to watch the oscillation frequency slow, and the wavelength of the emitted radiation increase.

Credit: DMB & SS

Required Reading

NASA's web page on the Electromagnetic Spectrum [19] provides a brief, straight-forward discussion about the topic that I expect you to take a look at. As you read, make sure you understand at least one use for each classification of wavelengths. For example, radio waves carry radio signals. What are IR and UV useful for?

After reading the NASA page, you should know that the wavelength of microwaves is about a few centimeters (cm). This energy enters the food or liquid (placed in the microwave) and excites the molecules within, causing them to vibrate more. The technical explanation is that as the molecules move more, they have more kinetic energy, which, in the case of molecules, we call temperature... thus heating up the food, very convenient.

Here Comes the Sun (it's alright)

Going Solar - Energy from the Sun

Picutre of Dr. Mathew's living room which is facing the south and the sun is shining in to light the entire room.
This is my living room. We bought this particular house because of the bright, roomy living room. The house faces more or less south, so this room does not need any additional light until dusk. The brick chimney also acts as a heat sink, so the warmth of the day is released in the evening hours, lowering my heating cost.
Credit: JPM

We will find out in lesson 2 that the sun is the source of nearly all our energy (nearly all of the renewable energy and the chemical energy in the fossil fuels). In the winter, we crave the warm rays, and in the summer, we may hide from the sun and its oppressive heat. For most of us in America, we could obtain all our home energy needs directly from the sun year-round but it would require a quality house that was well designed and placed. For the rest of us, however, some of these solar options are a good way of reducing the heating, lighting, and cooling bills. Here, passive solar heating options are discussed. Passive means that no external energy is used. It is, in essence, good design (no pumps, no electrical energy).

Face the house towards the south (in the N. hemisphere) to maximize the exposure to the sun. Unfortunately, most of our homes are situated so they face the roadway regardless of the orientation towards the sun. Nor can we physically move our houses very easily, but keep these things in mind when you build your 4,000 square foot palace. Natural lighting reduces your electricity bill and reduces your pollution footprint. Most of us are interested in capturing the sunlight so we can live in bright locations. (Without sunlight, you can become depressed and lose out on vitamin D. Submariners, for example, have UV lamps so they can get a bit of a tan and avoid becoming "SAD" seasonal affective disorder). If you live in a very hot location, you might consider doing the opposite to prevent the solar energy from entering your house.

You need windows, of course, to let the light in. Have large windows at the front of the house (facing south) and smaller windows on the north side of the house. The traditional problem with windows has been that they let light in but also let heat out. The old window is both an energy source (in a sense) and an energy drain.

 Picture of a large tree providing shade to the side of a house.
These deciduous trees are providing ample
shade for the house during the summer months
but will let more light into the windows during
the fall and winter when the leaves are no longer
on the trees.
Credit: Kamil_k2p [20] / adobe.stock.com [21]

With modern windows, the insulation properties have dramatically increased with improvements and new materials, surface coatings to reflect certain wavelengths of light, and double or triple glazing with halogen molecules such as Xenon in between the panes. With all these changes, the window can be an energy source for the home rather than an energy drain. The materials and xenon are, however, expensive, so these windows do not come cheap.

You can plant trees that shed their leaves (those would be deciduous trees) and can also have overhangs on your house to limit the sunlight entering the house during the summer months when the sun appears to cross the sky at a higher angle. Once the (solar) energy is in the house, it needs to be stored. Even in desert locations, the day may be scalding, but the nights can be very cold. Our passive solar house needs a thermal mass to absorb the energy and radiate it back to the house during the night. Brick chimneys, brick walls, and adobe floors are often used. The house will need to have good insulation, also, to prevent the heat from escaping in the cool evening and nighttime hours or get in during the heat of the day. Heavy insulating drapes and airlock type doors can help prevent heat loss. Air leaks are also a significant source of heat losses/gains in many older houses.

A shadow of a person which appears to be 21 feet long.
Credit: JPM

I am not 21 feet tall. But this image does help explain why we think the sun is hotter during the hours of 12 to 1 in the afternoon. If the same picture were taken then, the shadow would be much smaller (okay, small bulge where my waistline is losing the battle of the bulge!) The sun is more or less directly overhead at noon and the same rays are concentrated over a smaller area. In the early morning, the same rays fall over a larger area (hence my 21-foot long shadow); they are less concentrated. The sun does not know what time it is and so does not become hotter or colder on our time schedule! If I took the picture in the winter at the same time, my shadow would be longer still.

 Picture of a house in Puerto Rico.
This is my in-law's house in Puerto Rico. Being closer to the equator, the trick here is keeping the heat out (not keeping the cool in, the heat flows from hot to cold). It is common on the island and the rest of the Caribbean and other hot locations to have overhangs to keep the direct rays of the sun from entering the house. The houses are also often white to reflect as much of the sunlight as possible to prevent the bricks from heating up the house.
Credit: JPM

Solar Panels

We will cover photovoltaic cells in the renewable electricity generation pages (lesson 03) where we cover generation at the utility scale. You can also add solar panels to your roof or to a community solar project (a collection of panels where you own the panels but that are clustered together away from your residence but still locally placed). By adding solar cells, you reduce your electricity consumption from the grid and are using a cleaner energy source.

2 men on a roof installing solar panels
Credit: mmphoto [22]/ adobe.stock.com [23]

Your Electric Bill & Energy Choice

 A standard home electric meter.
Credit: Maksym Yemelyanov [24] / adobe.stock.com [25]

These sit on the outside of many of our homes and apparently at least once every 2 months someone comes and reads the dial (I have never seen this elusive individual).On the bottom, there is a wheel that spins. The faster it spins the more electricity you are using. Try looking at 3:00 AM do you think you will be using more, the same or less electricity than noon? We are now moving to digital smart meters that can be accessed remotely.

When you are a homeowner, a trivial thing, like the temperature, impacts you where you notice it the most, in your wallet (or purse). If you have electric heating and cooling in your home (I have 1,600 square feet of finished living area), it is a considerable expense. Waiting for the dreaded electric bill in February is just one of the many joys of homeownership awaiting you! We have seen that our use of appliances requires energy.

In the past, the electricity market was regulated. This means that instead of using market forces, the price of electricity was controlled by a regulatory authority. If you moved into State College, home of University Park campus and Beaver Stadium, before 1996, you would have had no choice other than to purchase your electricity from Allegheny power. They, in return, had a guarantee of a catchment area for customers. To ensure that this would not be a monopoly (a single provider who can set their own price); the maximum price that they could charge was regulated. Allegheny Power, being a private company, still needed to make a profit for the shareholders and have the money to meet the environmental regulation expenses (more on this in Unit 3). Many of the states looked at their neighbors and wondered why their constituents were paying more than the constituents of other states. Deregulation opened up the generation component of electricity so there is now competition (also with natural gas). Competition helps to lower prices and is the American way! (Well, the US still regulates milk prices!) Most of the US now has a deregulated electricity market. Unfortunately, this deregulation also caused challenges related to electricity planning, delivery, reliability, and emissions. The management of electricity generation and delivery is regionally controlled by either a regional transmission organization (RTO's) and often cover multiple states or parts of states. Or are locally controlled in regulated systems.

Map of regulated systems in the US
Click for a text description.
  • ISO New England = Conneticut, Massachusets, Vermont, Rhode Island, Maine
  • New York ISO = New York state
  • PJM Interconnection = Pennsylvania, New Jersy, Ohio, West Virginia, Delaware, Maryland, Viginia, Eastern Kentuck, a small part of NE North Carolina, and small parts of Indiana and Illinois
  • Midcontinent ISO = Minnesota, Wisconsin, Michigan, eastern North Dakota, Most of Iowa, eastern Missori, most of Arkansas and Louisiana, western Mississippi and a very small part of south eastern
  • Texas Electric Reliability Council of Texas = vast majority of Texsas
  • Southwest Power Pool = Most of North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, north-west Texas, and eastern New Mexico
  • California ISO = vast majority of California
Credit: Homeland Infrastructure Foundation-Level Data (2019)

Electricity Generator Choice

We have a choice of electricity generators to choose from. Listen or read my explanation below

Listen to my audio explanation [26].

Or read

In Pennsylvania when you move to a new area like I did coming to State College essentially whoever provided your electricity was more or less a controlled monopoly. I had to go through Alleghany Power, they were the only people that could sell me electricity. Now we have an electric choice. I can decide how I would like the electricity made. Now it is somewhat of a con because if I say buy wind power there is no way of getting those electrons from wind delivered to me. It is just electricity that gets dumped into the system. And I will take out the appropriate quantity of electricity. And so it is not quite right in that you are choosing how your electricity it made. But you are choosing how components of the electricity are made. And of course, you can either go with the cheapest, which is generally coal, or you can go environmentally sensitive and decide to go with wind. Either way, what you are picking is how the electricity is made. The delivery, and the transportation across the country, and delivery to your home is, however, done via the existing entity, in this case, Alleghany Power. Now, this was done for several reasons. One if which is because with more choice and competition it is hoped that the electricity price will be reduced. And, in fact, they certainly will be when the transition period payments go away. And so that is certainly going to help lower the cost of electricity. Which currently runs about six or seven cents per kilowatt-hour. 

Since this audio was produced, the cost has increased to around 13 cents per kilowatt-hour.

Electricity Choice Map

Those states in blue are in deregulated (competitive) states where you have energy choice for your electricity generation. The other states are in regulated systems where you do not have the choice.
Click for a text description.
The following states are deregulated: Oregon, California, Montana, Texas, Illinois, Michigan, Ohio, Pennsylvania, Maryland, Deleware, New Jersey, New York, Massachusetts, Connecticut, Rhode Island, New Hampshire, and Maine
Source: EPA

One electricity bill, but three charges

Your electricity bill currently consists of 3 components: generation, transmission, and distribution. Bottom line is that competition and choice drive down prices or give the ability for green options (of course, at a cost!)

Generation here is shown as a fossil fuel plant but it could also be renewable or nuclear energy.
Click for a text description.
Infographic of how electricity is generated, transmitted, and distributed
  • A power plant generated electricity and sends it to the transformer
  • The transformer steps up voltage for transmission and it is sent to the transmission lines
  • The transmission lines carry electricity long distances and then send it to a neighborhood transformer
  • The neighborhood transformer steps down the voltage and sends it to to a distribution line
  • Transformers on poles step down electricity before it enters houses.
  • The distribution lines carry electricity to houses. 
Credit: Adapted from National Energy Development Project(public domain)

Electricity Supply & Demand

Watch the following 4:53 minute video about how electricity supply needs to meet the demand.

Click here for a transcript of the Electricity Supply & Demand Part 1 video.

OK. So today, we're talking about electricity and very much the piece that is the supply needing to meet the demand. So this is very much a case where this has to happen. I can't have electricity storage in the wires. They would heat up. They would melt. That management is quite interesting. And so you have to have the electricity as needed. Now, the piece that's obviously missing is storage. And if we get that right, then we're on to a game changing scenario. But right now, we have pump storage primarily is how we do this.

So let me remind you of a couple of things. So I'm going to show you three cases of what the electricity demand looks like in the week. And so we have Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday. And so this is some sort of measure of demand. And what typically happens is at night, we're using a little bit of electricity, but we're using some. We have these sort of weekly peaks. It might peak around four or six PM depending where you are. And then the weekend typically has a lower demand cycle. So along these lines.

I've drawn that to be relatively uniform. But if we just take a look, this is the lowest amount of electricity used during the week. And that would be the baseload. And, of course, maybe we'd have a day, that might have a higher usage than others, et cetera, et cetera.

But let's say that this is April in Pennsylvania. We don't use a great deal electricity. We are not heating. We are not cooling a great deal in Pennsylvania. We're still using lighting. We're still using hot water. We're still washing clothes, et cetera, et cetera. And, of course, industry is still running. This is probably why we see a reduction in commercial and industry over the weekend.

But if we look at some other cases-- let's go look at a case now where it is the demand for the winter season. And here we still see the same sort of ups and downs. Maybe there's a warmer day, colder day. And you can see that our base load is considerably higher. And we said this was winter, so let's say it's January. We're heating and some of us-- about half of us will use natural gas for heat. So that wouldn't come into here because this is electricity supply. But then the rest of us are using electricity and oil and other pieces.

If again, we do this for the summer. And so let's say, July, which is hot and humid and a bit rotten in State College, again we're going to see a very large peaking. Maybe it was a hot day. Maybe it was a cooler day. And we have a also much higher than the baseload that we had over here.

So what we've seen is there is considerable variability between the seasons. So we have a lower electricity use in April in Pennsylvania. We see a very significant-- almost a doubling, perhaps more than a doubling between the baseload and the highest generated need of electricity, highest electricity demand. Obviously, winter and the summer is where it might peak. In this particular case, we can see that the peak was actually in the summer, which is the case for Pennsylvania.

And so we have choices in how we get there. We've obviously seen that we can generate electricity with the fossil fuels. We can generate with nuclear and with renewables. But we need the policies to be in place so that we can achieve the right balance and have a stable, reliable, resilient grid where electricity prices are cheap. And so that's the next segment.

Credit: Jonathan Mathews © Penn State University is licensed under CC BY-NC-SA 4.0 [5]

Now watch the following 8:19 minute video about how we meet the changing demand for energy.

Click here for a transcript of the Electricity Supply & Demand Part 2 video.

So let's look at a little bit more detail about how we meet that changing demand. So let's just pick again. Let's pick a particular day.

And so here's our baseload. And we have a increase in electricity use. People are getting up, turning on coffee makers, making breakfast, turning on lights, having showers, using hot water, going to offices, turning on electricity. It reaches a peak.

They've gone home. They've turned on more appliances. They're cooking. And then there was a decline. And then it starts up the next day again. And so it might look something like that.

If we're in somewhere interesting like California, because they've got so many solar, you might see actually a reduction in demand right there, just at the peak of wherever noon is, as all the rooftop solar are maximizing their electricity production, and there isn't as much demand. But let's just ignore that.

So what do we use for the baseload? Well, for our baseload we want to use the cheapest electricity. And so here, in the old days that would be very much a combination of coal, nuclear, and hydro.

Now, we're limited in how much hydro we have in many locations. We're limited in how many nuclear power plants we have. And so we have a bit more flexibility in the number of coal-fired power plants that are producing electricity.

And so how do we meet this changing demand? Well, I don't want my nuclear power plant going up and down. It's not designed to do that. Hydro can certainly do that. But if we have a lot of hydro, we want to be using that hydro. And coal doesn't like to go up or down either.

And so we have a large number of plants operating. And so over some of these systems that cover multiple states, there might be 50, 60.

So this is the large coal-fired power plants that are running. And they might start off at 60% of their output and increase a little bit more. We might add a little bit more hydro coming into the system.

And so there was a system where which when it was regulated, we would control how we were meeting this electricity demand. And at the peak, we were paying much more for that electricity generation.

And so, again, in the old regulated days, this would have been natural gas because it was expensive. But we would turn on more power plants and more power plants. We would have the cheapest running the longest time and running at the higher capacity. And then we would turn more and more on.

Coal doesn't like to be turned on and off. And so we would use smaller and smaller natural gas peaking units, and we'd add more into the system. And so this was how we did things under the regulated.

And so even though when you pay for your electricity you had a standard cost, you can see that-- per kilowatt hour-- you can see that we have a variable cost going through the day.

So it was decided that we might be able to do better by going to a deregulated system. And so now, and in the change that we've seen if we take the same system, we have still our same baseload. But now, things have changed price-wise. So now we have significant contribution from wind as well as hydro. And that is growing.

We're likely to see solar come in. And solar, of course, is going to be coming in a particular contribution. It's not going to be running at midnight unless we have stored thermal solar, which we have seen with some of the concentrated powers.

We have nuclear still in the game. And that's producing as much electricity as these two pieces combined. Solar is not yet contributing very much in Pennsylvania to our total electricity supply.

But there are locations in the world where it's much higher. And there are places in the United States where it's much higher. And it's expected to grow.

We are still running coal. We are still adding in other pieces. But we have natural gas. And natural gas right now is very cheap. And so that went up dramatically, primarily at the reduction of coal.

And so now, as I'm writing this, it's about 30 something percent in each case. And so still heavy on the fossil fuels. But again, we're turning on the systems. But we no longer are able to just keep on turning more and more expensive units on because we have renewable portfolio standards.

And so now we have our wind and our hydro, which are now getting quite cheap contributing to our baseload. There's intermittency, obviously, in the wind and in the solar. And so that's problematic.

Again, I don't want to cycle my coal plants up and down. I don't want to cycle my natural gas plants up and down. And so we have an energy policy that was designed for this system that's transitioning into this system where we're competitively bidding in. And we need a system that's going to be reliant.

So here, everybody got paid/ In the regulated system where this is deregulated, if the system had a coal plant that wasn't used, everybody still got paid. It would have been used when needed.

Here, we're all bidding in when prices go up and down, then we have this system where we're checking very cheap. We're required to take some of our renewables. I'm requiring much more cycling up and down in these locations.

Again, we don't do it with nuclear. Nuclear is running a little bit harder. But every time the wind drops, then these other plants have to come in. Natural gas is very much that workhorse for being able to meet this changing demand. But there are limits on how much we have.

And so the advantage of this is that overall our electricity price is cheaper than we paid over in this system. The advantage of this system is the level of control. We have the ability to make decisions over the long-term and know what's going to happen ahead of time with our emissions and our prices.

But the policy side of this has yet to catch up. And, of course, the changing price of wind, and of solar. Anyway, those are the challenges that we face-- more in the lessons.

Credit: Jonathan Mathews © Penn State University is licensed under CC BY-NC-SA 4.0 [5]

Here are examples of weekly electricity demand cycle for various months. Note that the day and time has an impact on demand. Also, these are averages so the variance due to weather (especially cold/hot days and holidays are muted). When you use electricity it has a very significant impact on the cost to generate that supply (the peak will be more expensive than the electricity generated for the trough).

Average hourly U.S. electricity load during a typical a week, selected months
What else influences the non-averaged electricity demand? Would California differ from Vermont? Does season, or weather impact usage, perhaps the economy? Our electricity management in PA is controlled by the PJM which is a regional transmission organization for the movement of wholesale electricity. It covers PA and parts or all of 11 other states.
Credit: eia

We use a great deal of electricity regardless of the time of day. But there are daily and weekly influences. Most of us will sleep in on a Sunday when many of the factories and some of the shops are closed. We will also use less electricity at night when the nation sleeps (I know you are probably reading this well past midnight!) Think about the problems this demand cycle creates. We do not have a good method for storing electricity (with the exception of pumped storage and some emerging advanced battery options, more on that in the next lesson), so the supply must equal demand or it is blackout time. From the above graph, it looks like we need to go from the lowest output, which we call the baseload, to almost 1.7 times that value in a 24-hour period (July). We also need to do this safely (nuclear reactors do not like having to quickly increase or decrease output) and cheaply. Thus, the baseline electric load is generated by the cheapest utility sources that run 24 hours a day. As the demand increases, the generating capacity will be increased, and additional units will be brought online. Finally, if you need the electricity, the highest cost generators are turned on. With smart meters now being available, there are incentives to switch to using more of the electricity during the lower demand times as that electricity is cheaper to generate. So, dishwashing and clothes washing machines have delayed start options so they can be run at night.

Average renewable power generation costs in the fossil fuel range in 2017
Electricity costs will also vary according to the source. While coal and natural gas were among the cheaper options. Advances in renewable energy generation are driving the prices down so that they are in the fossil fuel range. The older and more expensive coal-power plants are being closed or switched to natural gas in the United States where natural gas is especially cheap. Of course, in addition to solar, you will need other sources to generate electricity for cloudy days/evenings or the ability to store large quantities of electricity.
Credit: IRENA (International Renewable Energy Agency)

The seasonal demands on electricity generation can also result in dramatic swings in demand. On cold winter weeks and hot summer days, the electric heaters or air conditioning units crank out hot or cold air 24 hours a day. So not only does supply need to meet demand but there needs to be excess capacity for those temperature extremes and to allow utilities to shut down for routine maintenance. The economy also has an influence. There is less pollution (lower electricity demand) during economic depressions.

Electricity Transport

 An electrical tower with the sunset in the background.
Credit: pdm  [27]/ adobe.stock.com [28]

The U.S. electricity transport and distribution system have grown into a complex network containing according to the EIA "the U.S. power grid is made up of over 7,300 power plants, nearly 160,000 miles of high-voltage power lines, and millions of miles of low-voltage power lines and distribution transformers, connecting 145 million customers throughout the country".

We tend not to transport electricity over great distances. There are problems with electricity losses over distance, but, more importantly, the connections from one part of the country to another are not there. We can send electrons (which is, after all how you are accessing this material) across the country but we cannot send lots of electricity. The capacity to carry enough of the electrons does not exist. Thus, if California was experiencing an electricity shortage, we in Pennsylvania could not increase our output to help. Thus instead of a national network, we have Regional 

This inability to transport electricity also means that industries that are electricity intensive tend to be close to cheap sources of electricity such as hydroelectric sites. (Las Vegas baby!) Adding intermittent renewable energy (such as wind and solar) into this mix is a challenge.

The Flow of Electricity

Electricity going from the plant, through transmission towers, through distribution lines, and ending up in our homes.
A simplified version of the electricity distribution system. Note the 3 parts: Generation, transmission, and distribution.
Credit: Electric Choice
 home circuit breaker
A modern-day circuit breaker box.
Credit: JPM

Somewhere in your house, there is a circuit box containing a number of circuit breakers. I can remember when fuse boxes were the standard. These contained huge fuses that would simply blow if the electrical current overwhelmed the circuit. Perhaps you've had this exact experience when running a hair dryer or space heater in an older house, sending you to the basement to find the box. Hence, the advantage of breakers over fuses - simply switch a breaker back on after it shuts down, but for a fuse, you'd better hope you have a backup waiting, or it's wet hair for you!

Breaker boxes are where all the electricity used in your home enters the house and is distributed to the electricity-hungry devices, such as electric dryers, electric ovens, electric heated hot tubs, and to all those lights, computers, fans, video game consoles, TVs, etc. The question is; How does the electricity make its way into your home?

Now, if you go outside and look around, odds are you will be able to find the meter, which conveniently keeps track of all the juice you use, and then the transformer, a drum-shaped piece of equipment sitting atop a pole somewhere close to your house. This has the important job of stepping down the voltage entering your home from several 1,000 volts to 240 volts. Volts is a measure of the "pressure" behind the electric current, and most home appliances use 110 V, but those dryers, hot tubs, etc. will need to have more electrons than the rest of your appliances, so a higher voltage is needed to "push" those extra electrons along.

 example of a home electric meter and a transmitter at the top of a power line pole
A home electricity meter and power lines.
Credit: left: Maksym Yemelyanov [24] / adobe.stock.com [29]
right: myimagination [30]/ adobe.stock.com [31]

In the images above, the electricity meter measures how much electricity you use, so the company can bill you for all those lovely electrons (Kwh). Poles follow the roads, carrying electricity to each of our dwellings. On those nights when you're forced to sit in the dark, odds are that the problem is at the transformer (right image). Lightning, falling tree branches, overzealous squirrels, and drunk drivers all take a toll on these poles and wires, and when they get disrupted, we go back to the age of the candle.

About High Voltage Power Lines

High voltage power line and a substation
High voltage line coming off of a mountain (left) and an electrical substation (right)
Credit: left: Pellinni [32] / adobe.stock.com [33]
right: jakit17 [34] / adobe.stock.com [35]

Up atop the mountain, the high voltage lines carry electricity over the mountains, rivers, and highways. Unfortunately, we have not been building new lines and are running out of carrying capacity for electricity. (Recall the blackouts?) For those of you who like Yoga: Ohm's law states:

V=IR (VOLTAGE = Current x Resistance)

P = VI (power = voltage x current).

A bit of magic mathematical manipulation and P=I2R

(don't worry about memorizing the equations here)

The losses we obtain by flowing electricity through wires (which causes them to heat up) is proportional to the current squared and the resistance of the wires. This is why we use high voltage lines, to keep the current low. For the math impaired, doubling the current results in quadrupling the losses, doubling the resistance only doubles the losses. Thus, we use very high voltages, 155,000 to 765,000 V, to do the long-distance trip at about 300 miles range.

These substations have switches and transformers to regulate the flow of electricity. Larger ones are close to the utility where the electricity is generated. In Lesson 2  we cover the wonderful world of electricity generation.

Note that our demand for electricity tends to increase as the population grows, and as we use more and more electronics. This puts an ever-increasing strain on the generation capacity and distribution network.

Renewable Intermittence

One of the items that we will come back to is the challenge of supplying electricity with the challenge of intermittency of renewable energy (specifically solar and wind). The following figure shows data for Spain for September/October. Notice the variability in the electricity generated by wind and solar (concentrated solar thermal in this case). Solar will have the obvious peak in the day with some overlap into the evening (solar thermal plants) but will also depend on the sunny days. The wind is also variable with some days having poor solar and poor wind (this would be a bad day in Germany because of their reliance on both wind and solar). Thus, we need to have the ability to generate much more electricity on those days and the electric grid has to cope with the variable renewable supply that adds extra stress. More on this later.

Graph showing the wind, solar, and thermal energy sources for electricity in Spain.
Figure showing solar and wind variability for Spain in September and October of 2015. A series of obvious spikes and valleys are present indicating a high intermittency

So as we are discussing electricity demand it is important to recall that the answer that is always right in aiding the reduction of pollution is conservation (not the only answer, however). Surprisingly, your local utility organization is happy to help you conserve electricity. Given the very large capital cost required to build a large utility, the more we can conserve, the longer that new utility construction can be delayed. Thus, assistance with weatherization can be obtained in some areas courtesy of the local utility. In the UK, it is common to have 2 prices for electricity: a peak demand price and an off-peak demand price. Similar to many service industries, if they lower the prices for certain times, more people will use those time slots. Hence, dishwashers, clothes washing and drying–appliances often have timers to turn them on when the electricity is cheaper (after 10:00 PM). Now the utilities can run the cheaper sources at a higher capacity, longer. We are moving in a similar direction and beyond with the adoption of smart grid technologies and smart meters that know when the electricity is used, not just the amount (so variable pricing is possible).

Lesson 1 Coverage Map

This map is a quick and dirty summary of the lesson you just finished. It's a quick way to get a refresher on the main points in the lesson. This is interactive so move your mouse over the topics.

Accessible Version (word document) [36]

Deliverable

When finished here, take the lesson 1 quiz.


Source URL: https://www.e-education.psu.edu/egee101/node/3

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