Add it up: Doing the math on electric cars

Editor’s note: The opinions expressed by our contributing staff writers are their own and do not necessarily represent the opinions of the Houston Museum of Natural Science.

Electric cars are a popular idea. You see them in movies, hear about them in songs, and especially get to know them via inventive commercials. They claim that they produce no pollution, unlike their dinosaur automobiles with the internal combustion engines. But are they as green as they claim to be? (Note: For this blog I’ll be talking about pure electric cars, not hybrids.)

Doing the math on electric cars

A normal gasoline-using car produces pollutants as a result of converting fuel into movement. An electric car uses stored electricity to propel the vehicle. But how much pollution was created while creating the electricity? To compare the two, we’ll have to find some way to make gasoline and electricity equivalent. Fortunately, we can convert both to one unit: joules. While you might want to wear a jewel, a joule will help you get work done. A joule (abbreviated by “J” ) is a unit of energy. It’s the equivalent of applying 1 ampere through a resistance of 1 ohm for 1 second, or the force of 1 Newton over 1 meter.

A gallon of gasoline contains about 1,300,000,000 joules. One kilowatt of electricity contains 36,000,000 joules. So 1 gallon of gas produces about 36 kilowatt hours.

Burning a gallon of gasoline to move your car produces about 20 pounds of carbon dioxide. One kilowatt hour can produce different amounts of carbon dioxide, depending on what energy source was used to make it. In the United States, much of our electricity (about 42 percent) comes from coal-fired power plants. One kilogram of coal can produce 2 kilowatt hours and 2.93 kilograms of carbon dioxide. That’s about 3.3 pounds of carbon dioxide per kilowatt hour, which means that 1 gallon of gas’ equivalent in electricity produces 118 pounds of carbon dioxide if all the electricity is made from coal-fired power plants. From this information, it seems that the internal combustion engine outperforms the electric, but not all electricity comes from coal.

While the majority of our electrical generation comes from coal-fired power plants, there are other energy sources. Thirteen percent of our electricity comes from renewables such as wind and solar power, which produce no carbon dioxide. Nuclear power gives us 19 percent of our electricity and produces no carbon dioxide, either. Using this division of power sources, the amount of carbon dioxide produced making electricity for an electric car has been reduced from 118 pounds to just 8. But what about natural gas?

Natural Gas is measured by the MMBTu (one million British thermal units), which is about 1,000 cubic feet (1 mcf). One mcf of natural gas produces 122 pounds of carbon dioxide and can produce about 29 kilowatt hours. Are you still with me? This means that natural gas produces about 4 pounds of carbon dioxide per kilowatt hour. So when we add that back into the mix, our electric car is producing about 9 pounds of carbon dioxide per kilowatt hour. A gallon of gas is about 36 kilowatt hours and produces 20 lbs of carbon dioxide, or about half a pound of carbon dioxide per kilowatt hour.

Does that mean that electric cars produce more carbon dioxide than ones that run on gas? Maybe, maybe not. All those numbers are based on the national average of the energy mix. If renewables provide more electricity in your area, the amount of carbon will decrease. If you get your electricity from an all-renewable company, then you’re producing no carbon. Also, this blog has only addressed the amount of carbon dioxide produced directly by energy sources. It has not included all the other pollutants produced. It has not included the entire life cycle of the energy source. For example, a nuclear reactor produces no carbon dioxide, but mining uranium is a very energy intense project. Wind turbines produce no carbon dioxide while creating electricity, but carbon dioxide is produced when they are built.

The amount of carbon dioxide produced by electric cars can be brought down easily, where the amount produced by internal combustion engines can not. yo could switch the source of electricity. You could take stored electricity and use it for you car. Because our grid is a stupid grid and not a smart grid electricity is put on the grid as needed. If there is a moment with high wind generation and a high need for electricity, then the amount of carbon produced decreases. If the wind stops blowing and the need is still there, then the more traditional sources kick in and the amount of carbon produced goes right back up.

So while an electric car, on average, may currently produce more carbon dioxide than a gas-powered car, depending or your location and your electric provider, your electric car may be producing no carbon dioxide. Also, while there is little hope to improve the internal combustion engine to eliminate the production of carbon dioxide, researchers hope to eventually eliminate the carbon produced by an electric car. So “Let’s take a ride in an electric car/To the west side in an electric car/How can you deny an electric car/Won’t you take a ride with me/Come on and take a ride with me!”

America’s New Energy Policy

On Wednesday, March 30 President Obama revealed an update on his energy policy for the country.  He called for a 1/3 reduction in the importation of foreign oil from 2008 levels in a decade or so.  His plans to pull this off include more domestic drilling, more reliance on other fuels and alternatives, and greater efficiency.

Every president since Nixon has tried to limit or end our reliance on imported oil.
“Let us set as our national goal, in the spirit of Apollo, with the determination of the Manhattan Project, that by the end of this decade we will have developed the potential to meet our own energy needs without depending on any foreign energy source.”
– President Richard Nixon (November 7, 1973)

Despite the fact that every president, regardless of party, has proclaimed the need to reduce oil imports and develop alternative energies, the amount of oil we import has almost always gone up. (There was a period in the mid eighties where it went down).  So what has changed?  What makes now different from 1973?

Technology has advanced; progress goes forward (if you’re a modernist).  But what has really changed is how we see energy in our lives.  From the 1980’s onward, the price of gasoline has continued to rise.  Two very different things happen as the price of gasoline rises.  One is that the gasoline costs more, not online dollars but as a per cent of our lifestyle.  The other thing is that alternatives become more attractive, cost effective, and more people use them.  It may not be worth my time and effort to pay a $1.25 to ride the light rail one way if gasoline costs $2.50 a gallon, but it does become time and cost effective around $3.75 a gallon. 

Barrels
Creative Commons License photo credit: barekim

The United States has 22 billion barrels (1 barrel = 42 gallons) of proved crude oil reserves.  Proven reserves are oil that we know where it is, have the technology to get to it, and it is economical to go after it.  Unproven oil reserves are what we think is probably there (based on the geology) or what we know is there but don’t have the technology to get to. Each year the amount of proved reserves changes.  This can be because new fields have been found; old fields are no longer producing, improvements in technology, and many other reasons.  To put that amount in perspective,  Saudi Arabia has 267 billion barrels in reserve and Mexico has 12.  We use 21 million barrels of oil a day, so if we had all our proven reserves producing 21 million barrels a day they would last almost 3 years.  So domestic drilling will help, but it can’t be the only way to go.

Other energy sources will have to be tapped.  One of the alternative fuels the presidents mentioned was natural gas.  Natural gas burns cleaner than coal or gasoline.  Right now natural gas is used mainly for electrical power generation and crude oil for transportation.  In order for natural gas to replace some or most of our crude oil use, there would have to be a major infrastructure shift.    Natural gas can not simply be put into gas tanks (it does not help that many different things are called by the same name).  A car would have to be retrofitted with a specially made natural gas tank.  That new tank would probably have some freezing element in it.  Natural gas in its gas state takes up a lot of space.  If you freeze the natural gas down to -258 degrees it is reduced in volume by 600%.  Also gasoline stations would have to be converted to be able to contain natural gas.

Full of Sparks
Creative Commons License photo credit: jurvetson

Electric powered cars could be added to the existing grid and infrastructure more easily. It would take a whole lot less work to convert gas stations into electric stations, although with the amount of time it takes to charge an electric car it might be easier to work with businesses to put electrical stations in parking spots.  That way you could charge your car while you shop for groceries (no matter the size of my shopping list it always takes at least an hour for me to grocery shop, partially because of all the free samples and partially to make sure I have all the spices for my Bouillabaisse).  The more electric cars on the road, the more electricity we need to produce.  This is where it makes sense to use the natural gas: burn it to create electricity instead of using coal.  However, not all the houses built in the past 30 years will have the ability to plug in cars

Conservation is where a lot of oil can be saved.  The president wants to increase the efficiency in the cars we drive.  Some of us drive nice little sedans that get 30 or more miles per gallon (some of us even drive hybrids), while others drive SUV’s that get 12 or so miles per gallon.  While the choice of vehicle is an individual one governed by affordability, space, and use (it makes more sense to haul around 7 kids and their sports gear in a SUV than in a 2 door sedan), all cars can be made more efficient.  Weight could be saved on the frame by using lighter materials, the software that runs the engine (yes, lots of cars have software now, but no apps yet) can be optimized, or any number of things that can even be done after you’ve bought the car. 

All in all, the president’s plan to reduce the amount of crude oil we import over the next decade or so is an achievable end.  In fact it has already started.  We reduced the oil we import by 1.7 million barrels a day from 2008 to 2009.  So now what happens?   Many people will sit on the sideline waiting to see what legislation and regulations the federal government hands down.  “Change will not come if we wait for some other person or some other time. We are the ones we’ve been waiting for. We are the change that we seek.” We should all start the change ourselves. There are many different things we can do to use less oil.  Regular maintenance on your car, not having a trunk full of stuff, and driving less are just a few things you can do (for more information check out the ECC).

Get Smart : Meter or grid?

Throughout the years there have been many different versions of “smart” electronics. Movies are full of ‘evil’ and ‘good’ appliances, from Robbie the Robot to R2-D2. And even some that are just part of the background, like most of the robots in Star Wars and Wall-E. The energy industry has also started to toss around ‘smart’ terms. Not just things like Ohm’s law or Restricted-Universe Census, but smart meters and smart grids. So what are they? Are they the same or are they different? What does “smart” mean?

First of all, smart is not an indication of how well a meter or a grid does on an intelligence test, how many times they beat me at checkers, or how well they plot to overthrow humans and use us as batteries. It has to deal with how well they respond with real time stimuli. Can the system adjust in a real time fashion; can it be run correctly by automation?

A smart meter is like any other electrical meter. It reads how much electricity you use, in terms of Kilowatt hours. The information that the smart meter can give you is far more than a Thomas meter. A smart meter can tell you in real time how much electricity you are using at any given moment. It can also show you your electrical usage over time. You can see when you use the most electricity (probably right after you come home). Armed with that data you can make informed decisions, such as deciding if you want air-conditioning to come on when you get home at 5 p.m. or if you want to avoid peak hours and have the air-conditioning running from 4 – 5 p.m. But a smart grid is something completely different.

Kraftwerksneubau Neurath
Creative Commons License photo credit: Neuwieser

Even though the electrical grid has been growing for over 100 years , it has yet to become smart. The current grid is set for a “use it or loose it” grid. That means that the grid should always have enough electricity to power everything that is currently on it. This creates two types of electrical generation. One is base load and the other is peak load. Base load is what is always on the grid. This is mostly created using coal fired power plants. A Coal fired plant takes a lot of energy to start up, but once you get it going it is easy to keep it going. Because of that coal fired plants are always burning coal. So when you’re at work and the refrigerator is still on, it’s part of the base load. Most of the time the base load handles all our electricity needs. However if there is a large spike of electrical usage, such as the one around 5 p.m. when most people get off of work, the base load is not enough. This is when they can bring on fast startup plants, usually using natural gas as the fuel, and supply the electricity during peak times.

The current grid is rigged for redundancy. The current electrical grid has grown up to offer multiple paths for electricity. This means that if one area of the grid goes down, the electricity can be maneuvered around the broken part. What that means in practice is that just because an area near you looses power, your power may not be interrupted.

Why would a smart grid be better? For our current grid we use mostly large scale power generation plants, but the smart grid would easily incorporate lots of small residential power generators like small solar panels on roofs and small wind turbines. The small solar panel and wind turbines on the current grid are unable to provide all your electrical needs. Even though they take in electricity all day long, they only have available what they are taking in at the moment. If there were a way to store all the electricity that they take in during the day when you aren’t using electricity, then it would help with the electricity you need, especially during peak times. Also in a smart grid, if you had an excess of electricity you could sell it to a power company. You could even sell it directly to people who need the electricity. You would go from one who can only consume, to a producer, seller and consumer of electricity.

Arrays from the right
Creative Commons License photo credit: Mike Weston

How can a smart grid help us save money on our electric bills? Currently most electrical companies charge a single rate for electricity. That means that you pay a constant price for a kilowatt hour. The real cost of electricity is always in flux. The price has to do with what time of day it is, what season, what it was priced at yesterday, which power plants are down for maintenance, which ones have been reopened, the weather and many other variables. A smart grid would allow us to purchase electricity in real time. What if power plant B is selling electricity cheaper than power plant B at 3 a.m.? What if power plant A sells cheaper electricity at 2 p.m. than it does at 5 p.m.? Which one would you like to buy electricity from? When would you buy your electricity if you could store it? It gets even more exciting by adding smart appliances. What if you could tell you dishwasher to only wash dishes during the night if the cost of a kilowatt hour fell to a certain price? What if your water heater could find you a better price for the electricity used to heat water for your morning shower?


So is it green? What do we mean by green, it looks like cooper to me. The real question is how can this help save the environment and money (or if you’re more cynical, money and the environment). A smart grid would have the ability to allow small scale renewables to have a larger effect. In a system where a lot of electrical production would be done on residential or small communal solar cells, wind farms, tidal farms, or back yard geothermal plants, the need for large scale power plants would diminish. Large scale power plants will never be done away with. Mother Nature is far too capricious for that.

electric car charging point
Creative Commons License photo credit: frankh

Why do we need to change the grid if it works? The electrical needs for the country are expected to grow 30 % over the next 25 years. That prediction is counting on nothing new happening. What happens if we all switch to the electric cars during that time? Gasoline prices would drop, but electrical prices would rise, because electricity would replace gasoline as the fuel of choice. Right now that would mean building more and more coal plants.

On a smart grid, with most households having some small renewable power generation, the rise in electrical need may not lead to the building of more coal fired power plants.

So how long will this take? So far it has taken over 100 years to get to where we are today. When electricity first started being used most power plants where small and only provided enough electricity for a few buildings. Over time it became cheaper and more reasonable to have power generation on a larger scale. While this would not require us to reinvent the electrical grid, it would mean upgrading all of it. And all that would take more then four years.