by Andy Silber
Should your next car have a plug?
One of my favorite stories ever on Prairie Home Companion was about a guy who couldn’t take the cold winters at Lake Wobegon anymore. He drove south until someone asked him about the plug hanging from the front of his car. He figured if it was warm enough that someone didn’t know what an electric block heater was, it was warm enough for him.
But starting late this year many people will be plugging in their car far south of Minnesota. Nissan is going to begin selling the Leaf, their fully electric car and Seattle is one of the initial markets. Not long after that the Chevy Volt will go on sale. Seattle received a federal grant to build a large number of charging stations, some in public and others in the homes of people who buy these cars.
We need to get off oil
There are lots of reasons we need to move beyond oil:
- As the leak in the Gulf of Mexico reminded us, the environmental impacts of extracting the oil are enormous. Worse than the Gulf is a normal day at the Canadian Tar Sands or Nigeria.
- The burning of oil for transportation is the largest source of greenhouse gas emissions in Washington State and is a major contributor to smog.
- Most of the oil sold internationally enriches dictatorships, some of whom fund terrorists bent on our destruction.
- Oil is a finite resource and we’re eventually going to run out. As it becomes harder to extract, supply will outstrip demand until the price increases to the point of pain, leading to a reduction in demand. It’s likely we are at or near that point. Just before this recession started the price of oil was growing quickly, driven by increasing demand from China and India that the suppliers were having trouble meeting. Once this recession ends, it’s likely the price of oil will rise once again, possibly high enough to bring us into another recession.
There are technologies like clean diesel that reduce the oil consumption, but that only delays the problem, not solves it.
Other than Electric Cars, what our the options
I remember the days when everyone was talking about hydrogen fuel cells; they were going to be the solution to all of our oil problems. We would produce the hydrogen by passing electricity from wind farms during off-peak hours through water then drive to our heart’s content without producing any greenhouse gases or sending money to nasty people in other countries (like Canada). So what happened to fuel cells?
First, fuel cells proved even more expensive and unreliable than expected. There are a few test cars driving around, but nobody has any announced plans to commercialize them. But even if Ballard or another company invented a perfect fuel cell tomorrow, we wouldn’t have solved the hard problems.
First we need to make hydrogen. Conceptually it’s easy; just pass an electric current through water and you get hydrogen and oxygen gas. But that’s too expensive. So what is typically done is to convert natural gas into hydrogen. Basically you take a fuel that burns cleanly and easily into something that’s much harder to store.
The biggest problem is that hydrogen is difficult to store and harder to transport. Because hydrogen is the smallest molecule in the universe, it leaks out of very tiny holes. Even methane (the primary gas in natural gas) leaks out of pipelines, but hydrogen would be much worse. We can get around that by transporting electricity or natural gas and making the hydrogen where we want it, like a fueling station. But we still need to store it. The current technology is to pump it at very high pressures into a very strong tank, like what is used in SCUBA diving. This requires energy to pump the gas and a heavy, large and expensive tank. There are some interesting concepts in the lab that might solve the storage problem, but nothing that’s even close to commercialization.
Ethanol, Biodiesel and other biofuels
Corn ethanol has many issues:
- It takes significant amounts of fossil fuels to plant, fertilize and harvest the corn, not to mention transport and refine.
- The runoff creates dead zones like at the mouth of the Mississippi river.
- It removes prime agricultural land from planting food, which just sounds like a bad idea today, and I’m sure that as populations grow and climate change stresses the food system it will become even worse.
Sugar ethanol, like that made in Brazil has similar problems, but it requires less input per gallon of ethanol. Still, do we really want to encourage cutting down the Amazon Rainforest?
Many tout the wonders of cellulosic ethanol, which would be made from agricultural by-products like corn husks and wood chips. This is much harder than making ethanol out of food. If it’s hard for us to eat it, what makes you think the yeast that makes ethanol is going to like it? The concept is you get another bug, maybe one that’s been genetically modified, to take the first bite, and then the yeast take over. As an example in nature, the termite can eat wood because of microbes living in his gut. This technology is worth watching, but is not ready for commercialization.
|Type||Energy density [MJ/kg]||Power [W/kg]||Efficiency[%]||Cycles|
Table 1 Approximate specifications of different battery technologies. High numbers are better for all properties.
The battery in most cars is lead-acid. They are inexpensive and fully recyclable, though they do contain a significant amount of a toxic material (i.e. lead). The biggest problem with them for electric cars is that they hold a small amount of energy per mass; they’re heavy. The EV1, GMs electric car that stared in “Who Killed the Electric Car” started with lead-acid batteries and then upgraded to NiCads, which hold significantly more energy and therefore the car has significantly better range.
The big break in battery technology was not driven by cars (pun intended) but by laptops, cell phones and other portable devices: lithium batteries. They have significantly more energy and power (the ability to deliver that energy quickly) than NiCads or NiMH batteries. Sure, they catch on fire occasionally, but if that were an insurmountable problem you probably wouldn’t put one in your pocket. There are interesting technologies in the lab like ultra-capacitors that will make electric cars even better.
A Toyota Prius is an electric car. It has two drive trains, one powered by electricity and the other powered by gasoline. The energy for the electric motor comes from two sources, burning gasoline in the other drive train or recovering kinetic energy from breaking that would otherwise be lost. The electric energy is stored in a NiMiH battery. The total amount of energy stored is enough to move the Prius a short distance at low speeds, but the gas engine kicks on before that to reduce wear and tear on the battery.
These hybrids reduce gasoline consumption in two ways. First, the recovered energy from breaking is used to get the car moving again. Secondly, the gasoline engine spends more of the time operating near its peak efficiency by running the electric motor when the car is moving at low speeds.
A second class of gas-electric hybrids is the plug-in variety, most notably the Chevy Volt. These cars have larger batteries based on lithium chemistry. The batteries can hold enough energy to move the car a significant distance (in the Volt’s case it’s about 40 miles). Once the battery is depleted a gasoline engine turns on. The idea is that the batteries are expensive and most people only go 40 miles a day or less, so that you have just enough capacity to be powered entirely by electricity on most days. On those days when you go further the gasoline generator gives you an extended range. Like a standard hybrid you capture the breaking energy, but you always run the gasoline engine at its peak efficiency, further improving the mileage when you’re burning gas. Another advantage of this model (which is known by a series hybrid, while the Prius is a parallel hybrid) is that you don’t need a transmission: electric motors provide good performance at low RPMs (or put in gearhead speak, they have a flat torque curve).
You can just charge your Volt or other plug-in cars using a normal 110 V plug, referred to as a level 1 charger. For the Volt it takes about 10 hours to get a full charge. You can also install a Level 2 charger and fill up the battery in only 4 hours. Installing a level-2 charger, which uses the same type of circuit as an electric clothes dryer, requires an electrician and special equipment. The good news is that the plug on a level 2 charger will fit any electric car.
Pure Electric Vehicle
Fully electric cars (e.g. the Nissan Leaf) have no internal combustion engine, gas tank, transmission, catalytic converter, and lots of other components one expects to see in a car. This reduces weight, complexity and cost. What remains is a fairly straightforward machine with one very expensive component: the battery. The bigger the battery the longer the range, the more expensive the vehicle and the longer it takes to charge. For instance, the Leaf will have a range of about 100 miles. For most 2-car families, a pure electric car could serve well for one of thems. How often do you drive more than 100 miles a day? For most people, not often. How often do you drive more than 100 miles a day without planning to? Personally, never.
A level-1 charger is pretty much useless for the Leaf; it would take 20 hours to fully charge the car. Even a level-2 charger takes about 8 hours, which should be acceptable most of the time. If you can find one, a level-3 charger can get the batteries up to 80% in 30 minutes. Not quite the filling station, but I can imagine restaurants along the interstate having level-3 charges in the future, but not until the range is much better than 100 miles.
CO2 emissions from making electricity
Current Fuel Mix
Though electric cars are often called “Zero Emission Vehicles”, that isn’t correct. The emission is just moved from the tailpipe to the generator. If the electricity comes from wind, solar or low-impact hydro then it’s reasonable to think of an electric car as a Zero Emission Vehicle. But half of the electricity in the USA is produced by burning coal, the dirtiest of fuels with a very high carbon content. Of course the emissions from your electricity depends on where you live. For instance, if you live on the west side of Lake Washington your utility is Seattle City Light, a utility that gets 89% of its electricity from hydro and about 1% from coal. If you live on the east shore of Lake Washington your utility is Puget Sound Energy and 36% of your power comes from burning coal.
Several studies have looked at the well-to-wheel emissions of both gasoline and electric powered cars and they have shown that in the US electric cars have significantly lower emissions than the average car. But if you’re electricity comes from coal your emissions will be higher with an electric car than with a Prius.
But this just assumes we’ll continue to do what we have done to supply the energy to charge electric car batteries. In fact we’ve already moved off that path. Most new power plants are either natural gas, which has about half the CO2 emissions of coal, or wind, which has no emissions. Electricity production by coal actually dropped between 2008 and 2009 as old, inefficient plants are decommissioned and replaced with natural gas. Regardless of what we do with transportation we need to replace these coal plants. The additional demand of electric cars will increase that challenge, but not significantly if we do it in a smart way.
But it’s not hard to do even better. Power plants can be categorized in one of three ways:
- Intermittent like wind, tidal and solar that come and go based on the whims of nature. They are predictable to some extent and sometimes nature is well timed, for instance solar is available when air-conditioning needs are high.
- Base-load like coal and nuclear. These sources operate 24/7, whether you need them or not. It takes several days to cool and reheat the boilers so you can’t respond to time of day variations. You can seasonally turn them on and off.
- Dispatchable like single cycle natural gas and hydro-power. These systems can easily turn on and off or vary their output. Operationally, this is the best.
Since most of our power comes from base-load power, in the middle of the night we have excess power. If most of the battery charging is done when this is the case, no excess fuel will have been burnt and no excess emissions will happen. This is what the Smart Grid is all about, the grid operators sending messages to the charging stations about the current price of electricity. The car owner can leave the station in default mode (charge when power is cheap) or hit an override saying that the car needs to be charged immediately. Even a simple $10 timer could make a big difference by starting charging at 10 p.m. every night. Ideally the charger would know what time you normally unplug the car, how much time it would take to top of the batteries and when the utility normally has excess power. This requires some communication and a little bit of smarts. A Smart Grid enabled charging system could easily bring the incremental emissions close to zero. This would also require no investments in new transmission or power plants and only a small investment in smart charging stations (they would probably cost about $100 more than a dumb charging station, assuming you could piggy back on an existing Internet connection for communication).
Eventually the demand from charging cars would exceed our excess capacity in the middle of the night and we would have to make investments in new power plants and transmission, but that would be many years from now at which time we’ve hopefully developed cleaner technologies. Also, we will need to make those investments anyway to replace our current fleet of coal plants. Having a dispactable load (e.g. charging cars) will help in integrating intermittent power sources like wind.
My family currently has two cars, a 14-year old Subaru and a 10-year old Honda. Given how long Subarus and Hondas usually last, I probably will need to buy a car within 5 years. My expectation is that car will have a plug and there will be a level-2 charger in my garage. Since my utility is carbon neutral, that car will be a greenhouse-gas neutral car, something a gasoline powered car could never do.