Kilojoules on the Breeze

We interrupt regular scheduled content here on Hill Junkie to discuss material a few readers may have some insight into. My dad is a retired autoworker. He has been keenly following the development of General Motors new electric car called the Volt. It is not a hybrid drive, but it does have a gasoline engine. What makes it different is that the electric motor always propels the vehicle. The gas engine simply runs a generator when batteries run low. A Toyota Prius uses the electric motor only to accelerate. It does not have enough battery capacity to drive under electric power even across town. The gas motor takes over the drivetrain after acceleration. The Volt will probably be the last evolutionary step before the day a fully electric car arrives with the same range as gasoline powered cars. The Volt theoretically should be able to perform short errands, up to 40 miles, without burning any fossil fuel. It can plug into household power to recharge.

My dad is also excited about new wind power technology coming on the market. Grand Valley University in Michigan, where I took an undergrad physics course many years ago, has developed a roof-top wind generator. Honeywell bought the rights to produce and market the EarthTronics WT6000. So the media gets a hold of this, doesn't understand the specs and limitations, and begins making all kinds of extravagant claims about what it can do.

I have a background in robotics, specifically battery powered automated guided vehicles. I've learned a thing or two about battery technology, electric motors and controllers over an eleven year span in that industry. So when I hear my dad say he can buy one of these windmills for a few thousand bucks and drive his new Volt with no fossil fuel and keep it off the grid, I think something is way too good to be true here.

So you PowerTap weenies out there, how many kilojoules of energy are there in one gallon of gasoline? How about 132,000kJ! Pick the hardest ride you've ever done. It was what, maybe 5000kJ for a 7-8hr effort? An efficient cyclist is about 25% efficient, so that meant you actually burned about 20,000kJ of energy. If we could ingest gasoline, we'd get about 33,000kJ of useful work from a gallon of gas. This is enough for 6.6 Six-Gaps rides for me! A small water bottle of gasoline would be all the calories I need to ride all of Six-Gaps, including post ride refueling. Gas has very high energy density. Cars are energy hogs, so it is no accident that gas works so well for this application. Batteries still have a very long ways to go to match this.

Back to the home wind turbine. The media states that it generates power with as little as 2mph wind. Yeah. I found and read the specs. Output power at 2mph wind is 6W. This is a typical nightlight bulb used for a kids bedroom. Use this to charge your electric vehicle, you'll wait many months just to get one trip to work out of it.

Now lets say we get more realistic, something closer to long term average wind speed around here, 10mph. The specs say the WT6000 puts out 105W. Not bad. It will power a single incandescent light bulb. Over 24hrs, you will get 2.4kWhrs, or 9072kJ. At this rate, with steady 10mph wind day and night, it will take 15 days to generate one gallon's worth of gasoline energy! Do you put more than one gallon per two weeks into your gas tank? I can think of only one person that might get away with this.

Because wind and power have a cubed relationship, when wind speed hits 25mph, you really start to get some power out of the WT6000. We get those days, but maybe only once a week, and usually only during the day. The last few days have been essentially windless. I think the year long average in most parts of the country is about 12mph. That's if you have no trees or buildings near you that obstruct the wind. As you can see, most people would not be able to power their electric car with this unit. It would barely make a dent in a typical commuter's energy needs. Cars are that way. I use about 10gal per week going to work and back. That is 1.32 gigajoules of energy. In comparison, our monthly home electric consumption is on the order of this. If our home electric power had to supply all of our electric car energy needs, our electric usage would go up at least four fold. I do factor in that electric cars are much more efficient in converting stored energy to motion than gas cars. Plugging our cars in would bump us into a very high utility rate, so the bill would go up a lot more than four fold.

I am not saying here that these new wind turbine generators are gimmicks. If you live on an open field or up on a hill, you will probably get a descent return on investment from one of these units. They claim you can get 15-20% of your home energy needs from this unit. Not sure what the neighbors would think. Back when everybody was putting 6ft satellite dishes up in their back yards, some communities passed zoning ordinances against them. My dad lives on a lake in Michigan. I think he would need to buy a couple WT6000's if he wanted to make a grocery run more than once every two weeks and keep his car off the grid. It would be more realistic understanding that you will be modestly reducing your dependency on grid power. Nothing wrong with that.

I fully support alternative energy source development. My favorites, in order of how I would prioritize investment are:
Photovoltaic
Nuclear
Wind
Geothermal
Tidal

And of course, advanced battery technology will be needed to make all of this work. It is not always sunny or windy or wavy, so you store energy up in batteries on the good days for the weak days.

Also note I did not list bio as an alternative energy source, especially if it has anything to do with powering our cars. This goes back to the 132,000,000 Joules of energy in one gallon of gas. How many acres of soybeans does it take to power one commuter for a year? Acres of Corn? Or one of many exotic species being considered? That's a topic for another post.