Wednesday, June 10, 2009

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:

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.


Big Bikes said...

I tried to follow your post, but half way through something in the back of my brain made a popping noise and I passed out for a while.

Where am I?


Michael Scott Long said...

My two cents:

At the very least, cellulose is needed for producing chemicals from renewable sources. A lot of land is already being wasted growing crops for meat production; end this, and use that land for biofuels.

Hydrogen will be a good energy storage material, as long as it is produced from renewable sources (this is in progress). This alludes to why plugging in a vehicle for the night isn't necessary good for the environment, if the energy you're using is from a non-renewable source.

Dave said...

How about instead of wind we use the Gulf Stream in the Atlantic.
Tether floating and sub-marine turbines in the current.
Typically, the Gulf Stream is 100 kilometres (62 mi) wide and 800 metres (2,600 ft) to 1,200 metres (3,900 ft) deep. The current velocity is fastest near the surface, with the maximum speed typically about 2.5 metres per second (5.6 mph). Sounds like a major untapped power source.

Anonymous said...

I just got my power bill today and my rate is about 20 cents/kWh. If you go to the Honeywell site, they claim the turbine can produce 2000kWh/year and it has an MRSP of $4500. So if you do the math on that, you're looking at 11.25 years to pay off the cost of the turbine. Granted, the quick math does not take into account future utility rate increases or tax credits, but it also ignores installation costs, upkeep, and how the $4500 might be invested if not spent on a turbine.

rick is! said...

I think those turbines were originally developed to be on the rooftops of building in cities where wind speeds tend to be consistantly higher. In those cases they make much more sense. Typical windmills for residences are no different, you need lots of wind for them to work. I see one on a regular basis that is NEVER turning. somebody got ripped off.

gewilli said...

i calculated it awhile back - i would have needed 4 acres of soybeans to make enough oil to convert into bioD to drive 40,000 miles/year. and soybeans are pretty low in the oil crop yield per acre.

The nice thing about using biofuels is they are nearly as energetic as petro but renewable annually. Essentially biod or ethanol (not as much due to the huge processing cost) is chemically stored solar power.

Stick a 2-3 cylinder turbo charged diesel in the Volt and you'll substantially increase the range and decrease the fuel consumption. BTUs in bioD are much higher than gasoline...

Plants do a great job of converting solar to chemical energy. We (as humans) aren't anywhere near ready to match them.

Hill Junkie said...

Gewilli, you're tapping into my next post I have planned on this subject - capturing solar energy with photovoltaics vs plants. The deal with plants is you get one, maybe two harvests per year. Soybeans yeild anywhere from 39 to 61 gallons of biodiesel per acre, depending on which source you use for your info. Bio fuel proponents love inflating or forward projecting these numbers. For 40,000 miles with 4 acres, you'd need to get 164 to 256mph with your vehicles. Optimistically at 60mpg, I'd bet you'd need about 17 acres to keep your diesels humming for a year. 17 acres can feed A LOT of people. In my opinion, it would be immoral to use food grade cropland to fill our auto tanks. If we converted 100% of USA cropland to soy diesel cultivation, it would meet only 1/8th of our auto transportation needs![1]

We need to find a weed that grows in the desert (like a weed) and provides volumous biomass. Then I'd start to be cool with the idea. Bio diesel is not much better than ethanol in efficiency either. Say you get 132,000BTUs per gal. You have to put more than half that into it to grow, fertilize, harvest and process the stuff to get something that will run your car.

I think solar will win the day here. Photovoltaics produce energy all year, year after year with only initial energy input to build the panels. You can place them on roofs and vast expanses of unproductive land. The world won't starve. We may have to run low on crude oil before they become economically viable though.