Tuesday, March 3, 2009

Yurt Plans, Part 2: The Juice

After people get used to the idea of a yurt, one of the first things they ask me is what I intend to do for electrical power. Usually followed by, "You will have electricity, right?" Oh, I shall have electricity. I will have my dual-core gaming computer and I will have my 720p DLP projection system with Dolby 5.1 surround sound. There are some things that I am simply not willing to give up. But how? That, dear reader, is where I have an idea. Wind power, but not in the way that most people think of it.

I considered three power generation methods as I was designing the electrical system: solar, wind, and hydroelectric. There aren't many sources of flowing water around here with enough of a drop to be effective, so hydro was out. Solar power is wonderful, but expensive. Major breakthroughs in solar panel manufacturing are being made by companies like Nanosolar and AVA Solar, but their solutions are years away from the consumer market. That leaves wind power. There's plenty of wind on the Colorado front range, and quality wind turbines can be built on the cheap by the determined DIYer.

I then got to thinking about the de facto power storage medium for off-grid residences: batteries. Batteries are expensive and full of toxic chemicals. They wear out after a few years, and must be repurchased. I decided that I don't like batteries. So I started searching for a better way to store energy.

Back to the basics: energy can be stored in several ways. This can include chemical (batteries), mechanical (reservoir for a hydroelectric dam), or thermal (geothermal plants). Utility companies in Huntorf, Germany and in McIntosh, Alabama have been storing energy mechanically in a process known as Compressed Air Energy Storage (CAES). This is done on a massive scale, with excess grid electricity being used to run gigantic air compressors that pressurize an entire underground cavern. The compressed air is then used to run air-powered generators when demand is at its peak. This process is inherently inefficient, with electricity being converted to mechanical energy then back again with all sorts of heat losses in the process.

[image from Wikipedia]

What if the process of storing energy in compressed air was streamlined? I think a process that uses a windmill that converts mechanical wind energy to electricity that is used to run an air compressor to store compressed air that is then used to make electricity all over again (whew!) is perhaps a bit complex and wasteful.

My system will use a windmill that directly drives an air compressor instead of a generator. The air will be pumped into storage tanks. When electricity is required, the compressed air will run an air motor/generator and supply the needed current.

This will take a considerable investment of time, research, and testing to properly implement, so for the first year I will be using a gas generator (possibly converted to run on cheaper propane) to supply my electrical requirements. If anyone out there manages to beat me to it, let me know how it turns out. Until next time(water system).


  1. Hi Chase,
    I think for this to work efficiently, you should definitely investigate variable speed wind turbine technology. If you've not familiar with this idea, check out:


  2. Jon,
    I've looked into variable pitch turbine systems (is that what you were referring to?). While those systems are much more efficient than a fixed-blade system, they are prohibitively expensive and complicated.

    For ease of design, construction, and maintenance I currently intend to use a fixed-blade system, but I'm still in the design phase of this. Thanks for the tip!


  3. yes i think you are on to a great idea. I worked for Ingersoll Rand at one time "I no longer have intrest in the company" I know compressing air is very wasteful, however if your drive power is free it is a great idea.
    an oiless compressor with low friction rings,or a rotory vane compressor would be cheap and reliable.One problem you would have to work out is storage space and the best pressure in wich to turn your generator.NOT A PROBLEM REALLY.I would like to look into this one more time.Great engineering mind keep it up. YAH NO MORE BATTERYS!!

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