Off Grid Power

/* Originally posted on 12/30/2009 */

I’ve been fascinated with off grid power production most of my adult life. In fact, I’ve been following solar and wind for at least 20 years, and for at least that long being told how $1/watt solar is just 4-5 years away. Still haven’t seen it, although progress is being made. Of course, I’m looking for systems with long lifetimes, not some of the systems where the cells degenerate over 5-10 years. They may be cheap, but not if one has to replace them.

Recently I’ve reviewing where wind power is at. There appears to be two camps: HAWT and VAWT (Horizontal vs. Vertical Axis Wind Turbines). HAWT are the typical “propeller” on a tower systems seen. VAWTs are a variety of designs from “egg beaters” to various cup designs to flap systems – but basically think of the aerometers in most weather stations. HAWTs tend to be the most efficient in uni-directional wind, in no small part because of their high towers. Think wind coming off the great lakes or off the ocean. VAWTs excel when the wind is multi-directional, and can harvest a LITTLE BIT of power from lower wind speeds. Alas, power available in wind is a function of turbine cross section (how much air is “swept” for wind) and the CUBE of the wind speed – so at low speeds, there simply isn’t much energy available for harvesting.

As of late 2009, VAWTs on short poles (placing them above head height as a safety and small efficiency gain) are still quite expensive. A “WindSpire” VAWT rated at 1.2KW and advertised to generate 2000KWHs in a year (perhaps $200 worth in 2009 dollars) cost $10K to purchase and have installed. Current Federal Tax Incentives reduce that to $7K, but its still a 35 year payback. This particular unit is also ONLY designed for Net-Metering – feeding power back into the grid, not stand-alone usage – although off-grid models are expected in 2010.

Larger units have better payback times, but its very questionable if in NE Missouri any unit could pay back in less than 10 years – even $50K+ ones.

So what to do? Well, building small units is always possible. Ed over at has a VAWT turbine capable of generating 500Ws or so in a strong wind that is easily home built. Suspect 50Ws is more likely in normal conditions, but that’s ok. I’m a firm believer in redundancy, so making 4-6 of these would be a fun project with expenses much less than a single commercial unit like the WindSpire. His design should also scale up fairly nicely – perhaps to a 8′ tall unit 4′ in diameter. Best of all, Ed answers E-mail!