Wednesday, January 20, 2010

Past Students. Current Projects: Wind Turbine

Shelter Institute students are some of the most talented, exciting, thoughtful and determined people in the world. And we love to keep in touch and hear what our graduates are doing. Check out this recent note from James and Kim Small Housebuilding Class of 2008.

We thought you might be interested to see photos of our newest project on the island. We are very excited to have wind power now (although the winds have been pretty slow these past few days).

The last photo (“CIP 006”) is a photo of James looking over a new charge inductive pulse battery conditioner. It is a novel device for rejuvenating any large battery and so far it seems to work pretty well. We are using it on our 16-battery PV bank, which has been in service for seven years now (and could use some rejuvenating).

We now have figures for the past few months on daily and average kWh production from our small wind project, a Bergey XL.1 turbine on a 56 foot tower.

I think the main lesson we have learned (and would like to pass along to others) is that PV panels (solar panels) are much more cost effective as a means of autonomous energy production than wind, unless the wind site is very unique (like the California or offshore sites that consistently get >20 mph. We did our own informal wind survey and felt fairly confident we'd get at least 1 kWh of production daily in the winter months (but only when the prevailing winds shifted to northerlies), and we've met that. However, many people we've spoken to have mistakenly used turbine specs rather than an integrated formula for wind speed and time to calculate what they will generate, only to be disappointed in the small amount of energy they actually are able to produce.

Our Bergey is rated for 1.1 kW instantaneous production at 20 mph. While it does this quite well, the actual time that we get constant 20 mph wind is fleeting compared to the average wind speeds. For most homes, windspeeds at 50 feet above ground level are 5-10 mph throughout the year. Given that the wind energy production is not a linear relationship between wind speed and electrical generation, consistent wind of even 10 mph (compared with a 20 mph constant site) drops electrical production by 800 percent (half the wind cubed).

With these things in mind, our daily kWh production average so far has been as follows:

Nov 09 = 0.7 kWh
Dec 09 = 1.7 kWh
Jan 09 = 1.9 kWH
This is consistently less than we produce with our 1,800 watt-rated PV system (ten 180 watt panels), even in a wintry January Maine. A friend of ours has a similar PV system with his panels angled for wintertime sun, and has been getting up to 7 kWh of production over the first days after New Years.

For our own situation, with a household electrical consumption closely monitored and very little traditional energy use (no incandescent lights, no electrical heat, and super-low-energy refrigeration), we use about 4 kWh of electricity every 24h. For comparison, if we lived in a more typical U.S. household, we would consume 24 kWh (based on an average per capita daily energy consumption of 12 kWh in 2007[...]).

Wholesale solar panels are now getting close to $1/watt in price (not production), which is a target many people think will make them competitive with grid-supplied power. Suntech, for example, is selling 10 kW of panels for $19,000 wholesale, which is under $2/watt. At this time, the lowest price individuals can get is somewhere around $3/watt. For example, we recently bought a 170 watt panel for $510 from Ramsond in Michigan.

So, for the biggest green generation bang, we recommend solar panels. Compared to wind, the sun is ubiquitous. Our situation is unique in that we know we'll get wind when the sun isn't out in the winter, so the wind project fills in a gap in our ability to generate power year round, and we have no other means of getting non-fossil power out here. An alternative would have been to double our solar PV bank and add batteries to our current 2,000 pound battery bank, storing excess energy on sunny days for those days when we have wind without sun.

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