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.

Bragging Rights: Past Students Current projects: Solar Integration

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 who took the Small Housebuilding Class of 2008.


The evolution of our back porch from an 1850’s-era summer shade piece to the backbone of a solar generating plant happened over seven years. We first designed and installed a 10-panel electrical system, wiring the house for both 12-volts DC and 120 volts AC, constructing a sixteen-piece battery bank, and hooking up everything to run through a panel with a smart charger and house-sized inverters. Our original intention was to start with wind as our power source, but fortunately we took a chance with sun first. Now that we have both wind and sun systems generating electricity for us, the sun has turned out to be much more reliable a power source, although the wind provides excellent supplemental power and provides charging on windy nights and stormy days, when the sun isn’t an option.

A year ago, we finished the design for a solar water heating system using a re-circulating antifreeze loop and a 3 watt DC pump controlled by a Maine-designed electrical solar thermostat. We had difficulty finding plumbers in our area who were familiar with this technology, though we hired one company that had little experience with our type of design. In the end, we ended up reworking many of the lines, flow-meters, and check valves the plumbers installed to get our system to work. Our experience has been that many contractors try to sell themselves as “green” contractors and as having experience with alternative energy systems, but we have not found many that live up to their claims.


Disappointingly, Maine winter sun is insufficient to heat our small 40 gallon hot water tank to bathing temperature, so we designed and built a second parallel antifreeze loop to run off our wood stove. The heat exchanger is a fabricated deep water-filled copper pan in which our closed antifreeze loop is immersed. The antifreeze is re-‘circulated through our hot water tank using a second 3 watt DC pump and electrical controller. Since we heat our home with wood in the winter, this system provides sufficient hot water for our winter domestic use.

Woodbutcher of the Month

Over the years our tool store has had the honor of being visited by a great many fine woodworkers and builders. They have helped us build our inventory and learn about tools. Once each month we'll feature one of our favorite customers, some of their best work, and some of their favorite finds in our tool store.

Neil Knecht, of Monroe Connecticut, was in a few weeks ago during one of his annual trips to Maine. As a fourth-generation woodworker, he creates custom furniture, built-ins, cabinets and architectural details for both residential and commercial clients.

Featured here is a Greene-and-Greene- inspired mahogany media cabinet. He was sure to let us know that he makes a point of stopping by Shelter Tools (formerly Woodbutcher Tools) to pick up a few hard to find pieces.

During his visit he picked up a number of hand tools including skew chisels, a flush cutting saw, and a hammer. But his favorite item . . . the one he really sought out is the Japanese Nail Set—a hard to find tool that is indespensible in the workshop and on site when doing any kind of fine woodworking.

Check back with us next month to see another real woodworker and to see their favorite tools.