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Guy Marsden and his wife live in coastal Woolwich, Maine, USA, where the winters are cold and snowy, but they stay warm and cozy thanks to the sun and green building. Guy's barn workshop is heated by a solar thermal system and the roof holds a solar electric system that powers more than 55 percent of the home plus two home businesses on an annual basis. A solar domestic water system feeds hot water to the house, and Marsden even converted a conventional lawnmower to solar power. Two hybrid vehicles provide transportation for the household. The workshop is heated via four four-by-eight-foot solar thermal collectors that heat a radiant concrete floor, with an 80-gallon Rheem tank to store the heat. The system is augmented by a Bosch Aquastar heat-on-demand propane boiler, with an efficient heat-recovery woodstove for backup in the coldest months. There is also a heat recovery ventilator that is tracked with real-time temperatures. The sustainable household uses rainbarrels to collect rainwater for the garden and employs water-efficient fixtures and dual-flush toilets. They have raised bed gardens for food growing, and they compost and recycle, among many other sustainable lifestyle choices. (Scroll down for additional resources)
Marsden installed a 4.5kW solar power array consisting of 26 BP175 photovoltaic panels that use Enphase M190 microinverters to produce 240VAC at each panel. The panels are mounted on the west facing roof of the workshop. Real-time performance statistics are tracked on the detailed installation blog on Marsden’s Art Tec web site. On average they use about 15-21kWh/day to power their home and two home-based businesses with all the computers and relevant equipment. For reference, the average US home consumes upwards of 25 kWh/day.
Marsden added real-time temperature monitoring in a heat recovery ventilation system that is also accessible on his website.
On the house, Marsden installed a solar hot water system that consists of four small thermal collectors on the south wall of the house and a 50 gallon pre-heat storage tank. He even converted his 24" gas lawn mower to run on a 12-volt battery and DC motor that is solar charged; the mower will run for 20+ minutes on a one-day charge from a 40-watt solar panel.
His personal Art Tec website is a virtual encyclopedia of information for do-it-yourselfers, where he chronicles all his efforts to reduce the waste and energy footprint of their lifestyle. He says, “The main reason I share this information is to inform and educate others who are equally committed to saving our planet from the impending disasters that climate change portends.”
The design goal of the system is to generate a slight surplus of power in July/August and generate about 25 percent of their needs in the middle of winter, averaging about 55 percent of thier needs annually. Their 26 – 175-watt panels produce 4.5kW of power in theory, but, according to Marsden, that ideal performance is derated by a factor of .87 due to various performance and efficiency issues so the actual peak power is 3.95kW.
Marsden also operates his business, Art Tec Solar, from his workshop, where he manufactures solar differential temperature controllers for solar thermal systems.
Solar Lawn Mower
For the solar-powered lawnmower project, Marsden replaced the gasoline engine of a used 22" gas powered mower with a 12-volt electric motor and battery - along with gauges, circuit breaker/power switch and charging connector. Using 12 volts kept the design simple and relatively safe. The solar charging system consists of solar panels that are wired to a charge controller with an extension cord that connects to the mower. Optionally, a standard AC-powered automatic battery charger can be used. The Electric Power Research Institute of Palo Alto claims that replacing half of the nearly 1.3 million walk-behind gas mowers used in the United States with electric mowers would eliminate the equivalent hydrocarbon emissions of 2 million cars.
Art Tec Microinverter Article 2012 (1,381 kb)