We believed we had a wind resource that was sufficient to justify a wind-electric system. Our chosen turbine, the Skystream, is predicted to produce about 2,600 kWh per year given an 11 mph resource, and about 900 kWh per year in 8 mph winds. After several years of operation, the system has produced roughly 500 kWh per year, or the equivalent of $50 of energy, which is expensive electricity when you consider the $21,000 installation cost.
It is clear now that the information we started with was not sufficient to justify using wind energy at our site. Factors contributing to our turbine’s lower-than-anticipated production include a tree line that sits about 800 feet to the west, resulting in turbulent wind from the prevailing wind direction. A taller tower would undoubtedly help with this problem, because the farther you get away from the earth and its obstructions, the more wind there is. As a well-known small-wind expert has said, we unknowingly chose expensive energy over an expensive tower.
Over the past several years, the cost of photovoltaic systems has come down dramatically. During that time, we collected information on the energy demand for Pura Vida. We found that during the fall and spring, when there was no energy use for heating or cooling, the average demand was between 600 and 700 kWh per month.
In 2011, we installed a 4.3 kW grid-tied PV system that should average about 400 kWh per month. Twenty-four batteries provide backup for power outages and provide enough energy to live without the grid periodically—assuming that the backup heating would be provided by the wood heater instead of electricity. Performance data is being collected by the OutBack MATE3 energy monitor and we should have an accurate performance picture by the end of 2012.
We believe that building super-energy-efficient homes will have a significant impact on U.S. energy use. If the building cost of an APH is within 15% of a conventional building method, a conservative energy cost savings estimate is more than $1,000 each year per home.
One outcome of the recent economic downturn has been that the American consciousness has been awakened to the importance of common-sense solutions to important challenges. For families paying to heat and cool their homes—and as a nation that needs to use less fossil fuel—emphasizing energy efficiency in homebuilding is a simple yet promising way to address these challenges.
Victor Zaderej has been passionate about energy use in homes, businesses, and transportation for 30 years. He holds two engineering degrees from MIT, and an MBA. Through his company, Solar Homes, he helps design energy-efficient buildings. He is currently the manager of Advanced Solid State Lighting at Molex.
Solar Homes • solarhomesus.com • Green building design
McCanse Builders • mccansebuilders.com • Builder
Pura Vida Systems:
EnerSys • enersys.com • Batteries
Nu-Air Ventilation • nu-airventilation.com • Heating, cooling & heat recovery system
Nyle Systems • nyle.com • DHW heat pump
OutBack Power • outbackpower.com • Inverter & charge controller system
Southwest Windpower • windenergy.com • Wind generator
Suntech • am.suntech-power.com • PV modules
WaterFilm Energy • gfxtechnology.com • Wastewater heat recovery
Water Heater Innovations • marathonheaters.com • Hot water storage