Paul Gipe, wind energy expert and author of Wind Energy Basics: A Guide to Home- and Community-Scale Wind Energy Systems, introduced me to the idea of using the power of the wind to heat your home or hot water. Solar domestic hot water systems have been gaining in popularity in recent months due to the energy crisis, but the idea of wind-powered heating systems has yet to make a blip on the renewable energy radar. So if sun is scarce where you are, and you want to supply carbon-free heat to your home, consider using wind energy—it can have some considerable advantages over solar.
The following is an excerpt from Wind Energy Basics by Paul Gipe:
Like wind-and-solar hybrids, using winter winds to heat your home has always seemed an ideal way to marry a technology with a natural cycle. Since heating loads are a function of heat-robbing winds, why not use those very winds to heat your house? The University of Massachusetts proposed such a Wind Furnace in the mid-1970s, and several companies have tried to market the idea to homeowners already on the grid. The concept never caught on in North America, where the economics never made sense, but it did briefly flourish in Denmark, where heating prices are considerably higher.
Denmark’s Folkecenter for Renewable Energy has found that a wind turbine that covers winter heating demand can easily cover domestic hot-water loads in summer. The Folkecenter also reports that it is economically more advantageous to use wind-generated electricity as electricity, rather than converting it to heat. Typically, electricity has double the value per kilowatt-hour of electricity converted to heat with resistance heaters (see figure 5-6, Home heating).
Proponents have argued that storing excess wind energy as heat is much cheaper than storing it in batteries. Thus heating with wind can play an important role in stand-alone systems that are usually remote and don’t have ready access to fossil fuel. Scoraig Wind Electric’s Hugh Piggott dumps his excess wind power into “storage heaters” that store heat in the form of hot water. These are common in Great Britain for storing cheap off-peak electricity at night for those on the grid, says Piggott.
To guarantee a reliable supply of wind-generated electricity for an off-the-grid system, you need a much bigger turbine than would be necessary to produce the appropriate number of kilowatt-hours for a grid-connected home. The bigger turbine eases the load on the batteries by generating current even in light winds. In moderate or strong winds the turbine produces more power than needed. The surplus can then be used for heating, thus saving fuel.
Dumping or diverting excess wind power to heating has become a common practice in stand-alone wind systems. For those off the grid, the situation in Alberta, Canada, is little different from Scotland’s. In Alberta, Jason Edworthy used a Bergey Excel in a battery-charging system where excess energy was diverted to a conventional hydronic system for in-floor heating.
The turbine’s electrical control system must be adapted to direct excess power to your dump or diversion load to ensure that this load is compatible with the wind turbine. You don’t want to stall the rotor, when the dump load switches on, by placing too great a load on the rotor. Modern solid-state electronics are well suited for this function.