The 'wind furnace' -- an energy source?
A calendar print of an 18th-century Dutch windmill hangs on the wall of Prof. William E. Heronemus's office here. Nearby is a watercolor of a sailing vessel of similar vintage. They are there because they illustrate the logic of the simple, uncomplicated use of wind power.
Far more wind energy blows across the United States every day than the nation uses to heat and cool its buildings, to propel its autos and its airplanes, and to power its mills and factories. So the absurdity of not tapping into this abundant energy source is all too obvious, in the opinion of the University of Massachusetts professor.
Moreover, Professor Heronemus discounts vehemently the claims that wind energy is as yet not cost-effective for anything more than pumping water. Those who make that claim haven't looked at the subject close enough. There is a thoroughly economic use for wind power right now, he asserts -- such as for heating and cooling. "these are the same needs that we burn so much oil for now ," adds the professor.
Indeed, the United States uses more energy for space heating and cooling these days than for anything else.
Using what he calls a "wind furnace," Professor Heronemus contends that a home in the North can be heated economically (using oil, gas, or perhaps a wood stove as a backup) right now. A smaller version of the same thing could be used to provide domestic hot water.
A home built on the university campus her to test wind and solar concepts has proved this. The two methods (sun power and wind power) work exceptionally well together, the professor points out, because "when the sun doesn't shine, the wind generally blows." Periodically, they both generate power at one and the same time.
Heat from the wind can be generated in either of two ways: electrically or mechanically.
The big drawback to electric-power generation using a windmill is the variability of wind speed. At times it might be producing enough current to power every light and television set in the house, along with the pop-up toaster; at other times it may barely light up more than a bulb or two. It is the equipment needed to smooth out this variability that makes domestic electric power generation so costly.
When Professor Heronemus began thinking of wind power 10 years ago, he asked himself: How can we use wind-generated electricity without having to worry about variable voltage? The answer came quickly enough: Feed the electricity into resistance heaters, which won't care about consistent voltage. The resistance heaters will heat the water that is circulated through baseboard heaters or that flows through the kitchen and bath room faucets. If the wind is blowing vigorously, the water will heat up rapidly; if it is blowing more gently the water will take longer to heat up.
In the mechanical approach the windmill drives a churn, as in a butter churn or blender, which heats the water by what is known as momentum exchange. The energy is transferred to the water as heat. If you use a high-speed blender long enough you will notice how the fluid in the blender heats up. (I once made a pea soup this way and the soup actually boiled in the blender).
This is not the result of friction, as is often believed, but rather the effect of "momentum exchange." Studies have shown that it is more efficient to place the mechanical churn up on the tower with the wind charger (piping cold water to, and hot water from, the churn) instead of having connecting rods drive a churn at ground level.
Experiments at the University of Massachusetts prove that a 1,500-gallon storage tank which is heated by a 25-kilowatt wind charger driven by 35 -foot-diameter blades and mounted from 60 to 100 feet above the ground is suitable for heating an average home of, say, 1,500 square feet. A 4- to 5 -kilowatt generator with 15- to 20-foot blades mounted 55 to 60 feet high would do nicely for domestic hot water.
These wind charges can also be used to air-condition buildings. Going the electric route, the generator would be connected to an induction motor of the same size to drive air conditioners using chilled water. For its part, the mechanical churn would provide the heat needed to power air conditioners on the same principle of gas- or kerosene-burning refrigerators. Boston's Museum of Science is cooled with this type of air conditioning, as are nuclear submarines, which make use of waste hot water.
A ballpark figure for a wind-charged, home-heating plant (installed witha 1, 500-gallon storage tank) would be $10,000 to $11,000, according to Professor Heronemus. In areas of moderately good winds, such a system could supply 80 to 85 percent of the heating needs of a 1,500-square-foot home.
A domestic hot-water plant for such a home might cost $7,000. While these figures might sound high, federal and state tax allowances would reduce the cost considerably. Meanwhile, the average cost of heating a home in the Northeast with oil runs in excess of $2,000 a year.
Obviously, there are drawbacks to the wind furnace. The blades have to be large (35 feet in diameter, for example) and they have to be high up (60 to 100 feet). In a nation once disturbed by the sprouting of so many "unsightly" TV antennas, such highly visible properties of an acre or more.
But Professor Heronemus sees wind-power solutions for the cities as well. Individual buildings might make use of rooftop wind chargers to lessen their heating and cooling load. An individual community at the foot of a hill, for instance, might, through public ownership, establish a wind-generating plant where the wind blows strongest -- on the hilltop. Similarly, coastal communities might establish power plants on wind-swept offshore islands.
Those interested in more details on the wind furnace can phone the Univesity of Massachusetts, Department of Mechanical Engineering, at (413) 545-2505.