Backyard Alternatives to Store-bought Electricity [A Diversity of Energy Sources]

Most promising among the new alter native power sources are sunlight, water power and wind. Each is widely available in virtually unlimited quantities, presents no environmental hazards in its use and in most cases can be employed even in remote areas not served by conventional utility lines. Although these natural sources are free, the equipment necessary to harness them is expensive. But recent advances have begun to bring down the cost and in some cases—particularly at the homes and homesteads of individuals who place a high economic value on self-sufficiency—photovoltaic cells, water wheels and windmills are proving practical.

Although the use of wind for power harkens back reassuringly to the tower- mounted pinwheels that have stood for generations in the barnyards of the Great Plains, modern windmills bear scant re semblance to their rural forebears. With their many blades, traditional windmills can spin efficiently with the lower-speed winds that blow close to the ground, so their towers rarely top 30 feet. Modern wind machines, which have fewer blades in most cases, are designed for the higher-speed winds that blow unobstructed above houses and trees. To harness these brisker airstreams, modern windmills are situated atop towers two or more times as high as those bracing the pinwheel designs.

Today’s wind-catching propellers are sleekly aerodynamic and sometimes take surprising shapes, resembling gigantic interlocked croquet wickets or the bowed blades of an enormous egg-beater. In fact, even the name has changed: Manufacturers now prefer the fancy name wind energy conversion system, or wind plant, to windmill, a venerable term that recalls the first use of the machines as grinders of corn and grain. But for all of the changes, the guiding principle remains the same: Onrushing air streams spin a propeller and the resulting rotation produces electrical current.

Within limits, the stronger the wind, the greater the quantity of free electricity produced. Moreover, the usable power in the wind builds up at a rate far greater than proportionate increases in the speed of the wind itself. Wind power experts call this principle the “cubed law” of wind velocity: Doubling the wind speed yields an eightfold (2 cubed—increase in potential electrical power.

The limits to this rule are reached only when winds grow strong enough to en danger the generating equipment itself— a possibility forestalled in modern machines by designs that slow or stop them when wind velocity nears 40 miles per hour. Some models automatically change the pitch of their blades, some deploy weights to slow the blades and some tilt the entire top of the tower to swing the blades out of the dangerous winds.

Although the wind is free, you will have to expend considerable effort re searching your locale before making a yes-or-no decision on erecting a wind plant. First, you must check local laws to determine whether a tower 60 or more feet tall is allowed in your area. Then you must test for a full year to be sure that winds averaging at least 10 miles per hour blow reliably at your site. In order to monitor your winds, you must estimate the height of any nearby hills, trees and buildings; the propellers of a wind plant have to rise at least 60 feet above the ground and 30 feet above any obstacle within 300 feet. Next, rent or buy a wind odometer (-- 118) that will telescope to the planned height of your wind plant.

During the year of testing, also tally your consumption of electricity—in kilowatts—by keeping monthly utility bills. If you are erecting the wind machine at a remote site that has no utility service, you will have to estimate the amount of cur rent you will need.

If utility lines are not available at your site, you should have them run in unless the cost is wildly prohibitive. You then will be able to interconnect your wind plant, an arrangement with definite ad vantages. For one, a utility-connected system requires neither a bank of batteries to store power for windless days, nor a device called an inverter for changing battery-stored, direct current to alternating current for use in the house—items that add thousands of dollars to the cost of installation.

Another advantage comes into play when the winds blow hard, generating more kilowatts than you can readily use. By law, utility companies in the United States must buy any excess power that is fed into their transmission lines by independent producers.

Once you have studied the wind at your site and calculated the number of kilowatts you require, you are ready to investigate different generating systems. Begin by contacting the Rocky Flats Wind Systems Program in Golden, Colorado, the federal program that tests and rates wind machines. Then check dependable manufacturers for literature, technical data and prices.

In comparing wind machines, pay particular attention to what the equipment companies call a power curve, actually a graph that represents the monthly power output of each specific machine at different wind speeds. A less expensive wind plant may produce less power and, over its expected 20-year life, yield fewer kilo watts per dollar than a machine with a higher price tag.

When considering cost, remember to figure in deductions from federal and ,state taxes for energy equipment that is powered by renewable resources.

Once you make a decision, ask the manufacturer for the name of the best installer in your area. While you may want to test your winds and plan your installation on your own, erecting a 60- foot tower and attaching a heavy, cumbersome wind machine is a project best left to a professional. In fact, some manufacturers won’t honor their warranties if the equipment is not installed by approved personnel.

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An independent wind system. Wind-driven blades atop a tower turn a generator to create direct current and send it through a buried cable to the house. There, a control box—containing electronic circuitry—regulates the voltage to match that of a bank of storage batteries. The control box also displays on its dials the volt age and amperage being produced by the system, and protects the batteries against excessive overcharging or discharging.

Beyond the batteries, an inverter converts the direct current to alternating current that can be fed into a conventional main electrical panel, which contains circuit breakers to protect the house wiring from overloads or short circuits. An optional, standby, gasoline- or diesel-powered generator can be added into the wiring system, as here, between the inverter and the service panel; should a long, windless period deplete the batteries severely, the generator can be run to power the house’s lights and appliances.

A utility-connected wind system. When wind speed reaches 10 miles per hour, the tower- mounted anemometer on this utility-connected wind system closes a switch, sending current to the specially designed generator, which can operate as a motor to twirl the blades into motion. Then the wind takes over to drive the generator, which is engineered to run at a near- constant speed—no matter how fast the wind blows—in order to produce alternating current identical to that of the utility.

Cables connecting the wind machine to the service entrance of the house are interrupted by a meter that indicates the amount of electricity produced from the wind. Two other meters, each of which can turn in only one direction, are in stalled along the line that connects the utility company transformer to the main electrical panel; one records the amount of current returned to the utility by the wind system, the other records the current drawn from the utility to cover periods when the generator is producing less power than the residence requires.

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Assessing the Site for Wind-power Potential

Finding heights of nearby obstacles. Step off, to within a yard or two, the distance between an obstacle to wind flow and the proposed site of the wind plant. In the illustration at right, this measurement is labeled A. Standing at the site, stretch your arm horizontally and hold a ruler vertically in your hand. Have a helper measure the distance—B—between your eye and the ruler in inches. Without moving your arm, measure the apparent height—C—of the obstacle on the ruler. To find the height of the obstacle, convert all measurements to inches, then multiply the measurement for A by the one for C, and divide the result by the measurement for B.

Determining average wind speed. Buy or rent a wind odometer that includes a cup anemometer (which resembles a small pinwheel), a counter and a telescoping mounting pole. Mount the cup anemometer on the pole, raise it to the planned height of the wind plant and secure it against toppling; most poles come equipped with guy wires that attach to stakes.

Set the counter to zero on the first day of each month --. Record the total on the last day of each month. Each revolution shown on the counter represents the passage of 1/60 mile of wind, so divide each month’s total by 60 to deter mine the number of miles of wind that have blown by the site. Divide the number of miles by the number of hours in a month—720 for a 30-day month—to determine the average monthly wind speed in miles per hour. At the end of the year, total the monthly averages and divide by 12 to find the average yearly wind speed at your site.

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An upwind horizontal-axis machine. Called upwind because the tail or vane of the machine keeps the spinning blades oriented toward the wind, and horizon because the axis of the propeller is parallel to the ground, this type of wind machine most nearly resembles the traditional windmill. The working parts are bolted to a steel tower; a cable connected to the generator runs down a tower leg. One virtue of this traditional design is that it has the longest history of reliability; a disadvantage is that it swings around with every change of wind direction, which wears down the machine’s yaw bearings relatively quickly. For this reason it’s best used where wind direction is steady.

A downwind horizontal-axis machine. Called downwind because breezes pass the generator before striking the blades, this machine for goes a vane; the sleek shape of the generator housing and blades keep it correctly oriented. Although simpler in design than its upwind cousin, this model oscillates before finding the wind direction and is best used where wind blows mainly from one direction. The power cable is housed within the hollow mast that supports the machine.

Modern Power Producers

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A vertical-axis pivoting-blade machine. A vertical-axis machine, such as the one shown at right, has blades that spin around an axis perpendicular to the ground. It can exploit wind blowing from any direction without the entire ma chine having to pivot, an advantage in places where the wind direction changes frequently. In stead, special pivoting hardware between the struts and the blades in this model shifts the angle of the blades slightly with each rotation in order to present the broad surfaces of the blades to the breezes for as long as possible.

A vertical-axis rotor machine. This high capacity vertical-axis model operates in much the same way as the one above except that its blades are fixed, unable to change pitch as they revolve around the center pole. Moreover, it cannot be started by the wind alone; it must be used in a utility-connected system so that electricity can spin the rotor until the wind takes over. It produces alternating current only. Unlike conventional wind machines that perch atop a tower, this one sits on a squat base, generally no more than 6 feet tall. The blades, sometimes as long as 70 feet, extend high into the air to catch the wind. Because the bottom ends of the blades are so close to the ground, this ma chine is best suited to flat areas or hilltops.

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How Professionals Install a Wind Machine

Some homeowners, chiefly those experienced in working at heights, have successfully erected their own wind-plant towers. Usually, however, this hazardous task is best left to practiced installers. A professional team has the expertise to accomplish the task safely, and it has ready access to costly equipment that can speed and simplify the job.

Before raising a wind-system tower, professionals assess soil conditions at the site and pour concrete footings to anchor the tower and brace it against anticipated stresses. The footings may have to be massive. The structure shown here, a 60-foot tower that is de signed to stand without guy wires, needs three reinforced concrete piers, each 2 feet across and 8 feet deep.

Once the concrete of the footings has cured, the assemblers bolt steel struts together into tower sections 10 to 20 feet tall. The bottom section is hoisted atop the piers by crane and then held steady while workers bolt it to anchors in the piers. Next, team members scale the bottom section, se curing themselves to it with harnesses so that their hands will be free, and grasp the second section as it’s delivered by crane (below, center). After bolting the second tower section into place, the installers climb up to position and secure the third section. This climb, catch and clinch sequence is repeated until the team has topped the tower.

Lastly, the crane operator raises the generator, which itself may weigh several hundred pounds; workers on the ground guide steadying ropes attached to the payload so that a sudden gust does not send it crashing into the tower. At the tower peak, a lone installer grasps the generator, guides it into place and bolts it down. Just before descending the tower, the installer connects an electrical cable to the generator, and then clamps the cable to a tower leg on the way down.

To join the wind plant to the house, the installers dig a trench, lay in electrical cable rated for underground use and cover it over. For an independent sys tem, an experienced electrician makes connections at the control box, the batteries, the main panel in the house and, if needed, the inverter. For a utility- connected system, utility employees come out after the cable is laid and interconnect it with the existing wiring system in the house; at the same time they install additional meters or safety devices called for in their locality.

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Windmills Helped Win the West

During the 1800s, settlers moving west across the Great Plains found huge expanses of wind-swept prairie so arid that it could barely support coarse, tough-rooted buffalo grass, much less nutritious crops, cows and families. Luckily, the settlers quickly realized that the same drying winds that were their bane could be their boon: Harnessed to drive pumps, the winds would dependably raise precious water from the depths— night and day, day in and day out.

The means of harnessing the western winds was the windmill, but perfecting a machine capable of withstanding the wild winds of Idaho and the tornadoes of Kansas was a challenge that required tenacity and ingenuity. At first, American manufacturers borrowed from the Dutch, trying to adapt the huge canvas sails of the familiar European windmill. But no matter how well sewn, the cloth sails could not stand the ferocity of western American weather. Crucial to the design of an Americanized windmill was a device that could both head the machine into the wind on a day of steady blowing and protect it from running wild in a gale. One early machine that fit the bill—a self-regulating wind mill—was put together by an inventor named Daniel Halladay.

Halladay’s breakthrough eschewed large sails in favor of dozens of thin wooden blades, similar to the slats of a venetian blind. Fixed to a ring around the hub, rather than to the hub itself, the slats stood upright before gentle breezes. In strong winds, however, the slats tilted away from the wind, so that they closed into a cylindrical shape that resembled an open-ended barrel; dangerous gusts could roar harmlessly around and through.

Simpler than the Halladay machines were the pinwheel fans turned out by Mast, Foos and Company, of Springfield, Ohio. Instead of using thin wooden slats, the Mast fans consisted of seven large fixed steel blades. A side vane, or rudder, perpendicular to the fan’s axle, swung the entire mechanism around edgewise when a heavy wind blew. When the wind’s pressure lessened, a hanging weight counteracted the effect of the side vane to pull the fan back into the wind’s path.

During the second half of the 19th Century, manufacturers marketed a vast array of models and makes of wind mills. At the World’s Columbian Exposition, held in Chicago in 1893, companies exhibited dozens of models that not only pumped water, but shucked corn, ran lathes and powered sewing machines. Wrote one newspaper re porter, “Each manufacturer claimed some superiority. Here a wheel would open to get more wind or shut against too much; one mill would go swiftly in the lightest breeze, another would work slowly in a hurricane.”

By the turn of the century, one of the largest sellers of windmills was Sears, Roebuck and Company. Its offerings included the high-capacity Suburban model, for those who wanted running water in their homes as well as their barnyards, and the Direct-stroke Steel machine, a durable, medium-capacity model, which could spin for years with little maintenance in remote pastures. While many manufacturers painted their own names on the rudder to advertize the product, Sears charmed its customers by offering to put the owner’s name on the rudder free of charge. Between 1830 and 1935, an astonishing 6.5 million windmills were produced by American factories. In time, however, demand declined. Municipal water systems began replacing individual wells in towns, and in the 1930s the Rural Electrification Act brought economical, utility-generated power to most of the farms and ranches in the western states. Wind-driven water pumps gave way to more reliable electric ones. Now, although several of the original manufacturers are still in business selling kits to modern homesteaders, the windmill water pump no longer occupies a central place on the American farm. And long past are the days when pioneer farmers would drawl that the prairie is “no place for a woman unless she can keep a sod house tidy, shoot a snake and climb a windmill.”

A 19th Century windmill. The seven curved blades of this iron-bladed machine not only pro vided the pumping power to water the cattle, but filled a storage tank on the top floor of the main house as well, ensuring a plenitude of running water for the then-rare indoor plumbing fixtures on this prosperous prairie farm.

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