Wind and Water Solar Power

Windmills and hydro-power generators are also sustainable solar resources. Both are energy sources derived from the sun, although indirectly compared to solar collectors (PV and hot water). Wind is caused by changes in air pressure brought on by different regions of the globe heating and cooling at different rates due to variations in solar exposure. Rain is caused by evaporation, which results from warming and cooling as well; hydro-power comes from rain storage in reservoirs, creeks, and the like.

The two methods are very similar in the way they generate voltages with spinning turbines. The concept is very simple: When you apply a power source to an electric motor, the shaft spins. On the other hand, if you reverse the process and manually spin the shaft of an electric motor, its two wires output power. The physics goes equally in either direction. Practical designs can be very complex, but at the heart is always the electric motor principle. Inverters are required (just as with solar PV panels) to convert the raw voltages from the rotors into usable power, typically 12VDC because batteries are the norm. Another style of inverter converts into standard 120VAC household current.

Although solar PV panels and water heater collectors work only when there's direct sunshine, both wind and water are available at any time of day or night. Wind, however, can come and go, from minute to minute. Water resources generally don't vary much over the course of a day, but they can vary over seasons and are also subject to droughts when there may be no power available at all for extended periods.

Hydro power is also a built-in energy storage mechanism because you can make a reservoir from which you can draw water any time you want it. In fact, a reservoir is generally a good idea because it makes pressures constant. Of course, the big problem with hydro power is that you need to be by a river or stream (or dam) to be able to use it. Most people don't have this luxury, but for those who do, this is an excellent and economical source of solar power.

The good news is that you can get rebates and subsidies for wind and water power the exact same as for PV systems and water heating systems. They're all solar power and are therefore grouped together in this regard.

In the following sections, I explain the general concepts of using both wind and water power so that you can decide whether they're viable options for you, and if so, how best to proceed.

Blowing with the wind

A wind turbine looks like a small airplane with a huge propeller — and that's because that's what it basically is. Wind pushes the vane (the opposite of what happens with an airplane propeller), which turns the propeller and forces the alternator to rotate, thereby outputting AC power.

Wind turbines (see Figure 14-2) work well under certain conditions, in which case the economics are good. They also have a number of operational drawbacks.

Here are the pluses of wind power:

^ Power can be generated anytime, day or night.

^ In some locations, wind is virtually a constant (magnitudes may vary, but output power is always available).

^ Wind speeds vary over terrain, so you can find locations on your property that provide maximum potential. Ridge lines, coastlines, and the tops of barren hills are the best candidates.

^ Wind is available almost everywhere, in all climates. In many of the worst climates, it's very powerful.

Figure 14-2:

A wind turbine.

Blades (Rotors)


And here are some drawbacks:

i Extremely high wind conditions may destroy or damage a unit. Turbines want a minimum amount of wind to begin working, but they also don't want to be subjected to tornadoes.

il Batteries are definitely required because you just never know when you'll get wind.

l In some communities, you may be prevented from installing a wind turbine due to noise and visual blight issues.

l Mounting is a bear. In general, the higher the unit, the better the output energy, all things being equal. One hundred feet is considered optimum, and that's a long way up there. The mounting must have a tremendous amount of integrity because of the torques that need to be withstood. And consider this: How do you raise the mount? You have to choose among a number of methods, each with pros and cons. And what if the mount were to break in high winds? Not only would this be very expensive, but imagine the unit crashing down onto something.

l Rotors are noisy and obtrusive when they're spinning (which they're hopefully doing quite a bit). The bigger the blades, the more power they'll generate, but they also make more noise because they're in contact with more air. They also attract a lot of visual attention and may clutter up a placid environment.

l Cost varies depending on how much wind is available. At some point, solar PV is a better investment. But if you get a lot of wind, wind is a cheaper and more reliable way to go than PV.

l Moving parts are never as reliable as stationary, so PV wins out in this category.

l Wind power is relatively obscure. Finding somebody to do your installation and servicing may be very difficult.

l Obstructions such as trees, houses, barns, and the like all affect wind speed. And because wind direction varies, obstructions in one direction may or may not be important in other directions. The best bet is to stay well away from all obstructions, and this may be prohibitive because of the topography or layout of your property.

In general, a wind turbine must be mounted at least 30 feet above the ground and at least 200 feet away from obstructions. There's 40 percent more wind at 100 feet than at ground level.

The smallest turbines (with 6-foot rotors) sell for around $1,000, not including installation (tower building and raising, plus wiring and so on). They output 400 watts of power at wind speeds of 28 miles per hour (this is a pretty good wind) and can withstand winds up to 110 miles per hour. You can use these numbers to get an idea of how many kilowatt-hours per day you can expect, on average; then you can devise a battery bank accordingly.

A turbine with a 15-foot rotor produces 3.2 kilowatts at 28 mile-per-hour winds for around $8,000, including installation. Fifteen feet is big, and the turbine makes a deep swooping noise. You'll know it's there.

Tower costs vary depending on height, but a typical tower kit for a small turbine runs around $700 (50' height). The installation is the tricky part. You better know what you're doing or somebody could literally be killed. The higher up, the more effective; but the higher up, the more expensive the tower.

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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