Going Off-grid: Wind or Solar?

The two most common options for off-grid electrical power are wind and solar. This post discusses the pros and cons of each option.

First off, I’d like to point out that the amount of power you get from either wind or solar is often OVERSTATED by companies and pro-renewable energy websites. Wind turbine manufacturers give a power rating for their product based on idealized wind conditions. But a wind turbine will produce far less power in light wind than at the “rated wind speed”. And if it is very windy, most wind turbines shutdown and produce zero power.

Solar panel manufacturers are no less guilty of exaggeration. The rating of a panel is typically given for “full sun”, which is basically noon on a cloudless day. Earlier and later in the day, the sun strikes the panels at an angle, reducing power output. And of course a cloudy day also reduces the available power. But if the panel is getting 50% less sunlight due to overcast conditions, does it produce 50% less power? Not necessarily. Some panels are much less efficient in less than full sun.

Off-grid is an admirable goal. But you might want to try a grid-connected system first, to see how much power you can actually generate. Then take into account that you will get less sun in the winter, and less wind on certain days or times of the year. You will also need a battery system that can hold enough reserve power for the least ideal conditions during the year.

Wind

I live close to the ocean, where it is very windy much of the time. But on my property, it’s not windy at all. The surrounding trees and houses cut down on the wind. An effective wind turbine usually needs to be 20 to 30 feet high, to get to where the wind is.

Most “small wind” turbines (as they are called), designed for home use, do not produce enough power for a single home. You either need multiple turbines or one rather large one. The expense, size, and noise are all cons to consider. Vertical axis wind turbines (VAWTs) are relatively quiet, but still expensive and big.

The unpredictability of wind is also a negative factor. Even if it is cloudy, you know that the sun will rise each morning. But it might not be windy. You can argue that there is always some wind each day. Sure, but wind turbines only produce an appreciable amount of power with an appreciable amount of wind. The power in the wind is described by a formula where the velocity of the wind is cubed. So a moderate velocity wind has a great deal more power than a light wind.

One big advantage to wind power, though, is you can do it yourself. Take a look on YouTube; there are many DIY wind turbine designs. You can’t really make your own solar cells and solar panels. Whatever you can make yourself, you can repair yourself. But there is not much you can do to repair a solar panel.

Another consideration is that wind complements solar. If you use both, the wind turbine can produce power at night, adding to your power stores. And if it is cloudy, due to bad weather, it might also be windy. So the times when solar panels don’t produce, wind turbines generally will produce power.

Sun

Solar panels are quiet. The noisiest solar panel is still silent. The nosiest wind turbine is pretty loud.

Solar panels are also reliable, as there are no moving parts. A wind turbine more easily breaks down. A strong wing might break a wind turbine. But solar panels, properly installed, will endure wind and storms.

The better solar panels still produce power on cloudy days, though not as much. And a sunny day produces plenty of power with no worries. By comparison, a wind turbine will generally shut itself down in high winds. The solar panel just keeps on producing power, as long as the sun rises.

You need plenty of roof space if you are going to power your entire home with solar panels. A single story home has a fair amount of roof surface area relative to its living space. But a two or three story home has proportionately less roof space relative to living space.

It can also be a problem if your home is shaded by trees. Solar panels do not work well in the shade; they need full sun. So not every home is a good fit for solar panels. By comparison, a wind turbine can be placed almost anywhere on your property, as long as it can be raised above the level of trees and homes.

Best Option?

As I mentioned above, having both wind and solar combined is probably the best off-grid option. It’s more expensive to set up both types of power generation. You probably need to use two different companies. And the electronics are more complicated. But if you want to go entirely off-grid, it’s better not to put all your eggs in one basket.

– Thoreau

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