Wind Energy vs. Solar Energy - Generate Electricity with Wind or Solar

Bangor Daily News Cautions Against Small Scale Wind Energy

April 5th, 2010

In today’s Bangor Daily News, an article titled
“Small-scale windmills generate mixed reviews” documents the unimpressive results that some Mainers have received from residential windmill installations.

In the article, as well as in the particularly lively comments section, there is a lot of discussion about site and design being key to a successful wind installation. We agree, and add this: very few areas have the potential to be a successful and economically viable site for wind.

Maine’s Limited Wind Resources

A glance at Maine’s 50-Meter Wind Resource Map shows that most of the state of Maine is a poor or marginal wind resource.

A US-DOE wind map confirms this, by showing most of the state of Maine being in “Zone 2″ for wind, meaning roughly 10mph wind speeds under ideal conditions at 33 feet – barely the minimum speed require to turn most wind turbines.

Even if your home sits in a windy spot, you need to account for trees, neighboring homes, hills, etc., not to mention the building code challenges and aesthetics of erecting a windmill.

Compare this to solar, which is basically ubiquitous. Provided you have a clear space that receives sunlight from 9AM – 3PM, you can enjoy the benefits of a solar electric or solar hot water system.

And unlike wind, if your site is initially too shady, you can add to your solar resource just by doing some tree work!

Wind Vs. Solar: The Fine Print

An average small-scale windmill costs about $15,000, prior to any rebates and incentives. This windmill, if we go by the optimistic specifications provided by the manufacturer, will produce 4,800 kWh a year.

For roughly the same cost, we could install a 3KW grid-tied solar installation. Using real-world data (the PVWATTS tool for Maine’s solar insolation), we estimate that the solar array will produce 3,840 kWh a year of electricity.

So, why not choose wind and get an extra 1000 kWh/year?

The reality is: very rarely will wind live up to its expectations.

From the Bangor Daily News article cited above:

While wind may be the fastest-growing electric energy source, home windmills aren’t for everyone, according to Richard Hill, professor emeritus of mechanical engineering at the University of Maine.

“If you have a great deal of money, and you hate the public utility and if you think you live in a windy place, you’ll be very disappointed when you put up a windmill,” Hill said recently. “You may, however, be justified because you’re interested in principle.”

… his windmill hasn’t delivered more than 100 kilowatt-hours a month, although it was advertised as capable of generating 400 kilowatts-hours a month. “I can tell you it doesn’t generate anywhere near that,” he said. Arnold has found that the wind must blow at least 8 mph to get his windmill going.

We also got this testimonial from some Shelter Institute graduates who installed their own wind system as well as solar power:

I think the main lesson we have learned (and would like to pass along to others) is that PV panels (solar panels) are much more cost effective as a means of autonomous energy production than wind, unless the wind site is very unique …

We did our own informal wind survey and felt fairly confident we’d get at least 1 kWh of production daily in the winter months (but only when the prevailing winds shifted to northerlies), and we’ve met that.

However, many people we’ve spoken to have mistakenly used turbine specs rather than an integrated formula for wind speed and time to calculate what they will generate, only to be disappointed in the small amount of energy they actually are able to produce.

The bottom line? Dollar-per-dollar, a solar system will outperform a wind system in nearly all real-world applications.

A Word on Reliability

It’s also worth noting that the value of a long-term renewable energy is directly related to the reliability of that investment. Solar panels have no moving parts, are warranteed for 25 years, and are expected to last double that.

An average warranty for a wind power system, in contrast, is only five years.

The expected life of a wind mill, under the best of circumstances, is around 25 years, half that of a solar installation.

Over the life of the system, the solar array will generate roughly 200,000 kWh, nearly double that of the wind – should the wind system perform to optimistic specifications over an optimistic lifespan.

Reliability, Economics, and Aesthetics

While ultimately we want to encourage everyone to find their personal path off of oil, we also have a duty to ensure that we recommend reliable, economically smart choices for our customers – which is why ReVision chooses to recommend and install grid-tied solar electric and solar hot water systems, and not wind.

With superior life expectancy, more reliable performance, better aesthetics, and better rebates, solar is the clear choice for clean, renewable electricity.

Shelter Institute Grads Share Observations on Wind Vs. Solar Power

January 25th, 2010

Wind energy works in certain regions of Maine, but most homeowners are better off with solar power
Photos courtesy of Blueberry

Last week, our friends at the Shelter Institute posted a report from two of their Small Housebuilding Class graduates.

James and Kim wrote about a small-scale wind project they have recently finished on one of the islands off of Friendship in Muscongus Bay, Maine.

Not only is their story fascinating and impressive, but they make some serious and thoughtful analysis of how wind compares to solar power as a renewable energy.

They remark that while their wind system is performing as expected, for most people they think solar is a better option:

I think the main lesson we have learned (and would like to pass along to others) is that PV panels (solar panels) are much more cost effective as a means of autonomous energy production than wind, unless the wind site is very unique … We did our own informal wind survey and felt fairly confident we’d get at least 1 kWh of production daily in the winter months (but only when the prevailing winds shifted to northerlies), and we’ve met that. However, many people we’ve spoken to have mistakenly used turbine specs rather than an integrated formula for wind speed and time to calculate what they will generate, only to be disappointed in the small amount of energy they actually are able to produce.

… So, for the biggest green generation bang, we recommend solar panels. Compared to wind, the sun is ubiquitous. Our situation is unique in that we know we’ll get wind when the sun isn’t out in the winter, so the wind project fills in a gap in our ability to generate power year round, and we have no other means of getting non-fossil power out here. An alternative would have been to double our solar PV bank and add batteries to our current 2,000 pound battery bank, storing excess energy on sunny days for those days when we have wind without sun.

We have to agree – while wind energy has great potential under the right circumstances, most homes are built on poor sites for wind while solar power is available anywhere the sun shines.

If you’re curious as to whether your home or business has potential for harvesting solar energy, ReVision offers a free solar site evaluation.

A complete write-up of their experience with both wind and solar is up on the Shelter Institute blog – there are also some great photos on Picasa.

We want to thank the Shelter Institute again for sharing this inspiring story!