Solar energy and wind power may not seem like a big deal, unless you’re talking about the future – or maybe even the present. For all of today’s talk about renewable energy, it still makes up a pretty small portion of the sources that generate our electricity. But it’s coming on fast, and it’s picking up speed.
Here’s your crash course in how the sun, wind and water generate electricity.
Solar energy generates only about 1 percent of the nation’s electricity, but that’s a stunning increase from just 5 years ago, when the number was too small for the U.S. Department of Energy to report. Solar growth will continue as costs fall, technology improves and people figure out better ways to use solar-generated power.
There are lots of ways to use energy from the sun. You can hang washed clothes outside to dry, and you can open curtains to warm your home on a sunny day. More ambitious projects use the sun to warm pipes full of water that’s pumped around a building for heat or used for showers and other household uses.
But what most people mean when they talk about solar energy is photovoltaic electricity. When sunlight hits certain materials, their atoms spit out an electron; electricity is just a stream of electrons. Over the decades, scientists and engineers had experimented with solar-sensitive materials to make them into lighter, longer-lasting and more affordable wafers called photovoltaic cells, which are combined and integrated into solar photovoltaic modules. One of their first uses was space travel, and continued improvements are allowing solar to become a more down-to-earth kind of energy.
Cost is one of those improvements. Solar panel prices have dropped 85 percent in the past 7 years, with improvements in materials and larger-scale production methods.
Another technological advance is about to give the industry an extra boost, says Dale Bradshaw, a technical consultant with the National Rural Electric Cooperative Association (NRECA). He says solar panels can now track the sun as it moves across the sky rather than sitting fixed in place, raising their productivity by collecting more sunlight throughout the day. This year, the U.S. Department of Energy’s Energy Information Administration reported that half the large solar installations in the country already use some kind of sun-tracking technology.
It’s also worth knowing that the solar industry is maturing with different forms of ownership: utility, industrial, commercial, residential and community solar installations.
Utility scale is what you might expect – large banks of solar panels owned and operated by an electric utility or other large organization, producing many megawatts of solar energy. Industrial and commercial solar installations can range from kilowatts up to multi-megawatts and be placed on rooftops, over parking lots or on land near industrial and commercial enterprises. Industrial and commercial installations are beginning to increase as the price for solar continues to drop. Residential solar installations are also being installed primarily on rooftops, especially in the southwestern United States.
NRECA’s Bradshaw says community solar can ease the higher expense of self-owned rooftop solar. With community solar, a utility builds a large solar installation and sells shares in the project to customers interested in an investment in renewable energy. That style of ownership and development is especially suited to consumer-owned electric co-ops, and many are offering solar shares to their members.
“Co-ops are doing a great job of building community-scale solar,” says Bradshaw. “They’re going full blast on that.”
Bradshaw also notes that community solar allows a homeowner to avoid both maintenance of their own system, and the hassle of sorting out different offers from rooftop solar vendors. Several electric co-ops in Iowa already have built community solar projects – or are talking with members about doing so.
Wind power has increased significantly as costs continue to decrease. Wind power generates nearly 6 percent of the nation’s electricity, and it’s growing at a pretty good clip, with an increase of about 35 percent during the past 4 years.
In a way, wind generates electricity the same way as coal, natural gas and nuclear – by spinning a turbine that creates an electricity-producing magnetic field. The huge difference is that enormous propeller-like blades designed to catch the wind turn the turbine.
It’s the size of those blades, and the height of the turbine towers (up to as high as 300 feet) that makes the difference, says NRECA’s Bradshaw.
“Wind is a really useful renewable, but it has to be utility scale,” he says.
A tall utility-scale tower can capture as much as 50 percent of the wind, but there’s not a practical, personal alternative to compare with rooftop solar. A rural residential customer or a rural commercial customer with a 50- to 100-foot tower will probably generate electricity only about 25 percent of the time.
“It’s really not cost-effective for small-scale home use when compared to utility scale wind turbines,” says Bradshaw.
Another way to turn an electricity-generating turbine is to store water behind a dam and then harness its power as it flows from the reservoir to the river below.
Industry specialists disagree on whether to count hydroelectric power as renewable energy. On the one hand, it doesn’t create greenhouse gas or other chemical pollutants by burning fossil fuels. On the other hand, large-scale hydro typically calls for building a permanent dam across a river valley and flooding the area behind it. Another option is to put hydroelectric generators directly into rapidly flowing rivers to capture power, but this is a significantly more expensive option. Then there’s the question of whether you consider flowing water as renewable, or as something that can be used up.
Hydroelectric power generates nearly 7 percent of the electricity in the United States. Although that number changes a bit during times of drought or heavy rain, the amount of electricity produced by hydropower has been relatively stable during the past several years.
Paul Wesslund writes on co-op issues for the National Rural Electric Cooperative Association, the service arm of the nation’s 900-plus electric cooperatives.