Shiny, black, space-age panels. Thin-film technology. Photovoltaics. The futuristic trappings of solar energy have many of us convinced that widespread installation is still a techie’s pipe dream—mere fodder for science-fiction novels, with heavy emphasis on fiction.
Solar energy technology may seem like a current innovation, but the discovery that allows us to convert energy from the sun into electricity—the photovoltaic effect—was made in 1839, and the first modern solar cell employing the photovoltaic effect was patented in 1946.
Since then, technological advancements have continually improved the capacity of solar energy production. New discoveries that decrease costs and increase efficiency come at a regular rate. Still, with all the advancements in the market, when people talk about solar power or solar energy, they’re referring broadly to three different types of systems: solar thermal, solar photovoltaics, or solar thermal for electricity generation.
Solar thermal: heat
Solar thermal technology concentrates heat from the sun and uses it to warm the air or water in a building. Fluid in solar heat collector units installed on roofs or freestanding structures is warmed by the sun’s rays, then circulated through a system to directly heat a water source like a hot water tank, swimming pool, or hot water boiler heating system. Alternately, the fluid can heat air that is forced through a duct system. Solar thermal is an efficient means to heat water or the air around us and utilizes a free, sustainable fuel source rather than relying on natural gas or electricity to do the same job.
Solar photovoltaics: electricity
When photons—bundles of energy from the sun—are absorbed by the semiconductor materials in solar panels, an electrical current is generated. Passing that current through an inverter creates utility-grade electricity—electricity that is abundant, local, and completely clean. This electricity can be used on site to power a home or business, or the electricity can be fed to the local grid and used somewhere else that it’s needed, displacing fossil fuel generated electricity.
Solar thermal: electricity
Most old-style power generators—like coal, nuclear, oil, and natural gas plants—heat water to make steam. The steam spins turbines, producing electricity. Using solar thermal to generate electricity works approximately the same, except the fuel source is sunlight. A large-scale example of this is concentrated solar power (CSP): the sun’s energy is concentrated to create steam, which then drives an electrical generating turbine.
CHASING THE SUN
The amount of usable solar resource available in a given area is measured by the amount of sunlight—not heat—the area receives. As the map above shows, the solar resource potential of the Midwest is very good, similar to parts of Texas and Florida.
An area’s solar resource doesn’t necessarily correlate to how much solar energy is produced there, however. According to the Solar Industries Association, the top 10 list of states with the most photovoltaic capacity includes New Jersey, Colorado, Pennsylvania, and New York, but few Midwestern states.
What’s the disconnect? If the Midwest has such a good solar resource, why aren’t we using it? The answer is simple, but not easy: we’re lacking policies to spur the industry. For example, Oregon policy makers have enacted a set of good public policies that entice solar businesses to put panels on rooftops at breakneck speed. As a result, Oregon has over 10 times more solar installed than Minnesota on a per capita basis, despite being less sunny and having lower utility rates.
It’s a similar story in Germany, which has a much lower solar resource than Minnesota (see map), yet leads the world in deployed solar. In fact, on a cloudless day in June 2012, Germany set a world record by producing 22 gigawatts of solar energy, equivalent to the output of 20 nuclear plants. On that single day, Germany met half of its electricity needs with solar photovoltaics.