Image Credit: Alex Wilson The Nellis Air Force Base PV installation provides a quarter of the facility's power requirements.
Image Credit: Nellis Air Force Base An aerial view of the entire 14.2-MB solar facility at Nellis Air Force Base.
Image Credit: Master Sargent Rovert Valenca, Nellis AFB The 2-MB rooftop PV array installed at Schüco's U.S. offices outside Hartford, Connecticut.
Image Credit: Schüco A detail showing the building-integrated PV (BIPV) module that Schüco used in its Connecticut installation.
When the economy-of-scale with wind power [no-glossary]led[/no-glossary] to larger and larger wind turbines, opponents of these installations took to referring to them as “industrial wind power.” Whenever I see a letter-to-the-editor or news story that uses this phrase, I can tell that it’s going to have an anti-wind bias.
Whether its marring their views of pristine mountains, blighting their night sky with blinking red lights, causing bird and bat fatalities, or producing the somewhat mythical “infrasound,” opponents almost universally refer to these wind farms using an industrial moniker.
So, I’m becoming troubled by recent reference to “industrial solar” in describing the larger photovoltaic (PV) installations that are cropping up in Vermont and nationwide. Some opposition seems to be emerging, for example, to a 2 megawatt (MW) array that’s being proposed for Brattleboro, and I’m hearing more and more such concerns nationally.
The economy of scale with solar
As with wind, there is an economy-of-scale with solar-electric systems. Bulk purchase of solar modules brings the costs down somewhat and, more significantly, larger inverters (the devices that convert direct-current electricity produced by PV modules into the alternating current that can be fed into the utility grid) and other balance-of-system components are a lot less expensive per kW or MW of capacity than the residential-scale components being installed for home systems.
But the differences in cost between large and small systems aren’t nearly as great with PV systems as they are with wind turbines. This means that the incentives for building very large solar systems (“industrial-scale” if you must) aren’t as great as they are with wind.
Advantages of smaller PV systems
Despite the (relatively minor) economy-of-scale that argues for larger PV systems, there are some benefits of small systems.
For starters, small systems are well-suited to rooftops. A typical house, if it has a reasonable orientation, can hold a 4-6 kW solar array, enough to handle a significant fraction of the home’s power consumption (as long as then home is reasonably energy-efficient). And commercial buildings, with large flat roofs can often hold hundreds of kW or even a MW or two of solar — which can provide a significant fraction of those buildings’ electrical demands.
Putting solar modules on roofs creates headaches with roof maintenance, and poor-quality installations sometimes result in roof leaks, but rooftop mounting allows us to preserve land area for agriculture, recreation, and wildlife habitat. Whenever possible, I prefer to see PV systems installed on rooftops or carports rather than ground-mounting, though I recognize that that isn’t always possible or practical.
Small PV systems also usually generate electricity close to where it is being consumed. Such “distributed power” is changing the face of the utility grid. From a resilience standpoint, generating power close to the point of end-use of electricity also opens up an opportunity for incorporating either some battery storage or specialized inverters with capability to draw power from the solar system even when the grid is down — something that most grid-connected solar systems can’t do today. (For more on that, refer back to my blog, Getting Power From Solar Equipment When the Grid is Down.)
Is big solar bad?
Not in my book. As I look toward the future and a growing imperative to dramatically reduce our fossil fuel consumption and carbon dioxide emissions, I’m convinced that we need a mix of facility sizes with renewable energy systems. There will be many places where large, ground-mounted multi-megawatt-scale solar systems make sense, such as along highways and utility corridors where the land is already degraded and agriculture may not be feasible.
In arid places with lots of open land, such as the American Southwest, it should be possible for large solar systems to be developed responsibly — as long as enough open space is maintained for wildlife.
This isn’t to say that huge arrays make sense everywhere, just as wind turbines don’t belong everywhere. Having served as a trustee of the Vermont Chapter of The Nature Conservancy for nine years, I am well aware of the need for natural, undisturbed habitat.
But I’m also aware that if we don’t address our greenhouse gas emissions, we will be doing far more damage to ecosystems than the solar arrays (and wind farms) that are coming under more widespread attack.
Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.