Friday, August 10, 2012

A problem with solar power

Like wind, direct solar energy is diffuse, requiring a rather large apparatus to collect a useful amount. On a rooftop — a large area that is already collecting/reflecting the sun — solar panels may make a useful contribution to a single home or office. To expect more, however, means taking more solar energy, i.e., taking more from nature.

Vermont mandates a high payment for electricity from approved solar facilities up to 2.2 MW in capacity. A couple of solar projects under this program are a 1.0-MW facility in Ferrisburgh and a 2.2-MW facility in South Burlington.

The latter takes up a 25-acre field. That acreage is now an industrial site, without life. The field has essentially been paved with solar panels. Over the past 12 months its output has averaged 17.5% of its capacity, an average rate of 385 kW. The Ferrisburgh site averaged 15.9%, or 159 kW. In January, their average outputs were 5.4% and 7.3%, respectively, or 120 and 73 kW. Of course, that output followed the curve of daylight, decreasing every evening to 0, so they require complete duplication with some other source of power. Such duplication in the form of battery storage, as an off-grid home system uses, is impractical at the grid scale.

These facilities are clearly not making any meaningful contribution to Vermont’s electricity supply, which must meet an average load of about 650 MW. If the cost to taxpayers to subsidize these projects (i.e., provide generous profits for their owners, such as the governor’s friend David Blittersdorf) is judged to be worth it to learn about grid-level or industrial-scale solar, then what have we learned so far?

Using a capacity factor of 15% for sun-tracking solar and the ratio of 2.2 MW capacity per 25 acres, we would need almost 50,000 acres, over 75 square miles, to provide Vermont’s average load. That’s more than all of the land area of Burlington, South Burlington, Winooski, Colchester, and Essex Junction combined.

(For comparison, the McNeil generating plant (wood and natural gas) in Burlington takes up about 16 acres and produces at a rate of 50 MW. Thirteen such plants, requiring 210 acres, would provide the state's entire average load. Using the McNeil plant to provide heat [instead of letting it escape up the chimney] as well as power has been explored in recent years and would essentially double its usefulness.)

If we based it on a January capacity factor of 5%, add the land areas of Shelburne, Williston, Essex, Milton, and most of Jericho.

Of course, the capacity factor represents output only during daylight hours, so less land might be required to meet demand during the day. On the other hand, demand is higher during daylight hours as well, so there would actually not be much leeway there.

And still, other sources would be needed as night falls — a complete duplicate system. In other words, solar would not replace any other sources. It would pave over more than half of Chittenden County to at best reduce the use of those other sources.

There’s a better way to reduce the use of existing energy sources — without taking from the earth yet more by building sprawling “renewable” energy facilities that require 100% backup. It is to reduce the use of energy.

But of course, no backers of politicians get rich by people consuming less.

Large-scale solar, like large-scale wind, is a consumption-based solution. It is a change of brand, nothing more.

Question, 11 July, 2014:  Has anyone compared the (minuscule) carbon effect of covering a field with solar panels versus letting it return to carbon-capturing forest, or even versus just leaving it as a green field?

solar power, solar energy, environment, environmentalism, animal rights, Vermont