The following post is by Earl Killian, guest blogger at Climate Progress.


Solar panelsTraditional photovoltaic (PV) is typically installed on rooftops and competes with retail electricity. Over 40 percent of the cost of a system can be in the installation, which must be customized to every rooftop. So technologies that dramatically lower PV cost end up having a less dramatic impact on total residential system cost. So it is natural that the next generation technologies, such as thin films of copper indium gallium selenide (CIGS) printed as ink on conductive substrates, need to look at non-rooftop applications, where the installation of a large solar farm is fairly turnkey.

Nanosolar, a thin-film PV startup, has just announced their vision in their blog and newsletter. They see the best fit for solar being municipal solar plants of 2-10 MW in size and suggest such plants can be done in 12 months, providing a significant advantage over coal or nuclear. Martin Roscheisen, Nanosolar’s CEO, writes:

A 2 MW municipal solar power plant requires about 10 acres of land to serve a city of 1,000 homes — that’s acreage generally easily available at the outskirts of any city of such size in even the most developed countries. Similar for a 10 MW plant for a city with 5,000 homes: This would require five such lots.

In a solar power plant, solar panels are mounted onto rails above the ground so that grass and flowers can continue to flourish in between and below the rows of panels. Care is taken that sufficient amounts of rainwater can drop through between adjoining panels so that the flowers and organisms below are not starved.

While rooftops are surely a good application too for solar panels, it is a business that’s difficult to scale rapidly in a truly meaningful way. Crawling onto rooftops and mounting solar panels in compliance with building codes is fundamentally always a somewhat more expensive proposition.

Roscheisen does not explain how grass and flowers are to grow below panels without sunshine (between rows makes more sense).

Currently Nanosolar is only pursuing utility-scale solar, and is sold out for 12 months. This isn’t a technology you will be able to put on your roof any time soon.

Another company with a similar vision is Coolearth, which uses a reflective balloon as a low-cost concentrator. They too are pursuing utility-scale applications, though they suggest ground-based (not rooftop) residential and commercial availability will follow. Whether there is a market for ground-based residential installation is unclear, however.

Coolearth claims that using balloons as concentrators instead of mirrors is 400 times cheaper, and uses 60 times less steel for the truss and rigging. The small PV inside the balloon is water-cooled. In their video, they claim a cost of 18 cents per Watt.

One disadvantage of PV compared to some Concentrated Solar Power technologies, with which it competes, is that PV does not have the possibility of nighttime generation from Thermal Energy Storage as found on some (but not all) CSP systems. However, with the daytime electricity demand often twice that of nighttime, PV can still be a useful addition to the grid.

Read Martin Roscheisen’s Municipal Power Plants for yourself.

This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.