New Record, Solar-to-Grid

Energy Blog commentator Big Tom states that California utilities have to meet a 20% renewables target by 2020 and are struggling towards this target. He critiques an analysis by fellow commentator Nucbuddy:

Two problems with your analysis, (1) These utilities are primarily interested in peak power, i.e. the hottest part of the day during the hottest part of the year. (2) For a tracker (or an overhead system such as the CoolEarthSolar) the solar component can intercept low angle solar radiation (it shades a considerable amount of land). If the land was only used for solar the whole land cost would count, but if the area between units (or under them for the other system), can be used for another purpose the land cost is reduced.

Again, nobody is seriously proposing these things for base load generation, I’d prefer a healthy Nuclear component for that. The real issue for the next decade or two, is can these sorts of solutions make sense for daytime power?

Sandia - Stirling Energy Systems Test Engine


To repeat Steve Heckeroth’s forewarning, there is no need to wait for a new technology to save us. “It’s time to harness the world’s virtually inexhaustible supply of solar energy and start building a brighter future.”

The commentary was prompted by Jim Fraser relaying1 the announcement of a new record set for solar-to-grid system conversion efficiency. With the sky almost 10 percent brighter than usual, Sandia (Sandia National Laboratories) and SES (Stirling Energy Systems) achieved a 31.25 percent net efficiency rate.

The old 1984 record of 29.4 percent was toppled on SES’s “Serial #3” solar dish Stirling system at Sandia’s National Solar Thermal Test Facility.

Several technical advancements to the systems led to the record-breaking solar-to-grid conversion efficiency.

The first and probably most important advancement was improved optics. The Stirling dishes are made with a low iron glass with a silver backing that make them highly reflective —focusing as much as 94 percent of the incident sunlight to the engine package, where prior efforts reflected about 91 percent. The mirror facets, patented by Sandia and Paneltec Corp. of Lafayette, Colo., are highly accurate and have minimal imperfections in shape.

Both improvements allow for the loss-control aperture to be reduced to seven inches in diameter — meaning light is highly concentrated as it enters the receiver.

Other advancements to the solar dish-engine system that helped Sandia and SES beat the energy conversion record were a new, more effective radiator that also costs less to build and a new high-efficiency generator.

Stirling Energy Systems


“Cadillac Ranch?” Nope. “Dali Redux?” Uh, no. SES.

Energy Blog commentator John Flagge has trouble seeing this tech becoming cheap enough and Big Tom replies:

For reasonable interest rates (discount rates actually) infinite lifetime needs a payback period of roughly 10-13 years. Lifetimes much larger than this will have little effect on the “present value” of the system. If these things are to make financial sense, the capital costs have to be kept relatively small.

The Energy Blog reports that SES has signed power purchase agreements with two major Southern California utilities for up to 1,750 megawatts (MW) of power. The contracts with Southern California Edison and San Diego Gas & Electric will require up to 70,000 solar dish engine units.

Energy Blog commentator Danzig is skeptical:

If the first phase of SCE’s project (500 MW, 20,000 dishes, 4 years of construction) is going to happen, it means that 100 of these babies must be built, transported, and erected PER WEEK for four years! A massive capital project, wouldn’t you say?

Big Tom replies:

I wonder if the contracts actually specify the purchase of that much capability? I wouldn’t be surprised if these were maximum amounts subject to contingencies (such as cost/performance of early systems, etc). If a cheaper technology came along, mid-build-up, I suspect the utilities could back out (perhaps with payment of a penalty).

Continue reading here: U.S., Sweden sign agreement on renewable energy / fuel efficiency

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