7 square miles is an enormous area when you have to fill it with high-tech machinery with large capital cost. I'd estimate roughly that it would be like parking that many vehicles. And 550 megawatts isn't that much, and that's probably peak power (important in CA for air conditioning I agree) so that's worth more like 250 megawatts of continuous power. Solar may be better not as wholesale but locally because there it competes at the retail rate. For stationary wholesale, I think wind and nuclear are better.
I went and investigated, this appears to be a product of Stirling Energy systems. They are talking about 12000 dishes for 3 square miles @ 300 megawatts. With dishes at maybe $25,000 each in bulk (they have a high tech turbine engine) that's $300 million for the engines alone. That's high, but not outrageous. But look on the other side. Prices may be $20-$30 a megawatt hour, so for 300 megawatts that's say, $8000 an hour in gross revenue. Given that it's solar, let's say it gets 5 hours per day (it will get more but not at peak output), so that's $40k a day, $14.6 million a year in revenue in 365 days, 5% of investment per year as revenue? Doesn't seem to be such a great deal, as that didn't include any operational costs at all.
Yes, looks like a good thing for the state to do nonetheless, especially if the price of the other fuels for electricity rise more. The article I read said the site was 4700 acres and 550 megawatts, apparently they are not building the whole thing out in the first phase. It does make electric cars look more feasable. If the state will underwrite the high start up cost they will have cheap energy [I suppose it is cheap after the initial build] over the long run, far, far less pollution costs, etc. The car of the future is a hybrid with external recharging capability maybe.
I agree that plug-in hybrids are a great idea. In reality a few things would make a large difference for petroleum consumption (which is more important than just energy) 1) requiring all light vehicles not diesel powered be 'flex fuel' alcohol/gasoline as in Brazil. This is very cheap. 2) eliminating tariff on fuel-grade ethanol imports 3) significantly raising efficiency requirements, and dissuading needless SUV/truck purchases 4) standardize plug-in hybrid technology and give breaks on nighttime electricity consumption 5) allow EU-spec smaller high-mileage cars to be imported or built here without requiring usual US modifications.