[CHsurfer]

"The plant will generate 110 megawatts at peak and store enough heat to run for eight to 10 hours when the sun is not shining."

Let's assume we get about the equivalent of 100 MW for 15 hours each day. That's 1500 MWh per day. Over 10 years at 365 days per year gives a total of 5'475'000 MW*hours.

The loan was 737 MUSD and let's assume that private investors will kick in the some to bring the total invest up to 1'000 MUSD. If you ignore operating costs this gives an average cost per MWh of 182.64 $/MWh.

The average cost of electricity in the US south west was around $40 MWh (http://www.eia.gov/electricity/monthly/update/wholesale_mark...).

This would indicate that the payback period for such a project must be longer than 10 years or that the expected cost of electricity will be higher in the future (or both).