Oregon Institute of Science and Medicine Dr. Arthur B. Robinson : Robinson cites an FPL estimate published in Renewable Energy News that the plant will produce 42,000 megawatt hours per year of electricity. Robinson calculates that level of output only makes the DeSoto plant a 4.8-megawatt facility, or roughly one-fifth the “25-megawatt” boast.
Robinson also criticized the project after comparing its purported energy savings to the $150 million it took to build the plant.
“Florida Power and Light brags that this new solar plant will power 3,000 homes,” Robinson writes. “This is $50,000 per home – for which the home gets 38 kilowatt hours per day. That 38 kilowatt hours is enough to power one ordinary one-room electric space heater.”
Just "crunching some numbers"...
IF we assume that the sun shines on average 6 hours a day year round in Florida with enough intensity to run the array at full power, then that is 6 hours/day *365 days/year = 2190 hours/year.
Based on the FPL estimate your source cites above of a yearly production of 42,000 megawatt hours per year of electricity, then the facility rating would be 42,000 MW-hours/year / 2190 hours/year = 19.17 Megawatt plant rating. I can see why it is rated 25 MW - the average sun hours/day is probably 5 hours/day estimated. When the sun shines, the plant produces 25 MW.
The only way that someone could claim that the DeSoto plant was a 4.8 Megawatt facility was if they assumed that the sun shone 24 hours a day. This seems somewhat disingenuous on the part of the quoted scientist.
A natural gas generating plant costs about $1500/kW capacity to construct. So, if you built a 4.8 MW natural gas generation plant, then the cost would be 4.8 MW x 1000 kW/MW * $1500/kW = $7.2 million. But natural gas plants have a yearly fuel cost. If that plant ran 24 hours/day to generate 42,000 MWh of electricity per year, and natural gas cost $4/1000 cubic feet (or $4/1 million BTUs), and the natural gas plant converted electricity at 50% efficiency (a pretty conservative estimate), then the cost in fuel to generate that much power each year would be 42,000 MWh/year / .45 = 84,000 MWh/year fuel required to have 42,000 MWh/year after losses. There are 3413 BTU/kWh, so this means 84,000 MWh/year * 1000 kWh/MWh * 3413 BTU/kWh = 286692 Million BTUs of yearly natural gas fuel required for the plant. That would cost 286692 MBTU * $4/MBTU = $1.147 Million/year in fuel cost. That assumes that natural gas prices stay near their historic lows. If gas prices returned to levels of two years ago, the fuel cost/year would be nearly $3 Million/year.
The cost of the natural gas plant to each homeowner would be $7.2 million / 3000 homes = $2400 + $382 in fuel costs (or +$1000 in fuel costs with natural gas at price levels two years ago).
So yes, the payback is probably near 60 years with historically low natural gas prices. With the natural gas prices of two years ago, payback seems quite a bit shorter. Roll the dice and take your gamble on the direction of natural gas prices. I'm betting they are heading higher.
As for nuclear power, being cost competitive with this installation....
Let's assume $8 billion to construct a nuclear power plant that has 2000 MWh of capacity (these are the types of numbers I'm hearing now for new construction). 2000 MWh *365 days/year * 24 hours/day * 85% average utilization = 14,892,000 MWh/year. At an $8 billion capital cost, that would supply 1,070,000 homes that use 38 kWh/day and cost those homeowners $7450 in capital costs. Not sure what it costs to fuel and maintain a nuclear reactor, but this is not free. So, I don't see the payback on the solar installation being 214 times longer than a new nuclear power plant. The scientist in the article must be assuming the cost of a nuclear power plant that has already been constructed and which has capital costs that have already been paid off by ratepayers. That's not exactly an apples to apples comparison of "new construction" to "new construction".
So the "facts" in the article don't add up for me.
