Interesting NYT Article on Solar Thermal + Natural Gas Power Plant

BB. · March 2010

The New York Times has a very interesting article on a new Solar Thermal array, using 750F synthetic oil, to assist a natural gas fired power plant. The hot oil is used as supplementary heat for operating steam turbines already installed at the fossil fuel plant. Unlike most articles--this one has a fair amount of hard facts (more facts in the slide show):

The Newest Hybrid Model

The plant also serves as a real-life test on how to reduce the cost of solar power, which remains much more expensive than most other forms of electrical generation. FPL Group, the parent company of Florida Power and Light, expects to cut costs by about 20 percent compared with a stand-alone solar facility, since it does not have to build a new steam turbine or new high-power transmission lines.

“We’d love to tell you that solar power is as economic as fossil fuels, but the reality is that it is not,” Lewis Hay III, FPL’s chairman and chief executive, said on a recent tour of the plant. “We have got to figure out ways to get costs down. As we saw with wind power, a lot has to do with scale.”

For solar power, scale is still a relative term. At its peak, the solar plant will be able to generate 75 megawatts of power, enough for about 11,000 homes. But that is dwarfed by the adjacent gas plant, which can produce about 3,800 megawatts of power. (A megawatt is enough to power a Wal-Mart store.)

500 acre solar collector field. 13 acre natural gas fired power station.

The cost to build the 75MW solar array is $476,000,000.

$476M/75MW = $6.35 per watt for array+plumbing

If you include the cost of building the steam turbine side of the plant which was 80% less expensive because using existing turbines:

$6.35 * 1.20 = $7.94 per watt with boilers and turbines.

The second largest solar array in the US will supply an additional:

75MW/ 3,800MW = 0.02 or 2% of peak capacity to existing power station

I guess we use a lot of electricity...

-Bill

AntronX · March 2010

Re: Interesting NYT Article on Solar Thermal + Natural Gas Power Plant

From article:

In 2008, for example, Texas narrowly avoided a blackout when wind power, which supplied 5 percent of demand at the time, experienced an unexpected lull, driving wind electricity generation down to 350 megawatts, from 2,000 megawatts, in less than four hours, according to Mr. Lave.

I hate seeing that incident blamed solely on wind power. There was a cold snap that produced higher than anticipated demand, and a power plant that went off-line (or was in maintenance). Wind was a minor contributor to that crisis. It was even forecasted that wind would drop down.

BB. wrote: »

75MW/ 3,800MW = 0.02 or 2% of peak capacity to existing power station
I guess we use a lot of electricity...
-Bill

That station does not run at peak capacity all the time. Especially right now, sky is clear and air is cool. Demand for air conditioning or heating must be low. A ratio of annual energy from 75MW array to energy generated from rest of the plant would be more telling.

BB. · March 2010

Re: Interesting NYT Article on Solar Thermal + Natural Gas Power Plant

Out "west"--Natural Gas is used many times for "peaker plants"... Because they can be quickly spun up and down (~15 minutes???). A coal or nuclear plant (steam boilers) takes on the order of 24 hours.

Problem with Sun (and wind) is that the power is only available for a limited amount of time per day... Solar, call it ~8 hours a day of useful power in summer (without thermal or battery storage). So, a fossil fuel plant has a 3x "ratio of annual energy" to a solar plant right from the get go...

In California, we have a power exchange (California Independent System Operator)... I think they "manage" something like 75% of the electric power in the state... and they have an interesting page that shows the current 24 hour window of estimated/actual power usage and spinning reserves...

Normally, from what I have seen, the day/night ratio of power usage is around 2:1 or less... So--assuming that this is also a major power supply for Florida in it own right--My guess is that the solar array would still be down in the low single digits for the annual power generated at this plant (which is the largest fossil fueled plant in the US?). It is even possible that ratio is even below 1% over a 1 year period.

Solar to fossil fuel is an apples to oranges comparisons in many respects... But current costs and even physical size comparisons are real (obviously, there is a natural gas infrastructure we are not looking at here, and that there is no external power supply/cost for the solar system).

3,800 MW * 1/75 MW * 500 acres * 1 sqm per 640 acres = 39.6 square miles for peak capacity in solar

Using PVWatts and 1.0 derating for West Palm Beach Florida, 75 MW of panels would generate: 159,191 MWH per year...

Lets assume that the 3,800 MW fossil fuel plant runs at 90% up time and 50% average power non-stop for one year.

3,800, MW * 365 days * 24 hours * 0.90 * 0.50 = 14,979,600 MWH per year

Ratio of solar plant to fossil fuel plant running at 50% output:

159,191 MWH / 14,979,600 MWH= 0.0106 = 1.06% solar/fossil ratio

For solar to generate 100% parity with fossil fuel plant running at 50% capacity and 90% up time, a solar array would need an area of:

500 acres * 1/0.0106 capacity ratio * 1 sqm per 640 acres = 74 sq miles / 190 sq. Kilometers

California probably has 10x the capacity of that one power plant... Do the numbers (we could switch to our deserts for more sun).

-Bill

Interesting NYT Article on Solar Thermal + Natural Gas Power Plant

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