Gemasolar – Solar Power 24/7

June 24, 2011

It used to be that the United States lead the world in technology. Most of the technologies powering the new energy revolution were born here, but are being perfected elsewhere.

Thank you, Wise and Benevolent Fossil Fuel Overlords!!

Gemasolar is a 19.9-MW plant with a 15-hour ‘battery’. Gemasolar’s expected production is 110,000 MWh per year—or about enough to fully power 25,000 households. Gemasolar to produce electricity about 6,400 hours per year – a capacity factor of 75%. Gemasolar’s power tower has a height of 140 meters (459.3 feet.)

The receiver on top of the tower is like a radiator that is heated to a temperature of about 565 degrees Celsius (1,050 degrees Farenheit) by the sunlight reflected by 2,650 heliostats with a total reflective surface of about 300,000 square meters (3.32 million square feet.)

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14 Responses to “Gemasolar – Solar Power 24/7”


  1. What about the cost though. In order to sell this technology to the public we need direct comparisons of the cost of this generating facility to other forms of generating facilities.


  2. I realize the cost is declining but the Gemasolar power plant cost $420 million to build vs. $30 million for an equivalent natural gas power plant. That’s a hard sale to make to the public.

    • greenman3610 Says:

      natural gas is one of the important short term solutions for driving down carbon emissions, but clearly the future is in renewables.

    • archaeandragon Says:

      Dunno where you are getting your numbers, but TVA is planning to build a natural gas plant that will cost $820M. Granted, it is an 880MW plant, compared to the 20MW Gemasolar plant, but remember two things: 1) it is a cutting-edge experimental plant, and 2) there is no fuel cost associated with solar. With natural gas, the cost to build the plant is only part of the total cost of operation.

  3. otter17 Says:

    In addition, this particular solution includes the cost of the battery energy storage. The cost of energy storage for natural gas is essentially “free” unless one counts the costs associated with transportation, potential leaks, etc. So, the fairest cost comparison of nat gas plant versus this solution may take some more thought to figure out.

    Hopefully, natural gas is a very short term solution if that Cornell paper on fracking emissions turns out to be approximately accurate.

  4. Anthony Hall Says:

    Interesting stuff. Can’t wait to see more data on total costs over the lifetime, as these technogies start to mature. I have often wondered what happens in a big hail storm! Do the mirrors retract somehow? The designers would have dealt with it, but hard to find info on that.

    • greenman3610 Says:

      not many hailstorms in the desert, but I suspect these are tougher than your bathroom mirror.

  5. sailrick Says:

    An area in the American southwest 42×42 miles, filled with these CSP plants could produce as many megawatt hours as all the coal plants in America.
    The 42×42 mile area is approximately twice the area now evacuated around the Fukishima nuclear plant in Japan. (my guestimate of the area)

    Regarding the cost and value of the molten salt heat storage:

    “Thermal Energy Storage (TES) and Solar Thermal power plants”

    “Adding TES provides several additional sources of value to a CSP plant. First, unlike a plant that must sell electricity when solar energy is available, a CSP plant with TES can shift electricity production to periods of highest prices. Second, TES may provide firm capacity to the power system, replacing conventional power plants as opposed to just supplementing their output. Finally, the dispatchability of a CSP plant with TES can provide high-value ancillary services such as spinning reserves.”
    (from: “The Value of Concentrating Solar Power and Thermal Energy Storage.” Sioshansi R.; Denholm, P. (2010))

    http://www.nrel.gov/analysis/pdfs/45833.pdf

    There is not much cost in storing the heat, the costs being upfront in the construction of the heat storage system.

    otter17
    How much difference is there between the cost to build natual gas storage infrastucture and that of molten salt? They are similar in many ways. A big tank and piping, valves etc.

    Some designs use the salts as both heat storage and heat transfer medium. Others only use the salt for heat storage, while some other liquid is used as transfer medium, passing through a heat exchanger that heats the salt.
    Added cost of including heat storage is another reason why solar thermal plants are more cost effective when they are fairly large- hundreds of megawatts. The capital cost is spread over more generating capacity.

    The NREL has said that CSP building costs should fall dramatically as the industry gets up to scale with mass production of components etc.
    One of their reports predicted power prices at 10 cents/kWh after an initial building period of early plants, followed by prices falling to 4-7 cents/kWh as economy of scale and experience bring costs down. Efficiency improvements are also happening. For example, Torresol just built a plant that runs 24/7 on solar, and operates at 900C as compared with the 565C temperature mentioned in the article.

    I don’t think you can compare PV panels to CSP plants with heat storage, as if they are equals. The ability to provide the services to the grid as the NREL describes, is a game changer to my mind. Steady Power from the sun, even at night, makes solar a whole different animal, and one which would be of great benefit in a clean energy future.
    It actually makes it easier to intergrate PV solar into the grid, same as for wind.

    CSP can also be combined heat and power, producing hot water and power.
    Or even just heat, for that matter. It can also desalinate sea water.

  6. sailrick Says:

    NREL says there is about 1,000 GW potential in the southwest, only including carefully selected areas that don’t infringe on anything of man, parks, rivers, lakes, roads, habitation, sensitive areas of the desert, and only flat land.
    Arizona 285 GW
    New Mexico 220 GW
    California 98 GW
    West Texas 127 GW
    Utah 74.3 GW
    Nevada 165.8 GW
    Colorado 38.2 GW
    Idaho 4.8 GW
    Kansas 6.7 GW
    Oregon 12 GW

    Arizona alone, at the 75% capacity factor in this article, is equivalent to about 200 nuclear power plants. (another guestimate, but not far off)

    Northern Mexico has a huge potential.

    “Solar thermal and heat storage”

    “Profit Maximization
    Energy storage allows the plant operator to maximize profits. During periods of low hourly power prices, the operator can forgo generation and dump heat into storage; and at times of high prices, the plant can run at full capacity even without sun.

    Peak Shaving
    Solar generating capacity with heat storage can make other capacity in the
    market unnecessary. With heat storage the solar plant is able to ‘shave’ the
    peak load.

    Reducing Intermittence
    The ability of thermal solar plants to use heat energy storage to keep electric
    output constant: (1) reduces the cost associated with uncertainty surrounding
    power production; and (2) relieves concerns regarding electrical interconnection fees, regulation service charges, and transmission tariffs.

    Increasing Plant Utilization
    Solar plants equipped with heat storage have the ability to increase overall
    annual generation levels by ‘spreading out’ solar radiation to better match
    plant capacity.”

    http://www.nrel.gov/csp/troughnet/pdfs/owens_storage_value.pdf

  7. sailrick Says:

    NREL (2001)
    “Even though some solar generating technologies could benefit from research and development, it was made clear that solar resources are abundant; are located where they are needed; that efficiencies from concentrating solar power (CSP) are good enough to justify deployment; and cost projections are very promising. All that solar power required, in the opinion of the experts, is an incubation period, where incentives are put in place that allow the transition of this emerging generating technology into the mainstream. It is our view that providing such an incubation period is not a leap of faith, but a proven recipe of success, as the emergence of wind generating technology in Europe has shown.”

    “The success of an incubation period for solar power is all but guaranteed. This is because, unlike similar promises by the industry to introduce electric cars, CSP plants have already achieved a level of performance that makes them practical. They have proven their merit in over a decade of operation in the Mojave Desert, and cost-reduction projections for CSP technologies are based on the fact that they use ordinary technology in an extraordinary way.”

    “Heat storage systems are not useful for large-amounts or long-term energy storage, but heat equivalent to up to 1-2 days of full plant output can still be stored for later use. In practice, stored energy would be used the following night or to keep the plant at full output when clouds pass over the plant location. Many of the high-load/high-price periods in the desert Southwest occur in the three to four hours after dark—a time period the operator could target for dispatch.
    Heat storage could also be used to store thermal energy on holidays or Sundays for dispatch during the higher-price periods the following workday. Thus, energy storage allows the power tower or parabolic trough plant operator to maximize profits, which may justify the cost of adding heat storage to the solar power plant.
    Additional flexibility in the operation of a thermal solar plant with storage comes from oversizing the solar collector field. That is, the collectors generate more heat than normally required by the steam turbine of the plant. For example, a 100-MW solar plant could have a solar field that generates enough heat for 150 MW of electricity at full sunshine. Of this, 100 MW would be used to generate electric power, while the other 50 MW would go into storage for later use.
    Such a plant would have a solar-multiple of 1.5 (150 MW/100 MW = 1.5.) This over-sizing of the solar field combined with heat storage allows the plant to run at a higher capacity factor. In the example, the capacity factor10 of the electric generator would increase from about 25% to 38%. Thermal storage can be designed to be cost effective to meet capacity factors as high as 50% for parabolic trough systems, and up to 70% for power tower systems. These capacity factors are commensurate with the hours of peak demand in the Southwest.”

    http://www.nrel.gov/csp/pdfs/33233.pdf

    your tax dollars at work

  8. sailrick Says:

    Here’s a how a CSP plant with 3.5 hours heat storage on typical summer day in Nevada would run.

    The plant would start saving heat at sunrise. A few hours later, it would start generating electricity and continue storing heat in the salt. By 1pm when the sun peaks, it would be at full rated power, say 1250 MW. It would continue to put out at least it’s full rated power, while increasing output and peaking at about 3,000 MW at 5pm, exactly when demand in the grid peaks in the southwest. It would continue putting out steady but declining power until midnight. No fluctuation when clouds pass by.
    Cloudy periods, which are rare in the southwest can be planned for by the plant manager and utility, from weather forecasts. In the daytime in what the NREL calls Premium Solar Resource areas, there is sunshine all but about 4% of the time.

    3.5 hours heat storage means enough to provide 3.5 hours at full rated power, without any input from the sun.

    The first plant with molten salt heat storage in the U.S. is being built in Arizona. It will have 6 hours heat storage.

    In the winter there is less solar resource due to the angle of the sun mostly, but demand falls even faster than output in non summer months. Air conditioning is the biggest demand, in the southwest. A plant would run about the same as described ,though at lower output.

    HVDC tranmission lines would enable solar thermal in this area to feed power into

  9. otter17 Says:

    Ah, thanks sailrick. Those are some good links to PDF files I may have to hold on to.


  10. [...] Peter Sinclair’s Climate Crocks Gemasolar is a 19.9-MW plant with a 15-hour ‘battery’. Gemasolar’s expected [...]


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