5 ms·

I guess that means that 370MW is the nominal optimal generating power? From what I read, thermal solar has a capacity factor of only about 20% [1], which means

by pieter 16y ago

I guess that means that 370MW is the nominal optimal generating power? From what I read, thermal solar has a capacity factor of only about 20% [1], which means this solar farm will average out to about 70MW, which isn't that much. Coal has a capacity factor of about 60% and nuclear 90% [2], so this is similar to a 120MW coal plant or a 80MW nuclear power plant. Of course, you can't really compare them only on total power provided, as solar provides most of its power during the day, which is also the time in which the energy demand is the highest. [1] http://en.wikipedia.org/wiki/Solar_thermal_energy http://en.wikipedia.org/wiki/Solar_thermal_energy [2] http://www.eia.doe.gov/cneaf/electricity/epa/epaxlfile5_2.pdf http://www.eia.doe.gov/cneaf/electricity/epa/epaxlfile5_2.pd...

alex_stoddard 16y ago
That wikipedia article seems to be citing somewhat conflicting references. Further down it says "The capacity factor for power towers was estimated to be 72.9%" [35] (http://www.nrel.gov/solar/parabolic_trough.html http://www.nrel.gov/solar/parabolic_trough.html). A heliostat based design is going to significantly raise the amount of usable insolation. And the mojave desert is probably close to an ideal location for such a plant.
nickolai 16y ago
Quoting your [1] (end of power tower desing paragraph http://en.wikipedia.org/wiki/Solar_thermal_energy#Power_tower_designs http://en.wikipedia.org/wiki/Solar_thermal_energy#Power_towe... ): >The capacity factor for power towers was estimated to be 72.9% and 56.2% for parabolic troughs. so the 20% figure is simply incorrect, and is probably the one applying to rooftop solar heaters, which are a totally different type of design.
- uvdiv 16y ago
  The NREL figures are for plants with heat storage (large tanks of high-temperature molten salt which accumulate heat, to power turbines at night). Without heat storage you only have 20-25% at most. Ivanpah has a capacity factor of 31%, but that's not solar; part of that comes from burning natural gas. http://www.nrel.gov/csp/solarpaces/project_detail.cfm/projectID=62 http://www.nrel.gov/csp/solarpaces/project_detail.cfm/projec...
- pieter 16y ago
  The 20% efficiency is, as stated in the other comment, about correct for a plant without thermal storage. See far example [1]. What happens with the higher efficiency ratings is that they put more mirrors on the tower, or have a smaller turbine. That is, the ratio between thermal input and electric output increases. They can do this because any heat that isn't used by the turbine right at that moment can be stored temporarily and then used later on when the incoming heat isn't enough to power the turbine at 100%. Which means that with an efficiency rating of 73%, you still need many more mirrors than with the capacity factor of 25%, but you just don't upgrade your turbine, and instead rely on thermal storage. Which one is preferred (bigger turbine or thermal storage) depends on the cost of turbines and thermal storage, and on whether you want to have baseload power or higher output during the day. As a note, the 72.9% and 56.2% you quoted were estimates made in 2003 for the year 2020, so I wouldn't put to much trust into them. As for Ivanpah itself, it appears to not have any thermal storage planned (which would have to be the biggest thermal storage ever created to be useful), according to [2], so it would be limited to about a 25% capacity factor. [1] http://www.nrel.gov/docs/fy11osti/49303.pdf http://www.nrel.gov/docs/fy11osti/49303.pdf [2] http://www.basinandrangewatch.org/IvanpahFSA-reliability.html http://www.basinandrangewatch.org/IvanpahFSA-reliability.htm...

by pieter 16y ago

alex_stoddard 16y ago

That wikipedia article seems to be citing somewhat conflicting references. Further down it says "The capacity factor for power towers was estimated to be 72.9%" [35] (http://www.nrel.gov/solar/parabolic_trough.html http://www.nrel.gov/solar/parabolic_trough.html). A heliostat based design is going to significantly raise the amount of usable insolation. And the mojave desert is probably close to an ideal location for such a plant.

nickolai 16y ago

Quoting your [1] (end of power tower desing paragraph http://en.wikipedia.org/wiki/Solar_thermal_energy#Power_tower_designs http://en.wikipedia.org/wiki/Solar_thermal_energy#Power_towe... ): >The capacity factor for power towers was estimated to be 72.9% and 56.2% for parabolic troughs. so the 20% figure is simply incorrect, and is probably the one applying to rooftop solar heaters, which are a totally different type of design.

uvdiv 16y ago
The NREL figures are for plants with heat storage (large tanks of high-temperature molten salt which accumulate heat, to power turbines at night). Without heat storage you only have 20-25% at most. Ivanpah has a capacity factor of 31%, but that's not solar; part of that comes from burning natural gas. http://www.nrel.gov/csp/solarpaces/project_detail.cfm/projectID=62 http://www.nrel.gov/csp/solarpaces/project_detail.cfm/projec...
pieter 16y ago
The 20% efficiency is, as stated in the other comment, about correct for a plant without thermal storage. See far example [1]. What happens with the higher efficiency ratings is that they put more mirrors on the tower, or have a smaller turbine. That is, the ratio between thermal input and electric output increases. They can do this because any heat that isn't used by the turbine right at that moment can be stored temporarily and then used later on when the incoming heat isn't enough to power the turbine at 100%. Which means that with an efficiency rating of 73%, you still need many more mirrors than with the capacity factor of 25%, but you just don't upgrade your turbine, and instead rely on thermal storage. Which one is preferred (bigger turbine or thermal storage) depends on the cost of turbines and thermal storage, and on whether you want to have baseload power or higher output during the day. As a note, the 72.9% and 56.2% you quoted were estimates made in 2003 for the year 2020, so I wouldn't put to much trust into them. As for Ivanpah itself, it appears to not have any thermal storage planned (which would have to be the biggest thermal storage ever created to be useful), according to [2], so it would be limited to about a 25% capacity factor. [1] http://www.nrel.gov/docs/fy11osti/49303.pdf http://www.nrel.gov/docs/fy11osti/49303.pdf [2] http://www.basinandrangewatch.org/IvanpahFSA-reliability.html http://www.basinandrangewatch.org/IvanpahFSA-reliability.htm...