3 ms·

I'd like to clear up your terminology a little bit, since the way you use "on demand" actually means two different use-cases. You're referring to "spinning res

I'd like to clear up your terminology a little bit, since the way you use "on demand" actually means two different use-cases. You're referring to "spinning reserve" versus "on-demand" sources of power. "Spinning reserves" are plants that we keep online in a "ready" state, but disconnected from the grid until we need them. "Spinning reserves" are kept online in the case of a failure elsewhere on the grid, or to adapt to load changes throughout the day. These plants are cost-effective for this use case. "On-demand" facilities are plants that have very fast spin-up time, and so they can be brought "online" from a powered-off very quickly. These kinds of plants are also cost-effective to cycle between both states. Natural Gas Combustion Turbines happen to have fast startup time (fast=minutes), and are cost efficient to keep running, so they're used on the grid for both "on demand" and "spinning reserve applications", as it's cheap to cycle them between both states and cheap to keep them spinning (as long as natural gas is cheap). Even better "on demand" sources of power are batteries, since they can be flipped on/off the grid like a lightswitch, but I digress. Nuclear power plants, on the other hand, are awful for "on demand" applications since they take many days, weeks or months to fully power on/power off, and it costs a lot of money to do so. But, they are good as "spinning reserve" facilities, since they produce very cheap electricity once they are online.

dredmorbius 12y ago
More on generating responsiveness, as I understand it. Natural gas plants can be "spun up" in about 15 minutes. This is because they run as directly-fired turbines, so there's no time required to build up a head of steam. Standby diesel generators can be fired up even more quickly (a couple of minutes), though these are expensive and somewhat less efficient. Hydroelectric power also has an activation response measured in single-digit minutes, or even seconds -- open a sluice gate, synchronize to the grid, and you're on. A fair amount of California's hydro power is used specifically to match against current demand and larger blocks of power bought from elsewhere. Geothermal is also fairly responsive, though it's got a limited total output. For California, The Geysers (among the largest geothermal generating plants in the world) has a total capacity of 725 MW (this is down from the peak largely due to groundwater exhaustion, with various re-injection schemes proposed and partially adopted). http://www.calpine.com/media/Geysers_Factsheet.pdf http://www.calpine.com/media/Geysers_Factsheet.pdf Coal (virtually unused in California) and nuclear (one plant, Diablo Canyon) have very long ramp-up periods, but can be operated as "spinning reserve" by wasting their unused thermal output. This is particularly expensive for

dredmorbius 12y ago

More on generating responsiveness, as I understand it. Natural gas plants can be "spun up" in about 15 minutes. This is because they run as directly-fired turbines, so there's no time required to build up a head of steam. Standby diesel generators can be fired up even more quickly (a couple of minutes), though these are expensive and somewhat less efficient. Hydroelectric power also has an activation response measured in single-digit minutes, or even seconds -- open a sluice gate, synchronize to the grid, and you're on. A fair amount of California's hydro power is used specifically to match against current demand and larger blocks of power bought from elsewhere. Geothermal is also fairly responsive, though it's got a limited total output. For California, The Geysers (among the largest geothermal generating plants in the world) has a total capacity of 725 MW (this is down from the peak largely due to groundwater exhaustion, with various re-injection schemes proposed and partially adopted). http://www.calpine.com/media/Geysers_Factsheet.pdf http://www.calpine.com/media/Geysers_Factsheet.pdf Coal (virtually unused in California) and nuclear (one plant, Diablo Canyon) have very long ramp-up periods, but can be operated as "spinning reserve" by wasting their unused thermal output. This is particularly expensive for