4 ms·

Your point is correct, but the details are wrong: coal (and nuclear) provide so-called "baseload" power, while natgas and hydro provide "peak" power (this is wh

by bdcs 12y ago

Your point is correct, but the details are wrong: coal (and nuclear) provide so-called "baseload" power, while natgas and hydro provide "peak" power (this is why natgas plants are called peakers). Coal has a very long spin-up (and spin-down) time. If you've studied process control, the first-order time delay is on the order of hours to days. Natural gas and hydro have time constants of ca. minutes. Moreover to your point, batteries have very short time constants (but a plethora of of other problems).

Florin_Andrei 12y ago
So, for coal, is it just because of thermal inertia? The size of the whole thing? Do they need to load the coal in a specific way?
- stcredzero 12y ago
  That's very likely due to size. Things like powerplants get more efficient as they get larger. (And as they get more complex by piling on more optimizing subsystems.)
- toomuchtodo 12y ago
  Thermal inertia. Boilers have to be brought up to temp, and do not take well to throttling like a combined cycle natural gas plant.
- WalterBright 12y ago
  For coal, I think it is because of the large turbines used. They have to be brought up to temperature gradually because they are very large precision made hunks of metal.
- akira2501 12y ago
  As has been mentioned, the boilers themselves do not heat up that quickly; however, you _also_ have to mix the pulverized coal with hot air and then pump it into the firebox for combustion. If you're coming up from a cold start, you're going to need to pre-heat the air, probably with electricity and/or natural gas. With this in mind, it's not so much that they don't generate power right away, it's that they don't generate enough power to overcome the cost of their initial inputs. From a power plant perspective, you aren't "started" until your output power is larger than your input power.
- Johnythree 12y ago
  Plus for Brown Coal, you must run dryers powered by the waste heat. These take DAYS to get up to speed.

by bdcs 12y ago

Florin_Andrei 12y ago

So, for coal, is it just because of thermal inertia? The size of the whole thing? Do they need to load the coal in a specific way?

stcredzero 12y ago
That's very likely due to size. Things like powerplants get more efficient as they get larger. (And as they get more complex by piling on more optimizing subsystems.)
toomuchtodo 12y ago
Thermal inertia. Boilers have to be brought up to temp, and do not take well to throttling like a combined cycle natural gas plant.
WalterBright 12y ago
For coal, I think it is because of the large turbines used. They have to be brought up to temperature gradually because they are very large precision made hunks of metal.
akira2501 12y ago
As has been mentioned, the boilers themselves do not heat up that quickly; however, you _also_ have to mix the pulverized coal with hot air and then pump it into the firebox for combustion. If you're coming up from a cold start, you're going to need to pre-heat the air, probably with electricity and/or natural gas. With this in mind, it's not so much that they don't generate power right away, it's that they don't generate enough power to overcome the cost of their initial inputs. From a power plant perspective, you aren't "started" until your output power is larger than your input power.
Johnythree 12y ago
Plus for Brown Coal, you must run dryers powered by the waste heat. These take DAYS to get up to speed.