4 ms·
Right, I like the "battery in front of a coal plant" option too. However, renewables (especially solar and wind) have the nice quirk that they require no fuel a
by NortySpock 6y ago
Right, I like the "battery in front of a coal plant" option too. However, renewables (especially solar and wind) have the nice quirk that they require no fuel and thus no fuel cost. So solar for example is charging a battery in the middle of the day when the sun is high and solar dominates the grid anyway (solar being over capacity at noon, rates are cheap at that hour because solar is just pouring power onto the grid at zero marginal cost). Coal at that time would be just burning fuel to charge a battery, only slightly better than keeping the plant running below-cost for the sake of keeping it on through the rate dip to keep the lights on for the 5pm load shift to the suburbs (you know, back in pre-COVID days when we had a commute)
Curtailing a coal plant (turning it off due to overcapacity) isn't fast, as the boiling water only slowly cools down (vs a natural gas turbine is typically faster to turn off as it's working on expanding combusted gas through a turbine, rather than hot steam through a turbine).
- PhantomGremlin 6y agoit's working on expanding combusted gas through a turbine, rather than hot steam through a turbine Recent gas plants are called CCGT, and use both combusted gas and hot steam. https://en.wikipedia.org/wiki/Combined_cycle_power_plant https://en.wikipedia.org/wiki/Combined_cycle_power_plant As Wiki explains it: combined cycle has a large gas turbine (operating by the Brayton cycle). The turbine's hot exhaust powers a steam power plant (operating by the Rankine cycle). This is a combined cycle gas turbine (CCGT) plant. These achieve a best-of-class real (see below) thermal efficiency of around 64% in base-load operation. Modern natural gas plants are very efficient. (But probably not as efficient as PV solar storing energy in grid scale batteries).
- Retric 6y agoThose are competing with a combined cycle steam to steam turbines. Which take much longer to heat up than a turbine to steam system. With combined cycle gas turbines you get some ramp up time, but about 1/2 of power outpost is available instantly. Also, as a general rule all energy required to heat up an engine to working temperatures is wasted when you turn them off.
- sp332 6y agoThe comparison isn't about efficiency - PV struggles to get over 20%. But the fuel is burned offworld which has plenty of benefits!
- jnsaff2 6y agoAnd it’s fusion energy!
- desipis 6y agoCCGT plants aren't generally used for handling peaks and unpredictable loads. They handle load change better than coal plants, however the grid usually has to depend on OCGT or batteries for stabilising the impact of unpredictable renewables (or unpredictable demand). Both these solutions are expensive and add significantly to the overall cost of pushing more energy generation to renewables.
- makomk 6y agoOCGT is used for short-term peaks, but at least here in the UK the bulk of the work of smoothing out the gaps left by renewables and demand variation over longer time periods (hours or more) is done by more efficient CCGT plants. This is usually pretty visible on gridwatch.co.uk - you can see the level of CCGT generation varying from day to day as wind generation rises and falls.
- Gibbon1 6y agoThere is this bad penny idea that solar at scale won't work without massive batteries. My belief is you can use CCGT plants to backstop solar and wind just fine.
- ZeroGravitas 6y agoSolar (and wind) is getting so cheap that the first option is to overbuild and throw some excess electricity away. Batteries are then well placed to shift a few gours worth of solar from day to night. Gas still has a place for seasonal demand far from the equator but even there you can dilute the gas with hydrogen to lower its carbon footprint.