Comment by chii
11 hours ago
> at night to burning fossil fuels only at night
only natural gas plants can do this. a coal plant cannot spin up just for the night and turn back off when the sun comes up - it's incredibly inefficient and probably causes more premature wear/tear too.
Full startup and shutdown of a coal plant can take days, but throttling down to about half power during low-load periods is normal. Power plants do this every day. Late at night, load decreases and plants throttle down. Every morning, between 0600 and 0900 local time, there's "morning load take-up" as load increases.
The big issue is what's called "ramp rate" - how fast can output power be increased or decreased? This tends to be around 1% to 3% of capacity per minute. See Figure B-2 in [1], which is a detailed discussion of how to improve your coal-fired power plant's ramp rate.
Natural gas plants have much higher ramp rates, and for batteries, it's under a second. Nuclear plants can be ramped up and down, slowly, but since it's all capital cost, cutting output raises the price of the power.
[1] https://www.epri.com/research/products/3002012979
Yep, I live in Finland where we are quite far ahead of the curve when it comes to renewables and nuclear. This is one large problem. When it's winter and cold and dark, solar does not help. Wind only helps when its windy.
Batteries are coming, and will solve it, but it will still take time for them to be come cheap enough.
Only once we have ~7 days of storage (~100 GWh of storage) will we be able to get rid of the last fossil plants.
>Batteries are coming, and will solve it, but it will still take time for them to be come cheap enough.
How long is the hope those batteries will last? There's surely no way Finland can run off battery power for even one month, much less a whole winter.
edit: perhaps I misunderstood and your comment on batteries was more related to the reliability of wind?
Yeah, the batteries are for wind. There are some days when the wind barely blows at all. That's when electricity prices really spike.
Finland's power grid stats are open to the public. You can click the month view to see how the different power sources fluctuate.
https://www.fingrid.fi/en/electricity-market/power-system/
Also fun fact: a lot of solar panels in Finland are mounted vertically to walls rather than rooftops. That's because we're so far north that the sun just hangs around the horizon rather than going directly overhead. You end up catching more sunlight pointing directly south.
Budgeting for over a month without power is unheard of. Extreme scenarios ("dunkelflaute") are measured on the order of hours, maybe days, and they get shorter and less frequent the larger the grid is.
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"Increased rates of component life consumption due to thermal fatigue, mechanical fatigue and wear caused by differential thermal expansion comprise the bulking of cycling (costs)," according to the International Energy Agency's Coal Industry Advisory Board.
"Every time a power plant is turned on and off, the boiler, steam lines, turbine and auxiliary components go through unavoidably large thermal and pressure stresses," the National Renewable Energy Laboratory (NREL) wrote in a report on cycling costs published in April 2012.
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https://www.reuters.com/article/business/energy/to-survive-c...
You don't get thermal and pressure stresses from throttling or even going into hot standby - the pressures and temperatures are the same, just the flow rate of steam changes. You only get thermal and pressure cycles from full shutdowns. As long as you keep the reactor/furnace warm then there's no issue here.
Well Coal is already cooked