Comment by lazide
3 days ago
It only makes sense if you have ‘more than free’ energy you need to get rid of, because not getting rid of it causes problems. Similar to flaring natural gas, but for actual electricity.
This is not a common occurrence or situation, or shouldn’t be anyway, or someone is screwing up pretty badly somewhere.
Electricity prices around here (Austria) are negative around noon on most summer days. They pay you to waste all that solar energy people are feeding into the grid.
Is it really screwing up? If solar panels are cheaper than batteries, then you can over-provision the solar panels and then you won’t need to use the batteries as much, so you can probably get away with smaller installations.
My gut would expect it to approach $0 if full communication were possible, based on the instinct that most people would run their dishwashers if the energy cost was $0.
Solar panels don’t produce excess power that needs to be dissipated - just don’t invert the unneeded current, and that’s it.
‘Overproduction’ in this sense is from something like a spinning generator which starts to overspin, or an inverter which oddly starts to overvolt the output for some inexplicable reason.
That only works if the grid operator has control over the inverters, which they often don't have.
We currently have the situation where operators of solar farms of all sizes get a fixed amount of money for each joule they feed into the grid. Of course those people have zero interest in turning down their inverters when the sun is shining and there's already a surplus in the grid.
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It’s actually quite common. You have base load generation stations and your highly variable solar and wind. There are often times when the power at a wholesale rate dips below zero. It’s too costly to turn off your base load plants and maybe both solar and wind are generating above normal.
Solar inverters can just not draw the solar current, and wind can generally just change the pitch on their rotors at the individual level. The only ones that generally can not help ‘over produce’ are baseload power stations as they have actual physical inertia in very large turbines and can’t respond as quickly to demand.
Baseload power stations sometimes over-produce on longer timescales than just a few seconds because they'd rather not turn them off for maintenance/operational reasons. E.g. imagine you have a big biomass boiler feeding a steam turbine. Turning it off for an hour or two means everything cools down, which is a thermal stress, reducing lifetime compared to keeping it at constant power.
But yes, certainly poorly managed solar/wind that doesn't have good mechanisms to turn off in response to lack of demand is mainly the issue. In the future, when control systems are better, I'm sure negative pricing will be much less common.
Right but keep in mind these events are generally short lived and depending on the market there may be reliability guarantees that keep these open or specific federal funding rates.
But like I said before when rates go negative you will typically see it in occurrences where you have abnormal conditions (wind and solar generating at the same time) or aggressive night winds. And it does not happen long enough to need to curtail generation.
With variable sources of electricity it can be cheaper to have capacity at a level that you sometimes overproduce than to have a capacity that produces at a lower level, and so mostly needs a backup source of power.