4 ms·
Why are there negative prices when wind and solar can mostly be shut down almost instantly to 0kw production?
by tcfhgj 2y ago
Why are there negative prices when wind and solar can mostly be shut down almost instantly to 0kw production?
- p_l 2y agoTL;DR - they are a signaling method. They are used to signal the producers to shut production down, actually - as in, the energy producer's dispatch team uses negative prices to signal to power plants to change production schedule. In case of wind power, some power plants can actually make money on negative prices because modern wind turbines can be dynamically made into an energy sink. Similarly negative prices are used as signal to storage providers.
- ForOldHack 2y agoYou would think they would mention that they are one of the very top users of pumping water storage, and developers of gravity systems, but marketing and economics take the front row seat? Seems short sighted. Battery storage is still in it's infancy. A large fleet of electric cars would help - but it looks like all this is an afterthought.
- aitchnyu 2y agoUmm, can you expand on wind turbines being energy sinks in a way solar cannot?
- p_l 2y agoSolar panels essentially give you DC output from light hitting them. You can't make a sink out of it in any way. You cannot connect power to solar panel and make it generate light or otherwise consume it (other than maybe melting it ;)) Wind turbines however provide rotational energy that has to be turned into electricity. Modern turbines use somewhat complex alternators, often with multiply of 3 phases, which is normally used to provide delicately adjusted power output in sync with the grid. Fine adjustments of phase skew are usually used to control power provided to the grid and to keep generated power in phase with the grid. However, such alternator can be driven in a way where the electricity provides braking power. You can think of it as similar to how many electric engines are both generators and sinks. It's however way more fine tuned than toy examples.
- vel0city 2y agoDue to the high variance of rotational speed I don't think most wind turbines are directly AC connected to the grid. From what I've read they often go AC -> DC -> AC so they can actually frequency match reliably.
- p_l 2y agoThe cost and inefficiency of DC conversion for the power-generation part is why new turbines use DFIGs[1]. Essentially it allows keeping chosen frequency despite changes in turbine power, and is core to tricks like I described. [1] https://en.wikipedia.org/wiki/Doubly_fed_electric_machine#Doubly_fed_induction_generator https://en.wikipedia.org/wiki/Doubly_fed_electric_machine#Do...
- vel0city 2y agoThat seems pretty cool. Good to hear they're rolling out newer tech to solve that DC conversion and have turbines help support frequency. Thanks for sharing! I wonder what percentage of turbines installed already have this technology versus the DC conversion. Or are pretty much all MW scale turbines using this?
- p_l 2y agoApparently they are quite common, but permanent magnet synchronous motors with double inverters are apparently increasingly common, though even there I've heard of similar tricks with polyphase winding as well as electronically "feeding in" power onto each phase to achieve whichever goals plant control wants.
- vel0city 2y agoNeat, time for me to do a good bit more reading it seems. I appreciate the insights you brought. As an aside, I find it funny so much of our power grid can have so many complicated parts but often boils down to boils down to "big thing spin fast!"
- rlpb 2y agoIn the UK at least, the government offers an incentive to build wind farms by providing a price guarantee: https://www.bbc.co.uk/news/business-67430888 https://www.bbc.co.uk/news/business-67430888 So they don't have to shut down to 0 kW, since they are guaranteed to be paid significantly for generating even when there is no demand. Or they have to be paid more to shut down, which corresponds to a negative price at the other end. This generally requires negative pricing for other suppliers and consumers to balance it out.
- knallfrosch 2y agoShutting down free and clean energy producers in order to keep the dirty ones running with manpower would be completely wrong.
- tcfhgj 2y agoObviously, you would shut dirty ones down first.
- itishappy 2y agoThey're not operating at a loss. Negative prices are offset by renewable subsidies. Pedantry: Solar panels are entirely passive and cannot be shut off. You can disconnect them from the grid, but they're still gonna sit there turning photons into electrons. Might as well capture that and incentivize storage.