from Hacker News

Solar farm has to switch off every second day due to negative prices

by arthurdenture on 11/7/19, 4:33 AM with 184 comments

• by ZeroGravitas on 11/7/19, 7:14 AM

  I'm not a fan of most reporting of these negative price events.

  First, they rarely explain why the price is negative. As the article explains, solar can switch itself off, so it's nothing physical about solar that can cause negative prices, as all solar can switch itself off before it goes negative it would bottom out at zero for those reasons.

  In most cases I've seen so far, contractual agreements with gas, coal or nuclear (who struggle to switch themselves off quickly without hurting themselves) have been the reasons for negative pricing and the grid wasn't actually at 100% renewable at the time of the curtailment. In other words, solar switches itself off, while other, dirtier plants get fined (negative price!) for demanding that they be allowed to still run.

  In South Australia they're doing pretty well on renewable, so it's possible they actually are at 100% renewable at these times (would be good for the stories to clarify). If that's the case then the negative price is most likely caused by subsidies to wind that are paid per generation. If the subsidies to two renewable plants are different then one will bid the other off the market at that point since the price can go down to the opposite of the subsidy before they make an actual loss.

  All in all, these negative prices are useful market signals. I wish the weren't covered by journalists who seem to think negative numbers are taboo for some reason.

  The fact that it's the same plant that gets switched off repeatedly (rather than all solar reducing output) makes me think this is either a contractual thing that only affects its owner or a regional transmission thing that only affects its geographic location. Again, would be nice for stories to find out which.

• by nabla9 on 11/7/19, 7:37 AM

  EXPLANATION: Some power sources can’t be shut down and restarted quickly and cost-efficiently. If the cost of stopping and restarting plant is higher than the cost of selling energy at a negative price for some time, prices go negative.

  This kind of price fluctuation can increase the overall cost of energy production. We need cost effective power storage solutions and better electric grids to make renewable more effective.

  https://en.wikipedia.org/wiki/Duck_curve

• by JMTQp8lwXL on 11/7/19, 5:16 AM

  An explanation of the mechanics of how I'd have to pay somebody else to take my electricity (e.g., a negative rate) would be helpful.

  As prices approaches 0, I could take the excess electricity and say, mine cryptocurrency. Is nobody considering the arbitrage opportunities here? Take the 0-cost electricity, move water up a hill, and convert it back to electric when it's needed, etc.

• by cetra3 on 11/7/19, 5:51 AM

  I wish these prices were reflected to the consumer. Electricity bills in South Australia are ridiculous, and as a renter you don't have the luxury of installing solar panels.

• by rosege on 11/7/19, 5:20 AM

  I'm in SA and I'm currently looking at getting solar panels and maybe a battery because we have the highest cost of electricity in the country. I'd like to know why we have the highest when the price seems to be going negative every other day?

• by brownbat on 11/7/19, 5:10 AM

  Storage is definitely the wise answer here, as the article mentions.

  The fun answer here is giant crypto farm.

• by jillesvangurp on 11/7/19, 7:40 AM

  The solution is to deregulate the market and allow multiple companies to buy and sell electricity. The problem here is not an over supply but poorly regulated demand that causes energy to be priced higher than is justified; mainly to protect expensive sources of energy such as coal and gas plants.

  The basic issue is not that there is no demand but that it is unevenly spread. People turn on their ACs when they get home after work. Peak demand is in the evening when the sun is about to go behind the horizon. Peak supply is in the late morning and early afternoon when people are at work.

  So, all you need is tuneable demand. Say you had a web service that simply announces the current price of electricity that updates in real time based on your production capacity and a whole bunch of things that can turn themselves on/off based on that price. Whenever there is excess demand it just continues to drop that price until demand picks up. Now say you have an apartment complex with a lot of batteries in the basement and a bit of simple electronics that controls the charging behavior based on the price several energy providers (why limit to one). Now basically you have an energy sink that charges cheaply that automatically picks the cheapest provider.

  Now imagine that battery has some overcapacity that can be sold back to the grid when prices are highest (aka. demand is high). Now you have an apartment building that buys energy when it is cheap and sells energy when it is expensive and it has enough capacity to serve its own needs.

  Add EVs to the mix and battery to the grid technology and you have a mobile battery capacity that when it is not driving around can be plugged in to act both as an energy source and sink as well.

  Now make the rest of the energy available to industrial users that can install their own solar panels and you have even more supply and demand.

  The key bottleneck in this system is the current oligarchy that controls prices: the existing energy companies. They make the most profit when prices are high. They don't mind buying in some excess capacity cheaply but they have no incentive to do that when they don't need it. And since they control the market, there's nobody else to sell it to. Worse, since they have fixed cost associated with legacy plants, they have to keep prices high to prevent those becoming loss leaders. The whole system is geared towards protectionism rather than efficiency. Once you create an open market for energy, that's no longer sustainable.

• by ISL on 11/7/19, 5:47 AM

  Sounds like someone needs a small aluminum smelter?

• by LAMike on 11/7/19, 5:33 AM

  Might want to buy some of the Power Miners:

  https://powerminingshop.com/

  As chips reach the limits of the cutting edge tech, the only advantage will be how expensive your electricity is rather than replacing chips every 12 months

• by jhoechtl on 11/7/19, 10:41 AM

  I think there is a fundamental flaw in the whole discussion. We are doing alternative energy for two reasons:

  1. As a means for alternative cheap energy; 2. As a means to gain independence from imported energy (oil, coal); 3. As a means to protect the environment

  If a solar farm has to be switched off, because the power can not be sold, apparently 1.) has dominance over 2 and 3. If environment protection would have precedence, consumers should be forced to consume higher priced energy?

• by teamonkey on 11/7/19, 9:02 AM

  Question: what happens to the solar energy when PVs are disconnected? I presume reflected or absorbed as heat, but is a PV under load cooler/less reflective?

• by jmpman on 11/7/19, 5:30 PM

  Would it be cost effective to have vats of aluminum oxide sitting idle, waiting for these negative pricing events? The raw material is cheap, and the electrodes are only worn away when actively smelting. With interest rates so low, the idle capital may not be a major impact to profitability.

• by growlist on 11/7/19, 9:42 AM

  I'll add my ideas to the others for using the excess power:

  1. drill a big storage hole of some kind. Surely Australia could use a gigantic underground reservoir 2. install a plant next to the solar farm and make compressed gases from the atmosphere

• by lightedman on 11/7/19, 6:01 AM

  It's a PV farm, they could just take parts of the PV grid offline instead of playing arbitrage games such as paying others to take their power or trying to build storage systems (though any half-smart PV solar farm has some minor storage on-site.) It's not like the entire system is hooked to a singular large MPPT controller. They aren't bound by the typical issues of energy generation which nuclear or constant hydro-electric have.

  BTW: Did you know solar panels can self-immolate if seriously defective during manufacture?

• by pbreit on 11/7/19, 6:34 AM

  This doesn't make a ton of sense and the article is so poorly written it's hard to understand what's going on.

• by lazyjones on 11/7/19, 8:22 AM

  Buy some Tesla Megapacks, install some DC fast chargers on-site and sell electricity for 0.2$/KWh or so all day long.

• by g82918 on 11/7/19, 5:01 AM

  It seems almost silly that we can generate more energy than we can use some, but not all of, the time.

• by alex_duf on 11/7/19, 10:14 AM

  I think this is a great news, there's now a financial incentive to invest into storage

• by tinus_hn on 11/7/19, 6:31 PM

  ‘Solar farm can switch off every second day in case of negative prices’

• by aussieguy1234 on 11/7/19, 7:50 AM

  Instead of switching off, why not just mine crypto?