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Paywall article so I’ll just share a random interesting fact. Solar is so prevalent in Australia that power prices regularly go negative as supply exceeds dema

Paywall article so I’ll just share a random interesting fact. Solar is so prevalent in Australia that power prices regularly go negative as supply exceeds demand. One interesting thing that is starting to happen is companies like Tesla build huge battery banks and buy cheap or negative price power and then sell it back a few hours later when it is much more expensive.

spoonjim 5y ago
Why would the price go negative? If you have excess solar capacity why would you need to pay someone to take it from you? Why not just sink it into the ground or something?
- foobar33333 5y ago
  It's some what of a recent thing. They are bringing in new laws to allow the grid to shut off your solar feed back when there is an oversupply but currently it just causes a big problem and negative prices.
- d1str0 5y ago
  That infrastructure might not exist. Also, you probably dont get money, you probably get credit. So having batteries connected benefits the grid rather than wasting electricity.
- adrusi 5y ago
  It's not actually that easy to burn away excess power when you're operating at grid scale.
  - jeffbee 5y ago
    It is trivially easy to disconnect solar panels from the grid in times of low demand.
    - adrusi 5y ago
      This is by no means something I know much about, but I understood that disconnecting a panel causes it to heat up from sunlight to the point that it can reduce its useful lifespan.
      - jeffbee 5y ago
        That is somewhat true of exotic panels that nobody uses for utility-scale power, but it's not a necessary outcome of disconnecting a source from the grid. It doesn't have to be disconnected from everything. When removed from the grid, they can just be shorted.
        adrusi 5y ago
        How does shorting it reduce the heat it experiences? Short it through something that creates a load, like a coil?
- Dylan16807 5y ago
  > If you have excess solar capacity why would you need to pay someone to take it from you? You don't. Usually there's some external reason that selling renewables at a slight loss is still profitable. Like tax incentives or production quotas or fixed-rate contracts. Then coal plants get dragged along because they can't change output quickly. > Why not just sink it into the ground or something? That takes equipment, which takes money. They won't install it if sporadic negative prices are cheaper.
- ezzaf 5y ago
  Utility scale generation of renewables in Australia creates tradable certificates. These are required by law to be purchased by energy retailers to meet the Renewable Energy Target. If that certificate trades at $50, I can sell my power for -$40 and still make $10 profit. Putting further downwards pressure on prices, small scale solar generators (eg homes) generally have a fixed price for solar exports. The spot price could be -$1000 but they will still be getting paid $100 under their retail contract. So they have no incentive to stop generating, even when the price is negative. The market regulator is attempting to change this, but consumers are resistant to having to pay to generate power or allow their system to be remotely switched off. Coal generators won't switch off either as they take a while to ramp up and down, and are sometimes are directed (and paid) to remain running to provide system stability.
- pridkett 5y ago
  With excess solar you usually just detach the inverter. In some areas, like Southern California, this can be forced during peak solar times. As for the price going negative - this isn’t a super new phenomenon. I remember learning about coal power plants in West Virginia having negative power prices in the late night. This is simply because it’s hard to spin down and scale up these loads. It’s more cost effective to pay people to take the energy for a short time than it is to shut down the plant and potentially destabilize the grid in the future. As for sinking it into the ground - there’s lots of research there. Tesla is pushing utility scale batteries. Other efforts move large rocks up and down hills, convert water to hydrogen and oxygen, or simply pump water up hill. Each of these has some losses and hardware costs to get going and efficiency isn’t great. At a home you can get a set of Tesla Powerwalls and essentially do this - but you’ll find they cost about $6k each and eat about $7/mo in electric losses (at the $0.23/kWh price I pay - thanks, Eversource).
  - DaiPlusPlus 5y ago
    Forgive this ignorant question… but what happens if people don’t “burn electricity” during negative pricing? Would the voltage on the grid start to fluctuate? What kinds of effects would we see? What happens to the generators in turbine-halls if they kept on running?
    - Armisael16 5y ago
      It becomes easier and easier to meet the needs of the grid (because less energy is being taken out), so the turbines speed up. This increases the frequency of the electrical oscillations on the grid. If the deviation is small this is mostly noticeable in clocks running too fast, but as the deviation increases large spinning structures start spinning too fast and break, often violently.
    - chihuahua 5y ago
      When demand exceeds supply, the grid frequency goes below the 60Hz target. From what I've read, the frequency of the grid is closely monitored at all times, and a lot of effort goes into keeping it at or near the target. I assume in this situation, the voltage also goes below the target, because people talk about "brown-outs" which I believe means that you get less than 120V from an outlet. I can speculate that when supply exceeds demand, this creates a similar problem, but in the opposite direction.
- imtringued 5y ago
  In Germany solar power has a feed in tariff of 8 cent per kWh. The operator of solar power can therefore feed it in at negative prices and still make money. Germany has an extremely perverse system called EEG. The feed in tariff is paid by a fee called the EEG surcharge. Large industrial users are exempt. Meaning retail consumers pay for the electricity bill of industrial companies. Therefore the cheaper the electricity on the spot market, the more expensive the retail rate. Hypothetical scenario: We have a persistent -8 cent spot market price. Industrial companies get paid for consuming electricity. However, retail doesn't benefit from the negative pricing. If the spot market is -8 cent and the feed in tariff is 8 cent then the EEG has to subsidize 16 cents. Thus electricity for retail gets 16 cents more expensive to get back to the original 8 cent. However, this isn't the whole story. We still have to pay for industrial consumption. If 33% of energy usage is industry and is exempt then every retail kWh has to pay 0.5 industrial kWH. So we now end up at 24 cents for electricity. If you were to add taxes (yes you pay them on top of the EEG surcharge) and grid maintenance costs, etc you would probably end up with 40 cents per kWH. This was just an extreme example but it explains around 16% of Germany's extremely high electricity price. Getting rid of the various taxes on electricity would lower the costs by 20% without changing anything about the grid or making it less profitable.
hoppyhoppy2 5y ago
Someone posted a mirror link to bypass the paywall here in the comments almost 90 minutes before your comment.

spoonjim 5y ago

Why would the price go negative? If you have excess solar capacity why would you need to pay someone to take it from you? Why not just sink it into the ground or something?

foobar33333 5y ago
It's some what of a recent thing. They are bringing in new laws to allow the grid to shut off your solar feed back when there is an oversupply but currently it just causes a big problem and negative prices.
d1str0 5y ago
That infrastructure might not exist. Also, you probably dont get money, you probably get credit. So having batteries connected benefits the grid rather than wasting electricity.
adrusi 5y ago
It's not actually that easy to burn away excess power when you're operating at grid scale.
- jeffbee 5y ago
  It is trivially easy to disconnect solar panels from the grid in times of low demand.
  - adrusi 5y ago
    This is by no means something I know much about, but I understood that disconnecting a panel causes it to heat up from sunlight to the point that it can reduce its useful lifespan.
    - jeffbee 5y ago
      That is somewhat true of exotic panels that nobody uses for utility-scale power, but it's not a necessary outcome of disconnecting a source from the grid. It doesn't have to be disconnected from everything. When removed from the grid, they can just be shorted.
      - adrusi 5y ago
        How does shorting it reduce the heat it experiences? Short it through something that creates a load, like a coil?
Dylan16807 5y ago
> If you have excess solar capacity why would you need to pay someone to take it from you? You don't. Usually there's some external reason that selling renewables at a slight loss is still profitable. Like tax incentives or production quotas or fixed-rate contracts. Then coal plants get dragged along because they can't change output quickly. > Why not just sink it into the ground or something? That takes equipment, which takes money. They won't install it if sporadic negative prices are cheaper.
ezzaf 5y ago
Utility scale generation of renewables in Australia creates tradable certificates. These are required by law to be purchased by energy retailers to meet the Renewable Energy Target. If that certificate trades at $50, I can sell my power for -$40 and still make $10 profit. Putting further downwards pressure on prices, small scale solar generators (eg homes) generally have a fixed price for solar exports. The spot price could be -$1000 but they will still be getting paid $100 under their retail contract. So they have no incentive to stop generating, even when the price is negative. The market regulator is attempting to change this, but consumers are resistant to having to pay to generate power or allow their system to be remotely switched off. Coal generators won't switch off either as they take a while to ramp up and down, and are sometimes are directed (and paid) to remain running to provide system stability.
pridkett 5y ago
With excess solar you usually just detach the inverter. In some areas, like Southern California, this can be forced during peak solar times. As for the price going negative - this isn’t a super new phenomenon. I remember learning about coal power plants in West Virginia having negative power prices in the late night. This is simply because it’s hard to spin down and scale up these loads. It’s more cost effective to pay people to take the energy for a short time than it is to shut down the plant and potentially destabilize the grid in the future. As for sinking it into the ground - there’s lots of research there. Tesla is pushing utility scale batteries. Other efforts move large rocks up and down hills, convert water to hydrogen and oxygen, or simply pump water up hill. Each of these has some losses and hardware costs to get going and efficiency isn’t great. At a home you can get a set of Tesla Powerwalls and essentially do this - but you’ll find they cost about $6k each and eat about $7/mo in electric losses (at the $0.23/kWh price I pay - thanks, Eversource).
- DaiPlusPlus 5y ago
  Forgive this ignorant question… but what happens if people don’t “burn electricity” during negative pricing? Would the voltage on the grid start to fluctuate? What kinds of effects would we see? What happens to the generators in turbine-halls if they kept on running?
  - Armisael16 5y ago
    It becomes easier and easier to meet the needs of the grid (because less energy is being taken out), so the turbines speed up. This increases the frequency of the electrical oscillations on the grid. If the deviation is small this is mostly noticeable in clocks running too fast, but as the deviation increases large spinning structures start spinning too fast and break, often violently.
  - chihuahua 5y ago
    When demand exceeds supply, the grid frequency goes below the 60Hz target. From what I've read, the frequency of the grid is closely monitored at all times, and a lot of effort goes into keeping it at or near the target. I assume in this situation, the voltage also goes below the target, because people talk about "brown-outs" which I believe means that you get less than 120V from an outlet. I can speculate that when supply exceeds demand, this creates a similar problem, but in the opposite direction.
imtringued 5y ago
In Germany solar power has a feed in tariff of 8 cent per kWh. The operator of solar power can therefore feed it in at negative prices and still make money. Germany has an extremely perverse system called EEG. The feed in tariff is paid by a fee called the EEG surcharge. Large industrial users are exempt. Meaning retail consumers pay for the electricity bill of industrial companies. Therefore the cheaper the electricity on the spot market, the more expensive the retail rate. Hypothetical scenario: We have a persistent -8 cent spot market price. Industrial companies get paid for consuming electricity. However, retail doesn't benefit from the negative pricing. If the spot market is -8 cent and the feed in tariff is 8 cent then the EEG has to subsidize 16 cents. Thus electricity for retail gets 16 cents more expensive to get back to the original 8 cent. However, this isn't the whole story. We still have to pay for industrial consumption. If 33% of energy usage is industry and is exempt then every retail kWh has to pay 0.5 industrial kWH. So we now end up at 24 cents for electricity. If you were to add taxes (yes you pay them on top of the EEG surcharge) and grid maintenance costs, etc you would probably end up with 40 cents per kWH. This was just an extreme example but it explains around 16% of Germany's extremely high electricity price. Getting rid of the various taxes on electricity would lower the costs by 20% without changing anything about the grid or making it less profitable.

hoppyhoppy2 5y ago

Someone posted a mirror link to bypass the paywall here in the comments almost 90 minutes before your comment.