4 ms·

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 g

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.
  - jordwest 5y ago
    > 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. Can confirm, did some work in a power station. The frequency is displayed in very large font front and centre of the control room. It's really a leading indicator of the health of the network, so any fluctuations are monitored very closely and the operators would sometimes jump on the phone with nearby generators if it starts doing something unexpected. Another interesting fact, in the control room there was also an indicator showing the frequency adjusted clock time. Older clocks (like many of those bedside alarms) used the 50/60Hz as a clock rather than using a built-in crystal, so it was important to make sure that over time the frequency did average out to 50/60Hz to keep clocks in sync.
- fy20 5y ago
  It's a bit unintuitive at first, but the voltage would stay the same, however the frequency would increase. For home users this isn't such an issue today (everything in my home with a motor, has a three phase motor, so there is an inverter inside to convert that from 2 phase AC -> DC -> 3 phase AC, so the frequency doesn't matter), but for industry it is as a lot of equipment needs 60/50Hz and will be damaged with something outside it's operating range. At multiple places in the power grid there are systems that will disconnect if the grid frequency falls or rises outside it's operating range. This is what caused the cascading failures and power outage over most of the country in the UK in 2019: https://www.ofgem.gov.uk/publications/investigation-9-august-2019-power-outage https://www.ofgem.gov.uk/publications/investigation-9-august...
- deleted 5y ago
  [deleted]
- liketochill 5y ago
  Turbine speed is controlled by a device called a governor. When the power in exceeds the power out and the speed (frequency) increases the governor lays off the throttle to stop then speed from increasing further. Throttle could be water, steam, gas, etc. Then the grid operator will have some units that operate in “AGC” automatic generation control which would reduce their output until the frequency is back at 60Hz. Units start to trip below 58 and above 62 Hz ish, and turbines should respond to 0.01 Hz change in frequency within 200 ms according to the IEEE 125 guideline, so even a 0.5 Hz deviation is huge. A 1 Hz deviation is a major event that would result from a mismatch on the order of gigawatts

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.
- jordwest 5y ago
  > 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. Can confirm, did some work in a power station. The frequency is displayed in very large font front and centre of the control room. It's really a leading indicator of the health of the network, so any fluctuations are monitored very closely and the operators would sometimes jump on the phone with nearby generators if it starts doing something unexpected. Another interesting fact, in the control room there was also an indicator showing the frequency adjusted clock time. Older clocks (like many of those bedside alarms) used the 50/60Hz as a clock rather than using a built-in crystal, so it was important to make sure that over time the frequency did average out to 50/60Hz to keep clocks in sync.
fy20 5y ago
It's a bit unintuitive at first, but the voltage would stay the same, however the frequency would increase. For home users this isn't such an issue today (everything in my home with a motor, has a three phase motor, so there is an inverter inside to convert that from 2 phase AC -> DC -> 3 phase AC, so the frequency doesn't matter), but for industry it is as a lot of equipment needs 60/50Hz and will be damaged with something outside it's operating range. At multiple places in the power grid there are systems that will disconnect if the grid frequency falls or rises outside it's operating range. This is what caused the cascading failures and power outage over most of the country in the UK in 2019: https://www.ofgem.gov.uk/publications/investigation-9-august-2019-power-outage https://www.ofgem.gov.uk/publications/investigation-9-august...
deleted 5y ago
[deleted]
liketochill 5y ago
Turbine speed is controlled by a device called a governor. When the power in exceeds the power out and the speed (frequency) increases the governor lays off the throttle to stop then speed from increasing further. Throttle could be water, steam, gas, etc. Then the grid operator will have some units that operate in “AGC” automatic generation control which would reduce their output until the frequency is back at 60Hz. Units start to trip below 58 and above 62 Hz ish, and turbines should respond to 0.01 Hz change in frequency within 200 ms according to the IEEE 125 guideline, so even a 0.5 Hz deviation is huge. A 1 Hz deviation is a major event that would result from a mismatch on the order of gigawatts