8 ms·

Because when you add non dispatchable energy sources to your grid, without storage you have to keep the rest ready to function. Unless you agree to have enough

Because when you add non dispatchable energy sources to your grid, without storage you have to keep the rest ready to function. Unless you agree to have enough electricity only when the sun shines or the wind blows... Otherwise at best you can adjust the output of your dispatchable energy sources (mostly coal and nuclear) to make up for the unpredictiveness of the solar and wind. But you still need the same capacity. This is why Germany and Spain, 2 countries who invested a lot in solar and wind, continued to grow their use of traditional power plant at the same pace as before they started on renewable. For Germany it's even worse because they decided to stop using nuclear, so they burn even more coal than before.

pydry 5y ago
Coal and nuclear are not dispatchable. Their output is constant. They take about a day or more to ramp up and down. This is the reason why electricity was traditionally cheaper at night. Germany also doesnt burn more coal than before. The amount of coal they burn has been falling steadily since about 2010.
- Krssst 5y ago
  Nuclear can do load following in France. According to this article (French), reactors can adjust power output by 80% in 30 minutes: https://www.lesechos.fr/2016/02/lelectricien-fait-de-plus-en-plus-varier-sa-production-nucleaire-210246 https://www.lesechos.fr/2016/02/lelectricien-fait-de-plus-en... (I am curious about more details since the figure lack context. It is not clear whether the 80% applies to nominal power.) Edit: the English wikipedia article on load following is actually much clearer: https://en.m.wikipedia.org/wiki/Load_following_power_plant#Nuclear_power_plants https://en.m.wikipedia.org/wiki/Load_following_power_plant#N... > Modern nuclear plants with light water reactors are designed to have maneuvering capabilities in the 30-100% range with 5%/minute slope.
  - pfdietz 5y ago
    Load following with nuclear is hideously uneconomical though. Even in France they use non-nuclear for much of that, for example by selling or buying power to/from neighboring countries. In any case, the problem with nuclear is that existing nuclear technology does not decarbonize the world. World primary energy demand is 18 TW. This would require 6000 nuclear power plants (3GW(th) each), if today's reactors are used they'd consume (the 235U in) 1.5 million tonnes of natural uranium per year. Total world uranium resource is a shade over 6 million tonnes, so it would run out in four years. To power the world with nuclear one either needs seawater uranium extraction (scaled up by 12 orders of magnitude from what's been done so far; 170 km^2 of ocean area for each of those reactors; the power/area is much worse than PV) or breeder reactors (which France has given up on.)
    - JamesBarney 5y ago
      Sure but surely we'll run into the same issues with rare earth metals when building out over 18,000,000 solar farms. The numbers you use for uranium resources, are the amount that is economically extractable right now at current prices. Given that only 14% of the cost of a nuclear plant is raw fuel we have lots of room to increase to increase the cost of extraction. And many places abandoned breeder reactors because the cost of uranium is cheap enough right now that fuel efficiency doesn't matter.
      - pfdietz 5y ago
        Solar farms don't use rare earth metals, so, no, it's not the same at all. France's abandonment of their breeder program is the tell that they don't think there's any significant chance that nuclear will scale to power the world anytime soon.
    - ZeroGravitas 5y ago
      This is the same numerical sleight of hand that fossil fuel boosters use. Roughly half of the primary energy demand isn't actually used, it's just wasted as heat. Replacing fossil fuels with nuclear or renewables would mean that much less primary energy would be needed due to the efficiency gains of electrification. The real issue with nuclear is that it needs all the same stuff as renewables (better grid connections, pink hydrogen production, demand management, EVs, hydrogen based flight and shipping) in order to keep costs reasonable but still just costs more because solar and wind are much cheaper.
  - nicoburns 5y ago
    They can, but as most of the cost of nuclear is fixed costs, they're very expensive per unit of energy when used in this way (as you get less energy overall over the lifetime of the plant). As nuclear is already one of the most expensive forms of energy this quickly becomes prohibitive.
- taneq 5y ago
  They take a day or more to start or stop. When running they're still not exactly nimble (which is why we have peaking plants) but their response time is an hour or two, not a day. Even old plants ramp at 1%+ of maximum power per minute giving one hour as a very achievable 40%-to-100% ramp up. Newer designs are 5-10x as fast. Not arguing against renewables here but this 1+ day response time figure gets quoted a lot. (eg. my father-in-law uses it and I've always thought it was sketchy, your post just pushed me over the edge to go look it up. ;) Source: Graph on page 10 of https://usea.org/sites/default/files/092014_Increasing%20the%20flexibility%20of%20coal-fired%20power%20plants_ccc242.pdf https://usea.org/sites/default/files/092014_Increasing%20the...
Gravityloss 5y ago
The big trick with natural gas, coal and oil energy is that if it exists but doesn't run, it doesn't produce much emissions. So, if you have medium amounts of solar and wind, it's fine keeping the gas plants in reserve and maybe having to use them on a particularly cold day once every other year. A gas plant is very cheap from investment perspective. From total emissions point of view it is also fine. (These exceptionally cold windless winter days are waved as examples of the unsuitability of wind and solar.) Of course if your gas pipes leak like crazy, maybe it's best to turn to decommission the plants and network.
_ph_ 5y ago
The point simply is, as long as renewables almost never exceed the grid load, there isn't much to store. Yes, as renewables are exceeding the grid load, storage becomes more important and then storage will be pushed harder. It would also help if some regulations limiting the commercial success of storage would be dropped, like paying the EEG fee on stored electricity. That said, storage is growing, a 1GW DC line to Norway was put into operations recently.
- phicoh 5y ago
  Solar can be switched off at a moments notice. Power from windturbines can also be controlled. So an excess amount of renewables is not a big issue for the grid. Owners of renewable sources may be less happy to switch them off. (In the EU) storage can take the place of fossil when fossil becomes expensive enough. No need to give more subsidies to storage than renewables would get. Excess amounts of renewable can also be used for other purposes, such as producing green hydrogen.
phicoh 5y ago
Without storage, you want a gas turbine to complement renewables. Having a large capacity in the form of gas turbines that is only use occasionally costs money, but has to advantage that all extra renewable energy results in less use of gas and therefor less CO2. So today, we can have a grid that consists of renewables plus gas turbines without any storage.
- pfdietz 5y ago
  And even tomorrow, if the natural gas is replaced with hydrogen. A combined cycle gas turbine power plant might cost 10% of a nuclear plant of equal output. So even if we have to back up the entire fricking grid with CC it's still much cheaper than doing it with nuclear.
  - phicoh 5y ago
    The problem with green hydrogen, is that producing hydrogen from electricity and then putting the hydrogen in a gas turbine to produce electricity is extremely inefficient. So a windfarm backed up by hydrogen may need a significant fraction of the farm to produce hydrogen. In the end, a nuclear power plant might be cheaper. Might be, because we just don't know. Nuclear power plants are insanely expensive at the moment.
    - pfdietz 5y ago
      Yes, it's inefficient. But not much of the grid's energy flows through that path, so the inefficiency doesn't cost you much. For long term storage, or rare outage storage, you want storage with low per-kWh-capacity capital cost, even if that means lower efficiency. And no, nuclear isn't cheaper, even if during the rare times you're burning hydrogen the cost/kWh is high. That's because nuclear needs to be selling at high prices most of the time, including when solar/wind/batteries are able to directly deliver. It's possible other technologies (transmission, demand dispatching, other storage technologies, even natural gas with atmospheric CO2 capture) will be cheaper than grid hydrogen storage. That doesn't help nuclear.
    - ZeroGravitas 5y ago
nicoffeine 5y ago
You have been misinformed, or you didn't do any research. Germany's coal usage was 407 million tons in 1991, and today it's 257 million tons.[1] The last new coal plant was finished last year. "What is expected to be the last new coal plant to come online in Germany entered commercial operation on May 30, more than a decade after it was first planned... The government last year said it would close all 84 of its coal-fired power plants by 2038 as the country moves toward cleaner sources of electricity."[2] Spain is also in a similar phase: "Spain has recently made headlines with good climate news. In May, the government announced plans for full decarbonization. At the beginning of July, half of the country’s coal plants were retired. REN21 analyst Duncan Gibb explains why this is the moment for governments to understand that spending taxpayer money to keep fossil fuel infrastructure afloat is a sunk investment."[3] [1] https://www.worldometers.info/coal/germany-coal/ https://www.worldometers.info/coal/germany-coal/ [2] https://www.powermag.com/germany-brings-last-new-coal-plant-online/ https://www.powermag.com/germany-brings-last-new-coal-plant-... [3] https://www.ren21.net/decarbonise-energy-spain/ https://www.ren21.net/decarbonise-energy-spain/

pydry 5y ago

Coal and nuclear are not dispatchable. Their output is constant. They take about a day or more to ramp up and down. This is the reason why electricity was traditionally cheaper at night. Germany also doesnt burn more coal than before. The amount of coal they burn has been falling steadily since about 2010.

Krssst 5y ago
Nuclear can do load following in France. According to this article (French), reactors can adjust power output by 80% in 30 minutes: https://www.lesechos.fr/2016/02/lelectricien-fait-de-plus-en-plus-varier-sa-production-nucleaire-210246 https://www.lesechos.fr/2016/02/lelectricien-fait-de-plus-en... (I am curious about more details since the figure lack context. It is not clear whether the 80% applies to nominal power.) Edit: the English wikipedia article on load following is actually much clearer: https://en.m.wikipedia.org/wiki/Load_following_power_plant#Nuclear_power_plants https://en.m.wikipedia.org/wiki/Load_following_power_plant#N... > Modern nuclear plants with light water reactors are designed to have maneuvering capabilities in the 30-100% range with 5%/minute slope.
- pfdietz 5y ago
  Load following with nuclear is hideously uneconomical though. Even in France they use non-nuclear for much of that, for example by selling or buying power to/from neighboring countries. In any case, the problem with nuclear is that existing nuclear technology does not decarbonize the world. World primary energy demand is 18 TW. This would require 6000 nuclear power plants (3GW(th) each), if today's reactors are used they'd consume (the 235U in) 1.5 million tonnes of natural uranium per year. Total world uranium resource is a shade over 6 million tonnes, so it would run out in four years. To power the world with nuclear one either needs seawater uranium extraction (scaled up by 12 orders of magnitude from what's been done so far; 170 km^2 of ocean area for each of those reactors; the power/area is much worse than PV) or breeder reactors (which France has given up on.)
  - JamesBarney 5y ago
    Sure but surely we'll run into the same issues with rare earth metals when building out over 18,000,000 solar farms. The numbers you use for uranium resources, are the amount that is economically extractable right now at current prices. Given that only 14% of the cost of a nuclear plant is raw fuel we have lots of room to increase to increase the cost of extraction. And many places abandoned breeder reactors because the cost of uranium is cheap enough right now that fuel efficiency doesn't matter.
    - pfdietz 5y ago
      Solar farms don't use rare earth metals, so, no, it's not the same at all. France's abandonment of their breeder program is the tell that they don't think there's any significant chance that nuclear will scale to power the world anytime soon.
  - ZeroGravitas 5y ago
    This is the same numerical sleight of hand that fossil fuel boosters use. Roughly half of the primary energy demand isn't actually used, it's just wasted as heat. Replacing fossil fuels with nuclear or renewables would mean that much less primary energy would be needed due to the efficiency gains of electrification. The real issue with nuclear is that it needs all the same stuff as renewables (better grid connections, pink hydrogen production, demand management, EVs, hydrogen based flight and shipping) in order to keep costs reasonable but still just costs more because solar and wind are much cheaper.
- nicoburns 5y ago
  They can, but as most of the cost of nuclear is fixed costs, they're very expensive per unit of energy when used in this way (as you get less energy overall over the lifetime of the plant). As nuclear is already one of the most expensive forms of energy this quickly becomes prohibitive.
taneq 5y ago
They take a day or more to start or stop. When running they're still not exactly nimble (which is why we have peaking plants) but their response time is an hour or two, not a day. Even old plants ramp at 1%+ of maximum power per minute giving one hour as a very achievable 40%-to-100% ramp up. Newer designs are 5-10x as fast. Not arguing against renewables here but this 1+ day response time figure gets quoted a lot. (eg. my father-in-law uses it and I've always thought it was sketchy, your post just pushed me over the edge to go look it up. ;) Source: Graph on page 10 of https://usea.org/sites/default/files/092014_Increasing%20the%20flexibility%20of%20coal-fired%20power%20plants_ccc242.pdf https://usea.org/sites/default/files/092014_Increasing%20the...

Gravityloss 5y ago

The big trick with natural gas, coal and oil energy is that if it exists but doesn't run, it doesn't produce much emissions. So, if you have medium amounts of solar and wind, it's fine keeping the gas plants in reserve and maybe having to use them on a particularly cold day once every other year. A gas plant is very cheap from investment perspective. From total emissions point of view it is also fine. (These exceptionally cold windless winter days are waved as examples of the unsuitability of wind and solar.) Of course if your gas pipes leak like crazy, maybe it's best to turn to decommission the plants and network.

_ph_ 5y ago

The point simply is, as long as renewables almost never exceed the grid load, there isn't much to store. Yes, as renewables are exceeding the grid load, storage becomes more important and then storage will be pushed harder. It would also help if some regulations limiting the commercial success of storage would be dropped, like paying the EEG fee on stored electricity. That said, storage is growing, a 1GW DC line to Norway was put into operations recently.

phicoh 5y ago
Solar can be switched off at a moments notice. Power from windturbines can also be controlled. So an excess amount of renewables is not a big issue for the grid. Owners of renewable sources may be less happy to switch them off. (In the EU) storage can take the place of fossil when fossil becomes expensive enough. No need to give more subsidies to storage than renewables would get. Excess amounts of renewable can also be used for other purposes, such as producing green hydrogen.

phicoh 5y ago

Without storage, you want a gas turbine to complement renewables. Having a large capacity in the form of gas turbines that is only use occasionally costs money, but has to advantage that all extra renewable energy results in less use of gas and therefor less CO2. So today, we can have a grid that consists of renewables plus gas turbines without any storage.

pfdietz 5y ago
And even tomorrow, if the natural gas is replaced with hydrogen. A combined cycle gas turbine power plant might cost 10% of a nuclear plant of equal output. So even if we have to back up the entire fricking grid with CC it's still much cheaper than doing it with nuclear.
- phicoh 5y ago
  The problem with green hydrogen, is that producing hydrogen from electricity and then putting the hydrogen in a gas turbine to produce electricity is extremely inefficient. So a windfarm backed up by hydrogen may need a significant fraction of the farm to produce hydrogen. In the end, a nuclear power plant might be cheaper. Might be, because we just don't know. Nuclear power plants are insanely expensive at the moment.
  - pfdietz 5y ago
    Yes, it's inefficient. But not much of the grid's energy flows through that path, so the inefficiency doesn't cost you much. For long term storage, or rare outage storage, you want storage with low per-kWh-capacity capital cost, even if that means lower efficiency. And no, nuclear isn't cheaper, even if during the rare times you're burning hydrogen the cost/kWh is high. That's because nuclear needs to be selling at high prices most of the time, including when solar/wind/batteries are able to directly deliver. It's possible other technologies (transmission, demand dispatching, other storage technologies, even natural gas with atmospheric CO2 capture) will be cheaper than grid hydrogen storage. That doesn't help nuclear.
  - ZeroGravitas 5y ago

nicoffeine 5y ago

You have been misinformed, or you didn't do any research. Germany's coal usage was 407 million tons in 1991, and today it's 257 million tons.[1] The last new coal plant was finished last year. "What is expected to be the last new coal plant to come online in Germany entered commercial operation on May 30, more than a decade after it was first planned... The government last year said it would close all 84 of its coal-fired power plants by 2038 as the country moves toward cleaner sources of electricity."[2] Spain is also in a similar phase: "Spain has recently made headlines with good climate news. In May, the government announced plans for full decarbonization. At the beginning of July, half of the country’s coal plants were retired. REN21 analyst Duncan Gibb explains why this is the moment for governments to understand that spending taxpayer money to keep fossil fuel infrastructure afloat is a sunk investment."[3] [1] https://www.worldometers.info/coal/germany-coal/ https://www.worldometers.info/coal/germany-coal/ [2] https://www.powermag.com/germany-brings-last-new-coal-plant-online/ https://www.powermag.com/germany-brings-last-new-coal-plant-... [3] https://www.ren21.net/decarbonise-energy-spain/ https://www.ren21.net/decarbonise-energy-spain/