3 ms·

Again, the demand curve is the opposite of what you claim: peak production happens during the night, at around 9 pm, not during the day. You'd need to supply mo

Again, the demand curve is the opposite of what you claim: peak production happens during the night, at around 9 pm, not during the day. You'd need to supply more energy during periods of non-production, not less. You can't get away with 50% output at night, unless you have some other energy source picking up the slack. And remember, during the winter you're getting less than 12 hours of sunlight, maybe even less than that if you consider that cloud cover eliminates 75-90% of solar power output. These factors do depend on geography. Hotter climates do see more energy use during the day to power A/C. But on the flip side, colder climates see even more energy demand during the night to heat homes. And unfortunately this also coincides when solar is producing the least amount of energy due to fewer sunlight hours, axial tilt, and more cloud cover. There are niches solar can carve out: Las Vegas and Australia have loads of empty space, clear weather, and hydroelectricity that can fill in periods of non-production. But nuclear power is a much more flexible solution. All you really need is water to cool the reactor, and 80% of the population lives within a hundred miles of the coastline (you just need water, not fresh water).

nicoburns 3y ago
Energy use for heating can be quite easily reduced just by insulating houses (and installing more efficient heating equipment such as heat pumps). Do we have any idea what the cause of that 9pm spike is? That seems like a bizarre time to be the peak to me (I can't work out what the primary energy users would be at that time).
- Manuel_D 3y ago
  Replacing gas heating with heat pumps is going to increase, not reduce, electricity use.
  - Retric 3y ago
    Replacing gas heating with solar thermal is even cheaper and doesn’t. Electric heat pumps are viable when electricity is cheap or demand is low and you want AC, the more they drive up electric costs the more alternatives become viable. Net effect you tend to see them in areas where there’s a surplus of winter electricity which also tends to be places with minimal demand for heating like Virginia rather than Mane. 46% in South Carolina, 42% in North Carolina, 30% in Virginia etc: https://www.statista.com/statistics/1327164/share-of-households-unsing-central-heat-pumps-by-state-us/ https://www.statista.com/statistics/1327164/share-of-househo...
    - Manuel_D 3y ago
      Solar thermal heating is not going to produce much energy in the winter when there's fewer hours of sunlight and more hours of cloud coverage - which just so happens to coincide with places that would need heating during the winter. Solar thermal performance is worse with diffuse light (read: overcast days) than PV solar, in fact that's a big part of why it was largely abandoned in the 2000s.
      - Retric 3y ago
        The main advantage of solar thermal is it’s really cheap so you can just scale collection to cover winter heating. That’s why adoption is so high in China even relatively far north. As to the US, the cost savings just isn’t that appealing for most people. It’s frankly ugly, complicated, and has minimal payoff at current prices.* Passive solar design can have significant benefits while looking much nicer. But if you’re increasing the cost of electricity or gas then suddenly it’s looking significantly more attractive. * Except of course when people want to heat a pool, that takes crazy amounts of energy. “Israel became the world leader in the use of solar energy per capita with 85% of households using solar thermal systems (3% of the primary national energy consumption)” https://en.wikipedia.org/wiki/Solar_water_heating https://en.wikipedia.org/wiki/Solar_water_heating
        Manuel_D 3y ago
        As per your link, solar thermal water heating is very variable depending on geography: > The amount of heat delivered by a solar water heating system depends primarily on the amount of heat delivered by the sun at a particular place (insolation). In the tropics insolation can be relatively high, e.g. 7 kWh/m2 per day, versus e.g., 3.2 kWh/m2 per day in temperate areas. Because of this, many solar thermal systems are supplemented by convention heaters. > In winter, the percentage of your hot water heated by the sun drops to as low as 10-20%—as you might expect with short days and weak sun in December. That’s why practically every solar water installed in the US will be connected to a backup conventional water heater to ensure that your hot water needs continue to be met even in January. https://www.aspessolarproducts.com/solar-water-heater/how-does-a-solar-water-heater-work-in-winter.html https://www.aspessolarproducts.com/solar-water-heater/how-do...
Retric 3y ago
Again batteries smooth over instantaneous demand. If you really want to model things you need to consider the vast drop off between midnight and 5 am in which that steady state I talked about would be wasted. Batteries don’t really care about when the peak is just the total demand minus power production. And again steady state like nuclear looks terrible by comparison. Running summer numbers you see an extension in the number of hours the panels are producing which then reduced the gap you need to fill with batteries. Winter sees the reverse as average output drops but conversely batteries are storing a higher percentage of total energy produced. Sizing is further adjusted based on expectations for daily output not hypothetical maximums. Which of those is more critical depends on local conditions but the grid is always sized for absolute worst case not the average one. There’s lots of micro optimization such as aiming panels East or West to shift production, local hydropower and wind resources etc etc. None of which is that important compared to the overall effect I was describing where batteries are sized to the daily output not the peak output. The important number is the cost which is running 60$/MWh vs the daily demand not whatsoever the nameplate numbers people love to talk about to make projects seem more important.
- Manuel_D 3y ago
  And yet again: batteries are not available at a scale where they can even remotely smooth over demand. Even just provisioning 1 hour of storage for the USA requires 500 GWh of storage. A steady state like nuclear works just fine for the grid: it's only a problem for intermittent sources that are made redundant by a source of decarbonized energy that works 24/7. The disparity between peak and trough energy demand is not that great: it's typically 20-30%. Pointing to one specific project is not relevant: we can't replicate this project to the point where demand is fulfilled because that would require an order of magnitude more batteries than are produced.
  - Retric 3y ago
    We don’t need batteries on that scale any time soon. Let’s project out 25 years and we might need 3-5 hours of 100% grid electricity storage nationwide depending on your assumptions but that’s about it. It’s not like hydroelectricity is going away anytime soon and that’s extremely flexible not just in terms of time of day but also days of the week, and wind doesn’t care when the sun is shining, and solar can shift east to west to cover more of peak evening demand on the east coast and peak etc etc. We can quibble about the numbers but it’s just not important. As to storage we’re talking 4h * 500 GWh +/- whatever that’s only 2,000 GWh ish, but the specifics aren’t important. By comparison we’re talking a nearly 100% EV cars so 75 kWh per car * 282 million, that’s ~ 21,150 GWh. Those numbers are so huge we could bump things to 16 hours of electricity and it’s still fairly trivial by comparison. Build enough generation and storage could actually be even lower, it’s just a cost tradeoff and renewables are really cheap. (Edit: There’s been a lot of research into it and there’s plenty of raw materials for a 100% EV transition and on this timescale ramping battery manufacturing isn’t an issue.) Also, that 30% number is wildly incorrect. Even just over a week the CA demand is expected to go from a low of 24,867 to a high of 42,007 in a single day, but you can’t design a grid for a single day. https://www.caiso.com/TodaysOutlook/Pages/default.aspx#section-7day-ra-capacity-trend https://www.caiso.com/TodaysOutlook/Pages/default.aspx#secti... Things look similar nationally, we don’t have enough interconnects to really smooth things out and even if you did the daily variation is quite significant. However, the actual disparity between peak annual demand and minimal annual is vastly higher and you can’t smooth it out. That delta is why idling a grid of mostly nuclear power would be so wildly expensive. Without France style exporting and importing from non nuclear countries cost go insane. The only way it’s even vaguely viable in the US is with similarly vast amounts of storage. But at that point adding just a little cheap solar + wind saves money, and that keeps being true as you use less and less nuclear. TLDR; Cost effective mostly nuclear grid needs even more storage due to capacity factor issues when you can’t follow France’s model of importing and exporting a large fraction of your power to non nuclear countries.

nicoburns 3y ago

Energy use for heating can be quite easily reduced just by insulating houses (and installing more efficient heating equipment such as heat pumps). Do we have any idea what the cause of that 9pm spike is? That seems like a bizarre time to be the peak to me (I can't work out what the primary energy users would be at that time).

Manuel_D 3y ago
Replacing gas heating with heat pumps is going to increase, not reduce, electricity use.
- Retric 3y ago
  Replacing gas heating with solar thermal is even cheaper and doesn’t. Electric heat pumps are viable when electricity is cheap or demand is low and you want AC, the more they drive up electric costs the more alternatives become viable. Net effect you tend to see them in areas where there’s a surplus of winter electricity which also tends to be places with minimal demand for heating like Virginia rather than Mane. 46% in South Carolina, 42% in North Carolina, 30% in Virginia etc: https://www.statista.com/statistics/1327164/share-of-households-unsing-central-heat-pumps-by-state-us/ https://www.statista.com/statistics/1327164/share-of-househo...
  - Manuel_D 3y ago
    Solar thermal heating is not going to produce much energy in the winter when there's fewer hours of sunlight and more hours of cloud coverage - which just so happens to coincide with places that would need heating during the winter. Solar thermal performance is worse with diffuse light (read: overcast days) than PV solar, in fact that's a big part of why it was largely abandoned in the 2000s.
    - Retric 3y ago
      The main advantage of solar thermal is it’s really cheap so you can just scale collection to cover winter heating. That’s why adoption is so high in China even relatively far north. As to the US, the cost savings just isn’t that appealing for most people. It’s frankly ugly, complicated, and has minimal payoff at current prices.* Passive solar design can have significant benefits while looking much nicer. But if you’re increasing the cost of electricity or gas then suddenly it’s looking significantly more attractive. * Except of course when people want to heat a pool, that takes crazy amounts of energy. “Israel became the world leader in the use of solar energy per capita with 85% of households using solar thermal systems (3% of the primary national energy consumption)” https://en.wikipedia.org/wiki/Solar_water_heating https://en.wikipedia.org/wiki/Solar_water_heating
      - Manuel_D 3y ago
        As per your link, solar thermal water heating is very variable depending on geography: > The amount of heat delivered by a solar water heating system depends primarily on the amount of heat delivered by the sun at a particular place (insolation). In the tropics insolation can be relatively high, e.g. 7 kWh/m2 per day, versus e.g., 3.2 kWh/m2 per day in temperate areas. Because of this, many solar thermal systems are supplemented by convention heaters. > In winter, the percentage of your hot water heated by the sun drops to as low as 10-20%—as you might expect with short days and weak sun in December. That’s why practically every solar water installed in the US will be connected to a backup conventional water heater to ensure that your hot water needs continue to be met even in January. https://www.aspessolarproducts.com/solar-water-heater/how-does-a-solar-water-heater-work-in-winter.html https://www.aspessolarproducts.com/solar-water-heater/how-do...

Retric 3y ago

Again batteries smooth over instantaneous demand. If you really want to model things you need to consider the vast drop off between midnight and 5 am in which that steady state I talked about would be wasted. Batteries don’t really care about when the peak is just the total demand minus power production. And again steady state like nuclear looks terrible by comparison. Running summer numbers you see an extension in the number of hours the panels are producing which then reduced the gap you need to fill with batteries. Winter sees the reverse as average output drops but conversely batteries are storing a higher percentage of total energy produced. Sizing is further adjusted based on expectations for daily output not hypothetical maximums. Which of those is more critical depends on local conditions but the grid is always sized for absolute worst case not the average one. There’s lots of micro optimization such as aiming panels East or West to shift production, local hydropower and wind resources etc etc. None of which is that important compared to the overall effect I was describing where batteries are sized to the daily output not the peak output. The important number is the cost which is running 60$/MWh vs the daily demand not whatsoever the nameplate numbers people love to talk about to make projects seem more important.

Manuel_D 3y ago
And yet again: batteries are not available at a scale where they can even remotely smooth over demand. Even just provisioning 1 hour of storage for the USA requires 500 GWh of storage. A steady state like nuclear works just fine for the grid: it's only a problem for intermittent sources that are made redundant by a source of decarbonized energy that works 24/7. The disparity between peak and trough energy demand is not that great: it's typically 20-30%. Pointing to one specific project is not relevant: we can't replicate this project to the point where demand is fulfilled because that would require an order of magnitude more batteries than are produced.
- Retric 3y ago
  We don’t need batteries on that scale any time soon. Let’s project out 25 years and we might need 3-5 hours of 100% grid electricity storage nationwide depending on your assumptions but that’s about it. It’s not like hydroelectricity is going away anytime soon and that’s extremely flexible not just in terms of time of day but also days of the week, and wind doesn’t care when the sun is shining, and solar can shift east to west to cover more of peak evening demand on the east coast and peak etc etc. We can quibble about the numbers but it’s just not important. As to storage we’re talking 4h * 500 GWh +/- whatever that’s only 2,000 GWh ish, but the specifics aren’t important. By comparison we’re talking a nearly 100% EV cars so 75 kWh per car * 282 million, that’s ~ 21,150 GWh. Those numbers are so huge we could bump things to 16 hours of electricity and it’s still fairly trivial by comparison. Build enough generation and storage could actually be even lower, it’s just a cost tradeoff and renewables are really cheap. (Edit: There’s been a lot of research into it and there’s plenty of raw materials for a 100% EV transition and on this timescale ramping battery manufacturing isn’t an issue.) Also, that 30% number is wildly incorrect. Even just over a week the CA demand is expected to go from a low of 24,867 to a high of 42,007 in a single day, but you can’t design a grid for a single day. https://www.caiso.com/TodaysOutlook/Pages/default.aspx#section-7day-ra-capacity-trend https://www.caiso.com/TodaysOutlook/Pages/default.aspx#secti... Things look similar nationally, we don’t have enough interconnects to really smooth things out and even if you did the daily variation is quite significant. However, the actual disparity between peak annual demand and minimal annual is vastly higher and you can’t smooth it out. That delta is why idling a grid of mostly nuclear power would be so wildly expensive. Without France style exporting and importing from non nuclear countries cost go insane. The only way it’s even vaguely viable in the US is with similarly vast amounts of storage. But at that point adding just a little cheap solar + wind saves money, and that keeps being true as you use less and less nuclear. TLDR; Cost effective mostly nuclear grid needs even more storage due to capacity factor issues when you can’t follow France’s model of importing and exporting a large fraction of your power to non nuclear countries.