4 ms·

You're at the low end for heat pump efficiency, but more importantly, you're overlooking the fact that the fossil fuel usage of heat pumps benefits from the abi

You're at the low end for heat pump efficiency, but more importantly, you're overlooking the fact that the fossil fuel usage of heat pumps benefits from the ability to use electricity generated by non-fossil fuel sources. In the US that's a significant fraction of electricity generation and in many places it's the majority of electricity. The ability to combine the electricity produced by chemical energy with nuclear, hydro, solar, wind, etc, gives heat pumps an significant advantage over directly burning fossil fuel for heat if what you care about is fossil fuel usage.

robocat 4y ago
Renewable fuel sources are already nearly 100% in use. So if you add electricity demand, that new demand usually comes from fossil fuel. That is, you need to consider marginal electricity generation.
- ec109685 4y ago
  At worse, it’s replacing natural gas with fossil fuel. At best, it increases demand so more renewables are built.
  - dragontamer 4y ago
    Heating and AC are unlikely to be powered by renewables, because they're highly correlated and bursty. Ex: Your town might be fine with 100MW of power at 60F. But if the temperature drops to 40F, everyone turns on their heaters more, so the entire town uses 150MW or more. So how much renewables do you build? Not 100MW, but 150MW. Which is absurd, no one is going to overbuild capacity like that. And even at 150MW, if the temperature drops to 20F or 10F, even more energy will be used. In contrast, the Fossil Fuel / Natural Gas peaker methodology is to overbuild on capacity, because capacity is extremely cheap. Maybe the town has a 200MW plant for example. You only use what the people need, so the 200MW plant consumes 100MW at 70F, 150MW at 40F, and everyone has capacity left to grow and expand the town. ---------- Renewables are great for baseload / constant loads that are predictable. But weather isn't always predictable. In this example, 100MW of baseload renewables would be ideal, and the gas-peaker plant is used for everything in addition to that.
    - mindslight 4y ago
      You're drastically overstating the case. No, it does not make sense to treat the entirety of heating as non base load (with your anchor of "60F"). On the scale from predictable to not predictable, heating loads are somewhere in the middle. For a given night that ends up having a low of 10F, it would be hard to know that exactly ahead of time, but we have a pretty good idea that it will be below 20F. So that's roughly only (65-10)/(65-20) - 1 = 22% additional heating load that wasn't predictable. Plus HVAC is highly dispatchable - if there is excess electricity that needs to be used, heating an X-to-water heat pump's storage a few extra degrees is a perfect place to use it.
      - dragontamer 4y ago
        You're dramatically underestimating the swing of electricity in practice. https://www.caiso.com/TodaysOutlook/Pages/default.aspx https://www.caiso.com/TodaysOutlook/Pages/default.aspx See September 22, 2022. California required 51,000+ MW of power capacity as the state reached record high temperatures. Just a few days earlier on Sept. 9th, 42,000 MW was all that was needed. See Yesterday: March 31st 2023. California only required 26,000 MW of power capacity. Even then, the low for March 31st was 17,000 MW at midday. Given these stats from the last year... How much baseload should California build out? And how much "peaker" production should California have? -------- The weather swinging +/- more than expected can cause 10,000MW (or 20% shifts) in power in just a couple of days. Seasonal differences are +100%/-50% differences in power capacity. Its because of this that natural gas peaker plants are used. That's why H2 fuel, as inefficient as it is (but a potentially green source) is still being considered. Having day-to-day, or seasonal, storage of power through the use of chemical energy storage is one of the most promising technologies to tackle this problem.
        mindslight 4y ago
        You've switched from talking about heating (presumably in climate that needs a significant amount), to talking about cooling California. I'm not versed in exactly how these numbers shake out to be making informed conclusions, but by your previous argument it doesn't seem like you are either. For example cooling load is going to be positively correlated with solar output. More bursty renewables (solar, wind) means less base load and more peaker plants to handle their droops. And just because a town builds one "200MW peaker plant" doesn't rule out adding renewables (and making the peaker burn less gas), even though the renewables only operate at their full capacity a small part of the time. The only way to figure out what to make sense is to tradeoff specific capex/opex/utilization/revenue, rather than talking in wide-sweeping generalizations. Storage is the general solution to the problem, yes. The easy form of storage that we've become accustomed to is the chemical energy of natural gas. Another is end-user thermal storage, where consumption is accelerated/delayed depending on what the grid needs. Moving away from fossil fuels requires figuring out storage, especially how to utilize the inherent storage/slack we already have, rather than continuing to just take fossil fuels' convenient advantages for granted.
  - legulere 4y ago
    Natural gas is a fossil fuel
- arrrg 4y ago
  We need to go to zero and gas furnaces cannot. (Horribly inefficient synthetic fuels excluded.) In that context current electricity generation does not matter. It‘s an infrastructure change that allows for future zero emissions. Just like EVs.
  - dragontamer 4y ago
    We're at like 12% renewable. The journey from 12% renewable to 30% renewable will be different than the journey from 90% to 100% renewable. The tools in our disposal to reach 20% or 30% are available today, if we can understand them. And also, as long as we don't let perfection be the enemy of good. We will probably never tackle the 90% to 100% problem in our lifetime. It is best to focus upon the problems that are in front of us, and that we can in fact solve or fix within our lives.
    - arrrg 4y ago
      We need to get to zero. Burning gas doesn’t get us to zero. That’s the issue. Given the lifetime of gas furnaces and what we know about climate change it is madness to even consider using them in brand new construction now. Gas was and is the right tech for transitioning. But you seem to be stuck in the 90s or early 2000s when that kind of policy would have made sense. It’s too late and getting later.

robocat 4y ago

Renewable fuel sources are already nearly 100% in use. So if you add electricity demand, that new demand usually comes from fossil fuel. That is, you need to consider marginal electricity generation.

ec109685 4y ago
At worse, it’s replacing natural gas with fossil fuel. At best, it increases demand so more renewables are built.
- dragontamer 4y ago
  Heating and AC are unlikely to be powered by renewables, because they're highly correlated and bursty. Ex: Your town might be fine with 100MW of power at 60F. But if the temperature drops to 40F, everyone turns on their heaters more, so the entire town uses 150MW or more. So how much renewables do you build? Not 100MW, but 150MW. Which is absurd, no one is going to overbuild capacity like that. And even at 150MW, if the temperature drops to 20F or 10F, even more energy will be used. In contrast, the Fossil Fuel / Natural Gas peaker methodology is to overbuild on capacity, because capacity is extremely cheap. Maybe the town has a 200MW plant for example. You only use what the people need, so the 200MW plant consumes 100MW at 70F, 150MW at 40F, and everyone has capacity left to grow and expand the town. ---------- Renewables are great for baseload / constant loads that are predictable. But weather isn't always predictable. In this example, 100MW of baseload renewables would be ideal, and the gas-peaker plant is used for everything in addition to that.
  - mindslight 4y ago
    You're drastically overstating the case. No, it does not make sense to treat the entirety of heating as non base load (with your anchor of "60F"). On the scale from predictable to not predictable, heating loads are somewhere in the middle. For a given night that ends up having a low of 10F, it would be hard to know that exactly ahead of time, but we have a pretty good idea that it will be below 20F. So that's roughly only (65-10)/(65-20) - 1 = 22% additional heating load that wasn't predictable. Plus HVAC is highly dispatchable - if there is excess electricity that needs to be used, heating an X-to-water heat pump's storage a few extra degrees is a perfect place to use it.
    - dragontamer 4y ago
      You're dramatically underestimating the swing of electricity in practice. https://www.caiso.com/TodaysOutlook/Pages/default.aspx https://www.caiso.com/TodaysOutlook/Pages/default.aspx See September 22, 2022. California required 51,000+ MW of power capacity as the state reached record high temperatures. Just a few days earlier on Sept. 9th, 42,000 MW was all that was needed. See Yesterday: March 31st 2023. California only required 26,000 MW of power capacity. Even then, the low for March 31st was 17,000 MW at midday. Given these stats from the last year... How much baseload should California build out? And how much "peaker" production should California have? -------- The weather swinging +/- more than expected can cause 10,000MW (or 20% shifts) in power in just a couple of days. Seasonal differences are +100%/-50% differences in power capacity. Its because of this that natural gas peaker plants are used. That's why H2 fuel, as inefficient as it is (but a potentially green source) is still being considered. Having day-to-day, or seasonal, storage of power through the use of chemical energy storage is one of the most promising technologies to tackle this problem.
      - mindslight 4y ago
        You've switched from talking about heating (presumably in climate that needs a significant amount), to talking about cooling California. I'm not versed in exactly how these numbers shake out to be making informed conclusions, but by your previous argument it doesn't seem like you are either. For example cooling load is going to be positively correlated with solar output. More bursty renewables (solar, wind) means less base load and more peaker plants to handle their droops. And just because a town builds one "200MW peaker plant" doesn't rule out adding renewables (and making the peaker burn less gas), even though the renewables only operate at their full capacity a small part of the time. The only way to figure out what to make sense is to tradeoff specific capex/opex/utilization/revenue, rather than talking in wide-sweeping generalizations. Storage is the general solution to the problem, yes. The easy form of storage that we've become accustomed to is the chemical energy of natural gas. Another is end-user thermal storage, where consumption is accelerated/delayed depending on what the grid needs. Moving away from fossil fuels requires figuring out storage, especially how to utilize the inherent storage/slack we already have, rather than continuing to just take fossil fuels' convenient advantages for granted.
- legulere 4y ago
  Natural gas is a fossil fuel
arrrg 4y ago
We need to go to zero and gas furnaces cannot. (Horribly inefficient synthetic fuels excluded.) In that context current electricity generation does not matter. It‘s an infrastructure change that allows for future zero emissions. Just like EVs.
- dragontamer 4y ago
  We're at like 12% renewable. The journey from 12% renewable to 30% renewable will be different than the journey from 90% to 100% renewable. The tools in our disposal to reach 20% or 30% are available today, if we can understand them. And also, as long as we don't let perfection be the enemy of good. We will probably never tackle the 90% to 100% problem in our lifetime. It is best to focus upon the problems that are in front of us, and that we can in fact solve or fix within our lives.
  - arrrg 4y ago
    We need to get to zero. Burning gas doesn’t get us to zero. That’s the issue. Given the lifetime of gas furnaces and what we know about climate change it is madness to even consider using them in brand new construction now. Gas was and is the right tech for transitioning. But you seem to be stuck in the 90s or early 2000s when that kind of policy would have made sense. It’s too late and getting later.