Right, but is it being counted when it is generated (one assumes so) and then again when the stored portion is later used?
DB2
Here is another hypothetical:
Installing a heat pump, rather than using a gas fired furnace to heat a house.
But the heat pump uses current generated by a gas fired power plant.
Burn a cubic foot of gas in the power plant, and only about a third of that energy actually makes it to the heat pump, to heat the house.
Pipe the gas to my house, burn it in my furnace, and 95% of the energy released by burning the gas go into heating my house.
There is another reason the generation fleet should be switched to carbon free sources first.
Steve
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You are mixing up generation and consumption.
Electricity is being counted when it is generated. When demand for electricity is low, then the excess generation goes into storage. Electricty that is consumed comes from direct generation and battery storage.
It has got to be more than a third, donât you think? A combined-cycle natural gas plant is about 55% efficient, and then line losses are like 5-10%. So more like half.
But more importantly, heat pumps are way more efficient than furnaces because heat pumps just move the energy around. So they use much less energy for the same heat output. On the order of two thirds less. So yes, switching to heat pumps is a net positive from a carbon standpoint*
Like others, I donât understand why both canât pursued at the same time. It is going to take decades. If we try to do it sequentially weâll never get there.
*The caveat is the heat pump is appropriate for the climate and youâre not running the strip heaters.
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The link I posted above says about 66% loss, by the time the current gets to your house. But lets take the best I can find: 60% efficiency for a state of the art gas, combined cycle, power plant, less 5% for transmission loss. So 55% of the energy from burning the gas makes it to your house. Heat pumps are not 100% efficient either. I have not found an explicit comparison of SEER or HSPF rating to electrical efficiency, but, the motors, compressor and heat exchangers of a heat pump are not 100% efficient.
My gas furnace is 95% efficient at blowing the hot air from burning the gas into my house. Yes, the furnace has an electric blower, but that blower uses a fraction of the power the central a/c uses.
The government needs to service Trillions in debt. We are assured that we need to spend Trillions more on âdefenseâ, because âGodless Commiesâ or âIslamic boogymanâ, or âyellow perilâ, or âbrown invasionâ. The Proles have a limit to how much they can be charged in taxes and utility bills. The âJCsâ, of course, must not be âburdenedâ. Canât do everything at the same time. Trying to do âeverythingâ in terms of soaring government spending, and tax cuts, is what got us that Trillions in debt in the first place.
So, switch the generation fleet first.
Steve
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You are missing one important thermodynamic fact. We donât measure a heat pumpâs performance with a traditional thermal efficiency number. Heat pumps actually move (or pump) heat and they pump more than one BTU for every BTU consumed. So by the traditional measure they would be more than 100% efficientâŚfar more. And they also double as air conditioners.
The coefficient of performance or COP (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required. Higher COPs equate to higher efficiency, lower energy (power) consumption and thus lower operating costs. The COP is used in thermodynamics.
The COP usually exceeds 1, especially in heat pumps, because instead of just converting work to heat (which, if 100% efficient, would be a COP of 1), it pumps additional heat from a heat source to where the heat is required. Most air conditioners have a COP of 2.3 to 3.5[citation needed]. Less work is required to move heat than for conversion into heat, and because of this, heat pumps, air conditioners and refrigeration systems can have a coefficient of performance greater than one.
source: wikipedia
Mike
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From the EIA link, "Solar and battery storage to make up 81% of new U.S. electric-generating capacity in 2024â Their numbers are 58% solar and 23% batteries.
So where does that 23% from batteries come from? Is it all from solar generation? Is part of it from hydro? Wind? Nuclear? It has to come from somewhere, and since (as you said) weâre counting generation you canât count the electrons as being generated by, say, nuclear and then count it again as being âgeneratedâ by a battery.
DB2
The usual comparison is coefficient of performance (COP). That is, the ratio between the ratio of useful heating (in this case) divided by the amount of energy required.
If a gas furnace was 100% efficient it would have a COP of 1. A typical heat pump though (depending on lots of factors) might have a COP of 3. Which is to say you get three times more useful heat output for each unit of energy input.
Again, thatâs because the heat pump isnât creating heat, it is just moving the heat around. Thatâs why they use less energy over all, even when you account for generation and transmission losses for electricity.
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Another good example. I installed a heat pump hot water heater in 2015. My previous 40 gallon hot water heater used about $30-35 of electricity every month. I replaced it with an 80 gallon heat pump hot water heater. It uses about $10-12 of electricity every month. Not only does it save me 20 bucks a month, but I got it on clearance at a ridiculously low price (it was about $300 which is much less than even a standard resistive water heater) from some outfit in Oregon and it very likely cost them more to ship it to me than I paid in total. Hereâs a photo of it in my garage just after it arrived.
I have to admit that the design is a little odd and it sometimes has weird issues, but it still produces hot water reliably. Though, unfortunately, I will likely have to replace it pretty soon (it is over 9 years old already). And I say unfortunately because prices for heat pump hot water heaters are really ridiculously high, a total ripoff when you look at the components in them. An 80 gallon one is $2700, damn thieves.
Anyway, @steve203, Iâm kind of surprised how you are being taken in by those talking points about how bad alternative energy is, or efficient new techniques in energy usage are. You canât argue against spending $10 a month instead of $30 a month for over 9 years. Thatâs $2160 saved and counting. If you donât believe in the efficiency story, then where exactly do you think that $20 savings is coming from? Not to mention that now I enjoy an 80 gallon water heater instead of the old 40 gallon one!
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Here is the sticker on my 40 gallon gas water heater. That price is based on $1.21/therm. My current cost for gas from DTE is 82.843 cents. Not as cheap as your fancy heater, but a lot less than your old resistive electric heater. 40 gallon gas water heaters at Home Depot, start at $519. A residential 40 gallon heat pump water heater starts at $1599. But the discussion isnât about immediate cost. I thought we were discussing carbon emissions.
Yes, I have seen those claims that heat pumps are 200%-300% efficient. What that ignores is the fuel burned at the plant, with the resulting losses at the plant and in transmission, to get the power to the heat pump. Add in the generation and transmission losses, of 50%-66%. How much heat does the machine blow, for the fuel burned at the plant to power it?
Steve
The EIA link is about capacity, not generation or consumption.
You are confused about electricity!!!
Electrical power generation, capacity, and consumption are all related to the amount of electricity produced, used, or available:
- Generation
The amount of electricity produced over a period of time. This can be measured in watt-hours or watts. Net generation is the amount of electricity produced minus the amount used to operate the power plant.
- Capacity
The maximum amount of electricity that can be produced at a given time under specific conditions. This can also be measured in watt-hours or watts, but is usually measured in megawatts (MW) or kilowatts. Capacity helps utilities predict how much electricity a generator can handle.
- Consumption
The amount of electricity used over a period of time. Consumption can vary by day or week, and can be reduced by identifying which end-uses are increasing consumption at certain times.
The calculation is pretty easy. Assuming electricity is 100% produced from natural gas with 55% efficiency, but the heat pump is 250% efficient, then a heat pump uses 50% less energy to generate the same amount of energy compared to using the natural gas directly. Half the energy.
To be sure, the upfront costs of heat pumps are higher which is a big reason why the JCs donât like them, but they save consumers money over the term which is another big reason the JCâs donât like them.
Iâm kind of surprised you of all people are advancing JC talking points.
Maybe here is an easier way to understand it.
A. You start with 100 BTUs of NG energy and you have a high efficiency hot water heater. This would be ~80% efficient. (Cheap ones are about 60% efficient)
B. Alternatively you take the 100 BTUs and generate electricity at a combined cycle NG plant which is 55% efficient. You then lose 5% transmitting the power to the home, so the home owner sees the kwh equivalent of 50 BTUs. The heat pump water heater has a COP of 2.5 or 3.0. This means that the heat pump uses 50 BTUs to move 125 or 150 BTUs of heat from the air into the water.
You can see that in case A you get 80 BTUs from the original 100 BTUs and in case B you get 125 to 150 â almost double the amount and thus ~1/2 the CO2.
Note: Iâve used fairly realistic numbers and Iâm ignoring the cost to deliver the NG to the home.
Of course, whether you save money depends on how much hot water you use, the costs of the two choices of water heaters, the cost of NG vs electricity and installation costs so you still have to be a smart shopper.
Mike
It is about electic-generating capacity.
DB2
Except that it isnât. Using the 200%-300% efficiency I see claimed for heat pumps, and the 50%-66% energy loss I see claimed for various sorts of generation plants, seems the system efficiency of a heat pump could range anywhere from 68% to 150%, vs 95% for my gas furnace.
Steve
Yes, there are some coal plants that are only 35-40% efficient (i.e. they lose 60-65% of their thermal heat). Nuclear plants also can be this lowâŚbut then they donât emit any CO2. And the best newer NG plants are up to 60% efficient.
So what?
We arenât making any new coal plants (in the US) and we are retiring the worst of them.
What matters is the overall average case else perfect becomes the enemy of good enough.As the grid gets cleaner and cleaner heat pumps get cleaner and cleaner in terms of CO2 along with the cleaner grid. While a NG furnace or water heater continues to emit the same CO2 every year.
If everyone waits until all the coal plants are retired- it will just be decades longer to convert.
Edit: if 25K people in your state installed new heat pump furnaces and hot water heaters where would the new power come from? Would your utility build a new coal plant or install more renewables and/or high efficiency NG plants?
Mike
Re: limits on taxes to fund green energy.
Return on investment from green energy investment is still the best way.
Ethanol from corn is an excellent example. Plants with much capacity were built by investors once government mandated the need and created a market. Consumers footed the bill but it was relatively painless.
Thatâs what a lot of companies are working on. FuelCell Energy for example has a project with the government to use nuclear waste heat to improve the efficiency of solid oxide hydrolysis to generate hydrogen. Low-cost hydrogen production from nuclear energy
It is part of a DOE effort to bring renewable/nuclear hydrogen production costs to $1/kg. Hydrogen is currently produced from natural gas for about that price.
A lot of folks disagree. This article summarizes the reasons why nuclear-generated hydrogen is expected to be a big deal and lists the projects currently happening worldwide. https://www.sciencedirect.com/science/article/pii/S0360319923049200
One simple example is that it provides an easy means for nuclear to provide dispatchable electricity. When solar/wind is plentiful a nuclear plant can divert energy to Hydrogen production, allowing reactors to run at full capacity 24/7.
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