That does sound like an excessive markup. But my point is even with the wholesale price, chemical batteries are nowhere near cost-effective for medium-term (days) electrical storage. Instead we should be doing pumped hydropower, compressed air energy storage, or building thermal energy storage (and eventually some utilization of vehicle battery storage because the battery is already paid for for the transport function). I talk about this more in my second 80k podcast.
At $150/kW-hr and assuming a somewhat low 3000 cycle lifetime, such batteries would cost $0.05 per cycled kW-hr which is very much cost-effective when paired with the extremely low cost but inconveniently timed nature of solar power. It would drop the amortized cost of a complete off-grid power system for my home to half that of grid power in my area, for example.
Even now at $1000/kW-hr retail it’s almost cost-effective here to buy batteries to time-shift energy from solar generation to time of consumption. At $700/kW-hr it would definitely be cost-effective to do daily load-shifting with the grid as a backup only for heavily cloudy days.
Pumped hydro is already underway in this region, though it’s proving more expensive and time-consuming to build than expected. Have there been some recent advances in compressed air energy storage? The information I read 2-3 years ago did not look promising at any scale.
If you have 3 days worth of storage, even if you completely discharge it in 3 days and completely charge it in the next 3 days, you would only go through about 60 cycles per year. In reality, you might get 10 full cycles per year. With interest rates and per year depreciation, typically you would only look out around 10 years, so you might get ~100 discounted full cycles. That’s why it makes more sense to calculate it based on capital cost as I have done above. If you’re interested in digging deeper, you can get free off grid modeling software, such as the original version of HOMER (new versions you have to pay).
Even now at $1000/kW-hr retail it’s almost cost-effective here to buy batteries to time-shift energy from solar generation to time of consumption. At $700/kW-hr it would definitely be cost-effective to do daily load-shifting with the grid as a backup only for heavily cloudy days.
Please write out the calculation.
Have there been some recent advances in compressed air energy storage? The information I read 2-3 years ago did not look promising at any scale.
Aboveground compressed air energy storage (tanks) is a little cheaper than chemical batteries. But belowground large compressed air energy storage is much cheaper for days of storage, with estimates around $1 to $10 per kilowatt hour. Current large installations are in particularly favorable geology, but we already store huge amounts of natural gas seasonally in saline aquifers. So we can basically do the same thing with compressed air, though the cycling needs to be more frequent.
Batteries are primarily used for intra-day time shifting, not weekly. I agree that going completely off grid costs substantially more than being able to use your own generated power for 80-90% of usage. That’s why I focused on the case where home owners remain grid-connected in my top-level comment:
With smart meters and cheaper home battery systems the incentives starts to shift toward wealthier solar enthusiasts buying batteries and selling excess power to the grid at peak times (or consuming it themselves), lowering peak demand at no additional capital or maintenance cost to the grid operators.
The only mention I made regarding completely off-grid power systems was about the counterfactual scenario of $150/kW-hr battery cost, which I have not assumed anywhere else. I didn’t say that it would be marginally cost effective to go completely off grid with such battery prices, just that it would be substantially more cost-effective than buying all my power from the grid. The middle option of 80-90% reduced but not completely eliminated grid use is still cheaper than either of the two extremes, and likely to remain so for any feasible home energy storage system.
That’s what I was referring to regarding $700 kW/hr. At $1000/kW-hr it’s (just barely) not worth even buying batteries to shift energy from daytime generation to night consumption, while at $700/kW-hr it definitely is worthwhile. Do you need the calculation for that?
At $1000/kW-hr it’s (just barely) not worth even buying batteries to shift energy from daytime generation to night consumption, while at $700/kW-hr it definitely is worthwhile.
Doesn’t this depend heavily on local utility rates, and so any discussion of crossover points should include rates? Ex: I’m at $0.33/kWh while a friend in TX is at half that.
Yes, it definitely does depend upon local conditions. For example if your grid operator uses net metering (and is reliable) then it is not worthwhile at any positive price. This statement was in regard to my disputed upstream comment “Even now at $1000/kW-hr retail it’s almost cost-effective here [...]”.
It would be helpful to see a calculation with your rates, the installed cost of batteries, cost of the space taken up, losses in the batteries and convertor, any cost of maintenance, lifetime of batteries, and cost (or benefit) of disposal.
That does sound like an excessive markup. But my point is even with the wholesale price, chemical batteries are nowhere near cost-effective for medium-term (days) electrical storage. Instead we should be doing pumped hydropower, compressed air energy storage, or building thermal energy storage (and eventually some utilization of vehicle battery storage because the battery is already paid for for the transport function). I talk about this more in my second 80k podcast.
At $150/kW-hr and assuming a somewhat low 3000 cycle lifetime, such batteries would cost $0.05 per cycled kW-hr which is very much cost-effective when paired with the extremely low cost but inconveniently timed nature of solar power. It would drop the amortized cost of a complete off-grid power system for my home to half that of grid power in my area, for example.
Even now at $1000/kW-hr retail it’s almost cost-effective here to buy batteries to time-shift energy from solar generation to time of consumption. At $700/kW-hr it would definitely be cost-effective to do daily load-shifting with the grid as a backup only for heavily cloudy days.
Pumped hydro is already underway in this region, though it’s proving more expensive and time-consuming to build than expected. Have there been some recent advances in compressed air energy storage? The information I read 2-3 years ago did not look promising at any scale.
If you have 3 days worth of storage, even if you completely discharge it in 3 days and completely charge it in the next 3 days, you would only go through about 60 cycles per year. In reality, you might get 10 full cycles per year. With interest rates and per year depreciation, typically you would only look out around 10 years, so you might get ~100 discounted full cycles. That’s why it makes more sense to calculate it based on capital cost as I have done above. If you’re interested in digging deeper, you can get free off grid modeling software, such as the original version of HOMER (new versions you have to pay).
Please write out the calculation.
Aboveground compressed air energy storage (tanks) is a little cheaper than chemical batteries. But belowground large compressed air energy storage is much cheaper for days of storage, with estimates around $1 to $10 per kilowatt hour. Current large installations are in particularly favorable geology, but we already store huge amounts of natural gas seasonally in saline aquifers. So we can basically do the same thing with compressed air, though the cycling needs to be more frequent.
Batteries are primarily used for intra-day time shifting, not weekly. I agree that going completely off grid costs substantially more than being able to use your own generated power for 80-90% of usage. That’s why I focused on the case where home owners remain grid-connected in my top-level comment:
The only mention I made regarding completely off-grid power systems was about the counterfactual scenario of $150/kW-hr battery cost, which I have not assumed anywhere else. I didn’t say that it would be marginally cost effective to go completely off grid with such battery prices, just that it would be substantially more cost-effective than buying all my power from the grid. The middle option of 80-90% reduced but not completely eliminated grid use is still cheaper than either of the two extremes, and likely to remain so for any feasible home energy storage system.
That’s what I was referring to regarding $700 kW/hr. At $1000/kW-hr it’s (just barely) not worth even buying batteries to shift energy from daytime generation to night consumption, while at $700/kW-hr it definitely is worthwhile. Do you need the calculation for that?
Doesn’t this depend heavily on local utility rates, and so any discussion of crossover points should include rates? Ex: I’m at $0.33/kWh while a friend in TX is at half that.
Yes, it definitely does depend upon local conditions. For example if your grid operator uses net metering (and is reliable) then it is not worthwhile at any positive price. This statement was in regard to my disputed upstream comment “Even now at $1000/kW-hr retail it’s almost cost-effective here [...]”.
It would be helpful to see a calculation with your rates, the installed cost of batteries, cost of the space taken up, losses in the batteries and convertor, any cost of maintenance, lifetime of batteries, and cost (or benefit) of disposal.