3 ms·

Why not just a 20kWh battery for energy time shifting. Or are you looking to sell the hydrogen?

noogle 4y ago
This will last less than a day. What to do in the winter? If the answer is "use the grid", then we just kick the can to someone else, who will probably use fossil fuels to provide the energy. The basic problem remains - solar/wind are intermittent and fluctuating.
- midasuni 4y ago
  Compressed air has a higher round trip efficiency than storage, and pumped hydro is twice as efficient as compressed air. However until zero kWh is generated from fossil fuels in summer, solar/wind and battery is a massive gain, even if gas is still used for 2 months a year.
  - noogle 4y ago
    But gas is used also in the summer. And energy is not only electricity - heating is currently done mostly by natural gas, and is often absent from those calculations. Efficiency is irrelevant. The only thing that matter is cost and feasibility. The cost of energy from solar is ~$0.02/kwh and sometimes even $0.00/kwh (when the grid curtails production). Even with 30% efficiency each kwh retrieved from storage will cost a record-low of $0.06/kwh (3-10 times lower than the consumer price). The biggest factor here is the capex and ease-of-use of the equipment. Not the energy input cost.
ajross 4y ago
The commenter's goal is presumably season-shifting, which is two orders of magnitude off from feasible battery capacity. In most areas in the US, a full-roof solar system will produce enough energy in aggregate to power the home's use year-round, but there's no way to get all those summertime watt-hours into the lines in winter when the panels are dark. But indeed, no, this just doesn't work. Best available efficiency for round-trip electrolytic fuel production / electricity generation is 40% or so, meaning that those roof panels wouldn't be enough anyway. (Also there's the problem of having every home store a winter's worth of pressurized hydrogen or whatever on-premises. Yikes.) It's not worth it. Home solar is attractive because unlike most infrastructure it scales down really well and is actually feasible to do at the level of an individual user. But, like most infrastructure, seasonal power management is a grid-wide problem and needs to be solved at the utility level. There are plenty of tricks available there that homeowners don't have access to.
- fbdab103 4y ago
  No interest in storing a season's worth of energy which would be infeasible without a ludicrously over provisioned system. More -what could you do with spare capacity that is not trash-tier net metering? Generating liters of fuel weekly would be enough to power my ICE car (I rarely drive). Or being able to generate and store a ~week of liquid backup energy. Such a system would be unlikely to ever payback for itself. Not deluding myself on that one.
  - ajross 4y ago
    Depending on where you live, simply electrifying your home and driving an EV should be enough to get you within a few percent of your peak summer output. You won't be wasting that much. Buy the heat pump water heater, the induction range, etc... Pick the low hanging fruit, then worry about using that last bit of juice in June. FWIW: net metering seems like "trash tier" precisely because that summer PV excess really is mostly wasted (this is true for big panel farms too). The utilities were taking a huge haircut on the old 1:1 billing that California just rolled back. It wasn't sustainable.
  - midasuni 4y ago
    If you drive say 300 miles a week that’s 100kWh for a typical electric car. Another 150 for domestic use and that’s 35kwh a day. You have a system that generates more than that if you have excess to pump into liquid storage, but why do you want a weeks worth of backup energy? Why not 3 days? Or 2 weeks?

This will last less than a day. What to do in the winter? If the answer is "use the grid", then we just kick the can to someone else, who will probably use fossil fuels to provide the energy. The basic problem remains - solar/wind are intermittent and fluctuating.

midasuni 4y ago
Compressed air has a higher round trip efficiency than storage, and pumped hydro is twice as efficient as compressed air. However until zero kWh is generated from fossil fuels in summer, solar/wind and battery is a massive gain, even if gas is still used for 2 months a year.
- noogle 4y ago
  But gas is used also in the summer. And energy is not only electricity - heating is currently done mostly by natural gas, and is often absent from those calculations. Efficiency is irrelevant. The only thing that matter is cost and feasibility. The cost of energy from solar is ~$0.02/kwh and sometimes even $0.00/kwh (when the grid curtails production). Even with 30% efficiency each kwh retrieved from storage will cost a record-low of $0.06/kwh (3-10 times lower than the consumer price). The biggest factor here is the capex and ease-of-use of the equipment. Not the energy input cost.

ajross 4y ago

The commenter's goal is presumably season-shifting, which is two orders of magnitude off from feasible battery capacity. In most areas in the US, a full-roof solar system will produce enough energy in aggregate to power the home's use year-round, but there's no way to get all those summertime watt-hours into the lines in winter when the panels are dark. But indeed, no, this just doesn't work. Best available efficiency for round-trip electrolytic fuel production / electricity generation is 40% or so, meaning that those roof panels wouldn't be enough anyway. (Also there's the problem of having every home store a winter's worth of pressurized hydrogen or whatever on-premises. Yikes.) It's not worth it. Home solar is attractive because unlike most infrastructure it scales down really well and is actually feasible to do at the level of an individual user. But, like most infrastructure, seasonal power management is a grid-wide problem and needs to be solved at the utility level. There are plenty of tricks available there that homeowners don't have access to.

fbdab103 4y ago
No interest in storing a season's worth of energy which would be infeasible without a ludicrously over provisioned system. More -what could you do with spare capacity that is not trash-tier net metering? Generating liters of fuel weekly would be enough to power my ICE car (I rarely drive). Or being able to generate and store a ~week of liquid backup energy. Such a system would be unlikely to ever payback for itself. Not deluding myself on that one.
- ajross 4y ago
  Depending on where you live, simply electrifying your home and driving an EV should be enough to get you within a few percent of your peak summer output. You won't be wasting that much. Buy the heat pump water heater, the induction range, etc... Pick the low hanging fruit, then worry about using that last bit of juice in June. FWIW: net metering seems like "trash tier" precisely because that summer PV excess really is mostly wasted (this is true for big panel farms too). The utilities were taking a huge haircut on the old 1:1 billing that California just rolled back. It wasn't sustainable.
- midasuni 4y ago
  If you drive say 300 miles a week that’s 100kWh for a typical electric car. Another 150 for domestic use and that’s 35kwh a day. You have a system that generates more than that if you have excess to pump into liquid storage, but why do you want a weeks worth of backup energy? Why not 3 days? Or 2 weeks?