I have not run any numbers on this, but the idea behind it is to stockpile your energy in the summer to be able to make it through the winter without having to resort to some outside source of energy like wood or gas delivery.
I initially thought about hydrogen, but given it's storage density, and the problems that SLS has had with leaks, taking the additional step to convert into methane would greatly simplify storage and use, and likely improve reliability since you'd be able to use COTS products for natural gas instead of custom hydrogen storage
Long-term energy storage with hydrogen, with 1-5x 300 kWh. Which allows for full electric independence (not including heating though). Price: 85,000-125,000 €, minus government subsidies.
Your energy consumption for heating might be ~ 3000 kWh/month during the winter months (Nov-Mar) for a moderately insulated house.
Assuming your PV produces only 10 % of the demand during these 5 months (so you have to rely on stored energy for the remaining 90 %) and your heat pump delivers a Coefficient of Performance of 3.5 then you'd need to store ~ 3900 kWh.
As to my back of envelope calculation, one standard 50 l bottle of hydrogen contains ~ 30 kWh worth of energy when filled at 200 bar.
So you'd need ~ 130 such standard bottles to store enough hydrogen.
That's quite a lot. But of course with a well insulated home, you'd maybe only need a third, so that'd be 3-4 bundles (with 12 bottles each).
Hydrogen embrittlement seems to be an unavoidable problem so not sure how that plays out.
For now and maybe always, it's probably more cost-effective to size the solar-electric system for winter months (if adequate roof / ground space).
Along with solar thermal and photovoltaics, I'd use a redox flow battery for long term storage, and a GEK for emergency generation (too loud for casual use).
Seems like it would work:
https://www.researchgate.net/figure/Concept-for-enabling-inc...
I mean sure but like in the worst case, window shades are a thing.
Edit: Or maybe this isn't about passive heating and you're saying long term storage might not be necessary in winter?
But used as a part of a more robust system, I think there's promise here. The other type of low-chemical physical potential energy storage that gets some attention nowadays is pumping water to a higher location, only to let it out via a hydro generator later. Not sure how that scales into winter though. (actually air tanks might lose a certain amount of pressure to cold as well; perhaps buried tanks would work better, so that the ambient temp is cooler?)
It's fun to apply this pattern to other types of gravity-based energy. Maybe take excess in the summer and use it to ratchet your water tower up higher, or roll a large boulder up a hill? Or force two magnets really close together :p
1 https://www.resilience.org/stories/2018-05-18/ditch-the-batt...
Might be worth playing around with vertical installation if that's an option, this lets you shift the power curve towards winter.
My question about completely off grid housing and renewable sources and energy stores is that an isolated small scale unit will assuredly operate industrial processes at a lower efficiency than a centralized industrial facility, barring transmission loss. Economy of scale is real for thermodynamic costs and monetary cost. So any gas compression or thermal cycle or liquid pumps is self serving with higher personal capital cost and cost of run and maintenance reliability. And if enough of your neighbors do it it’s “renewable” but nowhere near sustainable.
How to turn sunlight into methane? Electrochemistry and membranes or catalysts? That seems like not a worthwhile question facing us if there is earnest need for energy transition for sustainability.
If you’re wealthy enough to have an off grid ranch or cabin and don’t want the baggage of society to replenish your winter energy needs then purchase in W texas and build a boutique diesel rig and refinery. Or purchase a bunch of land with fast growing pines and run a logging operation. If you want to live off grid but can manage paying money for society goods and services run diesel generators with long term fuel oil contracts and rig up a decarbonization unit on the exhaust stack.
Localized next gen storage isn’t a pressing matter in my opinion. Especially that benefiting anti-social people with means to live off grid but comfortably. If you have millions of emissions points it’s harder to control than a centralized regulated plant.
Converting solar to hydrogen, then to methane, then to electricity requires a pretty big setup. If you want to be efficient, you have to do all that at a large scale with a proper power plant turbine. It will not work well at a scale of one house.
Hydrogen storage makes sense for a country, not for anything smaller. LNG storage may make sense for a city grid, if our tech advances. Anyway, you really don't want those on your backyard.
Anyway, even though they are simpler, flow batteries may create enough problems so that you don't want them on your backyard either. I will repeat the sibling that recommended just getting more panels.
Like this ? https://en.m.wikipedia.org/wiki/Gravity_battery
My friend has an off-grid cabin and his solar panels were easy to size for all other energy needs during winter by having them installed angled towards the winter sun position.
He does have a small generator just in case there is a particularly bad winter storm, but even in that circumstance it just has to run long enough to charge his batteries, so fuel consumption is minimal.
I understand it is an interesting problem and all that, just thinking the energy used to solve this esoteric problem might be better used for more large scale solutions?
These electrolyzers will then take up the excess electricity and convert it to hydrogen as seasonal storage and thus stabilize the grid.
Additionally, you'd combine these sites with either fuel-cell or hydrogen powered gas turbine plants, to then generate enough electricity when PV generation cannot meet demand.
Power to the people ;)
https://arstechnica.com/science/2022/08/new-aluminum-sulfur-...
In the UK we have a 5kw array, and a 13kwhr battery. this year we have been 93% self sufficient.
we have triple glazing and 90mm of external wall insolation (but its not passivehaus) to cover our heating as well, we'd need to do a proper insulation survey. I am reasonably confident that if we insulate the floor and loft properly(and figure out air exchanger) we could cover our heating and hotwater as well, (assuming solar water heater)
In the US, depending on where you are, you have aircon/heating as the main energy draw, but with the option to have a boatload more solar. However insulation/glazing standards are patchy, so with good insulation a 20kw array, plus 30kwhr battery would cover you for most things and a car as well.
The UK temperature averages are pretty close to LA, which is well known for being so moderate.
[1] https://www.timeanddate.com/weather/uk/london/climate
This would be my off grid project if i could get the land.
I would want that to be in it's own separate brick outhouse or on a concrete pad twenty feet from anything that should not be sprayed with fire.
See this video of taking apart a USB power pack that runs on hydrogen.
https://www.youtube.com/watch?v=y48wCuC3KcA
Lavo seems to be claiming that one of their devices will last 30 years, which is better than a flooded lead acid battery system, if that is actually true.
It also requires much smaller pressures to be useful.
Propane does not concern me. A big tank of acetylene would be of concern to insurance companies, the fire brigade and the local safety agency.
TIL: hydrogen soap bubbles float up
A 40 kWh LiFePO4 battery + grid tie inverter can be had for much less. Safe, well tested and already in high volume manufacturing. Shipped to your door tomorrow.
If they could get anywhere near lithium battery efficiency for a round trip then the breakthrough in fuel cell efficiency (and possibly also electrolyzer efficiency) required to do that would be the headline.
And if they can't, then they'd probably need to be implausibly low cost to make it worthwile, and they don't seem to be that either.
Maybe there's some way of using the waste heat that improves it? Still seems unlikely.
So just an expensive, awkward low efficiency battery, when cheap, commodity, high-efficiency batteries are available.
I have a ~60kWh battery sitting around in my garage, that I typically only use 10% for daily driving.
For reference, I'm currently waiting for delivery of a 10kWh battery that will cost me about €6100 (including VAT, excluding installation and government subsidy).
https://signaturesolar.com/eg4-ll-lithium-battery-24v-200ah/
I worked at a small company that had $1.5M in 'backorders'. But it was going to take more than $1.5M to fulfill the orders, which ... is not a place you want to be in (regardless of how many zeroes?). Half the company was laid off shortly after this 'milestone' was reached.
Now.. perhaps with more zeroes... there's seemingly enough wiggle room to move stuff around in the books to balance things out...?
Also, I realize it might be premature asking that type of question, but... having been burned once, it sticks to top of mind.
1) This battery is not affected by hydrogen embrittlement, in which hydrogen reacts with metals to form hydrides, and is not explosive like compressed hydgrogen, because it stores hydrogen in the form of metal hydrides (but note that hydrides are still very flammable). They did not disclose what metal(s) are used for storage.
2) They don't have a factory, but have been in talks to outsource the actual manufacture of the utility-scale version of the product.
I'm not a chemist, but I messed around with electrolysis decades ago when I was a teen who was into chemistry sets.
I am not convinced that tapwater is anywhere near pure enough that this system can work without frequently changing electrodes and removing gunge, even with some filtering.
Electrolysis does not just split the water molecules, there is a chemical reaction with whatever else is dissolved in the water.
It would likely require periodic replacement, proportional to use, of relatively expensive filter(s) - not regularly changing electrodes or invasive deep cleaning.
Copper will react with the chlorine in tapwater and make an insoluble green scum of copper chloride.
Electrolysis with stainless steel makes highly toxic hexavalent chromium.
Platinum is astoundingly expensive, even for plating.
How expensive a filter is needed to remove 99.999% of the chlorine?
The thing with electrodes is that a fiftieth of a millimeter of non-condutive crap on the surface hugely reduces the effectiveness. Around here the bottom third of my kettle has a tenth of a mil of limescale.
The other issue is how it compete with lithium battery it also used. May be unlike car …
You need a massive amount of excess grid energy for it to make any sense.
I do think it could be used in situations where the energy density benefits are important (planes, racing).
