this post was submitted on 05 Mar 2022
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[โ€“] AgreeableLandscape@lemmy.ml 3 points 2 years ago* (last edited 2 years ago)

Are you asking about personal energy storage, or grid scale energy storage?

With grid scale, pumped hydro is generally better, as you could potentially take advantage of existing geographical features, or falling that, it's largely a one time investment to dig two lakes at different elevations. The water can easily be obtained from naturally occurring sources, either it was already there or simply wait for rain and runoff to fill it. You can also use the lakes for other things, like recreation, potable water, or even as an ecological restoration project to bring back aquatic biodiversity.

For personal use, hydro gets dicey. Since you're doing it on a small scale, it's very likely that it will be very inefficient, because if you have a reservoir only a couple metres high instead of a hundred or so, you won't be storing much gravitational energy at all. Importantly, you'll have to worry about the tiny amount of energy in your water stream needing to overcome the frictional resistance of your turbine, maybe even friction in your pipes, because you'll be working with much lower pressures and flow rates. Mechanical systems like these are something that generally gets worse in efficiency the smaller scale you get. For example, you might be spending half your energy just overcoming friction with a tiny turbine, whereas only a few percent of a large scale pumped storage system's energy is spent getting things moving, even though the raw numbers of the larger turbine seems worse. Therefore, I'd say batteries would be better for small scale storage in terms of energy efficiency, but perhaps not in terms of longevity or the environmental impact of materials.

[โ€“] poVoq@lemmy.ml 2 points 2 years ago (2 children)

Feed into the electricity grid is the most efficient way ๐Ÿ˜‰

But the real question is what the end use is going to be.

[โ€“] UnreliantGiant@lemmy.ml 2 points 2 years ago (2 children)

Yeah feeding back into the grid has the least conversion losses and doesn't take additional material.

Local energy storage can be useful though for complete self-sufficiency (at least in summer), but with the currently available options there will be no return of investment, both financially and environmentally, or they just don't have enough capacity/power to keep a family powered over night. I hope EV manufacturers will continue experimenting with using EV batteries as storage for solar power, it could be a nice combo for people who need a car.

[โ€“] poVoq@lemmy.ml 2 points 2 years ago* (last edited 2 years ago)

I rather hope that there will be a large market for refurbished EV batteries in a few years that can be still used for stationary applications.

I doubt many people would want to shorten their car's battery life to run their washing machine with it.

[โ€“] wintermute@feddit.de 0 points 2 years ago* (last edited 2 years ago)

but with the currently available options there will be no return of investment, both financially and environmentally

Unless you build a DIY battery like this guy

he also has build a power-wall from recycled cells, which only costs a fraction and significantly improves the ecological footprint

[โ€“] AgreeableLandscape@lemmy.ml -1 points 2 years ago* (last edited 2 years ago)

A lot of places have ended their net meter programs. Supposedly it's because it threatens the economic sustainability big power companies because individual citizens sell electricity at "retail" prices whereas major power plants sell at "wholesale" prices, with the former higher than the latter. Apparently. It never made sense to me.

Like, okay? Why not just have everyone sell at the same price then? And why is there a difference between "retail" and "wholesale" prices in the first place? Electricity is electricity. Or, maybe decentralised power generation is the way to go if people are making so much electricity it's threatening to displace big power plants.

[โ€“] sagar@lemmy.ml 1 points 2 years ago

That's a very difficult technical question. You should ask someone who conducts research wrt solar energy. The key metrics there should be energy density of material, it's toxicity, it's repairability, it's lifetime which would decide it's pricing, and the loss of energy per unit time.

[โ€“] southerntofu@lemmy.ml 1 points 2 years ago (2 children)

The greener option is to not produce something to store energy.

If you know mechanics in your area, repurposing old car batteries (who're not powerful enough to start a car anymore but are powerful enough for quite many other things) is the greenest thing. If you have a water stream nearby, using excess energy to pump the water upstream (so it passes through your generator again when there is no excess) is the greenest thing.

We all have to remember there's not a one-size-fits-all solution because energy is never green. The greenest energy is the energy we don't use. Next greenest thing is to repurpose anything you find to produce/store energy, because whether we're talking about solar panels or battery or whatever, there's nothing green about that at all. So the greenest is a very localized solution depending on local context.

[โ€“] AgreeableLandscape@lemmy.ml 1 points 2 years ago* (last edited 2 years ago)

If you know mechanics in your area, repurposing old car batteries (who're not powerful enough to start a car anymore but are powerful enough for quite many other things) is the greenest thing.

I agree with the sentiment of this, reduce new products first, but keep in mind that car batteries are designed in such a way that the moment you drain them close to empty, they immediately take a giant hit in both performance and lifespan. Most car batteries can only survive being drained to zero a few times before dying completely. If I recall correctly, even moderately deep cycles like going between 100% and 50% can still reduce their lifespan drastically. They also just don't have that much capacity in general.

A much better option are deep cycle lead acid batteries if you want to go this route. They're less common and more expensive, but are still very commonly used on boats, trucks, RVs, basically any vehicle where you need a decent supply of power without having to run the engine. More importantly, they're also very common for uninterrupted power supplies, and, yes, off-grid energy storage. They behave like the "normal" batteries people are familiar with, and draining them to zero, while still not recommended, isn't that big of a deal. However, it's likely that they won't really be applicable for your example where the battery can still hold power but don't have enough cold cranking amps, because the original application didn't need much current anyway and they're most likely only replaced when they're actually dead. Maybe a marine deep cycle battery that's used both for cranking the engine and power storage can be applicable in that case, but again, they're a lot less common than car batteries.

[โ€“] UnreliantGiant@lemmy.ml 1 points 2 years ago

If you have a water stream nearby, using excess energy to pump the water upstream (so it passes through your generator again when there is no excess) is the greenest thing.

Do you have some resources on how to do that and what performance this could provide on a small scale?