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Geothermal may beat batteries for energy storage

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Re: Geothermal may beat batteries for energy storage

#191

Post by martin_a »

jandrese wrote: post #136
martin_a wrote: post #11

Earlier quoted context omitted.

I saw a video like a month ago on YouTube where somebody pumped something like 250 liters of water on his roof (7 meters elevation, if I remember correctly) and let it run through a homebuild generator. The power capacity of that setup was like that of an AA battery, if I remember correctly. You need huge amounts of water and lots of height difference.

Yeah, pumped hydro is one of those power sources that doesn't scale down at all. However, home scale conventional hydro is a thing. If you live on a hill with a creek that runs down it you can install a generator that produces a usable amount of consistent power for the cost of a few hundred meters of PVC pipe, a barrel, some connectors, and a small electric turbine. Search for micro-hydro if you want to know more. L…

> Search for micro-hydro if you want to know more.

I've probably seen everything YT has to offer on that. :-D

While I really enjoy those videos and the "let's just do it" vibe with old washing machines as generators, I'm also somewhat happy that Germany has rather strict regulations on how to use water from streams and rivers. Some installations are quite disturbing for local ecosystems. But being off-grid in remote areas these solutions seem like a probable compromise.

Re: Geothermal may beat batteries for energy storage

#192

Post by distances »

jws wrote: post #134
distances wrote: post #107

Earlier quoted context omitted.

This may work in mild climates, but the areas where winter heating is most needed will have the solar panels under a bed of snow during the winter months. Additionally, winter months are usually the cloudy ones. It's not very uncommon to have just a couple of sunny days per month in European winters, driving down solar gains even if there's no snow cover.

It's not as bad as this. In climates where you will have a bed of snow during the winter months, your optimum tilt angle for a fixed solar panel is something like 30° off of vertical or steeper. I find that on mine the snow falls off since it is a south facing, steep, dark surface. You engineer to make sure you have enough energy captured each month to meet that months needs. That might lead you to a tilting mount, o…

Interesting. Last winter my parents' rooftop solar had zero output until April, as it produces nothing until all the panels are clear of snow. Granted their installation is at a fixed angle that matches the roof, and this is in the Nordics.

During summer months the production mostly covers and partly exceeds their use, but the sell price is so much lower that it doesn't even begin to pay for the rest of the year. But that of course then relates to the installed capacity.

Re: Geothermal may beat batteries for energy storage

#193

Post by Dylan16807 »

rgmerk wrote: post #190
dahfizz wrote: post #108

Earlier quoted context omitted.

> Why there are no water storages on the roof. Quick math - 100 gallons of water 15 meters up off the ground has enough potential energy to run a microwave for 30 seconds. Gravitational storage is pathetically weak. It only makes sense on massive, massive scales. In a residential setting, the storage will never outweigh the extra cost and risk of having so much water on your roof.

One minor but interesting exception - farmers have historically often put domestic water tanks on top of towers to ensure even water pressure. Direct pumping leads to cycles where the pressure in the system rises and falls as the pump cycles on and off, which is very unpleasant if you’re trying to take a shower! I believe modern off-grid home water pumps use more sophisticated motor control to avoid the need for the…

That's not an exception, that's an entirely different use for a raised tank. And not a very big one either.

Re: Geothermal may beat batteries for energy storage

#194

Post by iancmceachern »

It's because of design efficiency. The most distilled and finest design utilizes each part for many things. Like a unibody car, or a fuel tank in the wing in an aircraft.

In this case the material doing the thermal storage is also part of the building. It's not like there is a building and a separate 100 tons of thermal storage stuff, just make the house and foundation out of that 100 tons of stuff and then you only have to buy 100 tons of stuff, not 200. It's the same economy of scale with the labor and digging. You can dig 1 hole and put all this geothermal stuff in it along with the foundation, or you can dig 2 holes and have twice the everything. If you just combine all the items into one big effort, look for design efficiencies where you can combine parts and systems, and these systems/buildings can basically run themselves with just what is provided by the environment. They don't change the environment inside the building, they just regulate it between the 2 extremes, taking the edge off the high and lows.

Re: Geothermal may beat batteries for energy storage

#195

Post by dahfizz »

smileysteve wrote: post #183
dahfizz wrote: post #179

Earlier quoted context omitted.

"high efficiency" turbines are not all that efficient. Burning gas releases 100% of the available energy as heat. Converting that gas to electricity is Also, electricity from gas is relatively expensive. Other sources like coal or hydro are cheaper, which lowers the average cost of electricity.

But gas turbines should be more efficient than a burner under a boiler or a burner in a furnace. Yes, solar, wind, hydro, nuclear should be cheaper per unit (coal is not usually cheaper than gas in the US)

95% efficient gas furnaces are the norm for newer houses[1].

Getting electricity out of gas is fundamentally harder than getting heat out of it.

[1] https://iwae.com/resources/articles/95-afue-gas-furnace-work...

Re: Geothermal may beat batteries for energy storage

#196

Post by adamc »

soperj wrote: post #173
throw__away7391 wrote: post #162

Earlier quoted context omitted.

Solar hot water is great, but that's not gravitational storage, e.g. pumping water up a hill with pumps and later using the flow of water back down to generate power.

You're right it isn't, but it is storing the water on top of the house.

Yes, but I'd expect it's much lesser amounts. 80 gallons is a decent sized water heater.

Re: Geothermal may beat batteries for energy storage

#197

Post by aappleby »

rgmerk wrote: post #190
dahfizz wrote: post #108

Earlier quoted context omitted.

> Why there are no water storages on the roof. Quick math - 100 gallons of water 15 meters up off the ground has enough potential energy to run a microwave for 30 seconds. Gravitational storage is pathetically weak. It only makes sense on massive, massive scales. In a residential setting, the storage will never outweigh the extra cost and risk of having so much water on your roof.

One minor but interesting exception - farmers have historically often put domestic water tanks on top of towers to ensure even water pressure. Direct pumping leads to cycles where the pressure in the system rises and falls as the pump cycles on and off, which is very unpleasant if you’re trying to take a shower! I believe modern off-grid home water pumps use more sophisticated motor control to avoid the need for the…

Off-grid domestic water uses tanks fitted with rubber bladders that keep the water at a roughly constant pressure and reduce the frequency the pump has to cycle.

Re: Geothermal may beat batteries for energy storage

#198

Post by Schroedingersat »

kansface wrote: post #149
Schroedingersat wrote: post #82

Earlier quoted context omitted.

Agri-PV is one way of using the thermal budget (and a great one from a habitat-harm perspective as it causes a net reduction in human-occupied land). The albedo problem is the opposite of what your are thinking as it is another source of radiative forcing from putting a mostly black thing in the sun. A Shockley-Queisser limited solar panel mostly only reflects IR. So where your plants/dirt might have an albedo of 0.3…

Doesn’t the nuclear heating happen regardless of us harnessing the energy or not?

Unenriched uranium will fission eventually, but you're talking trillions of years. In a fission reactor, the U238 atoms are placed close enough to a minority of U235 atoms and to each othekr that neutrons from one fission will trigger the next at a rate just short of running away exponentially.

There are some ore bodies that are concentrated enough to fission faster, but they are rare (and not the uranium that is typically mined for fuel).

Re: Geothermal may beat batteries for energy storage

#199

Post by surfaceofthesun »

aidenn0 wrote: post #138
LinuxBender wrote: post #67

Many of the greenhouse Youtube channels I watch do a smaller DIY version of this. They have either dark barrels of water in the greenhouse with the windows facing south to the sun, or a thin metal wall filled with clay and pipes acting as a sun-heat-battery. They pump the water through the barrels or clay battery into pipes that are under ground to store the heat. In winter time they extract the heat from the ground…

Forget geothermal, I'd love an air-exchange system for the summers where I live. It's not uncommon for the low to be in the 50s, with the high in the 80s. If I could just store some of that overnight cool in water and then run it through the central air system, I almost wouldn't need AC.

More thermal mass could help (e.g. lots of concrete or masonry might help)

Re: Geothermal may beat batteries for energy storage

#200

Post by jandrese »

martin_a wrote: post #191
jandrese wrote: post #136

Earlier quoted context omitted.

Yeah, pumped hydro is one of those power sources that doesn't scale down at all. However, home scale conventional hydro is a thing. If you live on a hill with a creek that runs down it you can install a generator that produces a usable amount of consistent power for the cost of a few hundred meters of PVC pipe, a barrel, some connectors, and a small electric turbine. Search for micro-hydro if you want to know more. L…

> Search for micro-hydro if you want to know more. I've probably seen everything YT has to offer on that. :-D While I really enjoy those videos and the "let's just do it" vibe with old washing machines as generators, I'm also somewhat happy that Germany has rather strict regulations on how to use water from streams and rivers. Some installations are quite disturbing for local ecosystems. But being off-grid in remote…

Most micro-hydro setups seem to divert only part of the stream and only do it for a few hundred meters or so. These streams are typically much too small to be salmon spawning grounds or the like so the ecological impact seems pretty minimal. It's not like they're drinking all of the water, it gets returned to the stream right below the turbine.
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