Geothermal may beat batteries for energy storage • Hacker News Board

Re: Geothermal may beat batteries for energy storage

#141

Post by pfdietz » Tue, Oct 11, 2022, 6:27 PM UTC

bjourne wrote: post #128

retrac wrote: post #103

The the ratio of area A to volume V for a sphere of radius R is 3/R. The larger the sphere, the less surface area to volume. A corollary of this is that a sufficiently large thermal tank has little in the way of heat loss to its surroundings in relation to its heat capacity. At large enough scale, it's probably the most efficient way to store energy for general heating purposes. Simple water has significant thermal c…

> Assuming no losses, That could heat many dozens of typical Canadian suburban homes all winter. This honestly seem incredibly optimistic to me. Even a high-end thermos will lose its heat in less than a day. Faster in a cold environment. And afaik, temperature loss is proportional to temperature difference, so the hotter the liquid the faster it cools.

The thermal time constant for a sphere scales as radius squared (one factor of r due to volume/surface area, and one factor due to the temperature gradient scaling as 1/r). Your thermos is quite small.

Re: Geothermal may beat batteries for energy storage

#142

Post by jandrese » Tue, Oct 11, 2022, 6:30 PM UTC

Mrdarknezz wrote: post #55

Energy storage is the monorail of energy technology, expensive, unnecessary and conventional technologies like nuclear, hydro and geothermal is better in every regard.

Nuclear has enormous political hurdles that translate into extreme project costs. Hydro and Geothermal are both geographically limited. Hydro especially is effectively tapped out at this point. You are chasing progressively less suitable locations for each install. Most of the best remaining places are far away from civilization and would require hundreds of kilometers of high tension wire to get to the nearest grid connection.

Meanwhile battery prices are dropping year over year and installed capacity is still skyrocketing. Eventually the curve will level off, but we are not to the point of diminishing returns yet. Solar and Wind + Battery is shaping up to be the dominant power source of the future. It's all down to economics. Solar cells and wind turbines are not only getting cheap to buy, but once installed they require little maintenance and no ongoing fuel costs. Batteries are similarly low maintenance and the purchase price continues to drop as economies of scale and advances in technology make them cheaper and better.

Re: Geothermal may beat batteries for energy storage

#143

Post by londons_explore » Tue, Oct 11, 2022, 6:32 PM UTC

titzer wrote: post #100

londons_explore wrote: post #83

Earlier quoted context omitted.

Even a modern air source heat pump typically doesn't beat gas for $/kwh. Even in europe where gas prices are sky high, electricity still costs more when you look at the seasonal efficiency of heat pumps, which is typically advertised around 4.4, but various studies show that in most real world scenarios you typically won't reach the quoted lab numbers, so expect to get more like 2.5-3.0. Study: https://www.sciencedir…

That's kind of disappointing news. I had a skim through the article and was surprised to find that it's all based on models. There wasn't a single empirical measurement of an installation of either kind. Not that I don't believe in modeling and its usages, but I am going to radically discount the findings of this paper because there was no actual experiment performed here, just fiddling with models.

Give it a re-read. They collected data from actual houses (although granted only 6 boiler-years worth of hourly data), then fitted a best fit model to that data, then used the model for their conclusions.

They did that because they needed to compare the manufacturers datasheet lab figures to the real world figures, but there are 10+ variables that affect efficiency, and a direct comparison isn't possible unless all the variables match - hence using a model to act as the 'convertor'.

Re: Geothermal may beat batteries for energy storage

#144

Post by teucris » Tue, Oct 11, 2022, 6:34 PM UTC

cinntaile wrote: post #111

teucris wrote: post #93

Earlier quoted context omitted.

Huh. We have a 1:1 credit system here in Washington.

Considering solar owners are all pushing electricity onto the grid at the same time, when it is needed the least, such a system doesn't make sense. There are real costs associated with getting rid of all that unwanted energy.

> when it is needed the least

I don’t think this is true in many areas. In our area, during the summer the neighborhood is running A/C when the sun is at its peak. During the winter, heating. Also the transport loss from a power station is nothing to sneeze at - my understanding is that locally produced power often just results in reduced demand on the larger grid.

Re: Geothermal may beat batteries for energy storage

#145

Post by jandrese » Tue, Oct 11, 2022, 6:35 PM UTC

londons_explore wrote: post #139

jandrese wrote: post #135

Earlier quoted context omitted.

However, the ASHP can also be used to cool your home in the summer. In the past this has been a dubious benefit for most of northern Europe, but heat waves have been getting stronger, last longer, and happen more frequently as time goes on. This is turning into a serious consideration. Also, you can theoretically power a ASHP with renewable energy, while there are few if any carbon neutral replacements for natural ga…

Most boilers purchased today allow use with a Hydrogen mix, and some under development allow 100% hydrogen. Before the widespread extraction of natural gas, towns were powered with 'town gas', which is ~50% Hydrogen, so this is very much proven tech. There are a bunch of potential ways to make green hydrogen too. So, there very much is a path to green with a gas boiler.

Green Hydrogen has not worked out so far. It is not clear that it even has a path forward. There are a lot of people hopeful that it will be a solution in the future, but as of today it is so uneconomical that even people willing to spend more to be green don't use it.

Re: Geothermal may beat batteries for energy storage

#146

Post by retrac » Tue, Oct 11, 2022, 6:37 PM UTC

bjourne wrote: post #128

retrac wrote: post #103

The the ratio of area A to volume V for a sphere of radius R is 3/R. The larger the sphere, the less surface area to volume. A corollary of this is that a sufficiently large thermal tank has little in the way of heat loss to its surroundings in relation to its heat capacity. At large enough scale, it's probably the most efficient way to store energy for general heating purposes. Simple water has significant thermal c…

> Assuming no losses, That could heat many dozens of typical Canadian suburban homes all winter. This honestly seem incredibly optimistic to me. Even a high-end thermos will lose its heat in less than a day. Faster in a cold environment. And afaik, temperature loss is proportional to temperature difference, so the hotter the liquid the faster it cools.

While literally zero loss is a violation of thermodynamics, with a really large tank and good insulation, it gets to self-discharge rates lower than most battery chemistries. A few percent per month. There's a small district heating system in Alberta driven with solar thermal power. It uses a large insulated soil heatsink. Most of the energy input is in the summer and it took four years to fully charge up to operating temperature. It holds enough heat to provide all required heating through the winter for ~50 large houses.

Re: Geothermal may beat batteries for energy storage

#147

Post by ncmncm » Tue, Oct 11, 2022, 6:49 PM UTC

helloooooooo wrote: post #57

ncmncm wrote: post #47

This is an example of "how can we keep X relevant in a world where it is not?" Geothermal is falling away because maintaining a steam turbine is expensive. There are plenty of efficient storage options that don't depend on a steam turbine. Those are favored except where the storage medium is also a transportable, valuable product, as for ammonia. (Ammonia is burned in combined-cycle turbines already built to burn NG.…

It depends what you want to use the geothermal heat for. In Norway, in the winter, a lot of the energy use is going to be heating. Geothermal heating systems are quite common in northern and don’t require lossy conversion

And pure thermal uses are not good storage for high-grade energy forms, e.g. electric, because of conversion losses. In Norway, pumped hydro is a good place to park high-grade energy.

That said, for rarely drawn-upon storage, conversion efficiency doesn't matter very much. It is why back when hydrogen electrolysis still lost 40% off the top, it was considered fine for long-term storage. Now that it has exceeded 90%, it is useful in more places.

Re: Geothermal may beat batteries for energy storage

#148

Post by lazide » Tue, Oct 11, 2022, 6:56 PM UTC

cogman10 wrote: post #119

cookiengineer wrote: post #68

Earlier quoted context omitted.

This reminds me a lot of the Earthship community in the middle of the desert, which always focusses on smart ways of reusing water for different purposes, and by not wasting water as much as possible. The houses usually have a clean/grey/blackwater + a rainwormbox system to process fecals and reuse it for growing plants. Their air conditioning system is basically just a pipe in the ground where the hot air flows thro…

> Why there are no water storages on the roof. Depends on the area, but sometimes collecting rain water is illegal. The other issue is that when dealing with rainwater, you need to clean it. Untreated, rainwater will likely develop a bad case of algae.

It’s also really heavy - any amount likely to even light up a lightbulb for an hour or two would collapse a house without major reinforcement. Which would far outweigh any value of the storage.

Re: Geothermal may beat batteries for energy storage

#149

Post by kansface » Tue, Oct 11, 2022, 7:05 PM UTC

Schroedingersat wrote: post #82

mschuster91 wrote: post #51

Earlier quoted context omitted.

> Solar, if you use more than ~1% of the land you're radically altering the albedo and habitat Both of these may actually turn out to be beneficial. Putting up solar panels above agricultural land ("Agri-PV") is not just avoiding clobbering up arable land with PV panels, but also has benefits for the plants [1]: they need less water because less sun directly hits the plants and heats up the soil which means both more…

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?

Re: Geothermal may beat batteries for energy storage

#150

Post by adrr » Tue, Oct 11, 2022, 7:13 PM UTC

newyankee wrote: post #17

More the competition the better for the world. I still feel a well designed Lithium Iron Phosphate or Sodium based battery with > 5000 cycles can prove very cost effective if used properly. The high no of cycles reduces the levelized cost of storage significantly. Difficulty is scaling this to beyond 1-2 days at most.

For places with high car ownership, you can use electric cars as the battery storage. Just need lithium iron phosphate batteries to be standard in EVs. Telsa is using them in some of their models in China.