Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Geothermal may beat batteries for energy storage

spectrum.ieee.org

Post reply on HN
Print view View original

151–160 of 293 posts

Re: Geothermal may beat batteries for energy storage

#151

Post by robocat »

Schroedingersat wrote: post #29
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.

The interesting thing is when they've been around for 30 years (providing they don't decay too much with time). A sodium battery with 100 useful cycles and 10 years left in it is great for cycling once a month. But even without that, if we see costs of $50/kWh then you only need to cycle 300 times to make it more worthwhile than some generation technologies..

Don’t some battery chemistries have much higher self-discharge rates as they get older? If so, it might be uneconomic/wasteful to try to use old batteries.

Re: Geothermal may beat batteries for energy storage

#152

Post by dzhiurgis »

mint2 wrote: post #123
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…

Claims like that really aren’t helpful without numbers backing them up the cited paper gives the efficiency of heat pump but we’re missing multiple crucial values to get from there to a comparison of heating costs Edit: https://great-home.co.uk/air-source-heat-pump-running-costs-... At current average British prices of 28p for electricity and 7p for gas, and using averages for both it looks like the commenter was mos…

I read somewhere there’s market failure too. Electricity price is largely proxy of gas price. While uk gov subsidises has they don’t electricity…

Re: Geothermal may beat batteries for energy storage

#153

Post by spywaregorilla »

bagels wrote: post #117
spywaregorilla wrote: post #115

It's interesting to wonder how profoundly different the world would be if everyone had access to geothermal energy at the scale of somewhere like Iceland.

I know they heat their homes with the geothermally warmed water, but their electricity rates don't seem to be significantly different than most places. "Iceland, March 2022: The price of electricity is 0.139 U.S. Dollar per kWh for households."

Iceland has the cheapest electricity in the world. They run heat under their roads so they don't need to be plowed. Aluminum is shipped to Iceland to be smelted just because the energy is so much cheaper.

Iceland's electricity usage per capita is 4x that of the United States, and more than 2x the next highest country (Norway). They're the largest producer per capita as well. The population is not large, mind you, but it's noteworthy.

https://en.wikipedia.org/wiki/List_of_countries_by_electrici...

The rate for businesses is 0.066per kWh vs 0.128 in the US.

All of which is obfuscated by taxes and subsidies of course. https://www.globalpetrolprices.com/Iceland/electricity_price...

Technically it may be cheaper in some small petrol states but that feels misleading.

Mind you I'm just regurgitating a quick google's worth + tourism fun facts.

Re: Geothermal may beat batteries for energy storage

#154

Post by manmal »

Retric wrote: post #16
jillesvangurp wrote: post #7

Interesting option. It's all about the cost and efficiencies in the end. Converting electricity into heat and then back into electricity is a lossy process that is constrained by the second law of thermodynamics. Basically generating heat is easy and efficient. But converting it back to electricity is typically less than 50% efficient. Basically, it's several energy conversions in one process: you use electricity to…

Using batteries for the grid requires roughly the same amount of batteries as EV’s do. A 100kWh battery pack for a car * 1,000 charge cycles / 25 years = 4,000 kWh of battery per year * ~290 million cars. That’s enough to store almost 1/3 of all current electricity used in the US while ignoring busses and farm equipment etc. Of course actual cost depends on how much storage we need and future battery prices but addin…

Depending on charging strategy, LFP batteries can do 4000 - 7000 cycles. 1000 is way too conservative, for any kind of EV battery.

Re: Geothermal may beat batteries for energy storage

#155

Post by m463 »

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…

I remember reading about the enertia house, which had an interesting system.

They used certain trees inside the house that would phase change at room temperature so would keep the temperature comfortable naturally.

I think using a phase change is much better than just straight heating or cooling

https://pogue.blogs.nytimes.com/2007/05/17/a-home-that-heats...

Re: Geothermal may beat batteries for energy storage

#156

Post by xienze »

jonstewart wrote: post #80
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…

It is probably far more cost effective to buy a new air source heatpump. They’re so efficient and work well at low temps now. I have infloor radiant heat at a rural house in upper Midwest, have thought a lot about using solar heat pipes and adding a storage tank, and it’s all so fiddly, pipes and pumps and manifolds and glycol and maintenance, all custom, all expensive. I’m almost certainly better off with PV panels…

> They’re so efficient and work well at low temps now.

Can someone provide me model numbers for these heat pumps that “work well” at low temperatures? I’ve been through more than a few over the decades and currently have a Trane from last year and yep, still doesn’t hold up very well once the temperature hits freezing. Don’t get me wrong, I like heat pumps, but my eyes roll into the back of my skull when I hear over and over again that they’re “so efficient now” at low temperatures.

Re: Geothermal may beat batteries for energy storage

#157

Post by manholio »

raphaelj wrote: post #60
manholio wrote: post #56

Earlier quoted context omitted.

This is never going to happen. As a car owner, you are in a market competing with large providers of grid scale storage, that have large purchasing power, control over the battery chemistry and finer specifications of their hardware which is made to order for their needs etc. Meanwhile, you have a mobility-optimized low weight battery that has a single, monopoly supplier that will very likely treat the spare parts ma…

Couldn't scheduling the EV charge when the demand is low while production is high help a lot balancing the grid, at basically no cost for the EV owner? Let's say I have a EV with a smart charger that will keep the vehicle at least 60% charged, but charge up to 100% when the energy price is low (e.g. during the night).

> at basically no cost for the EV owner?

Only if you have a battery with unlimited charge cycles. This doesn't seem possible with current technology - and even if it were, manufacturers would still optimize for higher density and reasonable longevity after 100,000 miles. Most people would average a charging cycle a week, so they can't see the difference between a 2000 cycles battery and a 50,000 cycles one in the life of the car, but they can definitely feel the effects of range anxiety.

When you do daily or multiple times a day cycles, as is typical for grid applications, that's a completely different beast, for example a shallow charge cycle at 70% which increases the life 5x is much more profitable because it reduces overall battery replacement costs.

And when you factor in the much higher costs per Wh for car batteries, which are custom spare parts not mass produced commodity cells, you will find that the cost you incur in vehicle depreciation far exceeds the value you could earn from intra-day energy market speculation.

Re: Geothermal may beat batteries for energy storage

#158

Post by psadri »

psadri wrote: post #112
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…

energy storage density of heating water >> lifting water. 1m^2 of water heated by 50C (20C → 70C) = 58KWh lifting 1m^2 of water by 10 meters (~ 3 stories!) = 0.03Kwh :-(

I think in the future we will see more homes with:

Gray water recovery

Thermal batteries (hot and cold)

- Excess solar energy can be use to "charge" the hot or cold reservoirs for later use depending on season.

Effluent heat recovery

- Home appliances generate lots of heat (clothes driers, ovens, refrigerators, ...) that is currently vented to the atmosphere. Capture and use it to "charge" the hot battery.

- I'd imagine a water (or other liquid) line that connects to each appliance's exhaust via a heat exchanger to make the above more efficient as a standard part of home plumbing.

Smart appliances that sync with the home's energy system

- eg: clothes dryer that has the option to turn only when there is excess electricity available. Same with EV charging, etc...

[Edited for typos]

Re: Geothermal may beat batteries for energy storage

#159

Post by JohnJamesRambo »

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…

Can you share some of these greenhouse channels? I’d love to follow them to learn about how to better take care of my greenhouse.

Re: Geothermal may beat batteries for energy storage

#160

Post by soperj »

dahfizz wrote: post #108
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. 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.

they do it a lot in NZ. Solar hot water heating.
Post reply on HN