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Comment by applied_heat | Hacker News Reader

I was hopeful that all of the unused drilling capacity after the shale boom/bust would allow some of the know how and equipment to be reallocated to geothermal but the grid operators and markets are not offering the premium to firm capacity that is required for the longer lead time and increased capital requirements and increased risk in geothermal projects vs wind and solar which can be augmented with battery storage.

It’s going to suck though when we hit a weeklong stretch of cloudy still weather if there isn’t enough spare capacity from other sources to compensate for the missing wind and solar.

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I'm trying to imagine the apocalyptic scenario that'd have all of Texas windless and cloudy for a week? Nameplate values for Texas wind & solar will eventually be well above peak required: excess power can be sold for silly things like bitcoin, desalination, fabbing, etc.

Right now wind is running at 16% capacity producing 6GW; you'd need ~308GW capacity to cover Texas needs from wind alone. Good luck.

That is why there is also solar

And there is also night. And clouds. Texas is good for solar but December and January still have relatively high variance - for example, in December 13 solar produced only 19.3 GWh while it produced 103 GWh two weeks later on December 27.

No single source has ever provided all electricity for any major region. To pretend otherwise is disingenuous.

Fossil fuels have done that trick, long before gridscale wind and solar ever existed.

So really you're the one being disingenuous.

Fossil Fuels aren't all one thing. There are different types, with vastly different infrastructures, etc.

Coal is not natural gas

Winter Storm Uri came pretty close to that. Very overcast every day. Pretty low wind compared to normal. I'm not blaming wind or solar for the failures; it was largely failures in gas production. But solar and wind output weren't close to their nameplate capacity.

Bitcoin sounds like the absolute worst thing to buy with excess electrical production. But desalination sounds like an excellent thing to buy. Silly is not the word I'd use.

The best thing to buy is just battery energy storage (or molten salt or hydro-pumped). Storage prices are falling even faster than the solar PV modules themselves, and there are dozens of huge factories being built every year, in the USA as well.

It seems like desalination is discussed on HN frequently but I have yet to see tech that makes any financial sense, even with somewhat cheaper power.

This is how Fervo Energy was founded. https://fervoenergy.com

I wonder if geothermal can offer mild battery storage by using excess energy to pre-heat the water.

Yes, though its not geothermal preciously - https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community

> The Drake Landing Solar Community (DLSC) is a planned community in Okotoks, Alberta, Canada, equipped with a central solar heating system and other energy efficient technologies.

> In 2012 the installation achieved a world record solar fraction of 97%; that is, providing that amount of the community's heating requirements with solar energy over a one-year time span.

> In 2015–2016 season the installation achieved a solar fraction of 100%. This was achieved by the borehole thermal storage system (BTES) finally reaching high temperature after years of charging, as well as improving control methods, operating pumps at lower speed most of the time, reducing extra energy need as well using weather forecasts to optimize transfer of heat between different storage tanks and loops. During some other years, auxiliary gas heaters are used for a small fraction of the year to provide heat to a district loop. The systems operate at coefficient of performance of 30.

https://www.dlsc.ca

https://www.sciencedirect.com/topics/engineering/drake-landi...

http://proceedings.ises.org/paper/swc2017/swc2017-0033-Mesqu...

I don't know about directly as a battery, but there is potential for energy storage. If you have geothermal HVAC at home, it can (sometimes) be use to heat water in a water heater. Dumping the extra heat into it. And I have heard stuff about using excess energy in the grid to put extra heat into home water tanks as well, so demand is reduced later. It is not getting converted back to electricity, but still a store for energy.

I don’t think thermodynamics lets that work. You can’t move heat from something cold to something hot so unless you are preheating your water to a temperature higher than your deep borehole rocks, all you’re doing is putting the first N joules of heat energy into the water you’re going to pump into your steam turbines using excess grid energy instead of geothermal energy.

Of course you can move heat from something hot to something cold, it’s called a heat pump. Though yeah I get what you meant. There are heat pumps that have entered production that are designed to generate the kind of industrial levels of heat required to heat the water to the level required to add heat to such reservoirs. Whether it makes sense, I can’t say. But it certainly makes sense for geothermal well used for district heating (not electricity). It’s already being done.

Funny thought: if you use a heat pump to store heat energy in summer to be used in winter.. and your reservoir can retain the heat efficiently (think the heavily insulated sand reservoir used in a project in Finland for instance)… could that make the battery effectively more than 100% efficient?

"Lisa! In this house we obey the laws of thermodynamics!" - Homer

> if there isn’t enough spare capacity from other sources to compensate for the missing wind and solar

This seems like a problem Elon would gladly dabble in, pushing out a NACS firmware update or something as an emergency limiter. Maybe first responders get priority, like they do for mobile network congestion.

Or dirtier power remains on cold standby for unusual peaks. This would eventually be outlawed, I imagine.

For week long storage there is always hydrogen, if alternative battery chemistries don’t pan out.

Hydrogen conversion is not only very inefficient, the hydrogen plants are also extremely costly.

Batteries are better bet.

Only for short term storage. Hydrogen is meant for longer term storage where batteries have too high of a losses. E.g. winter vs summer.

Way way way cheaper to 10x overbuild renewables than produce (and store) hydrogen at that scale.

It's actually not. There's a reason there are a lot of hydrogen storage projects for electricity generation going on.

Hydrogen is even better for longer-term storage (e.g. seasonal). Produce hydrogen via electrolysis from solar in the summer, then power things when it's cloudy + low sun angle in the winter. There are quite a few major hydrogen storage projects in progress that do exactly that, FWIW. E.g. https://www.energy.gov/lpo/advanced-clean-energy-storage (Disclaimer: My wife works on that project)

Batteries don't compete for long term storage. Losses are too high. Hydrogen is an excellent solution for longer term (weeks to months to years) storage.

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