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

What it will take to unleash the potential of geothermal power? (2021)

technologyreview.com

Post reply on HN
Print view View original

101–108 of 108 posts

Re: What it will take to unleash the potential of geothermal power? (2021)

#101

Post by pfdietz »

One possibility is further collapse of the price of other renewables.

If solar were nearly free (< $0.01/kWh, say) it could make sense to bank that energy as underground heat. The thermal time constant for hot rocks scales as the square of the linear dimensions of the rocks, and can easily reach many years even for relatively shallow systems (this is why geothermal works at all). Such a system would not need to drill as deeply as a natural geothermal system operating at the same temperature, and might be able to get much hotter than anything not drilling near a volcano.

Re: What it will take to unleash the potential of geothermal power? (2021)

#102

Post by pi-e-sigma »

angiosperm wrote: post #100
pi-e-sigma wrote: post #67

Earlier quoted context omitted.

That's not true at all. If any other liquids were more useful they would have been used long time ago, even in places where the cost is not of primary concern, such as nuclear submarines.

Nuclear submarines have no use for a working fluid that boils below 100 C. Indeed, they pressurize the water so that the boiling point is well above that point, because they have no difficulty heating water well above that. Steam is used everywhere despite that it is quite corrosive, mainly because it is cheap.

You clearly don't know what you are talking about. Water steam is a perfect medium for turbines because of its favorable thermodynamic properties, mainly high specific heat allowing water steam to absorb large amount of thermal energy. Also water steam is not corrosive because water itself is not corrosive. It's the dissolved minerals making it corrosive and that's why water used for turbines is purified first.

Re: What it will take to unleash the potential of geothermal power? (2021)

#103

Post by mr_toad »

pi-e-sigma wrote: post #67
angiosperm wrote: post #35

Earlier quoted context omitted.

There are fluids other than water that have usefully different boiling points. Problem is that mature turbines are designed for steam. Turbines for other fluids cannot approach their market volume.

That's not true at all. If any other liquids were more useful they would have been used long time ago, even in places where the cost is not of primary concern, such as nuclear submarines.

> That's not true at all. If any other liquids were more useful they would have been used long time ago,

Gas turbines are common when power to weight is more important than cost.

Re: What it will take to unleash the potential of geothermal power? (2021)

#104

Post by bequanna »

daveguy wrote: post #80
thechao wrote: post #57

Earlier quoted context omitted.

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.

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.

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.

Re: What it will take to unleash the potential of geothermal power? (2021)

#105

Post by rcxdude »

seiferteric wrote: post #83
this_was_posted wrote: post #74

Earlier quoted context omitted.

would it be possible to use a heat pump to increase the temperature to a more efficient range? Or would all of the efficiency gained be lost by operating the heat pump?

I have wondered about this as well... If your heat pump uses say 1kW, and they usually provide 4x-5x heat out, so say 5kW of heat out and your able to extract 50% of that as energy using say a turbine, you would get 2.5kW out? or maybe 1.5kW (subtracting the initial 1kW used to run it?) so maybe not great but maybe possible?

given perfect heat pumps/engines in that circumstance, you would get exactly as much energy out as you put in. Theoretically perfect heat engines are called 'reversable' for that reason: they give you the best possible exchange between heat and work. Said another way: heat pumps can give you 4-5x the heat out as work you put in precisely for the same reason you can't get much work out of that heat: the temperature increase is small. If you were to heat something up to a temperature where you could more efficiently extract work from it, it would require more energy to do so.

Re: What it will take to unleash the potential of geothermal power? (2021)

#106

Post by swamp_donkey »

WarOnPrivacy wrote: post #36
swamp_donkey wrote: post #29

Earlier quoted context omitted.

This was tried using money for 2010 olympics in Whistler BC as the athlete accommodation was sold as subsidized housing to local workers after the olympics. The geothermal district heating project had many ongoing issues with repair costs being borne collectively by the new owners. Some saved $150/mo by removing it and switching to electric [0] 0: https://www.piquenewsmagazine.com/opinion/letter-to-the-edit...

I appreciate the info. I'll give it a read.

There are probably a dozen articles on the issues in that pique news paper spanning a decade. Lots of finger pointing between the parties responsible for the design, installation and maintenance. The Vocal group of owners got bailed out by the local government at one point but it didn’t resolve the ongoing issues.

Not to say the technology is hopeless, just in this instance it wasn’t done properly so maybe it isn’t as easy as people think.

Re: What it will take to unleash the potential of geothermal power? (2021)

#107

Post by angiosperm »

pi-e-sigma wrote: post #102
angiosperm wrote: post #100

Earlier quoted context omitted.

Nuclear submarines have no use for a working fluid that boils below 100 C. Indeed, they pressurize the water so that the boiling point is well above that point, because they have no difficulty heating water well above that. Steam is used everywhere despite that it is quite corrosive, mainly because it is cheap.

You clearly don't know what you are talking about. Water steam is a perfect medium for turbines because of its favorable thermodynamic properties, mainly high specific heat allowing water steam to absorb large amount of thermal energy. Also water steam is not corrosive because water itself is not corrosive. It's the dissolved minerals making it corrosive and that's why water used for turbines is purified first.

Yet, steam turbines attached to nuke and coal plants spend 10-20% of their time offline, being overhauled mainly because of high-temperature/high-pressure steam's corrosiveness.

Cold distilled water is not corrosive. Superheated steam, howsoever pure, little resembles cold liquid water in any detail. Furthermore, hot water will pick up minerals from whatever it runs through.

Many materials that are not especially corrosive as cold liquids behave quite differently at extreme pressure and temperature. Water has uncommon valuable thermodynamic properties, but not uniquely so; its chief virtue is that it is good enough and cheap.

Re: What it will take to unleash the potential of geothermal power? (2021)

#108

Post by pi-e-sigma »

angiosperm wrote: post #107
pi-e-sigma wrote: post #102

Earlier quoted context omitted.

You clearly don't know what you are talking about. Water steam is a perfect medium for turbines because of its favorable thermodynamic properties, mainly high specific heat allowing water steam to absorb large amount of thermal energy. Also water steam is not corrosive because water itself is not corrosive. It's the dissolved minerals making it corrosive and that's why water used for turbines is purified first.

Yet, steam turbines attached to nuke and coal plants spend 10-20% of their time offline, being overhauled mainly because of high-temperature/high-pressure steam's corrosiveness. Cold distilled water is not corrosive. Superheated steam, howsoever pure, little resembles cold liquid water in any detail. Furthermore, hot water will pick up minerals from whatever it runs through. Many materials that are not especially cor…

OK, give me an example of one such liquid from your list of 'many' that has all the desired properties of water and doesn't have any undesired, such as being a poison. You can't because there aren't any.
Post reply on HN