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Hawaii First to Harness Deep-Ocean Temperatures for Power

scientificamerican.com

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Re: Hawaii First to Harness Deep-Ocean Temperatures for Power

#11

Post by sandworm101 »

dogma1138 wrote: post #7
sandworm101 wrote: post #4

I have to ask, but since so much of Hawaii's electricity production feeds air conditioners wouldn't it be more efficient to pipe this cold water into houses as coolant? Or to a datacenter?

The temperature of the littoral water in Hawaii isn't cold enough (77f/25c during winter an 85f/28c during summer) for efficient transmittance cooling not to mention that salt water can't be used for evaporative cooling like the one being used by commercial AC units for fairly obvious reasons.

The OP states that the cold water intake is a 5c. That would seem cool enough to either directly cool houses, or at least greatly increase the efficiency of their air conditioners. For the later you wouldn't need to evaporate anything. Just cooling the air conditioner with water rather than external air.

Re: Hawaii First to Harness Deep-Ocean Temperatures for Power

#13

Post by Steko »

dogma1138 wrote: post #2

Seems kinda pointless this only doubles the original pilot which was 50KW.... The plan was to build a 40-50MW plant within 3-5 years and expand it to 100MW+ over the following decade. http://www.bizjournals.com/pacific/print-edition/2010/11/12/... This tbh looks less like any type of commercialization but more of a consolation prize to LM since the Navy paid for the original pilot and was supposed to pay for the expa…

Your own link explains why it's not 'pointless':

There is no data on maintenance costs, possible environmental impacts on the marine environment or potential engineering problems that could arise with a full-scale model — not an enticing combination for private investment. ... The pilot is needed to produce the information necessary to attract investment for a large-scale model ...

Re: Hawaii First to Harness Deep-Ocean Temperatures for Power

#14

Post by dogma1138 »

Dylan16807 wrote: post #10
dogma1138 wrote: post #9

Earlier quoted context omitted.

It does't work that way crystals will still form, and salts mean free ions free ions mean corrosion.....

If you evaporate half of seawater, you're still down at one quarter of salt's saturation level. That will form crystals even if you keep things mildly mixed? Corrosion is a worry, but isn't that something you can fix with material choice?

Don't know most system that use that use the cold water for heat exchanging and have a closed / open sweet water loop for the actual cooling. But from every thing I've seen salt tends to accumulate on any surface under the right put a lid on a salt water container and the salt will form on the lid just with the internal evaporation/condensation cycle through sublimation

But there's only a handful of such systems in the world https://en.wikipedia.org/wiki/Deep_water_source_cooling

The largest is in Canada and they use sweet water, Norway and Finland have salt water systems that use water from the baltic sea but they seem to be simpler as they pump it into large water reservoirs under the city which won't really work for Hawaii.

Other limitations like the fact that the US builds with wood and drywall/plaster while Europe (and many other parts of the world, which were either deforested centuries ago or wasn't that much forested in the 1st place) uses concrete and concrete like blocks/materials almost exclusively even for internal walls might make it not that applicable for residential cooling.

Re: Hawaii First to Harness Deep-Ocean Temperatures for Power

#15

Post by dogma1138 »

Steko wrote: post #13
dogma1138 wrote: post #2

Seems kinda pointless this only doubles the original pilot which was 50KW.... The plan was to build a 40-50MW plant within 3-5 years and expand it to 100MW+ over the following decade. http://www.bizjournals.com/pacific/print-edition/2010/11/12/... This tbh looks less like any type of commercialization but more of a consolation prize to LM since the Navy paid for the original pilot and was supposed to pay for the expa…

Your own link explains why it's not 'pointless': There is no data on maintenance costs, possible environmental impacts on the marine environment or potential engineering problems that could arise with a full-scale model — not an enticing combination for private investment. ... The pilot is needed to produce the information necessary to attract investment for a large-scale model ...

Old link was for announcing the original pilot and they've built that one, they are already scaling it in China and other places why not scale it in the US?

Re: Hawaii First to Harness Deep-Ocean Temperatures for Power

#16

Post by sandworm101 »

Dylan16807 wrote: post #10
dogma1138 wrote: post #9

Earlier quoted context omitted.

It does't work that way crystals will still form, and salts mean free ions free ions mean corrosion.....

If you evaporate half of seawater, you're still down at one quarter of salt's saturation level. That will form crystals even if you keep things mildly mixed? Corrosion is a worry, but isn't that something you can fix with material choice?

Corrosion is an immense problem with salt water in large systems. Eliminating dissimilar metals across so many parts is tricky. Even then, unless you're going to plate everything in gold, corrosion will happen. The far easier solution is a heat exchanger between the saltwater and some other working fluid (ie radiator fluid) inside the system. I'm a bit surprised that the hawaii rig is pumping in actual sea water rather than dropping a radiator into the depths. That intake pipe will corrode eventually.

Re: Hawaii First to Harness Deep-Ocean Temperatures for Power

#17

Post by nashashmi »

Animats wrote: post #6

Hawaii is a chain of seamount islands, so the deep ocean isn't far away. That's unusual. Continents have a continental shelf, and it's usually a longer pipe run to the deep ocean, which means the 4°C cold water warms up along the way, plus pumping costs are higher. Solar works so well in Hawaii that the power company there is trying to stop it. Once batteries get a little cheaper, Hawaii will be mostly solar.

Pumping costs would not be higher due to depth. There is a whole lot of pressure at greater depths. That by itself can bring the water up. There might be a slight difference in density of warmer water over cooler water that could add to pumping costs.

But I agree with the first point: water warms up along the way unless they were to use insulated pipes like heat exchangers.

Re: Hawaii First to Harness Deep-Ocean Temperatures for Power

#19

Post by Steko »

dogma1138 wrote: post #15
Steko wrote: post #13

Earlier quoted context omitted.

Your own link explains why it's not 'pointless': There is no data on maintenance costs, possible environmental impacts on the marine environment or potential engineering problems that could arise with a full-scale model — not an enticing combination for private investment. ... The pilot is needed to produce the information necessary to attract investment for a large-scale model ...

Old link was for announcing the original pilot and they've built that one, they are already scaling it in China and other places why not scale it in the US?

> Old link was for announcing the original pilot and they've built that one,

You seem confused about something, that link is announcing a 5-10 MW system they didn't build. Or rather what they built is the system that you're calling useless.

> they are already scaling it in China and other places why not scale it in the US?

That question is answered in the comment you replied to. China doesn't care about things like marine life and runs on giant government capital investments.

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