Geothermal in Iceland, Hawaii
A reader offers: This concept in geothermal is interesting. And why isn’t Hawaii doing this? It’s not like they don’t have lava at their disposal.
The issue is sometimes cost-effectiveness vis-a-vis competitive forms of energy. Costa Rica has lots of geothermal resources, but they have huge hydro resources as well, the latter of which is easier and cheaper to have happen.
In Hawaii, we need to keep in mind that only the Big Island has an active volcano, and there is a 34 MW geothermal plant there. They’re considering geothermal in western Maui, which is where 90% of the population resides and the tourists hang out (which is weird insofar as the eastern part of the island is far cooler–see pic of Hana above). Unfortunately, Oahu, by far the largest consumer of electricity, has no geothermal resources at all.
Geothermal power is successfully used in Iceland, New Zealand, Hawaii, and a few other places as well. It works. However, it is not so simple as some might think.
The hot water used often contains highly corrosive minerals. That need not be a deal killer, but it does add complication. Also, the temperatures available are generally much lower than for modern coal burning power plants. That means that the turbines operate at a lower efficiency and have to be much larger for the power produced. Again, that’s not necessarily a deal killer, but it does add to costs and increases the amount of cooling required for the condensers.
It may be that the use of geothermal power will greatly increase and provide a significant percentage of global power needs.
Frank the cite explains that the technique is slightly different than typical geothermal wells. The wells are expected to tap into supercritical steam and produce about 50 MW / well vs 5 MW for a typical geothermal well.
These are also very deep wells into old magma fields.
Re Oahu, research is ongoing on geothermal – true, it does not have a resource like big island, but that does not mean it cannot be done. Given the very high cost of power, deep drilling may well be attractive. Note that some quite unlikely candidates like Germany have developed a small amount of geothermal power.
I wasn’t going to mention this as it is slightly off topic but two days ago a notice from the Office of Energy Efficiency came across my desk. It seems that they are offering funding for a studies into enhanced geothermal energy: geothermal energy at a lower temperature (that may use heat pump technology to produce electricity) or as it is called ““Geothermal Deep Direct-Use Feasibility Studies,” more likely it is to use geothermal heat directly in an industrial or space heating application.
As I am looking at this type of geothermal I speculate that it might be easily combined with several methods of grid level storage using heat. (Low level heat is used over time to “charge” a thermal battery which is then used for peak demands.)
This is at the opposite end of the thermal scale for geothermal energy applications from what is discussed in the article above. “Geothermal” is actually a big topic.
I understand that China uses a lot of geothermal energy in district heating. Likewise in Iceland where the majority of space heating across the island comes from geothermal sources. For Hawaii being in the tropics, space heating is not needed except at high elevations, so heat loads are mostly for process heat such as food processing. Adsorption chilling might also be considered, but with deep cold water available near to shore, I would have thought district cooling could be more cost effectively delivered that way.
District heating is usually yet another type of geothermal. In this case, much of the energy is actually solar that has heated the earth to a fairly common 55 deg F. Where wells are used rather than shallow loops or a body of water, they are relatively shallow, about 200 feet to an aquifer. Heat pumps take care of the difference for heat and AC. It is sometimes referred to as ground source heat pump. (ie condensers use liquid to liquid vs liquid to air like a radiator in a car) It is also more common in Europe than in the US. It works well with a radiant floor heating distribution system but seems overpriced by some contractors in the US… lots more could be said but this is truly a different topic.
In Iceland the geothermal heating is a byproduct of geothermal power. High pressure steam is used for power generation and the used now low pressure steam is piped through the streets. Lower Manhattan is also piped for steam which you might notice escaping in many movies.
There was somewhere in Hawaii an OTEC research station. Craig had a piece of this technology once. It uses similar technology to engineered geothermal. It seems like a great idea but it needs additional lines (desalinization, district AC that you mentioned…) to resolve efficiency and economics.
It seems as if co-generation is often a way to make an operation more economical or more efficient.
There is a difference in terminology across the Atlantic. In Europe, we would typically only use the term geothermal to describe heat of geological rather than solar origin. In Southampton UK, There is a geothermal district heating system which takes advantage of a low temperature geothermal resource at around 60 centigrade.
Re district cooling, the Swdish city of Stockholm has a system serving the financial district. Sea water is pumped through one side of a titanium heat exchanger to cool fresh water which is then circulated at around 4 centigrade around the district.
With a very steep drop off to extremely deep,water around each of the Hawaian islands, it should surely be possible to draw cool sea water from deep down into a heat exchanger and so run a district cooling system similar to the one in Stockholm but more cost effective as cooling it needed year round.
Yes, and seawater district cooling can be used in combination with OTEC, as well, since they both require a cold water pipe.
When I referred to the solar origin of geothermal, this may be a bit esoteric for some. Wiki has a reasonably good article about this kind of geothermal heat pump operation: https://en.wikipedia.org/wiki/Geothermal_heat_pump
World wide the relatively shallow ground remains at about 10 -16 deg C or below 6 meters at the annual mean air temperature for the location. Under the section “Differing terms and definitions it says, ” this is “Earth heat” … is largely influenced by stored energy from the sun.” Without the influence from the sun the ground temperature would be about 40 deg C colder. Hence the energy recovered is a form derived from of solar energy just as wind energy is derived from solar energy. No one refers to geothermal heat pump recovery as “solar energy.” However, it is sometimes useful to make the distinction when comparing this type of geothermal to volcanic geothermal which seems to have a strictly Earth based nuclear decay origin. (Rather than a solar fusion origin.) … but somewhat esoteric.
OTEC is/was involved in pumping cold water from the deep ocean around Hawaii but they were going quite deep. Craig may be aware of pumping costs vs energy recovery benefits, but it is unlikely such water could be used directly. A typical AC is producing air in the 30 to 40 deg F range (about -1 to 4.5C) Some heat pump operation would likely have to be used. The benefits of such a regional system would likely depend upon a comparison with existing private air source heat pump systems. There is also a bit of politics involved. Americans don’t easily go for a regional cooperative system when a private solution is available.