What do we do with an energy solution that only works in various parts of the world? Simple- we make sure that it becomes the modality of choice where it works well.
So, let’s consider this pretty brilliant idea. One that has been around for some 50 years (mostly investigated by the US Navy, but now finding applications in places like Polynesia).
We all know about geothermal energy. (This new process is similar in concept.) While geothermal is not available everywhere, there are places where we can harvest the thermal energy in the Earth’s crust. Given our improvements in the systems, the world is now using about 5 Gigawatts of thermal power (about ¼ in the US, 3.7 GW), at a cost of about a nickel a kilowatt-hour. Add to that about 28 GW of geothermal heating, and you can see that for limited regions where it obtains, geothermal is valid source of energy.
Well, Sea Water Air Conditioning (SWAC) is like that. It works around the tropical islands, where access to the deep ocean is viable and the cold water from the ocean can be used to air condition hotel resorts, homes, and hospitals. It also works for places near deep lakes (consider the Great Lakes region). And, given that those locations relied on fossil fuels before installing SWAC, we are talking about major changes for the climate. Moreover, these sites have a high- and year-round- demand for air conditioning, often at high costs (since they are remote from conventional cheap fossil energy sources). Often the AC demand is 40% of total energy consumption for the building or the area. (Right now, a hospital in Polynesia has switched to the system, which relieves about 2% of the island’s energy demands from fossil fuels. More on that later.)
The oldest such systems in Polynesia have been operating at the Intercontinental Bora Bora Resort (17 y) and the Thalasso Spa (9 y) There are two primary components to the system- the deep water pipe intake and discharge system and heat exchangers. (SWAC yields savings of $560K and $1.5KK each year for those two facilities, respectively.)
There’s even a system in Toronto (district cooling) using the water from the Great Lakes (Lake Ontario) as the cooling water source. It yields some 58000 tons of cooling capacity with a network of 3 four mile long, 63 inch diameter piping systems.
The French Polynesia Hospital (Papeete, Tahiti) system that hasa been running for about four months now had capital costs of 31 million Euros and will save 2.5 million Euros in electricity each and every year. Obviously, payback is going to be relatively rapid. Moreover, this system will reduce the energy demand in Tahiti by 2% all by itself. This is the largest SWAC system in the world, developed under the direction of David Wary, the Founder and Director of AIRARO.
Chilled water is transported throughout the buildings, via electric pumps. (But to pump cold water requires a fraction of the energy demands for a compressor in a conventional AC unit, as shown in the picture below.) Given that one is transporting sea water, the heat exchanger needs to be of more exotic materials- typically titanium- to preclude corrosion issues.
In lieu of the compressor, this system relies on an open sea water loop from the deep ocean (about 900 to 960 m), where the sea water is stable and routinely at 4 to 5 C. The pumps to draw this water up to the surface (suction pumps) also rely on electricity, but not much power is needed.
The key components are the piping system (the largest cost component), the pumps, and the heat exchanger. The capital costs are recouped from operation costs in 5 to 7 years. The cooling system source is basically non-depletable. (Except for global warming!)
The prime consideration for choosing such a system is to be contiguous to a source of deep cold water, a nearby shore, and large cooling loads (at least 1000 tons or 3500 KW), high electrical rates, and near yearlong air conditioning requirements.
This could be a start of yet another great alternative energy program.
