With temperatures on the rise we're on the lookout for new technologies that can help us keep cool and save energy too. One new tech is the refrigerant known as "R-718", or more commonly "Water Vapor".
But you've got to ask: How does it work? Is it efficient, and if it is so cool why doesn’t everyone use it?
It turns out water refrigeration been around for a long time. In Europe they have used it for years, primarily driven by their high energy prices. R718 can be more efficient than our current refrigerants (R134A for example), but it takes a special type of compressor to make it work. The compressors used in Europe use titanium turbines. Expensive titanium is used because R718 compressors have to spin very fast to get the right pressures. In Europe where the energy costs are relatively high, R718 makes good economic sense. Here in the United States, with historically cheap energy it takes too long to recover the initial expense through energy savings. That is ’till now.
The Stratos Company LLC (of which I am president) is working with Prof. Norbert Muller of Michigan State University on the development of a novel R718 air conditioner that is very inexpensive. The key to success has been the development of a special turbine that is made in a very cleaver way such that you can substitute relatively cheap carbon fiber plastic for titanium!
No expensive metal, no toxic refrigerants and more efficient designs. Who knew that it was all possible with water?
Additional Info: MSU (PDF Link)
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written by jsbarrie, May 21, 2007
refrigerant. It is non-flammable, odorless and non-toxic (although it can cause suffocation
at very high concentrations), has zero ODP and low GWP.
The main barriers to the use of CO2 is that it generally results in low energy efficiency
because it has a low critical temperature (about 31.3oC). In certain applications this problem
can be alleviated through special heat exchanger design. CO2 also operates at much higher
pressures (around 100 bar) and has a substantially higher volumetric capacity than most
other refrigerants, which means that existing equipment designs, including compressors, are
unsuitable. Considerable development is taking place on CO2 for small refrigeration
systems, including car air conditioning and cascade refrigeration systems in low temperature
food storage and freezing plant.
From an environmental and thermodynamic point of view, water is probably the ideal refrigerant for applications above 0C. However, there is a major practical difficulty caused
by its high specific vapor volume which is around two orders of magnitude greater than a
typical HFC refrigerant. This means that an extremely large compressor is required. The
best compressor type is probably an axial or centrifugal machine, but suitable versions for
water vapour are currently special items, are very expensive, and have long delivery times.
Their high cost, large size and not being off-the-shelf items therefore rules them out as
replacements for general air conditioning applications at the present time. Future
development of commercial products, and possibly alternative steam ejector systems, holds
out promise of water being a viable alternative in the longer term future.
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written by Moses, June 19, 2009
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written by Jason, June 28, 2009
The low GWP and zero ODP are not the only environmental qualities of using co2 as a refrigerant. Its high volumetric capacity can significantly reduce the material content of refrigeration systems, reducing compressor sizes and pipe sizes.
Although a lifecyle analysis of a refrigeration system indicated that over 90% of indirect CO2 emissons came from the energy used, there is still a need to reduce the indirect emissions from the manufacturing of refrigeration plant.
Co2 is the only refrigerant that can offer this.
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