NREL’s new AC process to ease the heat wave burdenPublished on July 6th, 2010 | By: firstname.lastname@example.org
I’m dreading my next electricity bill. With this heat wave, I don’t think my AC unit has stopped running once in the past week. NREL may have developed an AC unit that eases the burden of energy usage.
According to a press release, NREL’s new air conditioning process has the potential of using 50 to 90 percent less energy than today’s top-of-the-line units. It uses membranes, evaporative cooling and liquid desiccants in a way that has never been done before.
“The idea is to revolutionize cooling, while removing millions of metric tons of carbon from the air,” NREL mechanical engineer Eric Kozubal, co-inventor of the Desiccant-Enhanced eVaporative air conditioner, says.
“We’d been working with membranes, evaporative coolers and desiccants. We saw an opportunity to combine them into a single device for a product with unique capabilities.”
The DEVap relies on the desiccants’ capacity to create dry air using heat and evaporative coolers’ capacity to take dry air and make cold air.
“By no means is the concept novel, the idea of combining the two,” Kozubal says. “But no one has been able to come up with a practical and cost-effective way to do it. We bring the water and liquid desiccant into DEVap’s heat-mass exchanger core. The desiccant and evaporative cooling effect work together to create cold-dry air.”
The air is cooled and dried from a hot-humid condition to a cold and dry condition all in one step. This all happens in a fraction of a second as air flows through the DEVap air conditioner. The result is an air conditioner that controls both thermal and humidity loads.
Traditional air conditioners use a lot of electricity to run the refrigeration cycle, but DEVap replaces that refrigeration cycle with an absorption cycle that is thermally activated. It can be powered by natural gas or solar energy and uses very little electricity.
This means that DEVap could become the most energy efficient way to cool your house whether you live in Phoenix, New York, or Houston.
Eventually, NREL will license the technology to industry, “We’re never going to be in the air conditioner manufacturing business,” said Ron Judkoff, Principle Program Manager for Building Energy Research at NREL. “But we’d like to work with manufacturers to bring DEVap to market and create a more efficient and environmentally benign air conditioning product.”
Adding: A post at After Gutenberg reports some more detail about the dessicants:
“NREL uses a liquid desiccant, a syrupy solution of lithium chloride or calcium chloride, about 44 percent salt by volume. In this setup, another membrane separates the desiccant from air traveling through a channel. The polymer membrane has pores about 1 micrometer to 3 micrometers in diameter, big enough that water vapor passes through easily while the salty liquid stays put. The membrane is also coated with a Teflon-like substance to repel liquid water. The desiccant pulls moisture from the airstream, leaving dry, warm air. Then it’s back to indirect evaporative cooling: in a second channel, water evaporates to cool a secondary airstream, which in turn cools the first airstream, and out comes cool, dry air.”
Also, the NREL provides some additional information about the origins of the membrane and potential applications:
“NREL has leveraged advances in PEM fuel-cell membrane research to produce a desiccant membrane capable of transferring moisture nearly as well as metals transfer heat. These membranes retain the moisture transport abilities of their fuel-cell counterparts but don’t require their unique electrical properties, so they are more straightforward to produce. NREL and its industry partners are optimizing quasi-counterflow plate heat exchangers that recover more than 75% of the heat and moisture from waste energy flows. The resulting product, which is available in commercial HVAC sizes, is a drop-in replacement for existing heat-only recovery devices and performs as well as rotary exchangers, but without the complexity of moving parts.”
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