New Air Conditioner Process Cuts Energy Use 50-90%

necro81 writes "The US National Renewable Energy Laboratory has announced that it has developed a new method for air conditioning that reduces energy use by 50-90%. The DEVap system (Desiccant-Enhanced eVaporative air conditioner) cools air using evaporative cooling, which is not new, but combines the process with a liquid dessicant for pulling the water vapor out of the cooled air stream. The liquid dessicant, a very strong aqueous solution of lithium chloride or sodium chloride, is separated from the air stream by a permeable hydrophobic membrane. Heat is later used to evaporate water vapor back out — heat that can come from a variety of sources such as solar or natural gas. The dessicants are, compared to typical refrigerants like HCFCs, relatively benign on the environment."

Comments

Is this a closed system?

[OnePumpChump]

Swamp coolers use a LOT of water. Is this better than them in terms of water use? If not, it's just trading one environmental ill for another. The places that have water to spare also have humidity high enough that even this system might not do so well with its evaporative cooling, and the places where evaporative cooling works best don't have the water to spare.

Re:Is this a closed system?

[chrysrobyn]

We're currently running in the mid-90's with dewpoints in 80's. "Swamp coolers" just don't work well in this climate, so I don't know how useful this will be to us.

Wikipedia doesn't do the principle justice. A swamp cooler is essentially a big fiber mesh (which can look and feel similar to cardboard but holds up when it gets wet). This mesh is constantly sprayed with jets of water to keep it wet -- damp isn't enough. A big fan, bigger than a typical air conditioner, forces air through this mesh and pushes it into the house. Each room that needs to be cooled needs to vent air out, typically into the attic and out into the outside. The more air you move through this mesh, the cooler the house, so it's typical that the air volume is much higher than an air conditioner.

The humid air introduced into the house is essentially at dew point (if it's lower than dew point, the mesh / jets aren't doing their job forcing the water into the air), so the house will likely be warmer than that, making a few assumptions about the conditions outside. Now, if you had this pre-drier in Alabama, dropping the dew point to 40 or 50, you'd be able to cool the air 20 or so degrees -- about what your air conditioner does.

By the way, I grew up in Phoenix. Instead of the $400/month power bills from running the air conditioners, my parents opted to run swamp coolers. The water bill regularly got above $100/month, but the electric bill didn't. Financially, it was a good trade-off. I'm told there are health benefits from breathing more humid air instead of dry desert air, and the air was constantly being refreshed from the outside, so there certainly weren't any toxic house concerns that people in some areas of the country have. On the flip side, there's the monsoon season, which is typically the whole month of August; the dew point rises to the point where swamp coolers just don't cool much. Several of my Magic: The Gathering cards (mostly Revised aka 3rd Edition) felt like they had a powdery coating on them. I assume this is mold. If it was on my cards, I'm certain it was on countless other surfaces we just never touched enough.

Re:Is it better than this?

[hcpxvi]

Sheesh, RTFA, already. They mention the coolerado and explain exactly why this new idea has the potential to do better.

The key to TFA

[dtmos]

"By no means is the concept novel, the idea of combining the two," Kozubal said. "But no one has been able to come up with a practical and cost-effective way to do it."

Or, maybe,

Inventing a device simple enough for easy installation and maintenance is what has impaired desiccant cooling from entering into commercial and residential cooling markets.

As TFA states, desiccant cooling has been known since at least Carrier's work at the turn of the 20th Century. The trick has always been to make a practical desiccant cooling system.

Re:OK, so when can we buy one?

[stonewallred]

AZ and NM use a lot of swamp coolers if they can't afford AC. With 100 degree 0% RH, a swamp coolers does a decent job.

Re:It's not either/or

[Lumpy]

no they dont. 4" exterior walls are common now. it USED to be 6" was required for exterior walls. but contractors wanted to increase profit margins clamored to make houses more "shitty".

Homes should also be sheathed with 3/4" plywood instead of the craptastic fiber board they use now. I've been doing high end installs of whole house audio in $1,000,000+ homes on the side for 5 years now. Home construction has went down hill quite a bit from the late 80's where you had to have good construction quality.

Re:Well...

[EvilRyry]

The article never mentions sodium chloride, I though that sounded a bit off when I read the summary.

The kind NREL uses are syrupy liquids — highly concentrated aqueous salt solutions of lithium chloride or calcium chloride.