TRY IT RISK-FREE »

Coolerado:
Evaporative Cooling Without Added Humidity

 

Coolerado R600 cools the sleeping quarters and fitness area of a Denver Fire Station. The station had been contemplating replacing its swamp cooler with a conventional air conditioner. It would have had to upgrade the power service to the building to get enough power, at a cost of about $25,000, something the Coolerado helped it avoid.

Evaporative cooling lowers indoor-air temperatures without the high energy loads of conventional cooling (see page 20). But to get those lower temperatures, direct evaporative coolers have to pull sensible heat out of the air by adding water vapor (latent heat), or sacrifice efficiency with an indirect system mediated by a heat exchanger. A sophisticated system from Denver, the Coolerado, which BuildingGreen named as a Top-10 Green Building Product in 2006 (see EBN Vol. 15, No. 12), eliminates that tradeoff. The Coolerado is an indirect system, so does not introduce evaporative moisture into the building, but it’s nearly as efficient as a direct system—even more so as temperatures increase.

Coolerado’s standard R600 units are available with either a single-speed motor that draws 1,200 watts or an electronically commutated motor (ECM) that draws no more than 750 watts. A comparable high-efficiency air conditioner draws 6,000–7,000 watts, according to Coolerado president Rick Gillan, so the Coolerado can dramatically reduce peak power demand in the cooling-intensive southwestern U.S. The units retail for $4,795 with the basic motor and $5,295 with the ECM.

It would be a mistake to treat the Coolerado like a direct evaporative cooler, or swamp cooler, which works by blowing large volumes of cooled, humidified outdoor air through a home, explains Dave Emmitt of Boulder, Colorado, who has installed evaporative coolers of all kinds. Unlike a swamp cooler, the R600 delivers only 1,500 cubic feet per minute (cfm—700 l/s) of conditioned air. “If you’re looking only to cool the rooms in proximity to the cooler, then you’re fine [with the Coolerado],” Emmitt says, adding, “but if you only have 1,500 cfm [for an entire home], then you have to figure out how to distribute it—that’s the big trick.”

It makes more sense to compare the Coolerado, which provides the equivalent of five tons of cooling, to a standard central air conditioner, which needs help from fans and ducting to cool a whole building. As long as the incoming air is dry, the Coolerado uses one-fourth to one-third as much energy and draws only one-eighth as much power as a five-ton air-conditioner. “If you’re making that comparison, I’m in love,” says Emmitt. His most successful Coolerado installations have included ducting and a return-air loop that mixes 30% to 40% recirculated air with the fresh air going into the unit.

While the Coolerado works fine in homes if it is installed appropriately, it’s an even better fit in small commercial and light-industrial buildings. These facilities tend to have large, open spaces, so no ducting is needed, and they require large amounts of outdoor air for ventilation. (Because they depend on dry air, evaporative coolers generally work more efficiently with outdoor air than with recirculated air.)

Conventional wisdom says that evaporative coolers can cool air only to near its wet-bulb temperature, and indirect evaporative coolers—because their heat exchangers are never 100% efficient—can’t even get that low. Coolerado’s technology, however, as verified by scientists at the National Renewable Energy Laboratory, can achieve temperatures below the wet-bulb temperature of the incoming air, although the commercially available product doesn’t go quite that far. The trick is a patented system dubbed the Maisotsenko cycle after the Russian- born physicist who invented it.

In an indirect evaporative cooler, “working air” absorbs moisture and cools off, while “product air,” is cooled by the working air through a heat-exchange surface. That way, the product air (the air delivered into the building) doesn’t gain moisture. In the Maisotsenko cycle, however, the working air begins in a dry chamber and is incrementally drawn into a wet chamber, where it is saturated. This cooled air then acts through the heat-exchange membrane to cool both the product air and the remaining working air. That remaining working air has already been partially cooled but not wetted, so it can still absorb moisture and cool off to well below the wet-bulb temperature of the original incoming air. Thus, despite the imperfect heat exchange, the product air is also cooled to near the original wet-bulb temperature.

One drawback of this indirect cooling approach is the amount of water it requires. Unlike swamp coolers, the Coolerado doesn’t have a reservoir that must be purged regularly, but it does use up to 12 gallons (45 l) per hour, which is similar to the 2.3 gallons per ton-hour (2.5 l/kWh) or more used by evaporative cooling towers in larger-scale systems. Also, evaporative cooling advocates point out that it takes a lot of water to generate electricity (see “Save Energy to Save Water” in EBN Vol. 11, No. 10), so water used onsite is partially offset by water saved at the power plant. The moisture-laden working air, which is even cooler than the product air, typically goes unused.

Even though the Coolerado doesn’t add moisture to the air, it doesn’t remove it either (as conventional air conditioners do), so the air’s relative humidity goes up because air can hold less moisture as it cools. Gillan argues that this makes the Coolerado ideal for most Western states, where “people think it’s dry, but that’s only in the winter. In summer the humidity is ideal—you don’t want to add humidity or take it away.” If dehumidification is needed, it can be provided by linking the Coolerado to a conventional cooling coil or by other means. In fact, the Coolerado can be combined with other cooling equipment in various ways to significantly enhance the efficiency of the entire system. A hospital in Japan uses an array of Coolerado units along with a desiccant cooling system to achieve a 50% energy savings over conventional air conditioning, according to Gillan.

Where added humidity and constantly moving air are no problem, a high-quality direct evaporative cooler, such as those from AdobeAir or Seeley International, can provide more efficient cooling at a lower first cost than the Coolerado. A higher-end option, with lower airflow and less added humidity for the same cooling potential, is the OAsys from Speakman CRS. But for high-efficiency cooling in dry climates with no added humidity, the Coolerado represents a unique and attractive option.

For more information:

Rick Gillan, President
Coolerado, LLC
Arvada, Colorado
303-375-0878
www.coolerado.com

May 1, 2008

DISCUSSIONS

There are no comments for this page yet.

Log in to add comments - Help with comments

RELATED ARTICLES

EBN: Product News - April 2009
EBN: BackPage Primer - May 2008
EBN: Awards & Competitions - December 2006

RELATED PRODUCTS
Product Image: Coolerado Cooler
Coolerado Corporation
Coolerado Corporation

RELATED CATEGORIES

CSI DIVISIONS AND SECTIONS
CSI Section 23 76 00

LEED Credits
EA Prerequisite 2
EA Credit 1
EA Credit 4
EA Prerequisite 2
EA Credit 1
EA Credit 1.3

GREEN TOPICS


IMAGE CREDITS:
1. Photo: Coolerado
DISCUSSIONS
There are no comments for this page yet.


RELATED ARTICLES

RELATED PRODUCTS

RELATED LEED CREDITS
EA Prerequisite 2

RELATED GREEN DESIGN

RELATED CSI LISTINGS
CSI Section 23 76 00