The concept of evaporative cooling has been around for centuries. Anyone who has felt the cool breeze coming in across a lake has at least a rudimentary understanding of this physical law, one which has profound implications in the effort to reduce the energy needed to cool our indoor environments. “Swamp coolers” based on the principles of evaporative cooling served as early air conditioning units a century ago, but Memphis-based Evaporcool has elevated this timeless technology into a new and inspiring form: an externally mounted filter that fits over the air intake of any commercial air cooled HVAC unit, no matter the size or configuration.


Evaporcool’s low cost, easy-to-install externally mounted filter cuts HVAC unit energy consumption by 20% or more. Rendering: Courtesy of Evaporcool

This low-cost, easy-to-install approach typically cuts energy consumption of the HVAC unit by 20% or more, simply by dampening the incoming airstream of the HVAC unit, which often sits on urban rooftops and parking lots where air temperatures routinely soar into the triple digits.

Evaporcool’s lightweight polymer-framed filters house a series of tiny misters, which mist the air in short bursts of water (hooked up to standard city water and using as little as .9 gallons per day, per ton) as it is pulled through the condenser intake. One thing to note is that the water/mist doesn’t get onto the fins or coils to cause corrosion. Their proprietary technology goes much further than previous evaporative cooling systems by using a “smart controller” to sense eight different parameters, including temperature, humidity, and the electrical demand of the air compressor, to make minute-by-minute adjustments to the volume of water applied.

Ben Taube, senior vice president for corporate and strategic development at Evaporcool, describes the controller as if it’s a little robotic engineer living in a box on the side of the HVAC unit, crunching the numbers day and night to achieve the greatest efficiency. “The controller is constantly calculating the optimal conditions for the water to be 100 percent evaporated, which is what results in the greatest reduction in temperature from the outside air,” he says.


In addition to the 30% reduction in power consumption of the HVAC units at the NRG data center, a 26.75 kW photovoltaic array provides a portion of the power to the office space, while wind energy offsets account for the rest. Photo: Courtesy of Eric Melzer Photography

The controller includes a wireless transmitter that connects it to a cloud-based server, which is easily integrated with an existing building control system, to provide building operators real-time information on the unit’s efficiency, as well as the ability to conduct fault diagnostic tests. “If we see components that are not working correctly, we can send a signal to the controller and adjust those specific parameters,” Taube says.

Any moisture that is not immediately evaporated—or as Taube says, “flash evaporated”—collects on a thin filter media, which further cools the air entering the unit. But the filter media serves other important functions, as well. Dust and debris are prevented from entering through the air intake, so not only do building operators find that energy use plummets, but they are also freed from the time-intensive maintenance of cleaning the condenser coils. Plus, the harsh chemicals typically used for the job are no longer needed. By keeping the unit from working as hard to cool the air, and by keeping it cleaner, HVAC systems with Evaporcool technology typically have a longer lifespan.

Taube says the payback on the investment is typically in the one-to-three-year range, depending on the climate, availability of incentives (e.g., government or utility), and other factors. “By reducing the air temperature going into those units, they have a better load profile and the capacity for the unit increases,” Taube says. “So there are both operational savings and energy benefits.” Plus, installation is a breeze: Evaporcool custom builds each filter to fit the size of the air intake and uses industrial strength magnets to hold them in position on the metal frames of the HVAC unit, eliminating the need for invasive drilling and screws—making it easy to access the HVAC system.


Ben Taube describes the controller as “a little robotic engineer living in a box on the side of the HVAC unit, crunching the numbers for the greatest efficiency.” Rendering: Courtesy of Evaporcool

Evaporcool Technology in Practice

How Evaporcool Filters Save Water

The Evaporcool system uses approximately 1.9 gallons of water for each kWh saved, saving approximately 90% of water usage while also saving electricity.

Based on national averages, on a 75-ton HVAC unit, the Evaporcool system will use $78 of water in a year, while saving more than $7,000 annually in electricity.

The National Renewable Energy Lab (NREL) reports that “U.S. electricity production consumes more than 20 gallons of water per KWH created.”

Other studies confirm this water usage and state that depending upon the power plant type, the water usage can range from 10 gallons to 25 gallons of water consumed per kWh created.

Evaporcool’s pre-cooling system protects the HVAC equipment of some very high profile clients. NRG Energy, Inc., a company with the largest independent power producer and one of the largest solar power developers in the nation, recently cut the ribbon on a new data center in Katy, Texas, a hot and humid suburb of Houston, where the company houses some of its most critical IT infrastructure. Their arrangement with Skybox, the owner of the data center, which leases a 10,000 square foot space to NRG, allowed them to customize the build out of their “data hall” with the types of energy conservation features they like to include on all their facilities. A 26.75 kW photovoltaic array provides a portion of the power to the office space—wind energy offsets account for the rest. Evaporcool’s pre-cooling filters, which NRG is a strategic partner, can be found on the twin 400-ton Trane air chillers outside the building.

Pat Furr, director of IT infrastructure at NRG, says they’re seeing a 20-to-30-degree drop in the temperature of the air entering the data center chillers as a result of the Evaporcool filters, leading to an estimated 30% reduction in power consumption of the HVAC units. Combined with the other energy efficiency features at their Skybox data center, NRG is on track to achieve a PUE rating—which stands for power utilization effectiveness, the ratio of watts used by the actual IT equipment in a data center versus the total watts needed to power the data center (including lighting, HVAC, UPS, etc.)—of 1.3 at full load, which is pretty impressive, given that a PUE of 2 was considered standard in the industry in the not distant past. In other words, for every watt used by the servers, only .3 watts is used for ancillary systems, including cooling.

“If you could ever get to 1.0, that would be Nirvana, but of course there’s always going to be something that needs to run the IT support equipment,” Furr says. “But in the big picture this is an extremely energy-efficient data center, and the Evaporcool solution is one of the major components facilitating that efficiency.”

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