One of the most valuable paths to reducing HVAC costs is harnessing the air outside the structure. The optimal way of doing so — and the impact that is achieved — depends to a great extent on the local climate.
Free cooling has a lot of advantages. Navigant Research says that the market, which it more formerly calls airside air efficiency, is growing. The firm says that the worldwide sector will grow from $2.7 billion to $4.4 billion between this year and 2025. Local building codes, increasing density of cities in general and the desire to reduce energy use will drive the industry forward.
There are nuances between the particular approaches. Many can be attributed to differences in ambient temperatures between seasons and regions and associated ranges of humidity.
At the highest level, airside approaches are no-brianers: Using something that is all around, and freely available, makes sense. Navigant Principal Research Analyst Benjamin Freas told Energy Manager Today that the sector is comprised of airside air economizers and energy recovery ventilators. Economizers bring air in from the outside. Energy recovery ventilation (ERV) gears uses air that is exiting the building to mediate the temperature and humidity of that incoming air.
Location is key to how the technology is applied. “The climate of the geography where a facility is located is a key determinant for airside energy efficiency technology,” Freas wrote. “More extreme climates tend to favor ERVs to reduce conditioning requirements. Cooler climates favor economizers, especially for high-heat operations like data centers. In general, buildings with large cooling loads are good scenarios for economizers and buildings with large ventilation loads are good scenarios for ERVs.”
It is intuitively easy to understand that using the environment to handle a job as big as conditioning the air in buildings — including high-demand facilities such as data centers — is compelling. The attraction of this approach becomes even greater due to its potential use in meeting regulatory requirements. “Regulation is the largest factor driving growth in North America and Europe,” Freas said.
The use of this equipment is mandated by ASHRAE 90.1. Freas said that the rules require their use in buildings with more than a threshold heating load. There are exceptions and exemptions. The point is, however, that the equipment is not an option in many cases.
Free cooling is common. For instance, Modern Building Service today posted a story about the use of free cooling chillers from Tonon (and installded by Cool-Them) at the University of Lincoln, which is located in Lincoln, U.K. The installation, atop the school’s science building, features two 165 kW units. The free air cooling occurs by pumping a glycol solution around a chiller’s air handling unit when the outdoor temperature is low enough. The installation is expected to save 30 percent compared to a more traditional chiller installation, the story says.
Freas wrote that the use of the equipment goes way beyond simply doing what the government demands. “[I]n many existing building applications, retrofitting equipment with airside energy efficiency systems can provide substantial reductions on operating cost depending on climate and building use. Depending on the installed equipment, these savings can be generated with short payback periods.”
Of course, nothing in life is free. But, perhaps, some things come heavily discounted. Using ambient air to cool data centers and other structures makes a lot of sense. The part that is not free, of course, is associated with the need to filter out impurities, neutralize humidity and precisely set the temperature. Overall, however, it seems like a very good deal.