DOAS: A New Approach to HVAC
Heating, ventilation and air conditioning (HVAC) is perhaps the most money-intensive element of an energy manager’s mandate. These systems are big, vital and consume prodigious amounts of energy.
The sector is getting bigger. Research and Markets found that the global industrial HVAC market will expand at a compound annual growth rate (CAGR) of 4.12 percent between this year and 2020. That’s significant growth for a market that already is saturated – few buildings don’t have HVAC systems. The report covers HVAC use in manufacturing, food and beverages, pharmaceutical, biotechnology and other sectors.
The market is not just growing in size. Though it is mature, innovation continues. Among the new approaches to overall efforts to provide clean and comfortable air to the occupants of a building is the use of dedicated outside air systems (DOASs).
DOAS essentially divide to conquer – or, at least, to keep people comfortable. They do this by addressing the cooling and heating element and the ventilation element of the overall HVAC job separately. By doing this, two interrelated goals are achieved: The unique needs of a given space – be it a conference room, classroom, office or cafeteria – can be met without impacting adjoining areas. This improves comfort levels. It also by its nature a more efficient approach that leads to significant savings by limiting the use of electric devices to the specific space at hand.
The Northwest Energy Efficiency Alliance puts it simply: DOAS provide outside air to interior spaces independent of efforts to heat or cool that space. This, the piece says, creates economies: “Decoupling ventilation from space heating and cooling offers the opportunity for significant fan energy savings,” the article says.
This week, ACHRnews.com posted a story in which an executive from Modine Manufacturing commented that DOAS designs are becoming more common in commercial HVAC design. The story suggests that this evolution, as well as electronically commutated motor (ECM) fans and other innovative approaches, are being pushed by increasingly aggressive air conditioner and furnace standards from the U.S. Department of Energy (DoE) and the strong new construction and replacement markets.
Last year, facilitiesnet posted an article exploring new heating and cooling technologies. DOAS, the site said, have gained greater traction in Europe. Dave Callan wrote that the use of two systems can carry a higher “first cost,” but that the long-term benefits are great:
With dedicated outside air systems (DOAS), the advantages of constant air volume — namely, reliability and humidity control — can be more economically leveraged by specifying it only for the ventilation and dehumidification aspects of the system. The DOAS can then be coupled with a number of other systems — i.e., chilled beams, induction units, fan coils, etc. — to facilitate heating and cooling. With a high level of humidity control, the space doesn’t have to be cooled quite as much, because people are generally comfortable at higher temperatures if the humidity is controlled.
A comprehensive overview of DOAS systems was posted Consulting-Specifying Engineer by J. Patrick Banse, a senior mechanical engineer at Smith Seckman Reid Inc. After a technical explanation of how the system works, he sums it up the advantages of the system with a bulleted list. The key is that DOAS systems can address resources where they are needed. This highly flexible and addressable control leads to less stress on systems and the fans and other mechanical elements of which they are comprised.
Innovation continues in the world of HVAC. DOAS systems, which not tend to be used in higher end facilities, are one of several promising approaches.
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