Commercial Rooftop Unit Optimization Product Literature Review
In the United States, seven quads, or 7 X 1015 Btu, of primary energy is consumed per year for heating, cooling and ventilating commercial space (US DOE, 2012). According to the 2003 Commercial Buildings Energy Consumption Survey, approximately 2.7 billion square feet of commercial retail floor space is served by packaged air-conditioning units, or rooftop units. Not only are rooftop units high energy users, but compounding demand is the prevalence of units oversized to meet extreme and infrequent thermal loads (Studer, Romero, Herrmann, & Benne, 2012, p. iv).
While new, more energy efficient rooftop units are increasingly entering the market for new facilities or to replace retired units, most existing units serving commercial buildings remain in the useable phase of lifespan. Energy efficiency opportunities abound with these rooftop units and new retrofit devices are being specifically designed to capitalize on these opportunities. As demonstrated in review of retrofit device marketing literature and recent independent studies on advanced control strategies, such retrofit devices may offer favorable payback periods while providing a feasible option to simply replacing the unit.
To summarize current information on rooftop unit retrofit devices and advanced control strategies, Advanced Energy completed a literature review of manufacturer claims for select available retrofit devices as well as published studies from credible organizations on simulated field performance. The retrofit device literature review and studies from two highly credible organizations – the National Renewable Energy Laboratory and the Pacific Northwest National Laboratory – are summarized in this report.