When Root Elementary in Fayetteville, Arkansas needed to replace a handful of aging rooftop units, plant director David Tate saw a unique opportunity: upgrading with equipment designed to use the least energy possible, with the ability to produce some of its own energy needed for operation. Tate selected the SunSource® Commercial Energy System from Lennox, the industry’s only solar-power system integrated directly into a rooftop unit.
The SunSource system is a factory-installed option for Energence® rooftop units, the most energy-efficient light commercial rooftop unit1. For Root Elementary, Tate had three 17 SEER rated Energence units, each designed to accept up to 21 power-generating solar modules.
“In our school and our community, ‘green’ is extremely popular,” Tate says. “We’re trying some new things – not just using high-efficiency equipment but rain barrels, LEED® design principles and recycling programs – to see what can happen. It’s not only for the energy savings but also to educate our school system’s Green Team.”
For Root Elementary, Tate and his maintenance staff had six solar modules installed for one rooftop unit. Designed with a plug-and-play system for simple installation, the system with modules was installed in about half a day with no changes to the building’s electrical wiring infrastructure required. Tate was impressed that the modules not only capture the sun’s energy, but each also uses its own microinverter to convert the DC power harnessed to AC power and send it directly to the rooftop unit. Because the modules aren’t tied together with a high-voltage line, the system is both safer and more reliable: If shade or dirt hampers one solar module, other modules aren’t affected. By pairing a 17 SEER Energence unit with the SunSource system, the school can achieve an effective efficiency of 34 SEER and beyond* to lower its energy consumption.
The SunSource system is monitored by an online communication module that will provide real-time system status, allowing Tate to see how much energy the system is producing and the environmental benefits it provides 24/7. “David was really excited to see the installation of the monitoring system, which will allow him to track the reduction in greenhouse-gas emissions and energy usage the SunSource system allows,” Lennox Industries’ Donna Peoples says. “He and his school want to do everything they can to create a better environment for their students.”
* Effective SEER estimates for the SunSoure air conditioning system are based on the U.S. Department of Energy(DOE) annual performance factor (APF) method for heat pumps and air conditioners (10CFR part 430). Estimates of annual solar energy production are calculated for a centrally-located city in each DOE heating region, using National Renewable Energy Laboratory's (NREL) PVWatts, Version 1. The annual solar energy production is solely an estimate for that region and is based upon a fixed-tilt south-facing array free of shading, with a module tilt angle equal to the local latituted of the installation. The annual solar energy production is included in the APF calculation as a reduction of the cooling season power consumption. In this example, the air conditioning unit is an Energence LGH060H4ES1P (5-ton/17 SEER) located in Region IV (represented by Omaha, NE at 41degrees North latitude. and with six solar modules rated 175dc Watts each.
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