Solar photovoltaic roof-mounted systems are well known for efficiently, reliably, and quietly generating clean, renewable energy, with the added benefit of producing energy at the same location where it will be used. Given the popularity of these distributed energy systems, there have been an increased number of facilities noticing an indirect benefit: lower energy usage in addition to the green energy produced from solar.
In 2010 the U.S. Department of Energy reported that climate control systems constitute approximately 40% of commercial building’s energy use. Given a typical large, flat roof’s exposure to the sun, a majority of the heat a building generates is often absorbed through the roof, leading to large energy loads attributed to the building’s HVAC systems.
In 2011, a group at UC San Diego set out to quantify the effect roof-mounted solar has on the overall temperature of commercial buildings. The team used thermal imaging to monitor the rooftop temperature of a building that features a solar installation on a portion of the roof. Data revealed that the daytime heat reaching the roof was reduced by ~38% due to the increase in “albedo”, or solar reflectance, as a result of the solar module coverage and convective air flow beneath the modules. This translates to a ceiling temperature 5 degrees cooler and yields a 65% reduction in cooling load for a roof protected by solar panels compared to a conventional exposed roof.
The lead researcher on the UCSD study, Prof. Jan Kleissl, concluded, “If you are considering installing solar photovoltaics, depending on your roof thermal properties, you can expect a large reduction in the amount of energy you use to cool your residence or business.”
Overall, while roof-mounted solar is a great way to lower facilities energy costs by generating clean energy on-site, facilities can expect the added benefit of reduced HVAC usage and lower energy costs.