Solar Orientation of Photovoltaic Panels on a Community Scale
Through past research, the Building Industry Research Alliance (BIRA) and its partners have found that Near Zero Energy Homes (ZEHs) reduce peak electricity consumption by combining energy efficiency and solar electric generation. Working with the Sacramento Municipal Utility District (SMUD), the Building America Program (BAP) has gained insights to the ways Near ZEHs impact utilities and reduce peak electricity use. SMUD has been a pioneer in the electric utility industry working with BIRA to research and publish substantive results learned at the Near Zero Energy Community, Premier Gardens. Unlike many risk averse utilities, SMUD has boldly studied and shared research findings that will further promote the Near ZEH concept. Along with SMUD, Pacific Gas & Electric (PG&E) has shared gas data from Premier Gardens which will foster further study and research results.
The homes at Premier Gardens, a community of 95 homes in Sacramento, California, are monitored for energy consumption and PV production. The Premier Homes demonstrate well over 50% electricity savings as compared to an above code neighborhood next door. As Figure 8 displays, approximately half the peak savings are a result of efficiency, while the other half is generated by PV. This further supports incorporating cost effective efficiency measures first, then adding PV.
However with 25% of PVs facing east at Premier Gardens, greater savings were possible as Premier did not design photovoltaic orientation specifically for peak reductions.
Given the layout of the subdivision, BIRA investigated whether Premier Gardens could have been built with all west and south facing PV, thereby shifting PV production to later in the afternoon when the SMUD experiences it’s peak.
BIRA found that Premier Gardens as built could have eliminated all but four of the 23 homes with east facing PV, if PVs were placed on the front of the homes. And if planned for pre-construction, optional roof types could have been used to eliminate all east facing PVs. (Figure 11) As shown graphically, west facing PVs produce almost twice as much of their energy during SMUD’s peak compared to east facing PVs. (Figure 9)
BIRA additionally studied the community plans for Vista Palo Verde, a planned community by Clarum Homes. Clarum Homes of Palo Alto, CA is committed to energy efficiency and renewable energy. Clarum, like Premier, is open to placing PVs in the best location for overall energy and peak savings. At Vista Palo Verde it was found that all but one home could incorporate west to south facing orientations.
This research suggests that with planning, most communities can accommodate south to west facing PVs on all homes. This research contributed to California’s New Solar Homes Partnership’s requirements for west to southeast facing PVs to maximize the positive impact photovoltaic energy generation can have on utility peak.
Fig. 1: Peak Electricity Use for Premier Gardens homes vs. Cresleigh
Fig. 2: Percent of PV production by orientation during peak
Fig. 3: Premier Gardens as built highlighting photovoltaic orientations by home
Fig. 4: Premier Gardens with roof optimized for PV highlighting photovoltaic orientations by home
BIRA 2006 BA deliverable 11.B.1 Final Report: Results of Advanced Systems Research