Impact of roof integrated PV orientation on the residential electricity peak demand

Peak electricity demand has been an issue in the Desert Southwest region of the US, due to extreme summer temperatures. To address this issue, a consortium was formed between the University of Nevada, Las Vegas, Pulte Homes, and NV Energy. An energy efficient residential community was developed by the team in Las Vegas with approximately 200 homes to study substation-level peak reduction strategies. A summer peak reduction of more than 65%, between 1:00 PM and 7:00 PM, compared to code standard housing developments is the targeted goal of the project. Approximately 50 homes are already built and some are occupied. The energy performances of the homes have been monitored and are presented in this paper. Several peak electric load reduction strategies such as energy efficiency in buildings, roof integrated photovoltaics (PV) and direct load control have been applied. Though all the homes in the developed community are installed with 1.8 kWp PV systems, the orientation of the PV system depends on the building orientation. Focus of this paper is to find the impact of PV orientation on the peak load from a building. In addition, different time-of-use (TOU) energy pricing options are offered by the local electrical utility company. Hence it is important to find an optimal pricing option for each building. A computer model has been developed for one of the homes in the new development using building energy simulation code, ENERGY-10. Calculations on the PV orientations have shown that a south and 220° (i.e. 40° west of due south) orientations are economically optimal for homes enrolled to flat electricity pricing schedule and time of use pricing respectively. As predicted by the simulations, the energy efficiency methods in the home have decreased the total annual energy by 38% compared to a code standard home of the same size. Further, the energy efficiency methods in the building coupled with a 220° oriented PV and 1.1 °C increase in thermostat temperature for three hours (from 3:00 to 6:00 PM) reduced the peak energy demand by 62% compared to a code standard building of the same size. Battery storage is the other option that will be considered in the project at a later time which is expected to carry the project well beyond its peak reduction goals.

► A study to demonstrate peak load reductions at the substation.
► A new residential energy efficient community named Villa Trieste is being developed.
► The peak demand from the homes has decreased by 38% through energy efficiency.
► Orientation of roof integrated PV has less influence on the summer peak demand.
► Increasing thermostat temperature during peak by 1 °C can significantly reduce peaks.