Impact of electricity tariffs on optimal orientation of photovoltaic modules

Abstract

Maximum revenue (or cost saving) from non-tracking photovoltaic (PV) modules used for distributed generation can be achieved by a module orientation that depends on how the electricity tariff varies with time of day and time of year. Many jurisdictions have real-time market prices of electricity for large customers, time-dependent tariffs or tariffs that depend on peak demand. This paper quantifies the impact of such tariffs on the optimal orientation of non-tracking PV modules using example tariffs from California, Nevada and Ontario, and concludes that modules should be oriented to the west of south by 28°, 46° and 54° respectively. In order to focus on the impact of tariff, the results are based on simulations of a constant-efficiency PV system operating under year-round clear-sky conditions. A generalized relationship between optimal azimuth and the on- to off-peak ratio of time-dependent tariffs is also presented. The paper quantifies the sensitivity of the dollar value of the power generated to non-optimal orientation of the modules. Compared to conventional south facing modules tilted at an angle just under the latitude, the paper demonstrates that optimal orientation adds 4–19% to the revenue/cost savings, potentially affecting the economic viability of a PV installation. The peak demand components of the Ontario tariff have a much more substantial effect on the optimization and resultant revenues (cost savings) than variations in the real-time market price of electricity.