Model for evaluating impact of battery storage on microgeneration systems in dwellings

Lead-acid batteries are a suitable technology for on site storage of microgenerated electricity. In this paper, an algorithm is developed that will assess, with an appropriate temporal resolution of data, the ability of lead-acid battery storage in capturing AC and DC power generated from photovoltaic cells, combined heat and power and wind turbines. The assessment includes the impact that the storage element has on the import and export of energy from the electrical grid and is a valuable tool in determining an optimum storage capacity. Used effectively, storage can increase the versatility of a microgeneration system by satisfying the highly variable electrical load of an individual dwelling, thus changing usage patterns on the national grid. Empirical electrical load demands are considered with a 1 min temporal resolution and compared with microgeneration (and battery) supply profiles with a similar temporal accuracy. The results show that, when producing on site electricity through microgeneration, suitably sized storage can reduce export substantially (by over 90% in some cases) and store this energy at a typical round trip efficiency of 70-72%. The developed model accounts for typical losses in a battery storage system, including that associated with inverters, power electronics and the efficiency of charge/discharge cycles.