Multi-objective optimization for reducing the auxiliary electric energy peak in low cost solar domestic hot-water heating systems in Brazil

Domestic water heating in Brazil is commonly done by electric showerheads, characterized by a large installed capacity and a low load factor. In that regard, consumers and utility companies present opposite interests, the first aim to reduce their electricity bill, while companies are interested on shaving on-peak consumption. Solar technologies offer significant potential for domestic applications, but the implementation is commonly hindered by economic issues. The present work shows a methodology for addressing the impact of promotion policies in terms of the benefits for consumers and utility companies. It is proposed a weighting procedure that allows to examine both interests in a single objective function. It enables determining a trade-off curve and optimizing the design parameters of the solar system (collector area, storage volume and set point temperature). Two policy scenarios were analyzed: a rebate program and the implementation of a time-of-use tariff (TOU) scheme. The results derived from the first policy scenario show the existence of a trade-off curve between the initial investment and the yearly electricity consumption, which is useful for addressing the impact of the monetary incentive considered for rebating the initial cost of the solar system. The second policy scenario shows a trade-off curve between the annualized life cycle cost of the system and the yearly on-peak electricity consumption. That curve can be used for assessing the influence of the TOU tariff on the on-peak electricity utilization, allowing to measure the impacts of the tariff scheme, and providing the basic parameters for negotiation strategies between company planners and relevant consumers.