Water Heating Systems Performance in Multi-Family Residential Buildings in Brazil

Abstract

The performance of water heating systems must be evaluated considering energy consumption and efficiency in storing and distributing hot water, together with building and climate characteristics. This work aims to analyse the performance of different water heating systems compared to electric showers, which are widely used in Brazil. Systems with individual gas heaters and solar heaters with electric backup and gas backup were analysed in multi-family buildings. In addition, the influence of thermal insulation of hot water pipes was verified. The analyses were conducted using the EnergyPlus programme, considering three Brazilian cities with different climates: Curitiba, Brasília, and Belém. The results showed that solar heaters are a low primary energy consumption alternative, especially if combined with gas heaters. However, electric showers are the most efficient option for larger buildings and cold-climate cities, where thermal losses in distribution are more significant. Monthly, an electric shower can save up to 1.82 kWh/m2 of electricity compared to a solar heating system with an electric backup. The insulation has a limited influence on the performance of short-length pipes (temperature difference less than 0.3 °C in the instantaneous gas system). For longer pipes, the absence of insulation significantly reduces the shower temperature (up to 2.47 °C in solar heating systems), mainly in cold-climate locations. It is concluded that the most suitable water heating system should be determined according to the climate and characteristics of the buildings, such as the size and length of the pipe.