Energy Efficiency in Residential Buildings in Mozambique - Measurements and Simulations

Abstract: Mozambique, situated in south-east Africa, has sub-tropical and tropical climate and plenty of natural resources for energy production. The country is however poor, and only about 25% of the population has access to electricity from the grid. A very large part of the energy used in the country is used in the residential sector, and there is a general lack of knowledge, regulations and tools concerning energy efficiency in buildings. The aim of this work is to contribute to a framework of knowledge and tools that can improve the energy efficiency in buildings, which in turn can lead to better use of natural resources, better indoor comfort in residential buildings and better economy for the dwellers. The framework consists of several parts, such as measurement equipment, an energy balance simulation tool and analysis of the potential of efficient appliances and PV-systems, as described in the following. It is believed that this knowledge and tools can be a resource for professionals in Mozambique, which will improve their possibilities to work for better energy efficiency in the residential sector. A reference building, “3 de Fevereiro Residential”, in Maputo City was used in the project. This building is typical for the housing stock in Maputo City and can serve as a case study for studying energy improvement in buildings in Mozambique. The use of electricity in the reference building was examined, and it was found that the equipment that use the largest part of the electrical energy was the cooling system, 26%, water heating, 23% and lighting, 15%. Old, inefficient appliances and traditional light bulbs were used in the house. The effect of changing to new, more efficient, appliances and using LED lamps was analysed and the evaluation showed that this could result in 24% decrease in electrical energy use. Measurement equipment for monitoring outdoor and indoor climate was installed in the building. Outdoor climate variables measured included global and diffuse irradiance, temperature, wind speed and direction. Indoor temperature and relative humidity was measured. Measurements were performed for a continuous period of one year, and the equipment included a facility for collecting the data via internet. Different theoretical and experimental techniques for analysing and evaluating energy used in buildings were examined in order to find a suitable tool for the climatic conditions and building types prevailing in Mozambique. DEROB-LTH was considered to be the most suitable tool among the evaluated ones. DEROB-LTH is a dynamic simulation tool with three-dimensional modelling of the building geometry for analysis of the effect of solar radiation as a key feature. DEROB-LTH was validated by comparing results of indoor temperature from simulations with measured indoor temperatures for the reference building. Measured outdoor climate data was used as input data. The comparison of simulation results with ones from the measurement equipment presented good agreement, which indicates that the selected tool can be used in Mozambican climatic conditions in particular, and in subtropical and tropical countries in general. An interesting way of decreasing electricity bought from the grid is the use of PVsystems. PV-systems could also be used where there is no grid, and as back-up for critical functions where the grid is unreliable like in Mozambique. To explore this possibility, a pilot PV-system was installed in the reference building. The system proved to work well, and its performance was monitored by measurement equipment. An evaluation of the life-cycle cost, however, showed that the electricity price when using the system would be about eight times higher than buying from the grid.