Numerical assessment of increasing photovoltaic self-sufficiency of a low energy residential building in Belgium by using heat pump and energy storage

Abstract

In the line of measures aiming to reduce the greenhouse emissions and the total energy use of residential buildings, all new buildings built from the year 2020 within the European Union must meet the requirements of so-called Nearly Zero Energy Buildings (NZEB). An NZEB represents a building with high energy performance and significant coverage of its energy demand by utilizing renewable energy sources through on-site energy generation. A self-sustained building represents a building, which is only using energy generated on site to meet its energy requirements. In this article, self-consumption and self-sufficiency of an NZEB are assessed through numerical, transient detailed models made in programming language Modelica and simulated in the software tool Dymola. The two-floor residential building is modelled as a dwelling with the space heating energy demand of 30 kWh/m²year. The energy use of the building coincides with the occupancy profile of a family with four members with the dominating domestic hot water use over the space heating need. The space heating comfort conditions are attained with the low-temperature underfloor heating system. The domestic hot water demand is provided through a 300 l water tank. Both systems are coupled to an air to water heat pump. The aim of the research is to investigate the potential of increasing the self-consumption and self-sufficiency values by using thermal load shifting and electrical energy storage in order to compensate for the direct unbalance in optimal energy generation and energy use. For aspirations in achieving a complete self-sustainable dwelling, different sizes of energy storage and photovoltaic panels are used for the analysed case study conditions. However, special attention is paid to the available south roof space of the dwelling. For the use of 28 m² of optimally positioned photovoltaic panels, the studied building achieves 49.1% of self-consumption and 27.2% self-sufficiency without any use of energy storages. With the electrical battery of 20 kWh and thermal energy storage of 1000 l, the building can meet self-consumption of 89.8% and self-sufficiency of 49.8% for specific boundary conditions.