Low energy buildings equipped with heat pumps for high self-consumption of photovoltaic electricity

Thygesen, R. (2016). Low energy buildings equipped with heat pumps for high self-consumption of photovoltaic electricity. Doktorsavhandling i energi och miljöteknik vid Mälardalens högskola.

Abstract

The building sector is a prioritized area in the European Unions (EU) ambition to reduce the total final energy use by 20 %; lower the emission of greenhouse gases by 20 % and using energy 20 % more efficient by 2020. The residential sector in the European Union accounts for 27% of the union’s final energy use and the EU views decentralized energy generation and heat pumps as important measures in reducing the energy demand in the building sector.

In recent years a rapid decrease in photovoltaic system prices has led to a growing popularity in Sweden. This fact in combination with a large in-crease of heat pump systems in residential buildings the last decade makes a combination of heat pumps and solar energy systems an interesting sys-tem configuration to analyze. In addition, the electricity price structure in Sweden and the uncertainty of the sustainability of the Swedish solar energy support schemes makes the topic of self-consumption an important research area.

Different solar energy systems for residential buildings and two different storage technologies, batteries and hot water storage tanks, have been analyzed with regards to profitability, solar energy fraction and self-consumption levels.

The results suggest that the system with a heat pump in combination with a photovoltaic system can be profitable and have high solar energy fractions and high levels of self-consumption and that the systems with storage are not profitable but give high levels of self-consumption and relatively high solar energy fractions. The hot water storage gives almost as high level of self-consumption as batteries but have half of the batteries levelized cost of electricity.

A system with a ground source heat pump and a solar thermal system are ineffective, unprofitable and give low solar energy fractions.

A system with a weather forecast controller gives a small increase in self-consumption and is unprofitable.

The proposed near energy zero building definition proposed by the Swedish National Board of Housing, Building and Planning in 2015 is unclear in terms of what electrical load the PV electricity reduces in the building. This has a fairly large impact on the building specific energy demand.