Globally, legislative measures and policies are being tabled and implemented with the aim to curb greenhouse gas emissions. For instance, the European union set a target of reducing greenhouse gas emission by 80-90% that of 1990 by the year 2050. For such goals to be realized, significant reduction will be required in the energy sector, namely: transport, electricity generation and thermal energy. This seems like an impossible goal judging by current population explosion which in terms puts more strain in the available resources. On the other hand, this can however be achieved through technological innovations, energy efficiency and replacement of existing power systems.
Previous research has shown that houses demand about 40% of the electric energy supplied for heating/cooling and cooking. In view of lowering greenhouse gas emissions, one feasible approach for the housing sector is by building near Zero Energy Buildings (nZEBs). nZEBs differ from passive buildings in that they combine energy efficient building design with on-site or nearby renewable energy technologies in order to reduce the net primary energy demand of the building to close to zero. As such, numerous studies focusing on design of nZEBs have been undertaken, however, a study aimed at examining the impacts of these low energy buildings based on a whole energy system level perspective and analysis, especially within a transitioning energy system, is yet to be undertaken.
Recently, Aalborg University scientists: David Drysdale (PhD candidate), Professor Brian Vad Mathiesen and Susana Paardekooper carried a thorough and expert analysis of the proposed nZEBs system in a bid to comprehend the implications of building new low energy buildings within an energy system that is (a) transitioning to 100% renewable energy and (b) has substantially improved supply-side energy efficiency. The researchers, from the Department of Development and Planning used a case study from their home country; Denmark, as the transitioning Danish building system that include both residential and service (office) buildings had available data. Their work is currently published in the research journal, Energy Efficiency.
From the onset, Denmark was chosen since the energy system is already advancing towards 100% renewable energy with an already high proportion of renewable (wind) power injected in the electricity system. In order to comprehend the impact of new buildings on the future 100% renewable energy system, an analysis for new buildings with different heat demands using six scenarios was done. The impacts were analyzed in terms of (1) the total heat demand of the building stock, (2) the impact on biomass demand and (3) the total energy system costs.
The authors highlighted it is possible to successfully transform to smart energy system (which will result in reduced primary energy demand) because of the use of the plan to use more efficient energy technologies including renewable electricity, electric mobility and an increase in cross-sector integration and energy storages such as utilizing wind power in district heating and reducing the use of solid fuel technologies.
The authors observed that in the current and future Danish energy system, buildings built from 2015 to 2050 with an average heat demand of around 56 kWh/m2 were sufficient. They also pointed out that new building having heat demand below the 56 kWh/m2 level would not significantly decrease the total heat demand, biomass demand or energy system costs in the future energy system. This is due to the heat supply mix of the energy system today and in the developing 100% renewable energy system.
In summary, the Danish scientists presented an in-depth expert analysis of the impact of new buildings in the Danish energy system as it transitions to 100% renewable energy. It was established that the current energy frames for new buildings in the Danish building code (BR15) were sufficient and therefore those levels should be maintained even after 2020. They further pointed out that existing buildings ought to be renovated in order to achieve an average heat demand of around 80 kWh/m2. Altogether, based on the Danish case study, for European countries aiming to decarbonize their energy systems, detailed energy system analysis to determine the extent to which heat demand should be reduced in buildings within the context of the transitioning energy system will be necessitated.
Future sustainable 100% renewable energy technologies “smart energy system” are able to accommodate buildings that are not near zero because the supply system is also renewable and more efficient. The production of heat for the new building stock is from different heat supply technologies (Heat pump, Solar thermal, District heating, and Biomass boiler) in the IDA 2050 Scenario. In fact, the authors believe for the future system it is counter-productive and unnecessary to push for near zero new buildings.
David Drysdale, Brian Vad Mathiesen, Susana Paardekooper. Transitioning to a 100% renewable energy system in Denmark by 2050: assessing the impact from expanding the building stock at the same time. Energy Efficiency (2019), volume 12: page 37–55.Go To Energy Efficiency