A new approach to evaluate the nearly zero energy concept of EPBD recast at district scale

Throughout the world, energy was the primary worrisome point for all nations as the sustainability of the daily life depends on it for conditioning the buildings, transportation and production. While the population and the need for consumer goods are increasing, the overall energy consumption is increasing, too. Researches and statistics show that worldwide energy demand is being met mostly by fossil fuels and continuously increasing energy demand awaken the concerns about extinction of the energy sources. Moreover, through the world, the most energy consumed and produced areas are distinct, which makes some countries dependent on external energy sources and some others exporters who benefit high profits. As a result, the potential source extinction and high financial sources spent on external energy sources created the need to take action for decreasing the energy demand and external dependency. Beside the other sectors, buildings are responsible about one third of the overall energy consumed in the World. European Union (EU), identified the incremental targets for the years 2020, 2030, 2040 and 2050 to be reached by building energy sector. Energy Performance of Buildings Directives (EPBD) was published in 2002 and 2010 to assure and instruct the Member States (MS) to reach the 2020 goals, which are 20% of energy efficiency, 20% of renewable energy share and 20% decrease in greenhouse gasses (GHGs), compared to 1990 levels. Other directives like Energy Efficiency Directive and Renewable Energy Directive are also supporting these goals. Turkey, where the case study takes place, follows also the EPBD. Building energy performance certification system was completed and started to certify the buildings in 2008 and energy performance targets for 2023 were defined in National Energy Efficiency Action Plan. However, further and stricter directives are expected as we are coming closer to 2020 and 2030 targets are ahead. The last EPBD, which was published in 2010, presented the new terms of cost optimal and nearly zero energy levels for buildings. According to the methodology that EPBD propose, energy efficiency improvement measures should be analysed together with long term costs (global costs) including investment, replacement, maintenance and energy costs. Cost optimal energy level was defined precisely as the solution of measures causing the lowest global cost. On the other hand, nearly zero energy building was defined questionably as the building which has very high energy performance with renewable energy contribution. Determination of the nearly zero energy levels were left to the MS's responsibility to be defined nationally. In line with the energy efficiency targets for the building sector, in the dissertation EPBD methodology was implemented to several types and numbers of buildings aiming to reveal the energy efficiency potential at the settlement scale. According to the hypothesis set in the dissertation, buildings energy performances cannot be dissociated from the location in the settlements. As well as the design parameters such as distance between buildings, orientation, heights, etc., district energy systems should be analysed to reach higher levels of energy efficiency. The contribution of the district energy systems to the energy efficiency was already proven in numerous studies in the literature. Differently, in the this study, EPBD methodology was proposed to be implemented not only to buildings, but also to the district energy systems, as a new approach. In this way, it was aimed to analyse the long term financial effects of the district energy system alternatives together with their contribution to the energy efficiency. As it was explained above, nearly zero energy levels require very high energy performance with renewable energy contribution. However, renewable energy contribution may be limited at building scale because of space limitations. Another objective of the study was the increasing the renewable energy usage at the district scale, while more convenient space would be available; so that nearly zero energy districts could be achieved. EPBD methodology phases can be decribed briefly as the definition of the reference building, definition of the energy improvement measures, calculation of the energy performance and global cost of the building with each measure and/or measure package and the determination of global cost and nearly zero energy solutions. In the new approach proposed in the study, additional phases were added for the district scale analysis. The proposed approach can be implemented both on existing and newly planned settlements and first step is the evaluation of the district scale parameters which affect the energy demand and consumption. In this step, all building types and numbers exist or will exist in the district is determined and for each type of the building, EPBD methodology is applied. Reference, cost optimal and nearly zero energy cases are determined for each type of the building by the application of EPBD methodology, which means the three cases of the settlement are also determined. Afterwards, the alternatives for the district energy systems are defined and similar to the building scale analysis, energy performances and global costs of each alternative with the three cases of the settlement is calculated. Finally, among each alternative and case, cost optimal and nearly zero energy solutions are determined. Proposed approach was implemented to a virtual district area close to Eskişehir, Turkey as a case study in the case study. In the case district area, it was assumed to be located 34 residential, 7 office and 1 data-center buildings. For each type of building, the reference, cost optimal and nearly zero energy cases were determined by EPBD methodology. Then 8 different district energy system alternative was proposed including cogeneration, boiler and chiller units with photovoltaic (PV) systems. The 8 alternative was applied to the settlement cases with reference, cost optimal and nearly zero energy buildings. Energy performances, as annual primary energy consumptions, and global costs, including investment, replacement, maintenance and energy costs, were calculated. According to the results of the case study, cost optimal levels provide about 35%-40% of improvement in primary energy consumption, while nearly zero energy levels provide more the 50% of improvement. Nonethless, improvement percentage of nearly zero energy levels depends on mostly renewable energy usage. In case of data-center building, available roof area for PV usage was extremely large and the primary energy improvement was about 70% compared to reference case. It should be remembered also that, nearly zero energy level definitions should be made nationally and in Turkey, the definition was not set yet, during the case study. Another interesting result of the building scale analyses was the investment cost differences obtained by cost optimal and nearly zero energy level buildings compared to reference cases. Cost optimal levels caused up to 3% of increase in the investment costs and even for the office building, investment cost of the cost optimal level was lower than the reference case. But when it comes to the nearly zero energy levels, investment costs were highly variable changing from 3% for office building to 40% for data center building. Again, this is the result of renewable energy usage levels. At the district level, district energy system (DES) alternatives were analysed with all cases of buildings. Thus the settlements with reference, cost optimal and nearly zero energy buildings had different results. If the alternatives were compared to the settlement cases without DES, then the energy performance improvement levels were the highest with reference case buildings and the lowest with nearly zero energy case buildings.Even more interestingly, in the analysis with nearly zero energy buildings, global costs of DES alternatives were always higher than the case without DES, which means usage of DES was not profitable with nearly zero energy buildings. On the other hand, if all the alternatives were compared to the settlement with reference buildings and without DES, then the best DES alternative with nearly zero energy level buildings had 17.4% of improvement in the global costs. It can be said that the decision making for district energy system alternatives were more complex than buildings and require further financial analyses. In the case study, payback periods were also analysed and different alternatives were found to be beneficial. The case study also showed the limitations, weak points and benefits of the proposed methodology. Reaching the energy efficiency target, maybe EU or national targets, political actions play a critical role, as the design of buildings and district energy systems should be in compliance with related regulations and standards. Furthermore, relatively high investment costs to reach nationally determined nearly zero energy levels in building or district design should be supported by governmental incentives, as their efficiency both in energy and finance are proven in the long term.