Abstract
This paper presents the methodology for conducting a cost-optimal energy performance calculation of a solar hot water system, used for space heating and domestic hot water needs. The calculation is based on dynamic hourly methods, according to the new Energy Performance of Buildings’ (EPB) set of standards EN 15316:2017, and a revision of the standard EN 15316-5:2017 from the year 2021, dealing with storage-tank water temperature calculations. The paper provides proposals for modifications to these newly introduced standards, in order to overcome the observed ambiguities and shortcomings. The calculation of annual energy performance of a building was performed on an hourly basis over a year for the reference of an nZEB multi-apartment building, for a climate area of the city of Zagreb, taking into account water temperature change in the layers of the storage tank connected to solar collectors and hot water boilers. The cost-optimal solution was then determined by varying individual parameters of the building technical system. The influence of these parameters on the energy efficiency of the building was analyzed in detail. Furthermore, the results were compared against those obtained by the Croatian calculation algorithm based on the previous set of EPB standards, EN 15316:2008, currently used EU-wide for the energy performance certification of buildings. The results indicated that the calculation methods of the present algorithm underestimated the consumption of building primary energy by 12%. The energy delivered by solar collectors was underestimated by 18%.
Highlights
In the context of tackling climate change and a possible energy crisis, the EuropeanUnion (EU) has recognized that a significant share of CO2 emissions (36%) and energy consumption (40%) in Europe can be attributed to the building sector [1]
One of the EPBD recast key requirements was that all new buildings by 31 December 2020 (31 December 2018 for public buildings) should be nearly zero-energy buildings
The primary energy was approximately 69% lower than the selected optimal solution, the delivered energy was approximately 86% higher
Summary
In the context of tackling climate change and a possible energy crisis, the EuropeanUnion (EU) has recognized that a significant share of CO2 emissions (36%) and energy consumption (40%) in Europe can be attributed to the building sector [1]. Performance of Buildings Directive, 2010/31/EU (EPBD), and the Energy Efficiency Directive 2012/27/EU (EED). One of the EPBD recast key requirements was that all new buildings by 31 December 2020 (31 December 2018 for public buildings) should be nearly zero-energy buildings (nZEBs). An nZEB is defined as a building that is highly energy efficient, with almost zero or a very low amount of required energy, which should be covered to a very significant extent by renewable energy sources (RES) [2]. The comparative methodology of cost-optimal analysis, described in the guidelines [4] supplementing regulation, is used to compare different design alternatives. Investment and operation costs (for the period of the estimated building renovation cycle) are determined for different design solutions, and the global cost is calculated for each. The solution with the lowest global cost is declared as the optimal building design
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