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Knowing the energy demand at the scale of neighborhoods allows the conception of efficient energy administration systems that aid to reach sustainability in the built environment. When energy demand data is not available, simulation models can provide estimations and thus enable the analysis of a neighborhood. To simulate the space heating demand of a residential building stock, often an aggregation is carried out. Aggregation implies using one or a few representative models to replace a larger number of building models. This paper explores the effect of the aggregation method on model accuracy when applying a first-order building model for the space heating demand of an urban residential district. The results show that aggregation leads to inaccuracies when the district includes buildings with varying values for their properties: the errors reach 14% if the district is highly polarized and 8% for more diverse districts. Aggregating buildings with identical properties diminishes the error compared to a total aggregation − aggregating the building stock as a whole. Aggregation with respect to certain building properties yields better results than others, with window area fraction and U-value of opaque surfaces leading to the first and second lowest error values. [ABSTRACT FROM AUTHOR]

Abstract: Energy efficient HVAC solutions may be obtained by combining different energy sources – fossil and renewable – into single hybrid systems. This leads to a variety of system concepts with specific boundary conditions. As a consequence, the definition of a unique representation method and a standardized performance evaluation procedure is a challenging task. Currently, two international projects promoted by the IEA are dealing with the representation and the performance calculation of a particular category of hybrid systems, i.e. integrated solar assisted systems. The HPP Annex 34 “Thermally Driven Heat Pumps for Heating and Cooling”, whose goal is to reduce the environmental impact of heating and cooling by the use of thermally driven heat pumps, has solar cooling as one of the systems under investigation. The joint project between SHC and HPP Task 44/Annex 38 “Solar and Heat Pump Systems” is focused on different system combinations of solar thermal collectors and heat pumps. The scope of the present paper is to show a systematic methodology to represent and evaluate the energy performance of complex hybrid systems. The proposed approach is a joint effort of the on-going IEA activities and will be discussed regarding the mentioned solar hybrid systems. However, the final goal of the work is to provide a basis for a simple, fair and transparent comparison of all systems for heating and cooling, regardless of the technology. [Copyright &y& Elsevier]

Abstract: This paper presents a detailed meta-analysis of end and primary energy use for heating, cooling and ventilation of 11 low-energy non-residential buildings and one residential building in Germany that belong to the EnOB research program launched by the German Federal Ministry for Economy. In particular, the analysis emphasizes the substantial impact of auxiliary energy use on the efficiency of heating and cooling performance. The investigated buildings employ environmental energy sources and sinks – such as the ground, ground water, rainwater and the ambient air – in combination with thermo-active building systems. These concepts are promising approaches for slashing the primary energy use of buildings without violating occupant thermal comfort. A limited primary energy use of about 100kWhprim/(m2 neta) as a target for the complete building service technology (HVAC and lighting) was postulated for all buildings presented. With respect to this premise, a comprehensive long-term monitoring in high time resolution was carried out over the course of two to five years, with an accompanying commissioning of the building performance. Measurements include the energy use for heating, cooling, and ventilation, as well as the auxiliary equipment, the performance of the environmental heat source and sink, and local climatic site conditions. [Copyright &y& Elsevier]

Abstract: A detailed analysis of the heating and cooling performance of environmental heat sources and sinks is presented for 12 low-energy buildings in Germany. In particular, the analysis focuses on the given temperature levels and the efficiency performance of the environmental heat sources and sinks in summer and winter. The investigated buildings employ environmental heat sources and sinks – such as the ground, groundwater, rainwater and the ambient air – in combination with thermo-active building systems (TABS). These concepts are promising approaches for slashing the primary energy use of buildings without violating occupant thermal comfort. A limited primary energy use of about 100kWhprim/(mnet 2 a) as a target for the complete building service technology (HVAC and lighting) was postulated for all buildings presented. With respect to this premise, comprehensive long-term monitoring in fine time-resolution occurred over a period from two to five years. An accompanying commissioning of the building performance took place. Measurements include water supply and return temperatures of the environmental heat sources/sinks, the generated heating and cooling energy, efficiencies of the system, and local climatic site conditions. The comparative evaluation of the systems in all buildings identifies weak points and success factors of the plant. Besides, it characterizes the single component and points out further potential for optimization measures. The annual efficiency performance of the geothermal heat sources and sinks results in a seasonal performance factor of 8–10kWhtherm/kWhend, where the end energy use is electricity. The ground, groundwater, rainwater and even the ambient air constitute efficient heat sources/sinks. Energy is needed only for distributing the heat and cold and not for its generation. The choice of suitable plant components, the accurate design of the hydraulic system and the correct dimension of the environmental heat source/sink play a central role in achieving higher efficiencies. [Copyright &y& Elsevier]

Abstract: This article investigates building thermal mass control of commercial buildings to reduce utility costs with a particular emphasis on the individual impacts of both adaptive comfort criteria and of heat waves. Recent changes in international standards on thermal comfort for indoor environments allow for adaptation to the weather development as manifested in comfort criteria prEN 15251.2005 and NPR-CR 1752.2005 relative to the non-adaptive comfort criterion ISO 7730.2003. Furthermore, since extreme weather patterns tend to occur more frequently, even in moderate climate zones, it is of interest how a building''s passive thermal storage inventory responds to prolonged heat waves. The individual and compounded effects of adaptive comfort criteria and heat waves on the conventional and optimal operation of a prototypical office building are investigated for the particularly hot month of August 2003 in Freiburg, Germany. It is found that operating commercial buildings using adaptive comfort criteria strongly reduces total cooling loads and associated building systems energy consumption under conventional and building thermal mass control. In the case of conventional control, total operating cost reductions follow the cooling loads reductions closely. Conversely, the use of adaptive comfort criteria under optimal building thermal mass control leads to both lower and slightly higher absolute operating costs compared to the optimal costs for the non-adaptive ISO 7730. While heat waves strongly affect the peak cooling loads under both conventional and optimal building thermal mass control, total cooling loads, building energy consumption and costs are only weakly affected for both control modes. Passive cooling under cost-optimal control, while achieving significant total cost reductions of up to 13%, is associated with total energy penalties on the order of 1–3% relative to conventional nighttime setup control. Thus, building thermal mass control defends its cost saving potential under optimal control in the presence of adaptive comfort criteria and heat waves. [Copyright &y& Elsevier]

Heat pumps are expected to play a central role in decarbonizing heat supply, but face challenges in existing buildings due to high temperature requirements of existing radiator systems. This paper links the performance analysis of heat pump systems with methods to reduce temperatures of the space heating circuit. Field data and system simulations of air and ground source heat pumps show a linear correlation between the seasonal performance factor SPF and the mean heat pump temperature over a wide temperature range. Every Kelvin of reduced heat pump temperature increases the SPF by 0.10–0.13 points. Applied methods to reduce heating temperatures are demonstrated at existing multi-family buildings. Thermal insulation reduces the building's heat load, allowing a reduction of heating temperatures with the existing radiators. A further temperature reduction is achieved by analyzing the required heating power per room and identifying critical, undersized radiators. In a studied building, the selective exchange of only 7% of all radiators is sufficient to reduce heating temperatures from 75 °C/60 °C–55 °C/45 °C. This corresponds to a reduction of the electricity consumption by 40–42%. However, the potential of these methods is specific for each building and depends particularly on its renovation state and installed radiator capacity. Nonetheless, an energy- and cost-efficient operation of heat pumps retrofitted in existing radiator heating systems is viable, if following the proposed system design method linking heat pump performance and reduction of space heating temperatures. • Performance analysis of retrofit heat pumps by field tests and system simulations. • Effect of heating temperatures on heat pump performance is analyzed. • Measures to reduce temperatures are applied in existing multi-family buildings. • Selective exchange of 7% of all radiators reduces electricity consumption by 40%. • Methods improve energy and cost-efficient operation of heat pumps in existing buildings. [ABSTRACT FROM AUTHOR]