Search

Abstract: This paper takes an overall energy system approach to analysing the mismatch problem of zero energy and zero emission buildings (ZEBs). The mismatch arises from hourly differences in energy production and consumption at the building level and results in the need for exchange of electricity via the public grid even though the building has an annual net-exchange of zero. This paper argues that, when looked upon from the viewpoint of the overall electricity supply system, a mismatch can be both negative and positive. Moreover, there are often both an element of levelling out mismatches between individual buildings and an element of economy of scale. For these three reasons mismatches should be dealt with at the aggregated level and not at the individual level of each building. Instead, this paper suggests to compensate the mismatch of a building by increasing (or decreasing) the capacity of the energy production unit. Based on historical data for the electricity supply area in western Denmark, this paper makes a first attempt to quantify mismatch compensation factors. The results indicate that such compensation factors are a little below one for buildings with photovoltaics (PV) and a little above one for buildings with wind turbines. [Copyright &y& Elsevier]

Abstract: Building designers are often limited in their ability to reduce the environmental impact of buildings, due to a lack of information on the environmental performance of building components as well as inconsistencies in the way in which this information is derived. Whilst numerous tools exist to help facilitate the low-energy building design process, these typically require large investments of time and money that are often beyond those available within any particular project. This paper describes an approach for streamlining the design process to reduce building life cycle energy consumption. Building assemblies are ranked based on an assessment of the life cycle energy requirements associated with their use within a building. This facilitates early stage assessment, negating the need for a resolved design before the relative energy requirements of alternate design solutions are known. Previous work assessed the initial and recurring embodied energy as well as the operational energy requirements for heating and cooling associated with the use of a range of building assemblies, using a simplified house model. This paper presents a sensitivity analysis of variations to the floor area, shape and orientation of this model, to test the reliability and applicability of the ranking approach across a broad range of circumstances. It was found that these variations did not influence the ranked order of the assemblies in terms of their life cycle energy requirements. Thus, the ranking of assemblies appears to provide an appropriate approach for streamlining the selection of construction elements during the building design process. [Copyright &y& Elsevier]

Abstract: Chiller sequencing control plays an important role in achieving air-conditioning system energy efficiency since chillers usually account for major part of system overall energy consumption in commercial buildings. This paper compares and evaluates the in situ performances of three commonly used chiller sequencing control strategies. These three control strategies are operating online in parallel on a management and communication platform in a super high-rise building in Hong Kong. The comparison and evaluation focus on the perspectives of chiller switch number, electrical peak demand and overall energy consumption in one week. Meanwhile, the different impacts of two systematic errors (i.e. positive errors which cause direct measurement larger than true value and negative errors which cause measurement smaller than true value) on each control strategy are also analyzed. The performance comparison demonstrates that the strategy, using fused cooling load measurement, achieved the best performance. The applications of the online computed chiller maximum cooling capacity and the advanced data fusion technique, which removes the negative impacts of sensor measurement uncertainties, can significantly improve the performance of chiller sequencing control. [Copyright &y& Elsevier]

Abstract: Energy use in the built environment represents a large part of total energy use in Sweden and is one important sector where energy conservation needs to be significantly improved in order to meet the national implementation of the European goals. One key question that needs to be investigated in relation to these goals is the performance and implementation of passive or low-energy houses. This paper presents results and an evaluation of a newly built house in an area with passive houses in Linköping, Sweden. Nine passive houses were built with the aim to be energy efficient, with an annual space heating demand of 21kWh/m2, and at the same time to have the same visual appearance as any other building in the surrounding area. This study evaluates the energy performance of a residential area with low-energy buildings based on Building Energy Simulation (BES) (IDA ICE 4), and measurements from the real object. Both annual and hourly validation is performed using room by room modeling and internal heat gains. A novel approach to internal heat gain modeling is presented using time-use data (TUD). The results show possible improvements in the design, the building envelope and in the heating control. [Copyright &y& Elsevier]

Abstract: The present paper suggests a procedure for identification of suitable models for the heat dynamics of a building. Such a procedure for model identification is essential for better usage of readings from smart meters, which is expected to be installed in almost all buildings in the coming years. The models can be used for different purposes, e.g. control of the indoor climate, forecasting of energy consumption, and for accurate description of energy performance of the building. Grey-box models based on prior physical knowledge and data-driven modelling are applied. This facilitates insight into otherwise hidden information about the physical properties of the building. A hierarchy of models of increasing complexity is formulated based on prior physical knowledge and a forward selection strategy is suggested enabling the modeller to iteratively select suitable models of increasing complexity. The performance of the models is compared using likelihood ratio tests, and they are validated using a combination of appropriate statistics and physical interpretation of the results. A case study is described in which a suitable model is sought after for a single storey 120m2 building. The result is a set of different models of increasing complexity, with which building characteristics, such as: thermal conductivity, heat capacity of different parts, and window area, are estimated. [Copyright &y& Elsevier]

Abstract: To streamline the design of the energy efficient buildings, appropriate tools are needed to assess their energy performance taking into account the microclimatic context. Numerical simulation seems to be the most suitable issue, but none tool is dedicate to the direct evaluation of the microclimate influence on the building energy consumption. A complete solution could be to use both CFD and thermoradiative simulation tools complementary with the coupling technique perspective. This paper presents both a developed CFD–thermoradiative coupled simulation tool and a typical application on an urban fragment. The results lead to two kind of observations: [•] Integration of the thermal model of a building in the microclimatic simulation platform enable a quantitative evaluation of the building energy demand regarding different urban design scenarii (e.g. mineralized vs vegetated). [•] Different physical phenomena do not contribute as much in the energy balance and it is important to compute precisely each one to obtain the small scale microclimatic influence. [Copyright &y& Elsevier]

Abstract: Looking to the EU''s 20/20/20 program, energy efficient retrofitting will be a key element in the 20% less primary energy in 2020 compared to business as usual. Within that context, field studies that put realizable efficiency in perspective are urgently needed. The dwelling evaluated was built in 1957. In those days energy efficiency was no concern. Houses got no insulation, ventilation was adventitious and heating systems scored badly. The retrofit started in the early eighties, stepwise as to follow the impact of separate measures on heating energy consumed. A solar boiler was installed in 2004. PV followed in 2009. The first 19 years a family of five inhabited the dwelling, then the parents only. Monitoring started in 1978. In the paper, predicted annual energy for space heating is compared with monitored result. The measured data, though showing a net decrease, consistently underscore predictions. Main reason is direct rebound. The benefits of the solar boiler and PV-panels are minimal compared to the energy avoided by better insulation, energy efficient windows, better air-tightness and upgraded ventilation and central heating. However, targeting passive house and zero energy quality is beyond optimal in terms of net present value and not doable in the dwelling. [Copyright &y& Elsevier]

Abstract: The paper discusses an assessment tool, used for the energy, economic and environmental evaluation of Thermal Insulation Solutions (TIS). The results of the assessment undertaken with this tool can take the form of a simple rating system in order to enable users to perform comprehensive comparisons amongst various building materials and TIS. A ranking expressed by A, B and C classes is used for energy, environmental and economic parameters. By evaluating the materials, the tool supports the users to make decisions, depending on preferences or priorities such as the energy efficiency achieved, the total cost and the environmental performance. The assessment tool is applied for the double cavity wall and the External Thermal Insulation Composite Systems (ETICS) as they are used throughout Europe, both in new constructions and in the renovation of existing buildings. [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: The large thermal time constant of thermally activated building systems (TABS) hampers communication between the system''s production and emission. Therefore, conventional building control strategies, typically using room temperature feedback, are unadapted to control thermal comfort efficiently. In this paper, measurement data and simulation results reveal that unadapted TABS control has a dramatic impact on overall energy performance. Measurements in a TABS building with room temperature feedback show the HVAC system switching between heating and cooling in a very short time frame. A simplified, generic room model is used to simulate, understand and evaluate this behaviour. For room temperature feedback control, only 45% of the cold and 15% of the heat produced actually controls room temperature. The remainder is stored in the TABS and exchanged between the heating and cooling system. Enlarging the heating-to-cooling set point band improves this ratio, while maintaining thermal comfort. On the other hand, night time operation control of the circulation pump, adapted to the TABS thermal time constant, eliminates this ‘unused’ energy completely. In this case, however, even with perfect heat gain forecasts, it is difficult to avoid room temperatures dropping below thermal comfort limits during initial office hours. Hence, a supplementary air-conditioning system seems inevitable. [Copyright &y& Elsevier]