| 1. |
- Björk, Folke, et al.
(author)
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Energy quality management and low energy architecture
- 2012
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In: World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conference. - : American Solar Energy Society. - 9781622760923 ; , s. 4558-4564
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Conference paper (peer-reviewed)abstract
- This paper puts forth energy quality management as the stepwise process of taking care of the quality of energy better. Energy quality can also be expressed as exergy, which measures the useful work potential of a given amount or flow of energy. Energy quality management is particularly useful to reduce the primary energy use in the built environment. This is achieved by reducing the heating and cooling demand, making use of passive building techniques, exploiting local renewable sources, and utilizing efficiently non-renewable energy. The application of the Rational Exergy Management Model further indicates how the integration of the building in the broader perspective of the community level is crucial to curb the building-related CO2 emissions. The paper concludes that exergy is a vital aspect for low energy and low CO2 emissions architecture.
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| 2. |
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| 3. |
- Brown, Nils W. O., et al.
(author)
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Sustainability assessment of renovation packages for increased energy efficiency for multi-family buildings in Sweden
- 2012
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In: Building and Environment. - : Elsevier BV. - 0360-1323 .- 1873-684X. ; 61, s. 140-148
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Journal article (peer-reviewed)abstract
- In this paper, we propose a method for assessing renovation packages drawn up with the goal of increasing energy efficiency. The method includes calculation of bought energy demand, life-cycle cost (LCC) analysis and assessment of the building according to the Swedish environmental rating tool Miljöbyggnad (MB). In this way the methodology assesses economic, indoor environmental quality (IEQ) and specifically environmental aspects associated with energy demand of such packages from a sustainability point-of-view. Through MB, energy efficiency packages are placed in context with other necessary measures required to improve environmental performance in buildings, providing a consistent and systematic basis other than simply financial performance by which to compare capital improvements. The method is further explained and analyzed by applying it in three case studies. In each case study a multi-family building representing a typologically significant class in the Swedish building stock is considered, and for each building a base case and two renovation packages with higher initial investment requirement and higher energy efficiency are defined. It is shown that higher efficiency packages can impact IEQ indicators both positively and negatively and that packages reducing energy demand by approx. 50% have somewhat higher LCC. Identified positive IEQ impacts point to added value for packages that may not otherwise be communicated, while negative impacts identify areas where packages need to be improved, or where MB indicators may be referred to as specifications in procurement procedures.
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| 6. |
- Jóhannesson, Gudni, et al.
(author)
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Exergy Analysis of Single and Multi-Step Thermal Processes
- 2012
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In: Journal of Civil Engineering and Architecture. - 1934-7359. ; 6:10, s. 1384-1391
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Journal article (peer-reviewed)abstract
- The present paper introduces the concepts of exergy and treats it applications to analysis of the gain in exergy efficiency between one-step and multi-step thermal processes. The analysis, which is carried out with the Excel-based SEPE program, is exemplified with the comparison between single-step and two-steps heat pump setup for providing heat to a floor heating system and for domestic hot water. The paper discusses the use of the concept of exergy efficiency as a measure of success for design of a heat pump application and how the use of information on exergy destruction and temperature levels in different parts of the system add a new perspective to the analysis and the evaluation of the system performance. The paper shows how this information can be used to improve the system configuration and also the operation of the system for given boundary conditions. This is especially useful when the energy from the low temperature sources can be utilized at different temperature or quality levels such as for space heating and domestic hot water.
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| 7. |
- Jóhannesson, Gudni, et al.
(author)
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Exergy analysis of single and multistep thermal processes
- 2011
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Conference paper (peer-reviewed)abstract
- The present paper introduces the concepts of exergy and treats it applications to analysis of the gain in exergy efficiency between one step and multi-step thermal processes. The analysis, which is carried out with the Excel based SEPE program, is exemplified with the comparison between single step and two-steps heat pump setup for providing heat to a heat floor system and a domestic hot water. The paper discusses the use of the concept of exergy efficiency as a measure of success for design of a heat pump application and how the use of information on exergy destruction and temperature levels in different parts of the system add a new perspective to the analysis and the evaluation of the system performance. The paper shows how this information can be used to improve the system configuration and also the operation of the system for given boundary conditions. This is especially useful when the energy from the low temperature sources is can be utilized at different temperature or quality levels such as for space heating and domestic hot water.
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| 8. |
- Molinari, Marco, et al.
(author)
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Dynamic exergy analysis of ground-coupled heat pumps for residential buildings
- 2011
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Conference paper (peer-reviewed)abstract
- Buildings have lower exergy demand than their energy demand. Heat pumps can exploit this potential. Their COP greatly increases for a reduced temperature difference between evaporator and condenser. Given a low-temperature heating emission system, the performance of the heat pumps can be maintained high throughout the year, even in cold climates, if a ground storage system or a ground heat source is present. The interactions between building, heat pump, circulation pumps and source systems are complex. The performance of ground-coupled heat pumps is commonly measured in terms of COP, but the mere energy analysis might be misleading in finding potential for further optimization. Instead, the concept of exergy has been chosen since it yields the thermodynamic value of its associated energy flow.In this paper exergy has been applied to practical study cases, involving ground-coupled heat pumps, to give a better understanding on such systems and explore the potential for improving them. Dynamic simulations of the buildings have been done with IDA and the storage has been modeled by means of MATLAB.
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| 9. |
- Molinari, Marco, et al.
(author)
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Exergy analysis of cooling systems and strategies
- 2011
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In: NSB 2011 - 9th Nordic Symposium on Building Physics. ; , s. 1153-1160
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Conference paper (peer-reviewed)abstract
- Energy use in the building stock represents a major share of the total energy use in developed countries. Ventilation and cooling of buildings constitute a constantly increasing part of the total energy use in buildings. One of the reasons for the increase of the energy use is increasing user demands. In combination with increasing ambient air temperatures, cooling of buildings will become a necessity. To minimise costs and energy demand, available cooling solutions must be optimised and innovative approaches encouraged. The growing awareness of climate change in combination with rising prices on fossil fuels have boosted the demand for energy efficient and even plus-energy buildings. By minimising the losses of energy used for conditioning the indoor environment, heating and cooling systems with a low temperature difference to the room can be used. Floor heating or cooling are common examples. Using distribution of heating and cooling at temperatures close to the room temperature opens the possibility to utilise low quality energy sources, for instance cooling with ambient heat sinks or heating with waste energy. Exergy analysis is a powerful tool for allocating the most relevant energy losses and suggesting technical solutions for improving cooling and heating systems. Aim of this paper is to illustrate the methodological issues with exergy analysis and to show what potential exists for improving the cooling systems by means of the exergy analysis. A program for exergy performance assessment has been developed for analyzing cooling systems. Different cooling systems have been analyzed from the generation to the heat emission system to the room environment. The analyzed systems comprise a chiller with high temperature lift, a hybrid cooling tower and floor cooling, a chiller with low temperature lift, hybrid cooling tower and floor cooling and a chiller with high temperature lift, hybrid cooling and air cooling. The results from simulations illustrate that the overall exergy efficiency of such systems is low and can be further improved by a more rational energy management.
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| 10. |
- Molinari, Marco, et al.
(author)
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Exergy analysis of different solutions for humidity control in heritage buildings
- 2011
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Conference paper (peer-reviewed)abstract
- Energy use in the building stock represents a major contribution to the total energy use in developed countries. Increasing limitations to the energy demand of the new buildings have been imposed by the building codes in the last decades, which resulted in improved building envelopes. Yet, in many cases it is not either technically or economically feasible to improve the existing building shells. A typical example is represented by historical buildings, such churches and old buildings, which often may not be improved for aesthetical or economic reasons. Often poorly insulated, such buildings would require a high energy demand to keep them at the preferable hygro-thermal conditions. As a consequence they are often left unheated, which also affects the usability of these buildings. However, the risk of moisture damage often requires them to be slightly heated to a certain temperature. As the energy demand is linked to the possibility of improving the building shell, the exergy approach gives interesting insights on the problem. Exergy analysis emphasizes the thermodynamic valuable part of the energy demand in the building and straightforwardly defines the minimum energy demand for a certain process. The energy demand being equal, it is still possible to lower the exergy demand and consumption. A lower exergy demand paves the way to the exploitation of renewable sources, such as solar power. Often the main task is to keep the RH humidity within a certain range. Aim of this paper is to perform a theoretical exergy analysis of three different solutions for lowering the RH in the building. The basic approach keeps the temperature of the indoor space at a constant level. A second approach-the so-called conservation heating- consists in letting the temperature vary according to the maximum allowed indoor relative humidity. In the third case the target is reached by means of a dehumidification process. Advantages and disadvantages of the different approaches are shown under the energy and exergy points of view. The present research is done within the framework of the "Spara och bevara" project, which targets cost-efficient solutions for the conservation and the use of heritage buildings in Sweden and the IEA Annex49 and ESF COSTexergy projects, which aim at energy-efficient buildings and communities through the application of the low-exergy approach.
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