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Measured and predicted energy demand of a low energy building: Important aspects when using Building Energy Simulation
Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
The Ångström Laboratory, Department of Engineering Sciences, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden.
2007 (English)In: Building services engineering research and technology, ISSN 0143-6244, Vol. 28, no 3, 223 -235 p.Article in journal (Refereed) Published
Abstract [en]

Three different simulation tools were used to simulate a low energy terraced house in the south of Sweden. The software tools all use dynamic models to calculate, for example, the energy demand for heating and the indoor temperatures. The aim of this paper is to discuss the relative importance to the annual energy demand of different energy aspects of a Swedish low-energy house. Both measured and simulated values are considered and compared. The focus is on the impact of choice of software, the habits of the tenants, and the relative impact of different design parameters such as ventilation rates.The measured values for total electricity demand range from about 6000 kWh to over 12 000 kWh, the average demand being 8020 kWh. The annual predicted total energy demand using three different simulation software tools deviated by about 2%. The energy use deviation due to airflow control was about 10%, and the deviation due to differences in heat exchanger efficiency was about 20% and the deviation in annual energy use due to differences in internal gains due to differences in tenant habits, assumed in the models, was 7%.Furthermore, when comparing the predicted energy use during the design process of the low-energy building with actual measurements after the tenants have moved in, these differ about 50% in average for this specific case.Practical application: Building energy simulation software is often used to make predictions of how different construction materials, design principles and operation influence the energy balance and indoor thermal comfort. It is therefore important that the output of these software tools is trustworthy and accurate. This paper discusses the importance of accurate input data during the design process in order to achieve a valid prediction of energy use with emphasis on tenants' behaviour. It was shown that the deviations in a parametric study were larger than the deviations in the comparison between the results from the three simulation tools. This indicates a need for more accurate models for modelling tenant behaviour and habits rather than more accurate building component models.

Place, publisher, year, edition, pages
SAGE Journals Online , 2007. Vol. 28, no 3, 223 -235 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-14155DOI: 10.1177/0143624407077393OAI: oai:DiVA.org:liu-14155DiVA: diva2:22753
Available from: 2008-11-14 Created: 2008-11-14 Last updated: 2009-05-04Bibliographically approved
In thesis
1. Energy efficiency and ventilation in Swedish industries barriers, simulation and control strategy
Open this publication in new window or tab >>Energy efficiency and ventilation in Swedish industries barriers, simulation and control strategy
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The energy issue is presently in focus worldwide. This is not only due to increasing environmental concern regarding energy related emissions, but also due to the trend of increasing energy prices. Energy usage in the industrial sector in Sweden today represents about one third of the national energy use. A substantial part of that is related to support processes such as heating, ventilation and cooling systems. These systems are important as they are related both to energy cost and indoor climate management as well as to the health of the occupants.

The purpose of this thesis is to reach a more comprehensive view on industrial energy efficiency and indoor environment issues related to industrial ventilation. This has been studied in three themes where the first part addresses barriers to energy efficiency in Swedish industries, the second theme discuss simulation as decision support, and the third studies the variable air volume system in industrial facilities.

In the first theme three different studies were made: the first studies non-energy intensive companies in Oskarshamn in Sweden, the second studies the energy intensive foundry industry and the third study was part of an evaluation of a large energy efficiency program called Project Highland. These studies had several findings in common, such as the importance of a strategic view on the energy issue and the presence of a person with real ambition with power over investment decisions related to energy issues at the company. The studies also show that several information related barriers are important for decision makers at the studied companies. This shows that information related barriers are one reason in why energy efficient equipment is not implemented.

In the second theme the use of simulation in the form of Computational Fluid Dynamics (CFD) and Building Energy Simulation (BES) are used as decision support for industrial ventilation related studies at two different industries, one foundry is investigated and one dairy. BES has mainly been used to simulate energy and power related parameters while CFD was used to give a detailed description of the indoor and product environment. Together these methods can be used to better evaluate the energy, indoor and product environment and thus enable the implementation of more efficient heating, ventilation and air-conditioning systems.

In the third theme the use of Variable Air Volume (VAV) systems was evaluated, and was found to be an efficient way to reduce energy use at the studied sites. At the studied foundry the VAV system is predicted to reduce space heating and electricity use by fans by about 30%, and in the dairy case by about 60% for space heating and 20% for electricity.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2008. 95 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1223
Keyword
Industrial energy efficiency, Industrial ventilation, Barriers, Driving forces. CFD
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-15531 (URN)978-91-7393-767-2 (ISBN)
Public defence
2008-11-21, ACAS, Hus A, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2008-11-14 Created: 2008-11-14 Last updated: 2009-05-12Bibliographically approved
2. Multi-dimensional approach used for energy and indoor climate evaluation applied to a low-energy building
Open this publication in new window or tab >>Multi-dimensional approach used for energy and indoor climate evaluation applied to a low-energy building
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The building sector alone accounts for almost 40% of the total energy demand and people spend more than 80% of their time indoors. Reducing energy demand in buildings is essential to the achievement of a sustainable built environment. At the same time, it is important to not deteriorate people’s health, well-being and comfort in buildings. Thus, designing healthy and energy-efficient buildings is one of the most challenging tasks. Evaluation of buildings with a broad perspective can give further opportunities for energy savings and improvement of the indoor climate.

The aim of this thesis is to understand the functionality, regarding indoor climate and energy performance, of a low-energy building. To achieve this, a multi-dimensional approach is used, which means that the building is investigated from several points of views and with different methods. A systems approach is applied where the definition of the system, its components and the border to its environment, is essential to the understanding of a phenomenon. Measurement of physical variables, simulations, and qualitative interviews are used to characterize the performance of the building. Both energy simulation and computational fluid dynamic simulations are used to analyse the energy performance at the building level as well as the indoor climate at room level. To reveal the environmental impact of the low-energy building studied in this thesis the CO2 emissions and embodied energy have been investigated regarding different surrounding energy systems. The evaluated building is situated at the west coast of Sweden and uses about 50% of energy compared to a comparable ordinary Swedish building. The building is well-insulated and an air-to-air heat exchanger is used to minimise the heat losses through ventilation. The houses are heated mainly by the emissions from the household appliances, occupants, and by solar irradiation. During cold days an integrated electrical heater of 900 W can be used to heat the air that is distributed through the ventilation system. According to measurements and simulations, the ventilation efficiency and thermal environment could be further improved but the occupants are mostly satisfied with the indoor climate. The control of the heating system and the possibility for efficient ventilation during summertime are other important issues. This was found through quantitative measurements, simulations and qualitative interviews. The low-energy building gives rise to lower CO2 emissions than comparable buildings, but another energy carrier, such as district heating or biofuel, could be used to further improve the environmental performance of the building. The total energy demand, including the embodied energy, is lower than for a comparable building.

To understand the functionality of a low-energy building both the technical systems and the occupants, who are essential for low-energy buildings, partly as heat sources but mainly as users of the technical systems, should be included in the analysis.

Place, publisher, year, edition, pages
Institutionen för konstruktions- och produktionsteknik, 2006
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1065
Keyword
Low-energy building; energy; indoor climate; simulation, Lågenergihus; energi; inomhusklimat; simulering
National Category
Building Technologies
Identifiers
urn:nbn:se:liu:diva-7819 (URN)91-85643-21-1 (ISBN)
Public defence
2006-12-15, C3, Hus C, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2009-03-02

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