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A pressure and thermal exergy analysis of a waterborne and an airborne system
KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.ORCID-id: 0000-0002-2300-2581
2009 (engelsk)Inngår i: Proceedings of the 15th International Conference on Building Services, Mechanical and Building Industry Days, 2009, s. 73-80Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

The exergetic performances of two different heating systems, a full air system with a gas boiler and a floor heating with a heat pump, have been analyzed from the generation to the emission system. Exergy thermal and pressure losses have been evaluated to illustrate which potential exists for improving the energy use. Simulations have been performed by means of SEPE, a steady state tool that makes use of the iterative cycles in Excel.

sted, utgiver, år, opplag, sider
2009. s. 73-80
Emneord [en]
Exergy, energy, buildings, systems performances
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-25403OAI: oai:DiVA.org:kth-25403DiVA, id: diva2:357971
Konferanse
15th Building Services, Mechanical, and Building Industry Days. International Conference, Debrecen, 15-16 October 2009
Merknad
QC 20101020Tilgjengelig fra: 2010-10-20 Laget: 2010-10-20 Sist oppdatert: 2022-10-24bibliografisk kontrollert
Inngår i avhandling
1. Exergy Analysis in Buildings: A complementary approach to energy analysis
Åpne denne publikasjonen i ny fane eller vindu >>Exergy Analysis in Buildings: A complementary approach to energy analysis
2009 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Though mandatory to be pursued, improved energy efficiency is not the only target to reach. The quality of energy has to be assessed as well. Most of the overall energy use in residential building is for low temperature heat, i.e. temperatures relatively close to the outdoor conditions. From a thermodynamic point of view, this is a degraded form of energy with low potential to be converted into work. On the other hand energy demand is mostly met with high quality energy, such as electricity and natural gas. There is a mismatch between supply and demand, which is not clearly shown by the sole energy analysis. Target of this thesis is to analyze the energy use in buildings from the point of view of its quality, to provide effective theoretical and calculation tools to investigate this mismatch, to assess its magnitudo and to propose improvements aiming at a more rational use of the energy. The idea behind the quality is clarified with the concept of exergy.

The potential for improvement in space heating is shown. In no heating system the overall exergy efficiency is above 20%, with fossil fuels. Using direct electricity heating results in exergy efficiency below 7%. Most of the household appliances processes have low-exergy factors but still are supplied with electricity. This results in poor exergy efficiencies and large exergy losses.

Systems are poorly performing because little consideration is explicitly given to energy quality. Policies to lower the energy demand, though vital as first step towards an improved use of energy, should not neglect the exergy content.

The problem is then shifted to find suitable supplies. Electricity can be exploited with low exergy losses with high-COP heat pumps. Use of fossil fuels for heating purposes should be avoided. District heating from cogeneration and geothermal proves to be a suitable solution at the building level. The issues connected to its exploitation forces to shift the boundary layers of the analysis from the building level to the community level. A rational use of energy should address the community level. The system boundaries have to be enlarged to a dimension where both the energy conversion and use take place with reduced energy transportation losses. This is a cost-effective way to avoid the waste of the exergy potential of the sources with exergy cascade and to make it possible the integration of with renewable sources. Exergy efficiency of the buildings is a prerequisite for a better of energy in this field.

sted, utgiver, år, opplag, sider
Stockholm: Byggvetenskap, 2009. s. viii, 35
Serie
Meddelande. Inst. för byggnadsteknik ; 1651-5536
Emneord
Exergy; Energy; Building systems performance; Built environment.
Identifikatorer
urn:nbn:se:kth:diva-11537 (URN)978-91-7415-519-8 (ISBN)
Presentation
2009-12-11, Seminarierummet, Brinelsvägen 34, KTH- Inst. för Byggvetenskap, 16:00 (engelsk)
Opponent
Veileder
Prosjekter
IEA ECBCS Annex 49: Low Exergy Systems for High Performance Buildings and CommunitiesESF Cost C24: Analysis and Design of Innovative Systems for Low-EXergy in the Built Environment: COSTeXergy
Tilgjengelig fra: 2009-11-25 Laget: 2009-11-19 Sist oppdatert: 2022-10-24bibliografisk kontrollert

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