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Energy efficient and economic renovation of residential buildings with low-temperature heating and air heat recovery
Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology. KTH. (SERC)ORCID iD: 0000-0002-6722-3220
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

With the building sector accounting for around 40% of the total energy consumption in the EU, energy efficiency in buildings is and continues to be an important issue. Great progress has been made in reducing the energy consumption in new buildings, but the large stock of existing buildings with poor energy performance is probably an even more crucial area of focus. This thesis deals with energy efficiency measures that can be suitable for renovation of existing houses, particularly low-temperature heating systems and ventilation systems with heat recovery. The energy performance, environmental impact and costs are evaluated for a range of system combinations, for small and large houses with various heating demands and for different climates in Europe. The results were derived through simulation with energy calculation tools.

Low-temperature heating and air heat recovery were both found to be promising with regard to increasing energy efficiency in European houses. These solutions proved particularly effective in Northern Europe as low-temperature heating and air heat recovery have a greater impact in cold climates and on houses with high heating demands. The performance of heat pumps, both with outdoor air and exhaust air, was seen to improve with low-temperature heating. The choice between an exhaust air heat pump and a ventilation system with heat recovery is likely to depend on case specific conditions, but both choices are more cost-effective and have a lower environmental impact than systems without heat recovery. The advantage of the heat pump is that it can be used all year round, given that it produces DHW.

Economic and environmental aspects of energy efficiency measures do not always harmonize. On the one hand, lower costs can sometimes mean larger environmental impact; on the other hand there can be divergence between different environmental aspects. This makes it difficult to define financial subsidies to promote energy efficiency measures.

Abstract [sv]

Byggnader står för omkring 40 % av den totala energianvändningen i EU. Energieffektivisering av byggnader är och fortsätter därför att vara en viktig fråga. Även om stora framsteg har gjorts när det gäller att minska energianvändningen i nya byggnader så är det stora beståndet av befintliga byggnader med dålig energiprestanda förmodligen ett ännu viktigare område att fokusera på. Denna avhandling behandlar energieffektiviseringsåtgärder som kan lämpa sig för renovering av befintliga hus, i synnerhet lågtemperaturvärmesystem och ventilationssystem med värmeåtervinning. Energiprestanda, miljöpåverkan och kostnader utvärderas för en rad systemkombinationer, för små och stora hus med olika värmebehov och för olika klimat i Europa. Resultaten togs fram genom simuleringar med energiberäkningsprogram.

Lågtemperatursystem och värmeåtervinning framstod båda som lovande lösningar för energieffektivisering av europeiska hus, särskilt i norra Europa, eftersom dessa åtgärder har större effekt i kalla klimat och på hus med stort värmebehov. Prestandan för värmepumpar, såväl av utelufts- som frånluftstyp, förbättrades med lågtemperaturvärmesystem. Valet mellan frånluftsvärmepump och värmeåtervinning till ventilationsluft kan antas bero på specifika förhållanden för varje fall, men de är båda mer kostnadseffektiva och har lägre miljöpåverkan än system utan värmeåtervinning. Värmepumpen har fördelen att den kan återvinna värme året runt, förutsatt att den producerar varmvatten.

Ekonomiska och miljömässiga aspekter av energieffektiviseringsåtgärder stämmer inte alltid överens. Dels lägre kostnad ibland betyda större miljöpåverkan, dels kan det finnas divergens mellan olika miljöaspekter. Detta gör det svårt att fastställa subventioner för att främja energieffektiviseringsåtgärder.

Place, publisher, year, edition, pages
Stockholm: Universitetsservice AB , 2015. , 27 p.
National Category
Energy Engineering
Research subject
Energy, Forests and Built Environments, iNSPiRE
Identifiers
URN: urn:nbn:se:du-20270ISBN: 978-91-7595-664-0 (print)OAI: oai:DiVA.org:du-20270DiVA: diva2:872437
Presentation
2015-09-18, Brinellvägen 23, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2015-11-19 Created: 2015-11-18 Last updated: 2016-10-19Bibliographically approved
List of papers
1. Energy performance comparison of three innovative HVAC systems for renovation through dynamic simulation
Open this publication in new window or tab >>Energy performance comparison of three innovative HVAC systems for renovation through dynamic simulation
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2014 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 82, 512-519 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, dynamic simulation was used to compare the energy performance of three innovativeHVAC systems: (A) mechanical ventilation with heat recovery (MVHR) and micro heat pump, (B) exhaustventilation with exhaust air-to-water heat pump and ventilation radiators, and (C) exhaust ventilationwith air-to-water heat pump and ventilation radiators, to a reference system: (D) exhaust ventilation withair-to-water heat pump and panel radiators. System A was modelled in MATLAB Simulink and systems Band C in TRNSYS 17. The reference system was modelled in both tools, for comparison between the two.All systems were tested with a model of a renovated single family house for varying U-values, climates,infiltration and ventilation rates.It was found that A was the best system for lower heating demand, while for higher heating demandsystem B would be preferable. System C was better than the reference system, but not as good as A or B.The difference in energy consumption of the reference system was less than 2 kWh/(m2a) betweenSimulink and TRNSYS. This could be explained by the different ways of handling solar gains, but also bythe fact that the TRNSYS systems supplied slightly more than the ideal heating demand.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
Energy performance, Dynamic simulation, HVAC, Micro heat pump, Heat recovery, Ventilation radiator, TRNSYS, MATLAB Simulink, Renovation
National Category
Energy Engineering
Research subject
Energy, Forests and Built Environments, iNSPiRE
Identifiers
urn:nbn:se:du-15163 (URN)10.1016/j.enbuild.2014.07.059 (DOI)000343781400050 ()
Projects
iNSPiRe
Funder
EU, FP7, Seventh Framework Programme, 314461
Available from: 2014-09-04 Created: 2014-09-04 Last updated: 2017-12-05Bibliographically approved
2. Economic and environmental analysis of energy renovation measures for a district heated multi-family house
Open this publication in new window or tab >>Economic and environmental analysis of energy renovation measures for a district heated multi-family house
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Renovation of existing buildings plays an important part in the work towards European climate and energy goals. The present paper treats energy efficiency renovation measures for a district heated Swedish multi-family house, evaluated through dynamic simulation. Five HVAC systems were studied in combination with three renovation levels, starting from basic renovation to maintain functionality and then adding 1) better insulating windows and flow-reducing water taps, and 2) additional insulation on roof and façade. The HVAC systems were based on the existing district heating substation and included mechanical ventilation with heat recovery and different configurations of exhaust air heat pump. Life cycle cost, discounted payback period, primary energy consumption, CO₂ emissions and non-renewable energy use were assessed for all combinations.

The system with the lowest cost and environmental impact was, in most cases, the one where district heating and heat pump were combined for both heating and DHW. Low-temperature heating improved the performance factor of the heat pump, but reduced the heat output and increased the need for backup heating. Changing windows and water taps was found to be profitable, while additional insulation reduced the environmental impact but increased the life cycle cost.

Keyword
District heating, air heat recovery, low-temperature heating, heat pump, LCC, environmental analysis
National Category
Energy Engineering
Research subject
Energy, Forests and Built Environments
Identifiers
urn:nbn:se:du-20269 (URN)
Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2016-10-19Bibliographically approved
3. Comparison of two HVAC renovation solutions: A case study
Open this publication in new window or tab >>Comparison of two HVAC renovation solutions: A case study
2013 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Within the aging building stock of Europe, there is great potential of saving energy through renovation and upgrading to modern standards, and to thereby approach the internationally set goals of lower energy use. This paper concerns the planned renovation of the building envelope and HVAC systems in a multi-family house in Ludwigsburg, Germany. Five systemic HVAC solutions were compared, with special focus on two systems: A) Balanced ventilation with HRC + Micro heat pump, and B) Forced exhaust ventilation + Heat pump with exhaust air HRC + Ventilation radiators. Given the predicted heating demand and ventilation rate of the house after renovation, the performance of the two systems was compared, alongside three common systems for reference. Calculations were made using TMF Energi, a tool developed by SP Technical Research Institute of Sweden.

   Both systems A and B were found to have the lowest electrical energy use together with the ground source heat pump system for the assumed conditions. For other assumptions, including different climate and degree of insulation, some differences between these three systems were noted. Most significant is the increased electrical use of system B for higher heating loads due to limitations in the power available from the heat source, exhaust air, which is dependent on the ventilation rate.

Place, publisher, year, edition, pages
Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA), 2013
Keyword
Energy renovation, HVAC, system comparison, low-energy house, ventilation radiator, micro heat pump
National Category
Energy Engineering
Research subject
Energy, Forests and Built Environments
Identifiers
urn:nbn:se:du-15164 (URN)
Conference
11th REHVA world congress Clima 2013 - Energy efficient, smart and healthy buildings, Prague, June 16-19, 2013
Projects
iNSPiRe
Funder
EU, FP7, Seventh Framework Programme, 314461
Available from: 2014-09-04 Created: 2014-09-04 Last updated: 2016-12-12Bibliographically approved
4. Techno-economic analysis of three HVAC retrofitting options
Open this publication in new window or tab >>Techno-economic analysis of three HVAC retrofitting options
2014 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Accounting for around 40% of the total final energy consumption, the building stock is an important area of focus on the way to reaching the energy goals set for the European Union. The relatively small share of new buildings makes renovation of existing buildings possibly the most feasible way of improving the overall energy performance of the building stock. This of course involves improvements on the climate shell, for example by additional insulation or change of window glazing, but also installation of new heating systems, to increase the energy efficiency and to fit the new heat load after renovation. In the choice of systems for heating, ventilation and air conditioning (HVAC), it is important to consider their performance for space heating as well as for domestic hot water (DHW), especially for a renovated house where the DHW share of the total heating consumption is larger.

The present study treats the retrofitting of a generic single family house, which was defined as a reference building in a European energy renovation project. Three HVAC retrofitting options were compared from a techno-economic point of view: A) Air-to-water heat pump (AWHP) and mechanical ventilation with heat recovery (MVHR), B) Exhaust air heat pump (EAHP) with low-temperature ventilation radiators, and C) Gas boiler and ventilation with MVHR. The systems were simulated for houses with two levels of heating demand and four different locations: Stockholm, Gdansk, Stuttgart and London. They were then evaluated by means of life cycle cost (LCC) and primary energy consumption. Dynamic simulations were done in TRNSYS 17.

In most cases, system C with gas boiler and MVHR was found to be the cheapest retrofitting option from a life cycle perspective. The advantage over the heat pump systems was particularly clear for a house in Germany, due to the large discrepancy between national prices of natural gas and electricity. In Sweden, where the price difference is much smaller, the heat pump systems had almost as low or even lower life cycle costs than the gas boiler system. Considering the limited availability of natural gas in Sweden, systems A and B would be the better options. From a primary energy point of view system A was the best option throughout, while system B often had the highest primary energy consumption. The limited capacity of the EAHP forced it to use more auxiliary heating than the other systems did, which lowered its COP. The AWHP managed the DHW load better due to a higher capacity, but had a lower COP than the EAHP in space heating mode. Systems A and C were notably favoured by the air heat recovery, which significantly reduced the heating demand.

It was also seen that the DHW share of the total heating consumption was, as expected, larger for the house with the lower space heating demand. This confirms the supposition that it is important to include DHW in the study of HVAC systems for retrofitting.

Keyword
HVAC, retrofit, techno-economic, heat pump, ventilation radiator, gas boiler, LCC, primary energy, dynamic simulation
National Category
Energy Engineering
Research subject
Energy, Forests and Built Environments, iNSPiRE
Identifiers
urn:nbn:se:du-15162 (URN)
Conference
Roomvent 2014, São Paulo, Brazil, in 19-22 October 2014
Projects
iNSPiRe
Funder
EU, FP7, Seventh Framework Programme, 314461
Available from: 2014-09-04 Created: 2014-09-04 Last updated: 2016-12-12Bibliographically approved

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