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Thermodynamic and thermal comfort performance evaluation of two geothermal high-temperature cooling systems in the mediterranean climate
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.ORCID iD: 0000-0001-5141-3559
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. College of Urban Construction and Safety Engineering, Shanghai Institute of Technology, Shanghai, 201418, China.ORCID iD: 0000-0003-0550-1149
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.ORCID iD: 0000-0002-5938-4614
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Bravida Holding AB, Mikrofonvägen 28, Hägersten, SE-12637, Sweden.ORCID iD: 0000-0001-5902-2886
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2022 (English)In: Journal of Building Engineering, E-ISSN 2352-7102, ISSN 2352-7102, Vol. 56, p. 104738-104738, article id 104738Article in journal (Refereed) Published
Abstract [en]

The European Commission aims to reduce the greenhouse gas emissions of the European Union's building stock by 60% by 2030 compared with 1990. Meanwhile, the global demand for cooling is projected to grow 3% yearly between 2020 and 2050. High-temperature cooling systems provide cooling with lower exergy use than conventional cooling systems and enable the integration of renewable energy sources, and can play a crucial role in meeting the growing cooling demand with less energy use. The aim of this study is to analyse and critically evaluate two high-temperature cooling systems in terms of their energy and exergy use in a case study. We also consider thermal comfort performance, CO2 emissions, and sensitivity to changing operating conditions. The two systems considered are a mechanical ventilation system with heat recovery combined with geothermal cooling (GeoMVHR) and a radiant cooling system with ceiling panels connected to the same geothermal cooling (GeoRadiant) system. The study is conducted using building energy models of a typical office building belonging to a three-building school complex located in Sant Cugat near Barcelona, Spain. IDA ICE 4.8 simulation software was used for the simulations. The results show that the two different installations can produce near-identical thermal comfort conditions for the occupants. The GeoRadiant system achieves this result with 72% lower electricity use and 60% less exergy destruction than the GeoMVHR system. Due to the higher electricity use, the CO2 emissions caused by the GeoMVHR system are 3.5 times the emissions caused by the GeoRadiant system.

Place, publisher, year, edition, pages
Elsevier BV , 2022. Vol. 56, p. 104738-104738, article id 104738
Keywords [en]
Heat exchanger, frosting, condensation, air preheating, laminar forced convection
National Category
Building Technologies
Research subject
Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
URN: urn:nbn:se:kth:diva-316351DOI: 10.1016/j.jobe.2022.104738ISI: 000878602700004Scopus ID: 2-s2.0-85131952345OAI: oai:DiVA.org:kth-316351DiVA, id: diva2:1687590
Note

QC 20221205

Available from: 2022-08-16 Created: 2022-08-16 Last updated: 2023-05-17Bibliographically approved
In thesis
1. High-Temperature Cooling Systems for Sustainable Buildings Using Geothermal Energy: Holistic Assessment in the Mediterranean Climate
Open this publication in new window or tab >>High-Temperature Cooling Systems for Sustainable Buildings Using Geothermal Energy: Holistic Assessment in the Mediterranean Climate
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sustainable development is increasing its significance in both the scientific and political agenda. In light of this development, the United Nations have published 17 Sustainable development goals (SDGs). The SDGs relate to all aspects of sustainable development, the most significant for this thesis being energy decarbonisation and sustainable industry.

Space cooling is increasing in significance globally, on the one hand because of a global rise in temperatures due to climate change, on the other hand because of the rising living standards in developing countries mean more people will have access to cooling. Cooling has been linked to all 17 SDGs, and affects not only energy use but also health, well-being and productivity. Radiant cooling is gaining popularity as an alternative for conventional, air-based cooling systems. The main advantages of radiant cooling are lower energy requirement for transportation and the ability to use low-grade renewable energy resources such as geothermal cooling.

Building retrofitting is also a significant topic in sustainable development. Currently, while 75% of buildings in European Union (EU) are inefficient according to current building standards, 85-95% of these buildings are still predicted to be in use in 2050. This means retrofitting existing buildings to improve their energy efficiency is vital for reducing the EU's greenhouse gas emissions. Most of the work presented in this thesis relates to a European research project, Geofit, which sought to make retrofitting buildings with geothermal heating and cooling systems viable and cost-effective. Most of the work was done using building energy modelling, and focused on one of the project's pilot sites, in Sant Cugat, Spain. The pilot was selected for showcasing the potential of an innovative high-temperature radiant cooling system, supplied with geothermal energy.

The results showed that retrofitting the building with the radiant cooling system would achieve significant benefits in thermal comfort, reducing the highest temperature reached during the cooling season from 32 °C to 27.9 °C. The fraction of the cooling season, when indoor temperature exceeds 26 °C was reduced from 83% to 23%. The results also show that the radiant cooling system can achieve this improvement with higher efficiency and lower environmental impact than a conventional all-air cooling system.

It should be noted that in the hot and humid climate of Spain, the radiant cooling system has to contend with the risk of water condensing on the surfaces of the cooling panels. This risk can be mitigated in two ways: limiting the system's cooling capacity or dehumidifying the air entering the building. Limiting the cooling capacity leads to thermal discomfort, while dehumidification approximately doubles the system energy use. Therefore, the needs and requirements of the retrofit case need to be carefully evaluated and balanced when planning a retrofit project.

Abstract [sv]

Hållbar utveckling ökar sin betydelse i både den vetenskapliga och politiska agendan. Mot bakgrund av denna utveckling har Förenta nationerna publicerat 17 mål för hållbar utveckling (sustainable development goals, SDG). SDG relaterar till alla aspekter av hållbar utveckling, de viktigaste för denna avhandling är hållbar energi och hållbar industri.

Komfortkyla ökar i betydelse globalt, å ena sidan på grund av en global temperaturökning till följd av klimatförändringen, å andra sidan på grund av den stigande levnadsstandarden i utvecklingsländerna, vilket innebär att fler människor kommer att få tillgång till komfortkyla. Komfortkyla har kopplats till alla 17 SDG, och påverkar inte bara energianvändningen utan även hälsa, välbefinnande och produktivitet. Vattenburen strålningskyla blir allt populärare som ett alternativ till konventionella, luftbaserade kylsystem. De främsta fördelarna med strålningskyla är lägre energibehov för distribution och möjligheten att använda lågvärdiga förnybara energiresurser som geotermisk kylning.

Renovering av byggnader är också ett viktigt ämne inom hållbar utveckling. För närvarande är 75% av byggnaderna i Europeiska unionen (EU) inte energieffektiva enligt nuvarande byggnadsstandarder, och 85-95% av dessa byggnader förväntas fortfarande vara i bruk år 2050. Detta innebär att befintliga byggnader måste renoveras för att uppnå högre energieffektivitet. Detta är avgörande för att minska EU:s utsläpp av växthusgaser. Huvuddelen av arbetet som presenteras i denna avhandling är kopplat till ett europeiskt forskningsprojekt, Geofit, med avsikt att göra eftermontering av byggnader med geotermiska värme- och kylsystem genomförbar och kostnadseffektiv. Det mesta av arbetet gjordes med hjälp av energimodellering av byggnader med fokus på en av projektets pilotplatser i Sant Cugat, Spanien. Byggnaden valdes ut för att visa upp potentialen hos ett innovativt strålningskylsystem med hög framledningstemperatur, försett med geotermisk energi.

Resultaten visar att eftermontering av strålningskylsystemet i byggnaden avsevärt förbättrar den upplevda termiska komforten, och minskar den högsta rumstemperaturen som uppnåtts under kylsäsongen från 32 °C till 27.9 °C. Delen av kylsäsongen, när rumstemperaturen överstiger 26 °C minskades från 83% till 23%. Resultaten visar också att strålningskylsystemet kunde uppnå denna förbättring med lägre energianvändning och miljöpåverkan än ett konventionellt luftbaserade kylsystem.

Det bör noteras att i det varma och fuktiga klimatet i Spanien behöver strålningskylsystemet styras så att kondensation på kylpanelernas ytor undviks. Detta kan uppnås på två sätt: genom att begränsa systemets kylningskapacitet eller genom att avfukta luften som kommer in i byggnaden. Begränsning av kylningskapaciteten leder till ökad termiskt obehag, medan avfuktning fördubblar systemets energianvändning. Därför måste behoven och kraven i renoveringsläget noggrant utvärderas och balanseras när man planerar ett renoveringsprojekt.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2023. p. 55
Series
TRITA-ABE-DLT ; 2313
Keywords
Radiant cooling, Geothermal cooling, Energy efficiency, Thermal comfort, Sustainable development, Strålningskylsystem, Geotermisk kyla, Energieffektivitet, Termisk komfort, Hållbar utväckling
National Category
Energy Engineering
Research subject
Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
urn:nbn:se:kth:diva-327077 (URN)978-91-8040-602-4 (ISBN)
Public defence
2023-06-12, D3, Lindstedtsvägen 9, KTH Campus, https://kth-se.zoom.us/j/67160823845, Stockholm, 13:00 (English)
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Note

QC 20230522

Available from: 2023-05-22 Created: 2023-05-17 Last updated: 2023-05-22Bibliographically approved

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Pieskä, HenrikkiWang, CongNourozi, BehrouzPloskic, AdnanWang, Qian

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