As sustainable development increases its significance in policy-making, methods for quantifying the sustainability of a project become more important. One such method is life-cycle assessment (LCA). In this study, an LCA assessment of a radiant cooling system was conducted for a retrofit project of a small office building. The studied building is located in Sant Cugat in north-eastern Spain. The radiant cooling system was also compared with a conventional alternative, an all-air variable air volume system. The goal of the study is to provide a generalisable methodology for conducting an LCA-assessment in a retrofit project involving cooling. The methodology of the assessment consists of two parts. Building energy models in IDA-ICE 4.8 were used to determine the energy use of the systems and the resulting thermal comfort conditions in the building, while SimaPro 9.4 was used to carry out the LCA assessment. A major novelty in the study is the use of thermal comfort as the functional unit for the LCA assessment. The results show that the radiant system has a lower environmental impact in all ReCiPe2016 midpoint impact categories during the systems' estimated lifetime of 50 years. However, a sensitivity analysis revealed that while the radiant system's environmental impact is mainly dependent on the manufacturing process, the conventional system's impact is largely determined by its operational energy use. Therefore, the conventional system is significantly more sensitive to decarbonisation of electricity production.

 Space cooling demand is increasing globally due to climate change. Cooling has also been linked to all 17 sustainable development goals of the United Nations. Adequate cooling improves productivity and thermal comfort and can also prevent health risks. Meanwhile, policy initiatives such as the European Union’s Green Deal require participants to cut greenhouse gas emissions and reduce energy use. Therefore, novel cooling systems that are capable of efficiently producing high levels of thermal comfort are needed. Radiant cooling systems provide a design capable of fulfilling these goals, but their application in hot and humid climates is limited due to the risk of condensation. In this study, we compare the performances of radiant cooling systems with and without dehumidification.The studied systems are supplied by geothermal energy. The study is conducted using building energy models of a small office building belonging to a three-building school complex located in SantCugat near Barcelona in Spain. The studied location has a Mediterranean climate. The simulations are conducted using IDA Indoor Climate and Energy 4.8 simulation software. The results show that the radiant cooling system with dehumidification (RCD) produces considerably improved thermal comfort conditions, with maximum predicted mean vote (PMV) reached during the cooling season being 0.4 (neutral) and the maximum PMV reached by the radiant cooling system without dehumidification (RC) being 1.2 (slightly warm). However, the improved thermal comfort comes at the cost of reduced energy and exergy efficiency. The RCD system uses 2.2 times as much energy and 5.3 times as much exergy as the RC system. A sensitivity analysis is also conducted to assess the influence of selected input parameters on the simulation output. The results suggest that maximising dehumidification temperature and minimising ventilation flow rate can improve the energy and exergy efficiency of the RCD system while having a minor effect on thermal comfort.

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.

In recent years, the increasing occurrence of heatwaves raises the cooling need of residential buildings in Scandinavian countries, which are traditionally not equipped with active cooling systems. Indoor overheating caused by such heatwaves leads to severe consequences for occupants, especially kids and seniors. Efficient and economical cooling solutions are urgently needed to cope with frequent heat waves. The present study investigated the novel usage of the geothermal-assisted mechanical ventilation with heat recovery (GEO-MVHR) system for cooling purposes in typical Swedish multi-family dwellings. The cooling potential of the system and its contributions to thermal comfort were evaluated. Dynamic simulations were conducted to assess the system’s cooling performance under two climate scenarios: the climate of 2018 representing an extreme year with excessively hot summer and the climate of a typical meteorological year. The GEO-MVHR system shows great potential in mitigating indoor overheating with improved thermal comfort. A ventilation airflow rate of0.50–0.70 l/s/m2 is suggested for multi-family dwellings to maximize the cooling potential of the GEO-MVHRsystem. The indoor operative temperature could be reduced by up to 3 ◦C with the GEO-MVHR system operating for cooling. Modulating the supply air temperature of the GEO-MVHR system based on indoor thermal conditions is recommended, as it shows the advantage of avoiding unnecessary overcooling and energy saving.

Cooling demand in Europe is predicted to grow 25-50% between 2020-2050. Meanwhile, the EU aims to lower the greenhouse gas emissions from its building stock by 60%. Therefore, it is essential to find solutions that can meet the growing cooling demand with less energy and integrate renewable energy sources. The goal of this thesis is to technically evaluatehigh-temperature cooling systems and their contributions to the targets mentioned above. The study was conducted using advanced building energy simulations and developing analytical methods. IDA Indoor Climate and Energy 4.8was selected as the simulation tool. The study is a part of GEOFIT project, and the used building physics and measurement data were based on one of the project pilots. The selected building is a representative office building that is a part of a three-building school complex. The building is located in Sant Cugat near Barcelona, in an area which has a typical Mediterranean climate. The simulated building model was validated using onsite measurement data. Two types of high-temperature cooling systems were studied: a radiant cooling system and an all-air cooling system. For the study, the systems were designed to create equal thermal comfort conditions, so that their energy and exergy use could be compared. In the studied case, the radiant cooling system was found to use 40% less energy and consume 85% less exergy than a conventional low-temperature all-air cooling system. It was also found that a passive geothermal radiant cooling system requires 66% less electricity for pumps and fans than a passive geothermal all-air cooling system. The results demonstrate that radiant cooling systems have the potential to lower exergy consumption in cooling applications thanks to the high supply temperature and that using water as a heat transfer medium is more efficient than using air.

Kylningsefterfrågan i Europa förutses att växa 25-50% mellan 2020-2050. Samtidigt strävar EU efter att sänka utsläppen av växthusgaser från sina byggnader med 60%. Det är därför viktigt att hitta lösningar som kan tillgodose det växande kylbehovet med mindre energi och att integrera förnybara energikällor. Målet med denna avhandling är en teknisk evaluering av högtemperatur-kylsystem och deras bidrag till ovan nämnda mål.

Studien genomfördes med avancerade simuleringar av byggnadsenergi och utvecklade analytiska metoder. IDA Indoor Climate and Energy 4.8 valdes som simuleringsverktyg. Studien är en del av GEOFIT-projektet och den använda byggnadsfysiken och mätdata baserades på en av projektpiloterna. Den valda byggnaden är en representativ kontorsbyggnad som ingår i ett skolbyggnad med tre byggnader. Byggnaden ligger i Sant Cugat nära Barcelona, i ett område som har ett typiskt medelhavsklimat. Den simulerade byggnadsmodellen validerades med hjälp av mätdata på plats.

Två typer av högtemperatur-kylsystem studerades: ett strålande kylsystem och ett luftkylsystem. För studien designades systemen för att skapa lika termiska komfortförhållanden, så att deras energi och exergianvändning kunde jämföras. I det studerade fallet visade sig att det strålande kylsystemet använde 40% mindre energi och förbrukade 85% mindre exergi än ett konventionellt högtemperatur-kylsystem med låg temperatur. Man fann också att ett passivt geotermiskt strålkylsystem kräver 66% mindre el för pumpar och fläktar än ett passivt geotermiskt luftkylsystem. Resultaten visar att strålningskylsystem har potential att sänka exergiförbrukningen i kylapplikationer tack vare den höga framledningstemperaturen och att användning av vatten som värmeöverföringsmedium är effektivare än att använda luft.

Radiant cooling systems are a subject of increasing scientific interest due to their efficiency and ability to use high-temperature cooling sources. In hot and humid conditions, they have generally been studied in combination with dehumidification systems. For retrofit projects, a control system that would eliminate the need for dehu-midification would be beneficial. In the present study, a passive geothermal-based radiant high-temperature cooling system is studied in a Mediterranean climate. The system is operated with supply water temperature control using dew point temperature as a controlling variable. The system’s performance is compared with that of an all-air cooling system. The systems are evaluated using IDA-ICE building energy simulations, validated with on-site measurement data. The results show that the radiant cooling system produces the same level of thermal comfort with 40% lower energy use and 85% lower exergy consumption than the all-air system. The risk of condensation limits the cooling capacity of the radiant cooling system. Consequently, insufficient cooling ca-pacity causes thermal discomfort for the occupants due to the operative temperature exceeding 26 ◦C.

A novel high-temperature cooling (HTC) system combining cooling panels with humidity control and a mechanical ventilation system was evaluated in retrofitting. The studied system was compared with an all-air cooling system that was used as areference system, using building energy simulations. The studied case was a typical single storey office building located in Sant Cugat in Spain. The system’s performance was evaluated by comparing the energy and exergy use as well as CO2-emissions of thecompared systems. The studied HTC system was found to decrease the cooling energy use by 40%, the exergy use by 85% and the CO2-emissions by 83% in comparison with the all-air system.