Life Cycle Cost Analysis of two high temperature cooling systems supplied by geothermal energy : A Case Study in Sant-Cugat, Spain

Sammanfattning: Energy efficiency in the building sector is an important matter all over the world. The business of energy efficiency is especially highlighted in the European Union, where several directives and projects are directed to increase the knowledge and encourage and force property owners to implement new energy efficient solutions. Besides studying the primary energy demand of building as the only measure of the sustainability, it is also beneficial to study the exergy performance of building services to achieve a more correct picture of sustainability in the building sector. The objective of this Master Thesis is how two high temperature cooling systems connected to a local geothermal heat sink can be compared in terms of cost-effectiveness. The thesis is based on a case study where the two systems are evaluated in an administrative building in Sant-Cugat, Spain. Life Cycle Cost Analysis is used as a methodology and a complementary sensitivity analysis is conducted to highlight how different included parameters, such as maintenance cost, discount factor and electricity escalation rate impact the Life Cycle Cost of each system. The two systems compared are an all-air cooling system connected to a vertical ground heat exchanger/sink and a radiant cooling system also using the same arrangement as a heatsink.A study period of 30 year is implemented and in addition of the comparison of the two system, a comparison against a baseline scenario with no retrofitting is conducted, where the cost of the baseline scenario is quantified as the loss of work productivity due to overheating. The study shows that both systems are feasible to implement, since the loss in work productivity is fairly high. The all-air cooling system shows to be slightly more beneficial from an economical viewpoint during the study period, although the sensitivity analysis shows that the result is sensitive and not especially significant. To sum up, the thesis gives answers regarding the economic feasibility of the two systems and provide material for a hypothetical decision maker regarding which of the systems that would be most suitable to implement in the studied building.