Transició energètica residencial: Avaluació tècnica, ambiental i econòmica d'alternatives per a la descarbonització d'un habitatge unifamiliar a la zona climàtica D1

Abstract

The decarbonization of the residential sector is a critical step towards achieving global climate neutrality, given that building operations account for approximately 28% of global final energy consumption and 37% of energy-related CO2 emissions. In Spain, domestic heating and domestic hot water (DHW) remain heavily dependent on fossil fuels, highlighting the urgent need for a clean energy transition. This Master's thesis aims to evaluate the technical, environmental, and economic feasibility of various renewable alternatives to replace an existing fossil fuel (diesel) heating and DHW system. The case study is a single-family home located in Santa Maria d'Oló, a severe winter climate zone (D1). The study employs a rigorous multi-criteria evaluation. The building's thermal envelope and current energy demands were modeled using dynamic simulation software, primarily DesignBuilder and CE3X. Based on the baseline demand, four main decarbonization alternatives were dimensioned and analyzed over a 25-year life cycle: 1) Advanced Biofuel (HVO 100), 2) Biomass (pellet boiler), 3) Aerothermal heat pumps (using R32 and R290 refrigerants), and 4) Geothermal heat pumps. The comparative analysis assesses final and non-renewable primary energy consumption, Life Cycle Assessment (Well-to-Wheel) for CO2 emissions mitigation, and financial metrics including Net Present Value (NPV), Internal Rate of Return (IRR), and Payback period, considering scenarios with and without public subsidies. The findings demonstrate that heat pump systems (Geothermal and Aerothermal) achieve the highest thermodynamic efficiency, reducing final energy consumption by up to 84% and 80%, respectively. However, their long-term economic performance is penalized by high initial investments (CAPEX) and the rising cost of grid electricity. The application of HVO 100 acts as an excellent zero-CAPEX drop-in transitional measure, cutting emissions by 87%, but its high market price makes it the least financially viable option over 25 years. Conversely, the biomass pellet boiler achieves the greatest environmental impact mitigation, avoiding 96% of greenhouse gas emissions. Economically, biomass provides the most solid long-term financial performance, achieving the highest NPV and a 13-year payback period when public subsidies are applied. The final decision is heavily conditioned by two site-specific architectural limitations: the inability to install solar photovoltaic panels due to adjacent building shading, and the retention of existing high-temperature radiators. Under these specific constraints, the pellet biomass boiler emerges as the most robust global alternative, perfectly balancing optimal environmental commitment, thermal comfort, and structural economic viability required for residential energy transition.