Energy saving in existing buildings is of vital importance. In this work, the characterization of housing stock in Spain for energy retrofitting purposes has been performed. The regulations in force when the existing stock was constructed (1980–2007) were considered to model the envelope and thermal systems of single-family and block housing. Building energy consumption and CO₂ emissions were estimated for each type of dwelling and location, ranging from 44.2 to 130.6 kWh/(m²·year) (13.6–32 kg CO₂/(m²·year)) for multi-family homes, and 85.5 to 213.5 kWh/(m²·year) (17.1–45.2 kg CO₂/(m²·year)) for single-family homes. A global picture of the energy performance and emissions for 13 different climate zones was obtained with a total of 504 simulations. Retrofitting of the envelope allowed the reduction of consumption and emissions from 37.7% to 58%, depending on the climate zone. Energy consumption per square meter in block housing was lower than in single-family housing; nevertheless, single-family houses responded more effectively to energy improvement actions. Finally, non-renewable primary energy savings seem a better indicator of the improvement by retrofitting than the energy label. The building models designed in this work may serve as a reference for subsequent research concerning energy retrofitting and energy savings of housing stock.

The scarcity of energy and water resources and rising temperatures due to climate change has set the focus on improving the energy efficiency of power plant thermodynamic cycles to adapt to higher heat sink temperatures and use fewer resources for energy production. In this work, a review of power production thermodynamic cycles is presented: from Brayton to Rankine and combined cycles, alongside particular cycles such as Organic Rankine Cycles, Kalina, Goswami or the more recently developed Hygroscopic Cycle. The efficiency of these cycles and their possible improvements are considered, as well as their environmental impact. Costs associated with existing power plants found in the literature have also been included in the study. The main existing facilities for each cycle type are assessed, and the most sustainable options in terms of resource consumption (fuel, water, etc.) and future perspectives to ensure both their energy efficiency and sustainability are identified.