• Energy Research
• 12. Responsible consumption close

Thermal energy storage (TES) is nowadays presented as one of the most feasible solutions in achieving energy savings and environmentally correct behaviors. Its potential applications have led to R&D activities and to the development of various technology types. However, so far there is no available data on a national scale in Spain and on a continental level in Europe, to corroborate the associated energetic and environmental benefits derived from TES. This is why, based on a previous potential calculation initiative model performed in Germany, this work intends to provide a first overview of the Spanish TES potential as well as an European overview. Load reductions, energy savings, and CO2 emissions reductions are tackled for the buildings and industrial sector. Results depend on the amount of implementation and show that, in the case of Europe for instance, yearly CO2 emissions may get to be cut down up to around 6% in reference to 1990 emission levels.

Catalonia (Spain) has a significant potential of biogas production from agricultural activities and municipal waste. In addition, there are plenty of industrial cogeneration plants, but most of them use conventional fuels, such as natural gas, and conventional energy conversion devices, such as internal combustion engines. Molten carbonate fuel cells are ultraclean and highly efficient power generator devices capable of converting biogas into electricity and heat. Located in Lleida (Catalonia), Nufri is a fruit processing company with a long tradition on biogas production and cogeneration, with an installed capacity bigger than 45 MW. This study analyzes the economic viability of a fuel cell operating on biogas in Spain, on a real case basis (Nufri). Different fuel cell capacities are analyzed (from 300 kW to 1200 kW). A parametric study of different fuel cell prices ($/kW installed) is performed. Additional biogas cleanup requirements are taken into account. The results are based on the Spanish legislation, which establishes a special legal framework that grants favorable, technology-dependent feed-in premiums for renewable energy and cogeneration. Results show that the payback period ranges from 5 years to 8 years depending on the fuel cell capacity and installation price.

A new research university building with a useful area of about 3000 m2 has recently been constructed in Lleida (Spain) as an example of a sustainable energy efficient institutional building. The building is provided with passive measures in the envelope as well as a wide variety of active measures in the installed energy systems. Non-conventional energy systems such as solar photovoltaic arrays, thermal collectors, an internal combustion engine cogeneration, and an absorption chiller are in place. The standard systems, namely two 320 kW condensation boilers and a 419 kW compression chiller, are also included in the building for back-up and for comparison purposes. To assess the potential energy, economic and CO2 savings of the building a simplified model is developed and the main results discussed. For nominal electricity and gas average prices about 11.5 k€ of savings are achieved. This represents energy cost reductions of 35–58%, a payback period of 20 years and about 56 tons per year of saved CO2 emissions. The presence of the absorption chiller is found essential to maximize buildings economic and CO2 emissions savings. This work also includes parametric studies for natural gas and electricity prices as well as results for other possible combinations with only one or several of the installed systems in operation.

Energy efficiency strategies, such as building insulation, improve the building performance without compromising comfort. This study presents a methodology for determining the optimal insulation thickness for external building surfaces. Our approach is based on a multi-objective optimization model that minimizes simultaneously the cost and environmental impact associated with both the energy consumption over the operational phase and the generation of the construction materials (including the waste produced during the disposal phase). The thermal loads of the cubicles were calculated with EnergyPlus, a widely used simulation program for buildings. The environmental impact was quantified following the life cycle assessment (LCA) methodology. Our approach was applied to a case study of a house-like cubicle located in Lleida (northeast Spain). Taking as a basis a standard cubicle without insulation, our approach identifies solutions that reduce around 40% both, the cost and environmental impact. Optimal solutions show also important economic and environmental improvements compared to cubicles constructed with the Spanish legislation requirements. Our method is intended to assist decision-makers in the design of buildings. The authors would like to acknowledge financial support from the Spanish Government (ENE2011-28269-C03-03, ENE2011-22722, DPI2012-37154-C02-02, CTQ2012-37039-C02) and to thank the Catalan Government for the quality accreditation given to their research groups GREA (2014 SGR 123). The research leading to these results has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under grant agreement no. PIRSES-GA-2013-610692 (INNOSTORAGE).