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Abstract Thermal energy storage (TES) systems are growing to a relevant role in solar cooling applications. Hence, high energy density is a desirable property of the TES system. Phase change materials (PCM) helps to increase this characteristic. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly of three parts: heating system, cooling system, and different storage tanks. Two identical storage tanks based on the shell-and-tubes heat exchanger, one of them including 196 squared fins in the bundle of the tubes and the other without, were experimentally tested. Hydroquinone was selected as the storage material, having a latent heat of 205 kJ/kg and a phase change temperature between 168 and 173 °C. The aim of this paper is to test experimentally, and compare the average effectiveness of the TES systems analyzed using PCM for solar cooling and refrigeration applications. It was found out that for the same tank configurations (shell-and-tubes) even changing drastically the dimensions of the tank or the number and the diameter of the tubes, the average effectiveness curve proposed in the literature fits well with the results showed here.

The building and construction sector is a large contributor to anthropogenic greenhouse gas emissions and consumes vast natural resources. Improvements in this sector are of fundamental importance for national and global targets to combat climate change. In this context, vertical greenery systems (VGS) in buildings have become popular in urban areas to restore green space in cities and be an adaptation strategy for challenges such as climate change. However, only a small amount of knowledge is available on the different VGS environmental impacts. This paper discusses a comparative life cycle assessment (LCA) between a building with green walls, a building with green facades and a reference building without any greenery system in the continental Mediterranean climate. This life cycle assessment is carried according to ISO 14040/44 using ReCiPe and GWP indicators. Moreover, this study fills this gap by thoroughly tracking and quantifying all impacts in all phases of the building life cycle related to the manufacturing and construction stage, maintenance, use stage (operational energy use experimentally tested), and final disposal. The adopted functional unit is the square meter of the facade. Results showed that the operational stage had the highest impact contributing by up to 90% of the total environmental impacts during its 50 years life cycle. Moreover, when considering VGS, there is an annual reduction of about 1% in the environmental burdens. However, in summer, the reduction is almost 50%. Finally, if the use stage is excluded, the manufacturing and the maintenance stage are the most significant contributors, especially in the green wall system.

Artículos en revistas Liberalization policies, the challenges of integrating distributed generation resources, and the recent flattening of electricity demand due to the economic crisis and technological change have led to lower returns for European electricity suppliers. Innovative and sustainable business models are needed to serve electricity customers while reflecting the operational needs of the system and maintaining supplier financial viability. This paper describes a novel model of Integrated Energy Services that encompasses distributed generation (DG) and demand response (DR) resources for industrial customers. We further reflect on some of the market opportunities and regulatory drivers for the development of similar schemes across Europe. info:eu-repo/semantics/publishedVersion

A Life Cycle Assessment (LCA) with focus on carbon footprint, followed by Life Cycle Costing (LCC) of municipal solid waste (MSW) management were conducted in a residential area of a medium-sized European city of 80,000 inhabitants. The initial results showed high environmental impacts and lack of economic sustainability, due to the high amounts of waste landfilled, the low extent of separate collection, low performance of mechanical-biological treatment as well as absence from alternatives to landfilling of non-recyclable materials. Taking this result as a baseline scenario, three improvement.s were tested with the aim of turning the carbon footprint of the local MSW management system into a neutral value: (i) increased separate collection of recyclables, (ii) enhanced biogas production and (iii) refuse-derived fuel (RDF) production. Successively adding the improvements, three alternative improved scenarios were defined, until reaching a negative carbon footprint, meaning that an optimised system would avoid GHG emissions. The proposed changes were sufficient to achieve carbon neutrality, as well as reduce overall environmental impacts, but were not enough for achieving economic sustainability due to the great influence of collection costs, especially for separate collection. It was concluded that by using an adequate combination of several treatment options and increasing the separate collection of recyclable materials it is possible to turn MSW management into a carbon neutral activity as well as improve its economic balance.

Artículos en revistas Numerical models of transmission-constrained electricity markets are used to inform regulatory decisions. How robust are their results? Three research groups used the same data set for the northwest Europe power market as input for their models. Under competitive conditions, the results coincide, but in the Cournot case, the predicted prices differed significantly. The Cournot equilibria are highly sensitive to assumptions about market design (whether timing of generation and transmission decisions is sequential or integrated) and expectations of generators regarding how their decisions affect transmission prices and fringe generation. These sensitivities are qualitatively similar to those predicted by a simple two-node model. info:eu-repo/semantics/publishedVersion

Abstract The organic Rankine cycle (ORC) has been growing in importance as a technology for producing electricity from low temperature waste and renewable heat sources. In small-scale applications, the most used working fluid has been HFC-245fa, although this is being substituted for low GWP alternatives. A new HCFO working fluid, HCFO-1224yd(Z), has appeared as a possible alternative for HFC-245fa. In this study, this alternative working fluid is analysed and, finally, the working fluid is experimentally tested as drop-in alternative in a commercial ORC system. The main purpose is to determine the feasibility of using HCFO-1224yd(Z) as a drop-in replacement for HFC-245fa in a real facility that was initially designed to operate with HFC-245fa. The results show how the use of HCFO-1224yd(Z) offers power output that ranges from 7.5% to 17.4% lower than that provided by HFC-245fa. Although HFC-245fa offers higher power output, the results show that HCFO-1224yd(Z) offers up to 7.7% higher cycle net efficiency; this is due to the higher input thermal rate required by HFC-245fa. Finally, HCFO-1224yd(Z) has been stated as a suitable alternative to HFC-245fa as a drop-in replacement in a small-scale, low-temperature ORC, which increases its attractiveness for heat source with higher temperatures.

Coherence in Photosynthesis It is unclear how energy absorbed by pigments in antenna proteins is transferred to the central site of chemical catalysis during photosynthesis. Hildner et al. (p. 1448 ) observed coherence—prolonged persistence of a quantum mechanical phase relationship—at the single-molecule level in light-harvesting complexes from purple bacteria. The results bolster conclusions from past ensemble measurements that coherence plays a pivotal role in photosynthetic energy transfer. Hayes et al. (p. 1431 , published online 18 April) examined a series of small molecules comprised of bridged chromophores that also manifest prolonged coherence.