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Abstract Generally, the majority of the linear concentrating photovoltaic (LCPV) systems incorporated with active cooling systems use liquid water pump loop or conventional vapor compression refrigeration system. In this study, a new cooling system, so-called two-phase mechanical pumped loop (TMPL), is proposed to be used with LCPV system. The excess heat from photovoltaic (PV) cell is used to heat up water stored in a tank for residential purposes. The case study is Bogota in Colombia and we develop a dynamic simulation model for the LCPV-TMPL system. The design parameters of the TMPL system are the flow volumetric rate and saturation temperature of the refrigerant as well as the tube length of the condenser. Moreover, low global warming potential (GWP) refrigerants such as R1234yf and R1234ze(E) were evaluated, both showing the same performance compared to R134a. The results showed that the use of TMPL system to eliminate the generated heat of PV cell improves its temperature stability and efficiency. It also shows how the proposed model can be used to design the thermal/photovoltaic system for a local, showing also the expected performance before the system installation. In the case study region, the LCPV-TMPL system, using four PV cells with 5 m × 10 mm, produces power with an average monthly of 2 kW with a peak of 5 kW under average and peak monthly solar radiation of 400 W/m2 and 600 W/m2, respectively. The storage tank can heat up 2.2 m³ water per day from 8 °C to approximately 28 °C, in an average sense. This means that the LCPV-TMPL system could save 9000 kWh and 1900 kWh per year in electricity and thermal energies (water heating). This system can be used locally with low or medium solar radiation and cold weather.

Abstract One of the first steps for the exploitation of any energy source is necessarily represented by its estimation and mapping at the aim of identifying the most suitable areas in terms of energy potential. In the field of renewable energies this is often a very difficult task, because the energy source is in this case characterized by relevant variations over space and time. This implies that any temporal, but also spatial, estimation model has to be able to incorporate this spatial and temporal variability. The paper deals with the spatial estimation of the wind fields in Sicily (Italy) by following a data-driven approach. Starting from the results of a preliminary study, a novel technique resulting from the integration of neural and geostatistical techniques was developed in order to obtain the wind speed maps for the region at 10 and 50 meters above the ground level. The mean values of the theoretical Weibull distribution function describing the wind regime at each of the available measurement sites were used to train a multi-layer perceptron (MLP) whose goal is to compute the most of the wind spatial trends. Other pieces of information about the territory (altitude, land coverage) were also used as inputs of the network and organized into a geographic information system (GIS) environment. The remaining de-trended linear means have been computed by using a universal kriging (UK) estimator. The results of these steps were then summed up and it was thus possible to obtain a map of the estimated wind fields.

This article analyses the current state of the debate over competition for land use, by means of an index of the main arguments in favor and against the production of liquid biofuels and the impacts on food production. Based on this index, an analytic framework is constructed to establish the causal relations indicated by the existing studies on this competition. We find that the emergence of agro-energy has altered the land use dynamic, albeit not yet significantly, with a shift of areas traditionally used to grow foods over to crops to produce biofuels. This has been contributing to raise food prices in the short run. However, it is probable that this is not the only factor determining this trend, nor will it last over the long run. The challenge is to conciliate the production of biofuels with the production of foods in sustainable form.

Solid oxide fuel cell (SOFC) is a mature opportunity for producing power energy in remote areas like islands, where access to the electrical grid is not favoured, and gas distribution is the only viable approach. In this context, generally, biogas represents the most convenient fuel resources in these areas. However, the direct use of biogas in SOFCs is still an issue to be solved due to its negative effect on the conventional Ni-YSZ anode. In this study, to overcome this issue, we suggested using a protective layer coated on the anode of a commercial SOFC. A nickel manganite showing mixed ionic and electronic conductivity tailored specifically for this approach was investigated. The preliminary characterisations showed that the formation of a Ruddlesden-Popper (RP) n ¼ 1 structure supporting fine encapsulated particles based on Ni was formed around 800 C in consequence of the reducing environment. The electrochemical experiments carried out for 270 h demonstrated for the coated cell significant stability in the presence of dry biogas, albeit an ageing effect was noticed in the electrical percolation of both cell electrodes. The post mortem analyses revealed an attractive redox property for the nickel manganite, which partially returned to the RP n ¼ 2 phase. Moreover, the absence of carbon deposits on the anode suggests possible applications for this approach.

Abstract The exploitation of the renewable energy sources plays a key role for achieving the CO 2 emissions reduction targets established by the Kyoto Protocol, as well as for facing the shortage of world fossil fuels reserves. In countries like Italy, with an high potential in terms of wind power generation, an efficient energy planning based on renewables is a very complex task. It encompasses many aspects: the resource availability assessment, the compliance with environmental and legislative constraints and last, but not least, the technical aspects linked to the safe integration to the grid of the intermittent power generated by the wind farms. This paper is the first part of a study addressing the first of the aforementioned issues. The wind measurements recorded in several stations of Sicily (Italy) were used for the spatial modelling of the wind fields over the region. A statistical analysis of the wind data has allowed the estimation of the parameters of the wind probability distribution function, that is a Weibull, as predicted by theory. In the last sections of the paper the results of some traditional deterministic and geostatistical interpolation techniques are shown. In the companion paper the maps of the estimated wind fields have been obtained by using the results of the statistical investigation accomplished here and coupling neural and geostatistical techniques. For a comprehensive evaluation of the forecasting accuracy of this neural kriging approach, those maps have to be compared with the maps showed in this paper.

Hybrid renewable systems increase electricity production by reducing the randomness of sources without greenhouse gas emissions. Literature indicates that further research is still required for large systems connected to the grid. The energy storage capability of hydroelectric plants provides an opportunity to develop new renewable energy generation. This work presents the results of a hybrid preliminary design between an existing hydropower plant (HPP) in Brazil, Santa Branca, and a simulated floating photovoltaic plant (FPV), occupying only 2.8% of reservoir's surface. The study analyzed 20 years of HPP historical data, the methodology proposed the injection of the FPV full power into the system during daytime and the HPP adjusting the production. As this process changed the HPP generation profile, operational limits such as reservoir level needed to be verified. In the period, while HPP generated about 4 TWh, the FPV could add 2 TWh without significantly changing the daily generation of HPP. This increase of 50% in production was possible since there was space available in the reservoir to store water during the day and use it during the night, working as a free virtual battery for the FPV. A 50% increase of the grid connection capacity factor was also observed.

This paper discusses the oil palm expansion in the State of Para, located in the Brazilian Amazon. It focuses on land use change aspects put in perspective with the sustainability criteria for biofuels of the European Renewable Energy Directive (RED). The study shows that palm oil production for energy purposes appears very promising in Brazil. In parallel to local targets, the mandatory European biofuel targets represent an important market potential for the country. It seems too early to know whether the export of palm oil biodiesel from Brazil to Europe will be significant or not. However, it is likely that palm oil exports for biodiesel production in Europe occur in the coming years. Although the RED includes some essential conditions for sustainable production of biofuels, we argue that the values imposed for calculating carbon stocks do not reflect diversity of pastureland where oil palm expansion occurs in the Brazilian Amazon. The use of certain land areas authorised within the RED may also represent a significant limit in terms of biodiversity protection. This study provides new insights that may be used to improve life cycle assessment of biodiesel from palm oil in order to avoid unintended policy consequences.

Fil: Zeng, Kuo. Centre National de la Recherche Scientifique; Francia. Processes Materials and Solar Energy Laboratory; Francia