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The aim of this work is to show the effects in a PV cell of the combined profiles of non-uniform temperature and radiation. Particular attention is paid to the modelling of cell operation at open circuit voltage with those profiles, as long as they serve as a general model in different circumstances: combined direct Gaussian temperature and radiation profiles, with several temperature amplitudes and movement of these profiles across the cell; analysis under Gaussian concentrated illumination and inverse Gaussian temperature profile simulating a general cell cooling device. In addition, we will study the cell behaviour under truncated radiation and temperature profiles. Irregular radiation and temperature distributions will also be studied.

Millions of people have no access to a secure source of fresh water. Nevertheless, since many arid regions are coastal areas, seawater desalination is a reasonable alternative. On the other hand, the energy requirements of desalination processes are high. Then, the energy supply in low development countries or isolated areas may be a problem, especially if electricity is required. Since most arid regions have high renewable energy resources, the use of renewable energies in seawater desalination exhibits an interesting chance, or even the only way to offer a secure source of fresh water. The status and perspectives of development of coupling renewable energy systems with desalination units are reviewed. It is pointed out that there are place of development even for such technologies that seem to be the most mature ones.

Ventilated glazed facades are formed by two layers of different materials, opaque or transparent, that are separated by an air channel, used to collect or evacuate the solar radiation that is absorbed by the facade. For architectonic reasons, the outer layer is usually made entirely of glass, while the indoor layer may be partially opaque. This allows direct solar gains to be reduced and increases the thermal inertia of the building. This paper is a presentation of a code for the numerical simulation of ventilated and conventional facades. It is based on time-accurate, one-dimensional discretizations for the channel and the different solid zones, and allows heat fluxes and temperature distributions in the facade to be obtained over the course of one year. The numerical code allows advanced elements to be integrated into the facade, such as phase change materials, selective surfaces and improved glasses. The code has been validated by comparing it with analytical solutions where possible, with reference situations and with experimental measurements obtained in real-site test facilities in different climatic conditions. The numerical code is a useful tool for optimising the design of facades so as to take advantage of different materials, orientations, geometries and to address different climatic conditions.

We present an evaluation of a new version of the web-based clean power estimator (CPE) capable of evaluating the effectiveness and value of solar load control (SLC) for commercial applications in the US. Three experimental building case studies are used as a validation benchmark. The selected buildings include a large office building near New York City, a department store in Long Island, and another department store in Hawaii. The results of the CPE calculations are compared against results obtained using actual building load and colocated hourly actual solar radiation data.

Abstract Thermocline storage tanks are considered one of the most promising options to reduce levelized electricity costs in solar thermal power plants with a storage system. Due to thermocline degradation, the annual electricity yield of a plant with thermocline storage is always lower than the same plant with a two-tank storage system. In this way, an annual performance analysis has been carried out for different charge and discharge operation strategies in order to find out the best operation mode that minimizes the difference in annual yield between both systems. 50 MW e plants based on parabolic trough technology have been analyzed and both synthetic oil and molten salts have been used as heat transfer fluids. The simulation model has been developed with the TRNSYS© software tool and the advantages and disadvantages of specific operation strategies for both kinds of storage systems have been identified. As a result, differences in fossil fuel consumption, annual yield and startup time for power block have been obtained together with some required changes in hydraulic circuit configuration. The main advantage of these results is that they can provide a useful guideline for further economic assessment associated to thermocline storage systems.

In this paper, a clear day is defined as one generating a thermal load, and its daily level of solar energy, HgIT, is higher than the daily threshold energy imposed by the process, Hmin. In Madrid, for the air-conditioning of indoor spaces, Hmin varies from about 24 MJ m−2 day−1 in June to about 18 MJ m−2 day−1 in September. Using the representative input data of a clear day in Madrid and applying the Hottel-Willier, Duffie, Beckman and Klein model, taking into account the heat capacity effects and the variable regime, a theoretical simulation of a lithium bromide absorption cooling system was performed to obtain a daily collector efficiency of about 22%, a daily COP of the cooling machine of about 55% and a daily efficiency of the solar energy-cooling conversion of about 12%.

Abstract Parabolic trough is the most extended solar thermoelectric technology. Solar radiation is converted into heat and transferred to the heat transfer fluid in the solar receiver tubes. The thermal energy obtained feeds a conventional Rankine power cycle. The performance of the receiver tube can be broken down into three single components: the optical transmittance of the outer glass envelope or capability in transmitting the radiant energy; the optical absorptance of the metal tube or capability to absorb the radiation; and heat losses of the tube or capability to retain the heat which depends of inner tube coating emissivity and the vacuum between both tubes. In this paper a novel test bench implementing both thermal and optical measurement systems is described and compared with other systems referred in the literature. The results obtained from the evaluation of three different solar receivers with different diameters are presented. Optical measurements of transmittance and absorptance parameters are carried out in the wavelength range of 300–2500 nm. Optical evaluation of trough receivers at operating temperatures up to 450 °C is feasible. The receivers can be heated using a high intensity electric current flowing through the internal tube. Uniform Joule heating results a reliable heat losses measurement method at temperatures up to 650 °C.

Abstract Daily radiation on slopes in usually computed by the Liu and Jordan method. Measurements of the global and diffuse radiation fluxes at various tilt and azimuth angles have been made in clear days with a pyranometer equatorially mounted upon a modified theodolite system. The resulting data have been used to evaluate the validity of the Liu and Jordan model with the assumption of an isotropic distribution of diffuse radiation in the sky. It is concluded that the model yields significantly better results when the reception surface is oriented in the azimuth of the Sun, but not for other azimuthal orientations of the slope. Although an evident anisotropy has been found in the diffuse radiation distribution, the results obtained by this modeling approach are considered sufficient for flat-plate collector applications.