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Abstract Even under the powerful thrust of 20–20–20 measures, solar thermal systems are experiencing a slow-down in their development in most EU countries. One reason is their traditional confinement to sanitary hot water (SHW) production; another one is the growing competition with photovoltaic (PV) systems. In order to widen the use of solar thermal collectors, they should also be able to contribute to space heating and cooling and become Multi-Purpose Solar Thermal Systems (MPSTS). This paper addresses the issue of optimal sizing of MPSTS. The criterion adopted is based on maximization of Net Present Value and has been applied to some cities in Italy and in Pakistan with diverse climate conditions. Results show that optimal thermal collector areas per peak cooling demand ( A c / P c ) can be conveniently expressed as a function of Peak Heating to Cooling Ratio ( P h / P c ). Optimum A c / P c varies between 3 and 5 m 2 /kW c and decreases with increasing P h / P c . The paper also analyses and compares a MPSTS with a multi-purpose PV-based heat pump system using a traditional one (boiler and compression chiller) as reference. Results show that steadily decreasing prices have made PV systems more favorable, even without consideration of public subsidies.

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.

This paper investigates the influence of solar radiation on thermal comfort inside an indoor environment and its effect on the building energy consumptions. Furthermore, it draws up a procedure which allows the rating of the thermal comfort quality of indoor environments in the presence of solar radiation, to be used in correlation with the energy classification of building in order to refer the energy performance to the indoor environmental conditions. Mean Radiant Temperatures (MRT) for a subject exposed to solar radiation in different positions of the environment were calculated, with an hourly time step and for a whole year. These values were utilized to assess the Predicted Percentage of Dissatisfied (PPD) and its variation with time and space, so that long term thermal comfort evaluations were able to be carried out and comparisons among irradiated and not irradiated positions were able to be made.

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%.