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This paper presents the outcomes of the project HYMENSO – Hybrid Concentrated Solar Thermal Power (CSP) and Photovoltaic (PV) plants for MENA Region –which had the main goal to investigate the optimal configuration of solar power plants for selected sites in Jordan, Tunisia and Algeria. This technology hybridization is becoming popular since it can harvest the advantages of both systems: easy installation and low LCOE (levelized cost of electricity) for PV, versatility and dispatchability of CSP. Additionally, fossil back-up with natural gas is also analyzed. The project HYMENSO was funded by the participants’ countries in the framework of ERANETMED. This paper presents results with focus on the simulation of the hybrid CSP-PV systems, due to its innovative character and current relevance. It has been demonstrated that there are many configuration options for hybridizing CSP and PV systems, therefore requiring the definition of further boundary conditions to determine an optimum, such as limitation of CO2 emissions in case that fossil back-up is used, expected satisfaction of the electricity demand, available land or water limitations. Important to notice is that for countries with a high fossil fuel price, the hybridization with natural gas reduces the overall LCOE only until a share of the generated energy of about 20%, higher use of fossil fuel is for such sites rich in solar irradiation not of noticeable advance.

Summary The objective of the paper is to analyse parametric studies and optimum steam extraction pressures of three different (subcritical, supercritical and ultra-supercritical) coal fired power plant cycles at a particular main steam temperature of 600 °C by keeping the reheat temperature at 537 °C and condenser pressure at 0.09 bar as constant. In order to maximize the heat rate gain possible with supercritical and ultra-supercritical steam conditions, eight stages of feed water heater arrangement with single reheater is considered. The system is optimized in such a way that the percentage exergetic losses are reduced for the increase of the exergetic efficiency and higher fuel utilization. The plant cycles are simulated and optimized by using Cycle Tempo 5.0 simulation software tool. From the simulation study, it is observed that the thermal efficiency of the three different power plant cycles obtained as 41.40, 42.48 and 43.03%, respectively. The specific coal consumption for three different power plant cycles are 0.56, 0.55 and 0.54 Tonnes/MWh. The improvement in feed water temperatures at the inlet of steam generator of respective cycles are 291, 305 and 316 °C.

Precise knowledge of the optical properties of the components used in the solar field of concentrating solar thermal power plants is primordial to ensure their optimum power production. Those properties are measured and evaluated by different techniques and equipment, in laboratory conditions and/or in the field. Standards for such measurements and international consensus for the appropriate techniques are in preparation. The reference materials used as a standard for the calibration of the equipment are under discussion. This paper summarizes current testing methodologies and guidelines for the characterization of optical properties of solar mirrors and absorbers.

Das heute als Kulturdenkmal gesch��tzte Kraftwerk ���Energie und Licht��� in Belgrad wurde in den Jahren 1930 bis 1932 von der Schweizerischen Elektrizit��ts- und Verkehrsgesellschaft Basel projektiert und errichtet. Als gr����tes Kraftwerk seiner Art in Belgrad trug es zu einer signifikanten Verbesserung der Versorgung der Stadt mit elektrischer Energie bei, bevor es u.a. auf Grund veralteter Technologie 1967 endg��ltig stillgelegt wurde. Infolge seiner architektonischen, kulturellen und historischen Werte z��hlt das Kraftwerk zu den bedeutenden Baudenkm��lern Belgrads. Die schlichte und schn��rkellose Architektur repr��sentiert die Neue Sachlichkeit im Verst��ndnis der europ��ischen Zwischenkriegszeit. Das Ziel der Diplomarbeit liegt in der analytischen und deskriptiven Rekonstruktion des Kraftwerks, um es im Rahmen einer denkmalgerechten Revitalisierung als attraktiven Ort im st��dtischen Raum zu erhalten., The ���Power and Light��� power station, now protected as a cultural monument in Belgrade, was designed and built between 1930 and 1932 by the Swiss Electricity and Transport Company of Basel. As the largest power station in Belgrade, it has contributed to a significant improvement in the supply of electricity to the city, before it was finally shut down in 1967, due to obsolete technology. As the result of It��s architectural, cultural and historical values, this power station is one of the most important monuments of Belgrade. The simple and unpretentious architecture represents the New Objectivity in the understanding of the European Interwar period. The goal of this master thesis is the analytical and descriptive reconstruction of the power station, within the frame of the historical monument revitalization in an order to preserve and develop it��s attractive place in the urban space of the city.

Reflectors are a vital part of a concentrating solar thermal power plant. One of their most important characteristics is their durability, which entails the maintenance of their optical properties throughout their service lifetime, aimed at 10–30 years or more. The assessment of their optical durability involves the design of two types of aging tests, outdoor exposure testing under real ambient conditions and accelerated exposure testing in weathering chambers under simulated conditions. After exposure to different stress factors for certain periods of time, the optical performance of reflectors is evaluated mainly in terms of reflectance, but also regarding qualitative parameters such as their visual appearance and degradation patterns. The ultimate goal of a durability study is to conceive meaningful accelerated testing procedures that simulate real outdoor degradation in a short time and provide service lifetime estimates for a certain type of reflector at a specific site. To achieve this, more research on service lifetime prediction should be conducted and the standardization of accelerated testing procedures and reflectance evaluation methods should become widespread, to obtain comparable representative results. In this article, the most significant durability studies performed on the three main types of solar reflectors (glass-based, aluminum and silvered-polymer) and prospective approaches for improving future endeavors are discussed.

Concentrated solar power plants with integrated storage systems are key technologies for sustainable energy supply systems and reduced anthropogenic CO2-emissions. Developing technologies include direct steam generation in parabolic trough systems, which offer benefits due to higher steam temperatures and, thus, higher electrical efficiencies. However, no large scale energy storage technology is available yet. A promising option is a combined system consisting of a state-of-the art sensible molten salt storage system and a high temperature latent heat thermal energy storage system (LHTESS). This paper discusses the systematic development and optimization of heat transfer structures in LHTESS from a technological and economic point of view. Two evaluation parameters are developed in order to minimize the specific investment costs. First, the specific product costs determine the optimum equipment of the latent heat storage module, i.e. the finned tube. The second parameter reflects the interacting behavior of the LHTESS and the steam turbine during discharge. This behavior is described with a simplified power block model that couples both components.

The convective heat losses of cavity receivers for solar thermal power towers are of great importance for the overall efficiency of the whole system. However, the influence of wind on these losses has not been studied sufficiently for large scale cavity receivers with different inclination angles. In this present study the impact of head-on and side-on wind on large cavity receivers with inclination angles in the range of 0° (horizontal cavity) to 90° (vertical cavity) is analyzed numerically. The simulation results are compared to data published in literature. When no wind is present the losses decrease considerably with increasing inclination angle of the receiver. In case of a horizontal receiver wind does not have a huge impact on the losses: they remain constant on a high level. In case of an inclined cavity wind increases the heat losses significantly in most of the cases, although the highest absolute value of the losses occurs for the horizontal receiver exposed to head on wind. In some cases, when wind is flowing parallel to the aperture plane, a reduction of the heat losses is observed. The temperature distribution in the cavity is analyzed in order to explain the impact of wind on the heat losses. Wind in general causes a shrinking of the zone with uniform high temperature in the upper region of the cavity, whereas wind flowing parallel to the aperture plane additionally inhibits hot air from leaving the cavity and therefore leads to an increased temperature in the lower zone.

A scaled model of a gas turbine (GT) burner with coaxially mounted swirlers has been used to study the effects of fuel staging on the behavior of lean premixed methane air flames. Lean flames are known to be susceptible to instabilities that can lead to unsteady operation, flame extinction, and thermo-acoustic oscillations. High speed (10 kHz) laser and optical diagnostic techniques have been used to investigate the fuel staging effect on the mechanisms involved in such instabilities. Methane air flames at atmospheric pressure have been investigated at a constant thermal power of 58 kW. The global equivalence ratio was kept constant, while the fuel staging was varied. The bulk flow velocity at the exit plane was kept constant at 20 m/s. Simultaneous high speed OH PLIF, OH* CL, and acoustic measurements were performed at kHz repetition rate to characterize the flames and determine the operability limits of the combustor. The characterization measurements reveal significant changes in flame shape for variou...

Thermal energy storage is a key technology for the commercialization of solar thermal power plants. This paper gives an overview of a coupled system comprised of concrete regenerators and latent heat storages for direct steam generation, as developed by the German Aerospace Center. Methodologies for an effective transient numerical description of the heat conduction processes inside the single modules and in the whole storage system are presented and their validity is proven by experiments. The presented process has a nominal system pressure of 105.6/80.0 bar for charging/discharging; the corresponding boiling temperatures are 315/295°C. As storage material of the latent heat storage, sodium nitrate with a melting point of 305°C is applied. With the presented models, a prediction of the storage system's temperatures, capacities, and effectiveness is possible. As a result, the design of a 1000-MWhth storage system is presented.

Existing solar thermal power plants are based on steam turbine cycles. While their process temperature is limited, solar gas turbine (GT) systems provide the opportunity to utilize solar heat at a much higher temperature. Therefore there is potential to improve the efficiency of future solar thermal power plants. Solar based heat input to substitute fuel requires specific GT features. Currently the portfolio of available GTs with these features is restricted. Only small capacity research plants are in service or in planning. Process layout and technology studies for high solar share GT systems have been carried out and have already been reported by the authors. While these investigations are based on a commercial 10MW class GT, this paper addresses the parameterization of high solar share GT systems and is not restricted to any type of commercial GT. Three configurations of solar hybrid GT cycles are analyzed. Besides recuperated and simple GT with bottoming Organic Rankine Cycle (ORC), a conventional combined cycle is considered. The study addresses the GT parameterization. Therefore parametric process models are used for simulation. Maximum electrical efficiency and associated optimum compressor pressure ratio πC are derived at design conditions. The pressure losses of the additional solar components of solar hybrid GTs have a different adversely effect on the investigated systems. Further aspects like high ambient temperature, availability of water and influence of compressor pressure level on component design are discussed as well. The present study is part of the R&D project Hybrid High Solar Share Gas Turbine Systems (HYGATE) which is funded by the German Ministry for the Environment, Nature and Nuclear Safety and the Ministry of Economics and Technology.

Direct steam generation (DSG) is one alternative to the current oil-based parabolic trough solar thermal power plants. Within the German research project ITES, the dynamic behavior of a DSG collector field and the interactions with the conventional power block are assessed in detail. A transient solar field model developed by DLR is used to simulate the steam temperature behavior. Artificial irradiance disturbances as well as real irradiance data are used as input to the system. The resulting main steam temperature gradients are then analyzed by Siemens considering the standards for steam turbines. This paper presents the transient simulation results of the steam temperature as well as the corresponding results of the steam turbine analysis. It is found that the occurring temperature gradients are challenging for a safe turbine operation, if a conservative control system is used. Therefore, the use of an additional thermal inertia to stabilize the steam temperature is suggested. Its impact is also analyzed and discussed in this paper.

A sustainable future power supply requires high fuel-to-electricity conversion efficiencies even in small-scale power plants. A promising technology to reach this goal is a hybrid power plant in which a gas turbine (GT) is coupled with a solid oxide fuel cell (SOFC). This paper presents a dynamic model of a pressurized SOFC system consisting of the fuel cell stack with combustion zone and balance-of-plant components such as desulphurization, humidification, reformer, ejector and heat exchangers. The model includes thermal coupling between the different components. A number of control loops for fuel and air flows as well as power management are integrated in order to keep the system within the desired operation window. Models and controls are implemented in a MATLAB/SIMULINK environment. Different hybrid cycles proposed earlier are discussed and a preferred cycle is developed. Simulation results show the prospects of the developed modeling and control system.

Receiver tubes (or heat collecting elements — HCE) are a key component of parabolic trough solar thermal power plants. They are mounted in the focal line of the collectors, absorb the concentrated solar irradiance and transfer the absorbed energy to the heat transfer fluid flowing through them. During the design phase of the receiver tubes and for the performance prediction of solar thermal power plants it is helpful to derive their technical properties, like the thermal losses or the temperature field in the receiver tubes, from their physical and geometrical properties. For this purpose, several models have been developed in the past [1–3]. In this paper, the different existing models are presented, compared and assessed. It is found that a simple analytical model is a helpful tool for the fast prediction of the temperature distribution in the receiver tube. Furthermore, a 2-dimensional and a 3-dimensioanl model are compared regarding the heat losses of a HCE at different operation conditions. Both tools show a good agreement with available measurements. Finally with these tools the efficiency factor F′ is calculated that considers the heat losses of an irradiated receiver compared to that of an un-irradiated receiver. According to the performed calculations, the efficiency factor of parabolic trough receivers is higher than expected.Copyright © 2010 by ASME

The direct steam generation (DSG) in parabolic trough collectors is a promising option to improve the mature parabolic trough solar thermal power plant technology of the Solar Energy Generating Systems (SEGS) in California. According to previous studies [1-3], the cost reduction of the DSG process compared to the SEGS technology is expected to be 8 to 25%. All these studies were more or less preliminary since they lacked detailed information on the design of collector fields, absorber tubes required for steam temperatures higher than 400°C and power blocks adapted to the specific needs of the direct steam generation. To bridge this gap, a detailed system analysis was performed within the German R&D project DIVA. Power blocks and collector fields were designed for four different capacities (5, 10, 50 and 100 MWel) and different live steam parameters. The live steam temperature was varied between saturation temperature and 500°C, and live steam pressures of 40, 64 and 100 bar were investigated. To assess the different cases, detailed yield analyses of the overall system were performed using hourly data for the direct normal irradiation and the ambient temperature for typical years. Based on these results the levelized costs of electricity were determined for all cases and compared to a reference system using synthetic oil as heat transfer fluid (HTF). This paper focuses on two main project findings. First, the 50 MWel DSG system parameter comparisons are presented. Second, the detailed comparison between a DSG and a SEGSlike 100 MWel system is given. The main result of the investigation is that the benefit of the DSG process depends on the project site and can reach an 11% reduction of the levelized electricity cost (LEC).

Power production in LWRs is economic and very efficient. A by-product of the fission process, which generates the thermal power, is radioactivity associated with fission and activation nuclides. This article describes the ways in which radionuclides are produced and then dissipated in the systems of a LWR. Radionuclides in and on the surface of components create radiation fields which can cause harm to workers. The article describes methods which help to minimize the buildup of these radiation fields. The difficulties in determining the radionuclide inventories for structural materials in LWRs are discussed and appropriate code packages are discussed. The basic principles adopted in the context of treatment of radioactive waste are summarized, including an overview of typical conditioning strategies. Radiation protection issues are briefly described and methods used to protect workers are discussed.