Parabolic Trough Solar Power Plant Research Articles

Demonstration of Pilot Scale Large Aperture Parabolic Trough Organic Rankine Cycle Solar Thermal Power Plant in Louisiana

During the calendar year of 2012 the University of Louisiana at Lafayette in conjunction with CLECO Power LLC (CLECO) has constructed and commissioned a pilot scale parabolic trough solar thermal power plant for the first time in Louisiana. The large aperture trough (LAT) solar collectors were provided by Gossamer Space Frames and are coupled with an organic Rankine cycle (ORC) power block provided by ElectraTherm, Inc. for study of the feasibility of cost-effective commercial scale solar thermal power production in Louisiana. Supported by CLECO and providing power to the existing CLECO grid, the implementation of state-of-the-industry collector frames, mirrors, trackers, and ORC power block is studied under various local weather conditions which present varied operating regimes from existing solar thermal installations. The solar collectors provide a design output of 650 kWth and preliminary actual performance data from the system level is presented. The optimal size, configuration and location for such a plant in the given solar resource region are being studied in conjunction with CLECO’s search for optimal renewable energy solutions for the region. The pilot scale size of the facility and implementation of the simpler ORC allow remote operation of the facility and flexibility in operating parameters for optimization studies. The construction of the facility was supported by the Louisiana Department of Natural Resources, the U.S. Department of Energy, and CLECO. The continued operation of the plant is supported by CLECO Power LLC and the University of Louisiana at Lafayette.

Modeling and optimizing parabolic trough solar collector systems using the least squares support vector machine method

Investigating the complicated thermal physics mechanisms of the parabolic trough solar collector systems plays a vital role in efficiently utilizing the solar energy. In this paper, the least squares support vector machine (LSSVM) method is developed to model and optimize the parabolic trough solar collector system. Numerical simulations are implemented to evaluate the feasibility and efficiency of the LSSVM method, where the sample data derived from the experiment and the simulation results of two solar collector systems with 30m2 and 600m2 solar fields, and the complicated relationship between the solar collector efficiency and the solar flux, the flow rate and the inlet temperature of the heat transfer fluid (HTF) is extracted. Some basic rules, such as the solar collector efficiency increases with the increase of the solar flux and the flow rate of the heat transfer fluid, and decreases with the increase of the inlet temperature of the HTF, are obtained, which indicates the LSSVM method is competent to optimize the solar collector systems. As a result, the new approach will provide meaningful data for developing the parabolic trough solar thermal power plant in China.

Analysis of the influence of operational strategies in plant performance using SimulCET, simulation software for parabolic trough power plants

Abstract This paper analyzes the influence of operational strategies on the performance of parabolic trough (PT) solar power plants with the aid of SimulCET a computer program for the simulation of the energy behavior of PT plants developed by the National Renewable Energy Centre of Spain (CENER). SimulCET uses state of the art techniques to simulate solar energy absorption and others energy conversion processes that take place in a PT plant. The simulation of these energy conversion processes is based on both empirical and physically derived expressions and produces highly accurate electricity generation estimates. The holistic approach adopted in SimulCET to carry out the analysis of PT solar power plants makes this program a very effective tool in optimizing the operation of such plants. Furthermore, SimulCET’s capabilities for simulating the operation of gas boilers make it possible to compare different operational strategies scenarios, and enable the testing of new hybrid plants concepts. To assess the validity of the results generated by SimulCET, these results were compared with current experimental data. The comparison showed good agreement among daily averaged estimates and the corresponding measured energy values. The comparison of SimulCET daily estimations against twelve reference days of measured data showed a mean deviation of −3.14% in terms of daily total gross electricity production. This paper focuses on the simulation and analysis of different PT plant operational strategies to explore the consequences and side effects of the way the fossil fuel is used, which have been seldom analyzed up to now, although they may significantly affect the long term performance of the plant. Four different operational strategies were compared. In all of them, the yearly amount of gas used was the maximum allowed for a solar PT power plant to be considered eligible to receive the benefits of the Spanish feed-in tariff legislation. Differences in gross electric energy output larger than 10% and differences in yearly gas consumption of up to 15% were obtained during the simulation of the PT power plant running for a year under each one of the four operational strategies considered. The results of these simulations make clear the need for further techno-economic optimization of the operational strategies defined, since revenues, costs and other operational factors depend not only on the amount of gas used, but also on when this gas is burned.

Economic impacts of solar thermal electricity technology deployment on Andalusian productive activities: a CGE approach

Solar thermal electricity is a type of renewable energy technology of special interest for Andalusia (southern Spain) because of the large number of annual sunshine hours. This paper estimates the impact on productive activities of increasing the production capacity of the installed solar thermal plants in Andalusia. Using a computable general equilibrium (CGE) approach, estimates of the changes in the economic sectors’ activity under two different scenarios are obtained: i) based on two types of solar thermal electricity plants currently in operation and ii) based on an increase from 11 MW in 2007 to 800 MW installed capacity by 2013 to comply with the ‘Plan Andaluz de Sostenibilidad Energetica (PASENER)—Sustainable Energy Plan for Andalusia’. For the case of a parabolic trough solar collector power plant, results show that compliance with the PASENER goal would increase the level of the productive activities by around 30%. For the alternative technology—a solar tower power plant—results show that activities would increase by around 5% for 30 years, the estimated lifetime of this type of plant. Thus, the impact of the solar thermal electricity plants on the productive activities of the PASENER compliant production goal would be remarkable.

Performance model for parabolic trough solar thermal power plants with thermal storage: Comparison to operating plant data

Abstract This paper describes a simulation model that reproduces the performance of parabolic trough solar thermal power plants with a thermal storage system. The aim of this model is to facilitate the prediction of the electricity output of these plants during the various stages of their planning, design, construction and operation. Model results for a 50 MW e power plant are presented and compared to real data from an equivalent power plant currently operated by the ACS Industrial Group in Spain.

A heuristic method to minimise the chattering problem in dynamic mathematical two-phase flow models

This paper introduces the chattering problem in dynamic mathematical two-phase flow models. The real system object of study is also introduced, the DISS test facility, a parabolic-trough solar power plant using as heat transfer fluid the steam–water mixture. A dynamic model for studying its behaviour was previously developed using Modelica as the modelling language, in this model the chattering problem arises and therefore not allowing to take full advantage of dynamic simulations. The chattering problem increases the computational time needed for simulation and sometimes dynamic simulations do not finish at all. A heuristic method, which minimises the effects of the chattering problem, is discussed and results which reduce the computational time for dynamic simulations are given.

Steam temperature stability in a direct steam generation solar power plant

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.

Economic Potential of Solar Thermal Power Plants With Direct Steam Generation Compared With HTF Plants

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 [Langenkamp, 1998, “Revised LEC Projections and Discussion of Different DSG Benefits,” Technical Report No. DISS-SC-QA-02, Almeria, Spain; Price, et al., 2002, “Advances in Parabolic Trough Solar Power Technology,” ASME J. Sol. Energy Eng., 124(2), pp. 109–125; Zarza, E., 2002, “DISS Phase II Final Report,” Technical Report EU Contract No. JOR3-CT98-0277, Almeria, Spain], the cost reduction in the DSG process compared with the SEGS technology is expected to be 8–25%. 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. Power blocks and collector fields were designed for four different capacities (5 MWel, 10 MWel, 50 MWel, 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 bars, 64 bars, and 100 bars 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 with a reference system using synthetic oil as heat transfer fluid. 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 SEGS-like 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 in the levelized electricity cost.

Experimental investigation on a parabolic trough solar collector for thermal power generation

Developing solar thermal power technology in an effective manner is a great challenge in China. In this paper an experiment platform of a parabolic trough solar collector system (PTCS) was developed for thermal power generation, and the performance of the PTCS was experimentally investigated with synthetic oil as the circulate heat transfer fluid (HTF). The solar collector’s efficiency with the variation of the solar flux and the flow rate of the HTF was identified. The collector efficiency of the PTCS can be in the range of 40%–60%. It was also found that there existed a specified delay for the temperature of the HTF to response to the solar flux, which played a significant role in designing the PTCS. The heat loss effect on collector efficiency was also studied, which was about 220 W/m for the receiver with a 180°C temperature difference between the collector temperature and the ambient temperature, amounting to about 10% of the total solar energy incident on the collector. The encouraging results can provide fundamental data for developing the parabolic trough solar thermal power plant in China.

Optimal Design of a Molten Salt Thermal Storage Tank for Parabolic Trough Solar Power Plants

This paper presents an optimal design procedure for internally insulated, carbon steel, molten salt thermal storage tanks for parabolic trough solar power plants. The exact size of the vessel and insulation layers and the shape of the roof are optimized by minimizing the total investment cost of the storage system under three technical constraints: remaining within the maximum allowable values of both temperature and stress in the steel structure, and avoiding excessive cooling and consequent solidification of the molten salt during long periods of no solar input. The thermal, mechanical and economic aspects have been integrated into an iterative step-by-step optimization procedure, which is shown to be effective through application to the case study of a 600MWh thermal storage system. The optimal design turns out to be an internally insulated, carbon steel storage tank characterized by a maximum allowable height of 11m and a diameter of 22.4m. The total investment cost is about 20% lower than that of a corresponding AISI 321H stainless steel storage tank without internal protection or insulation.

The calculation and analysis of glass-to-metal sealing stress in solar absorber tube

The failure or degradation of solar absorber tubes is the single largest cost factor for current parabolic trough solar power plant. The main failure reason is that there are residual stresses in the glass-to-metal joint which are generated during the cooling process of sealing. According to the thin shell theory and thermal stress theory, this paper presents the analytic solution for the glass-to-metal sealing residual stress. It also analyses how the thickness of glass tube, thickness of metal ring, and thermal expansion coefficient affect the residual stress distribution. In order to verify the calculation results, the photoelastic technique is used to measure the residual stress and the tensile test is used to obtain the point of the most dangerous stress and the tensile strength for the sealed specimens. It can be concluded that the maximum tensile stress happens at some distance near the sealing interface on the outer surface of glass tube. The seal strength increases when the thickness of the glass tube is increased. The analytic solution is proved feasible to analyze the residual stress of glass-to-metal seals in solar absorber tubes.

Performance of a direct steam generation solar thermal power plant for electricity production as a function of the solar multiple

This paper describes the influence of the solar multiple on the annual performance of parabolic trough solar thermal power plants with direct steam generation (DSG). The reference system selected is a 50 MW e DSG power plant, with thermal storage and auxiliary natural gas-fired boiler. It is considered that both systems are necessary for an optimum coupling to the electricity grid. Although thermal storage is an opening issue for DSG technology, it gives an additional degree of freedom for plant performance optimization. Fossil hybridization is also a key element if a reliable electricity production must be guaranteed for a defined time span. Once the yearly parameters of the solar power plant are calculated, the economic analysis is performed, assessing the effect of the solar multiple in the levelized cost of electricity, as well as in the annual natural gas consumption.

Assessment of SEGS-Like Power Plants for the Brazilian Northeast Region

The potential for parabolic trough solar power plant implementation in the semiarid area located at the Brazilian northeast region, throughout the São Francisco river basin, has been estimated as being 94,190MWe, based on the simulation results of a typical 30MWe solar energy generating systems (SEGS)-like power plant modeled using experimental solar irradiation measured at an eligible site. The use of electricity generated with SEGS-like power plants will help to save water that otherwise will be necessary to run in hydroelectric turbines and will contribute to diversify the Brazilian electrical energy matrix, which is predominantly hydroelectrical. The equivalent volume flow rate that can be saved with the implementation of solar power potential was estimated as 5125m3∕s, which is 1.8 times the mean flow rate of the São Francisco river.

Cascaded latent heat storage for parabolic trough solar power plants

The current revival of solar thermal electricity generating systems (SEGS) unveils the still existing need of economic thermal energy storages (TES) for the temperature range from 250 °C to 500 °C. The TES-benchmark for parabolic trough power plants is the direct two tank storage, as it was used at the SEGS I plant near Barstow (USA). With the introduction of expensive synthetic heat transfer oil, capable to increase the operating temperature from former 300 °C up to 400 °C, the direct storage technology became uneconomical. Cascaded latent heat storages (CLHS) are one possible TES alternative, which are marked by a minimum of necessary storage material. The use of a cascade of multiple phase change materials (PCM) shall ensure the optimal utilization of the storage material. This paper reports experimental and numerical results from the investigation of cascaded latent heat storages with alkali nitrate salts like NaNO 3, KNO 3 and others more. The experiments were conducted with vertical shell and tube type heat exchanger devices under realistic operation parameters. The experimental results were used for a numerical model to simulate different CLHS configurations. Dymola/Modelica was used to conduct the simulation. The outcome of this work shows on the one hand, that the design of CLHS for this temperature range is more complex than for the temperature range up to 100 °C. And on the other hand, the low heat conductivity of available PCM is an obstacle which must be overcome to make full use of this promising storage technology.

The application of parabolic trough technology under Jordanian climate

Parabolic trough solar thermal power plants are a proven technology in the utility scale since mid of the eighties. Between 1984 and 1991 nine power plants with an overall capacity of 354 MW have been installed in the Mojave Desert in California. Since, these power plants can be equipped with a thermal storage or a fossil back-up they offer a fully dispatchable electricity generation capacity. This technology will be a very interesting near term option for countries with high solar irradiation levels and small resources of fossil fuels like Jordan. This paper, discusses the use of parabolic trough solar thermal power plants for electricity production under Jordanian climate for two different sites (Amman, and Ma'an). An analysis of the daily power output, direct normal irradiation and the efficiency for the two sites has been carried out. The results showed that Ma'an site would be preferred than Amman site, so that it is recommended to erect the Parabolic Trough Concentrator (PTC) plant in the southern region of Jordan. Also this study aims to encourage the Jordanian government and the private sector to implement the solar thermal power plants for future expansion of power sector due to the increasing electricity demand and environmental degradation.

Two-tank molten salt storage for parabolic trough solar power plants

The most advanced thermal energy storage for solar thermal power plants is a two-tank storage system where the heat transfer fluid (HTF) also serves as storage medium. This concept was successfully demonstrated in a commercial trough plant (13.8 MW e SEGS I plant; 120 MWh t storage capacity) and a demonstration tower plant (10 MW e Solar Two; 105 MWh t storage capacity). However, the HTF used in state-of-the-art parabolic trough power plants (30–80 MW e) is expensive, dramatically increasing the cost of larger HTF storage systems. An engineering study was carried out to evaluate a concept, where another (less expensive) liquid medium such as molten salt is utilized as storage medium rather than the HTF itself. Detailed performance and cost analyses were conducted to evaluate the economic value of this concept. The analyses are mainly based on the operation experience from the SEGS plants and the Solar Two project. The study concluded that the specific cost for a two-tank molten salt storage is in the range of US$ 30–40/kWh th depending on storage size. Since the salt storage was operated successfully in the Solar Two project, no major barriers were identified to realize this concept in the first commercial parabolic trough power plant.

Advances in Parabolic Trough Solar Power Technology

Parabolic trough solar technology is the most proven and lowest cost large-scale solar power technology available today, primarily because of the nine large commercial-scale solar power plants that are operating in the California Mojave Desert. These plants, developed by Luz International Limited and referred to as Solar Electric Generating Systems (SEGS), range in size from 14–80 MW and represent 354 MW of installed electric generating capacity. More than 2,000,000m2 of parabolic trough collector technology has been operating daily for up to 18 years, and as the year 2001 ended, these plants had accumulated 127 years of operational experience. The Luz collector technology has demonstrated its ability to operate in a commercial power plant environment like no other solar technology in the world. Although no new plants have been built since 1990, significant advancements in collector and plant design have been made possible by the efforts of the SEGS plants operators, the parabolic trough industry, and solar research laboratories around the world. This paper reviews the current state of the art of parabolic trough solar power technology and describes the R&D efforts that are in progress to enhance this technology. The paper also shows how the economics of future parabolic trough solar power plants are expected to improve.

Direct Steam Generation in Parabolic Trough Solar Power Plants: Numerical Investigation of the Transients and the Control of a Once-Through System

Direct steam generation (DSG) in parabolic troughs was first studied in the early 1980s by Murphy (1982) and Pederson (1982). Intensive research on DSG then started in 1988, when Luz identified this technology as the desired system for a future generation of its power plants. These R&D activities were not terminated on Luz’s demise in 1991, but have been continued by several institutes and companies in Europe as well as in Israel (Dagan et al., 1991, Mu¨ller et al., 1992a, b, 1993, 1994). This paper concerns the dynamic reaction of the water-steam flow. In order to investigate this, a numerical simulation program was developed at the ZSW. The numerical approach, its verification, and results of an extended study concerning the reaction and the control (ability) of a once-through DSG system at different weather conditions are presented.