Solar Thermal Central Receiver Research Articles

Performance model of an additively manufactured micro-pin array solar thermal central receiver

Concentrated solar power (CSP) with thermal storage is a renewable approach for meeting baseload and peak load electric power. An additivelymanufactured (AM) supercritical carbon di-oxide microscale pin array receiver, MPAR, is introduced as an option for a gaseous receiver for CSP. A numerical model is developed to compare the performance of the additively manufactured pin array receiver (AM2PAR) and a microlaminated pin array receiver (µLPAR). Thermofluidic experimental data from an AM heat sink are used to validate correlations used in the model. When compared to traditional microlamination approach, which consists of etching and bonding, AM enables longer pin array lengths, thus reducing the complexity and mass of the header network, without compromising the thermal efficiency or peak surface temperature. Furthermore, the impact of non-uniform heat flux on an AM2PAR central receiver is characterized. To improve the creep life of the AM2PAR, a design with tunable pin array height in accordance to the flux on the module is introduced. Operational adjustments required to ensure the creep life of the receiver meets a 30-year lifetime for CSP are discussed.

Active Power Management of Virtual Power Plant under Penetration of Central Receiver Solar Thermal-Wind Using Butterfly Optimization Technique

Striving for the suppression of greenhouse emissions, the modern power network is facing fundamental changes with the utilization of renewable energies (REs) for the future carbon-free society. The utilization of intermittent renewable-green power needs a better power management system and virtual power plant (VPP) can be a vital candidate that meets this demand. This study investigates a coordinated control grid integrated virtual power plant (VPP) in the presence of Central Receiver Solar Thermal System (CRSTS), Wind Turbine Generator (WTG), and Electric Vehicle (EV). To this end, CRSTS employed with thermal storage acts as a dispatchable renewable generating unit and coordinated control of the system units are achieved using the available control strategy on interconnected microgrids in the modified form, employing communication time delay. The proposed control strategy employs the proportional-integral (PI) and PI-derivative (PID) controller. Coordinated power control with real-time communication delay in grid integrated VPP in presence of CRSTS, WTG, and EV is a novel approach. Genetic algorithm (GA), Particle Swarm Optimization (PSO), Slap Swarm Algorithm (SSA), and recent Butterfly Optimization Algorithm (BOA) are used for tuning the necessary control parameters. The results establish the superiority of the BOA over SSA and PSO in suppressing system frequency deviations and tie line power deviation. The analysis of the dynamic response reveals that the consideration of the communication delay in the system expressively impedes the stable operation of the power system.

Optimal Design and Sizing of Solar-assisted CHP System Based on Thermodynamic and Economic Analysis

This work develops a method for the optimal design of a solar-assisted combined heat and power (CHP) system, in which the solar thermal central receiver subsystem and the steam power cycle subsystem are integrated to meet the real-time requirements of steam and power from production process. A mathematical model with the objectives of minimum total annual cost (TAC) and environmental impact (EI) is formulated to optimize the configuration and the size of the major equipment units, and schedule the dynamic operation of entire system. This model accounts for the hourly variability of Direct Normal Irradiance (DNI) and the electricity load in a typical day, as well as the power losses caused by the partial load operation of steam turbines. Based on the presented model, the optimum level of solar capacity is determined through a comprehensive analysis considering the trade-off between TAC and EI of the system. At last, a case study is illustrated and the results are elaborated to demonstrate that the desired system configuration can be obtained by application of the proposed model.

Performance Analysis and Optimization of Central Receiver Solar Thermal Power Plants for Utility Scale Power Generation

The paper puts forth the design, performance analysis, and optimization of a 100 MWe central receiver solar thermal power plant with thermal energy storage capability, which can be utilized effectively to meet the renewable energy targets of the Kingdom of Saudi Arabia (KSA). In this paper, three representative sites in KSA are selected for analysis as these sites experience an annual average direct normal irradiance (DNI) of more than 5.5 kWh/m2/day. The optimization approach presented in this work aims to arrive at the best possible design parameters that suit a particular location in accordance with its DNI profile. From the analysis, an annual energy of 559.61 GWh can be generated in Yanbu with eight hours of thermal energy storage, 18.19% plant efficiency, and a capacity factor of 61.1%. The central receiver plant in Abha would be able to offer an annual energy of 536.31 GWh with the highest plant efficiency of 18.97% and a capacity factor of 60.7%. The performance of the proposed design in the two locations of Yanbu and Abha fares better when compared to the operational plant data of central receiver plant in Crescent Dunes. Based on the findings, the proposed 100 MWe central receiver Solar thermal power plants can be effectively implemented in KSA to meet the energy demands of the region.

Comparative System Performance Analysis of Direct Steam Generation Central Receiver Solar Thermal Power Plants in Megawatt Range

This work proposes and analyses several integration schemes specially conceived for direct steam generation (DSG) in megawatt (MW) range central receiver solar thermal power plants. It is focused on the optical performance related to the heliostat field and the arrangement of receiver absorbers, and the management of steam within a Rankine cycle in the range between 40–160 bar and 400–550 °C at design point. The solar receiver is composed of one single element for saturated steam systems or two vertically aligned separated units, which correspond to the boiler and the superheater (dual-receiver concept), for superheated steam solar thermal power plants. From a fixed heliostat field obtained after layout optimization for the saturated steam solar plant the heliostat field is divided in two concentric circular trapezoids where each of them independently supplies the solar energy required by the boiler and the superheater for the different steam conditions. It has been observed that the arrangement locating the boiler above the superheater provides a slightly higher optical efficiency of the collector system, formed by the solar field and the receiver, compared with the reverse option with superheater above boiler. Besides, two-zone solar fields provide lower performances than the entire heliostat layout aiming at one absorber (saturation systems). Optical efficiency of two-zone solar fields decreases almost linearly with the increment of superheater heat demand. Concerning the whole solar collector, heliostat field plus receiver, the performance decreases with temperature and almost linearly with the steam pressure. For the intervals of steam pressure and temperature under analysis, solar collector of saturated steam plant achieves an optical efficiency 3.2% points higher than the superheated steam system at 40 bar and 400 °C, and the difference increases up to 9.3% points when compared with superheated system at 160 bar and 550 °C. On the other hand, superheated steam systems at 550 °C and pressure between 60 and 80 bar provide the highest overall efficiency, and it is 2.3% points higher than performance of a saturated steam solar plant at 69 bar. However, if saturated steam cycle integrates an intermediate reheat process, both would provide similar performances. Finally, it has been observed that central receiver systems (CRS) producing saturated steam and superheated steam at 500 °C operating at 40 bar provide similar performances.

Liquid sodium versus Hitec as a heat transfer fluid in solar thermal central receiver systems

Selection of an appropriate HTF is important for minimising the cost of the solar receiver, thermal storage and heat exchangers, and for achieving high receiver and cycle efficiencies. Current molten salt HTFs have high melting points (142–240°C) and degrade above 600°C. Sodium’s low melting point (97.7°C) and high boiling point (873°C) allow for a much larger range of operational temperatures. Most importantly, the high temperatures of sodium allow the use of advanced cycles (e.g. combined Brayton/Rankine cycles). In this study, a comparison between the thermophysical properties of two heat transfer fluids (HTFs), Hitec (a ternary molten salt 53% KNO3+40% NaNO2+7% NaNO3) and liquid sodium (Na), has been carried out to determine their suitability for use in high-temperature concentrated solar thermal central-receiver systems for power generation. To do this, a simple receiver model was developed to determine the influences of the fluids’ characteristics on receiver design and efficiency. While liquid sodium shows potential for solar thermal power systems due to its wide range of operation temperatures, it also has two other important differences – a high heat transfer coefficient (∼an order of magnitude greater than Hitec) and a low heat capacity (30–50% lower than Hitec salt). These issues are studied in depth in this model. Overall, we found that liquid sodium is potentially a very attractive alternative to molten salts in next generation solar thermal power generation if its limitations can be overcome.

Modeling and simulation of the pioneer 1 MW solar thermal central receiver system in China

DAHAN, the pioneer 1 MWe CRS (central receiver system) funded by Ministry of Sciences and Technology (MOST), which can be regarded as the milestone in solar thermal power development in China, is now under construction at the foot of The Great Wall nearby Beijing. The major objective of the design and construction of DAHAN is to demonstrate the operation of CRS in China. A software tool HFLD is developed for heliostat field layout design and performance calculation. The simulation results from HFLD approximately agree very well with the published heliostat field efficiency data from Spain PS10. Based on that, the heliostat field layout of DAHAN is designed using HFLD and the whole CRS performance is simulated in the TRNSYS plant model. The modeling and simulation of this plant is presented in this paper.

Reflectance measurement in solar tower heliostats fields

Knowledge of the mean reflectance of solar thermal central receiver system heliostat fields is highly relevant for both operation and component evaluation. Calculation of the mean reflectance becomes essential to establishing a procedure by which its value can be found without measuring each and every one of the facets that make up the field, since this is a long, time-consuming and not very productive task. This article reports on the results of a statistical reflectance study of the Plataforma Solar de Almería Central Receiver Systems (CRS) heliostats field.

Assessment of the potential improvement due to multiple apertures in central receiver systems with secondary concentrators

When striving for maximum efficiencies in solar thermal central receiver systems (CRS) the use of gas turbines with bottoming cycles is inevitable. Pressurized volumetric receivers have proven their feasibility and good performance, and their integration into gas turbine cycles has been demonstrated. One disadvantage of this system is the necessity to use secondary concentrators. The sunlight has to be concentrated into the relatively small glass windows of the receiver, which leads to a limited view cone. This means that of all the possible heliostat positions around the tower, only those within the ellipse, resulting from the section boundary of the view cone with the ground plane, are usable. For small systems, for which tower costs are small, the resulting heliostat field layout is similar, with or without secondary concentrator. For large systems, which are more cost-effective, tower costs become significant, and the losses due to atmospheric attenuation and spillage dominate over the cosine losses. Thus, the purely North-oriented fields become increasingly sub-optimal. This article shall demonstrate at what power levels this problem can be alleviated by not using a single, North-oriented aperture, but up to six apertures—each of them associated with a separate heliostat field.

A promising large area VHE gamma ray detector with excellent hadron rejection capability

A new large area VHE gamma ray detector for detecting atmospheric Cerenkov light from very high energy celestial gamma rays is proposed. It will be constructed by converting Solar One, a 10 MW Solar Thermal Central Receiver Pilot Plant at Barstow, California, which uses the solar tower technology with heliostats as light collectors. Solar energy research at this facility has recently been terminated. The detector will cover an area of at least 200 m diameter, which is only about 5% of the total area available at Solar One, so that a significant fraction of the Cerenkov light pool is detected. Each heliostat will focus the Cerenkov light onto a photomultiplier tube (PMT) selected to match the optical quality of the heliostat. Its active reflecting surface is 71,000 m 2, which is about 375 times larger than the largest VHE gamma ray atmospheric Cerenkov detector, the twin 11 m dia. collectors at Sandia Labs, Albuquerque 1. It is expected to have the lowest energy threshold (≥10 GeV) for atmospheric Cerenkov observations. This will enhance counting rates significantly and bridge the gap between HE and VHE gamma ray astronomy with some overlapping. It will also have excellent inherent hadron rejection. One hundred million dollars worth of installation is already constructed and ready to use. The rest of the detector can be built for a small fraction, <1%.

The Power Production Operation of Solar One, the 10 MWe Solar Thermal Central Receiver Pilot Plant

Solar One, the 10 MWe Solar Thermal Central Receiver Pilot Plant near Barstow, Calif., completed a three-year period of power production testing in July 1987. During this period the plant’s capacity factor, system efficiency, and availability were studied to assess the operational capability of Solar One to reliably supply electrical power. The long-term performance of key plant components, such as the heliostats and the receiver, was also studied. During the three years of power production operation, Solar One achieved increases in capacity factor, system efficiency, and availability. Heliostat operation was reliable, and only small amounts of mirror corrosion were observed. Receiver tube leaks did occur, however, and were the main cause of the plant’s unscheduled outages. Solar One provided valuable lessons which will aid in the design of future solar central receiver plants.

Measurement and Analysis of Heliostat Images

A method is proposed allowing the physical interpretation of the sun image generated by reflecting systems, e.g., heliostats, on a target plane. The instantaneous flux distributions reflected from the target are measured by a distant video-type camera system in the visible spectrum and analyzed in terms of their constituents (sunshape, astigmatic aberration, mirror glass waviness, canting, and curvature errors). The single contributions to the total image are parmetrized by appropriate physically-based model functions and composed to a theoretical image to be compared with the measured image. Within a fit procedure, the parameter set is determined for every experiment allowing to check the consistency and uniqueness of the approach. A series of measurements on GAST heliostats performed between 1984 and 1987 was analyzed. They demonstrate the good optical performance of these systems, thus justifying their use in large solar thermal central receiver tower plants.

Cost Drivers for Solar Thermal Central Receiver Power Plants

Studies completed at the Pacific Northwest Laboratory have allowed an in-depth examination of costs for solar thermal central receiver power plants. Central receiver concepts were evaluated for plant power ratings ranging from 0.5 to 100 MWe, and plant capacity factors ranging from 0.25 to 0.60. The large number of plant configurations considered necessitated the development of cost estimating models. Cost models were developed for concentrator, receiver, transport, storage, energy conversion, balance of plant, and O&amp;M components. This paper presents a detailed discussion of costs for solar thermal central receiver power plants. Principal subcomponents and cost drivers are identified for each component. The impact of alternative design choices on cost and the tradeoffs involved between different working fluids are addressed. Cost uncertainties are examined qualitatively for each component. Finally, equations are presented for making preliminary estimates of direct capital and annual O&amp;M costs for solar thermal central receiver systems.

10-MWe Solar Thermal Central Receiver Pilot Plant

The Solar One Project is the world's largest solar electric generating station. This pilot-scale research and development experiment is a cooperative effort of government and private industry to demonstrate technical feasibility, economic potential, and environmental acceptability of the solar thermal central receiver concept. The project, which is formally known as the 10-MW Solar Thermal Central Receiver Pilot Plant, has been constructed in the Mojave Desert on 130 acres of Southern California Edison Company's Cool Water Generating Station near Barstow, California, and will supply 10 MW of electrical power to the Edison grid. Solar One is a joint project of the Department of Energy (DOE), Southern California Edison (SCE), the Los Angeles Department of Water and Power (LADWP), and the California Energy Commission. The solar portion of the facility was designed and constructed under the direction of the DOE, and the turbine-generator facilities, including the control building, were designed and constructed by SCE. This paper presents an overview of the project, discusses the costs and schedule, highlights the planned test program including operation and maintenance, and briefly discusses the experiences through October 1982.

A 1-MWe Central Receiver Type Solar Thermal Electric Power Pilot Plant

The design features, performance capabilities and operational experience to date of the solar thermal central receiver pilot plant at Nio-Cho, Japan, are discussed. Attention is given to the heliostat mirror structures and their alignment with respect to the receiver, the data acquisition system employed in performance tests, and the receiver efficiencies recorded at various times during daily operation. Also noted are heliostat tracking errors, and convective heat losses at the central receiver surface for a given air temperature and wind velocity.

Solar Thermal Power Towers

The solar thermal central receiver technology, known as solar power towers, is rapidly evolving to a state of near-term energy availability for electrical power generation and industrial process heat applications. The systems consist of field arrays of heliostat reflectors, a central receiver boiler, short term thermal storage devices, and either turbine-generators or heat exchangers. Fluid temperatures up to 550°C are currently achievable, and technology developments are underway to reach 1100°C. Six solar power towers are now under construction or in test operation in five countries around the world.

An LQ-solution to a control problem associated with a solar thermal central receiver

The linearized process dynamics of the steam boiler in a solar-powered central receiver change abruptly when clouds interfere with the sun's rays. The steam temperature regulator used to maintain proper exit steam conditions must control a system with variable structure and discontinuous state trajectories. This paper investigates the quadratic-optimal control of such a system, and gives the design equations for the optimal regulator.

A Method of Evaluating and Sizing Solar Cogeneration Systems

An analytical method for rapid evaluation and sizing of solar cogeneration systems is presented. The method, which utilizes a simplified system model and site-specific data on insolation and energy loads, is described herein and an illustrative application is discussed. The application considered is the use of a solar thermal central receiver cogeneration plant to supply the electrical and thermal energy needs of a hypothetical military base at Caliente, Nevada. The method has applicability to plants using other types of collectors.

Numerical Study of Local/Regional Atmospheric Changes Caused by a Large Solar Central Receiver Power Plant

A two-dimensional, vertical cross section, numerical atmospheric mesoscale model has been applied to study the potential local/regional atmospheric effects of the installation of a 100 MWe solar thermal central receiver power plant at Barstow, California. Such a plant consists of heliostats (mirrors) which cover a portion of ground surface and reflect sunlight onto a central receiving tower. The model can simulate the changes in surface characteristics associated with the installation of heliostats and other power plant ancillaries, and can simulate the effects of waste heat from cooling towers. The model equations have been integrated to simulate typical summer, and atypical summer. The results for typical summer conditions at Barstow and the surrounding region show that the power plant has the potential to increase local humidity and wind circulation but cannot induce the formation of clouds or rain. The results for atypical summer conditions show that the solar power plant has the potential to increase the wind circulation and to form clouds and rain. However, the life cycle of such formations is only 2–3 h. Sensitivity to the type and location of cooling tower has been tested and described. The atmospheric effects of a dry cooling tower located upwind are not as significant and intense as those produced using a wet cooling tower. However, this result is not conclusive and should be researched further. The effect of a wet cooling tower located at the downwind edge of the power plant is not as intense as is the case when the tower is located at the upwind edge of the power plant.

Materials-related design issues in the Solar Central Receiver pilot plant

The Solar Thermal Central Receiver program of the Department of Energy has for its objectives the harnessing of solar thermal energy for generation of electricity, (either monolithic or in combination with fossil power)and also the development of solar process heat for various applications. The aim is to develop solar thermal systems to the status of alternative energy sources for utilities by the mid 1980s, and to achieve economic competetiveness with fossil and nuclear plants by the 1990s1. The first electricity to be generated in the program will come from the ten MW pilot plant which is nearing the start of construction in Barstow, California. Funding for the project is being provided by the Department of Energy, Southern California Edison Company, Los Angeles Department of Water and Power, and the California Energy Commission. The Barstow pilot plant represents the first full scale U.S. application of solar central receiver technology and as such is a critical gate in the development program. The design is being developed by an industrial team lead by McDonnell Douglas Astronautics Company. Sandia Laboratories provides technical program management and supporting research and development for the Department of Energy in central receiver technology. The final design for Barstow will be based upon tradeoff studies and experiments conducted in support of the program. This paper summarizes these studies in the area of materials-related issues and describes the emerging technology.