The potential of concentrating solar power in South Africa

In this paper all provinces of South Africa with a good potential for the implementation of large-scale concentrating solar power plants are identified using geographic information systems. The areas are assumed suitable if they get sufficient sunshine, are close enough to transmission lines, are flat enough, their respective vegetation is not under threat and they have a suitable land use profile. Various maps are created showing the solar resource, the slope, areas with “least threatened” vegetation, proximity to transmission lines and areas suitable for the installation of large concentrating solar power plants. Assuming the installation of parabolic trough plants, it is found that the identified suitable areas could accommodate plants with a nominal capacity of 510.3 GW in the Northern Cape, 25.3 GW in the Free State, 10.5 GW in the Western Cape and 1.6 GW in the Eastern Cape, which gives a total potential nominal capacity of 547.6 GW for the whole country.     

Techno-economic evaluation of concentrating solar power generation in India

The Jawaharlal Nehru National Solar Mission (JNNSM) of the recently announced National Action Plan on Climate Change (NAPCC) by the Government of India aims to promote the development and use of solar energy for power generation and other uses with the ultimate objective of making solar competitive with fossil-based energy options. The plan includes specific goals to (a) create an enabling policy framework for the deployment of 20,000 MW of solar power by 2022; (b) create favourable conditions for solar manufacturing capability, particularly solar thermal for indigenous production and market leadership; (c) promote programmes for off grid applications, reaching 1000 MW by 2017 and 2000 MW by 2022, (d) achieve 15 million m² solar thermal collector area by 2017 and 20 million by 2022, and (e) deploy 20 million solar lighting systems for rural areas by 2022. The installed capacity of grid interactive solar power projects were 6 MW until October 2009 that is far below from their respective potential.     

Potential application of concentrating solar power systems for the generation of electricity in Thailand

This study aims to investigate a potential application of concentrating solar power (CSP) systems for producing electricity in the tropical environment of Thailand. An 8-year period (1995–2002) of satellite data was used to generate the direct normal irradiation map of the country. The map reveals that the areas which receive the highest irradiation are mainly in the Northeast and the Central regions of the country, with the yearly sum of direct normal irradiation in the range of 1350–1400 kW h/m² year. The location of Ubon Ratchathani (15.25 °N, 104.87 °E) situated in the Northeast was selected as a target area for investigating the potential application of CSP systems. The performance of three 10 MW CSP systems, namely the parabolic trough, the tower and the dish/Stirling engine systems was investigated. A software named TRNSYS together with the solar thermal electric components (STEC) subroutines were used to simulate the systems. The yearly production of electricity from these systems was estimated and used for the economic evaluation of the systems. It was found that the parabolic trough system afforded the lowest levelized electricity cost of 0.30 USD/kW h. Based on the technical and economic considerations, this system has a sufficient potential for producing electricity in this region.     

Siting guidelines for concentrating solar power plants in the Sahel: Case study of Burkina Faso

Selecting a site that meets the technical requirements for a concentrating solar power plant (CSP) is a very critical exercise. This paper points out crucial factors and provides guidelines regarding the selection of suitable sites. It especially focuses on Sahelian countries which have their own climatic peculiarities. These countries, characterized by low access to electricity, are well endowed in solar resources. They are potentially good locations for concentrating solar power plants since their mean daily solar radiation exceeds 5.5 kWh/m². CSP presents therefore, a good opportunity for them to increase in a sustainable manner, their energy supply. The guidelines developed in this paper are applied to Burkina Faso as a case study.     

Combining wind farms with concentrating solar plants to provide stable renewable power

We evaluate the extent to which a combination of wind power and concentrating solar power (CSP) may lead to stable and even baseload power by taking advantage of: 1) spatiotemporal balancing of solar and wind energy resources and 2) storage capabilities of CSP plants. A case study is conducted for the region of Andalusia in Spain. To this end, spatiotemporal variability of modeled CSP and wind capacity factors in a 3-km spatial resolution grid were analyzed based on principal component analysis (PCA) and canonical correlation analysis (CCA). Results reveal that renewable baseload power can be obtained in the study region by locating wind farms and CSP plants using balancing patterns derived from CCA and PCA. In addition, the power fluctuation reduction attained from these patterns was substantially higher than those obtained by interconnecting randomly-located wind farms and CSP plants across the study region. Results were particularly meaningful for the winter season. Upon considering storage capability of the CSP plants, results proved better. The main difference was a higher firm capacity value associated with spring and summer seasons. For the other seasons, the contribution of thermal storage capabilities of the CSP plants to stable power proved less relevant.     

Methods for probabilistic modeling of concentrating solar power plants

Probabilistic modeling of concentrating solar power technologies provides important information regarding uncertainties and sensitivities not available from deterministic models. Benefits of using probabilistic models include quantification of uncertainties inherent in the system and characterization of their impact on system performance and economics. This paper presents the tools necessary to conduct probabilistic modeling of concentrating solar technologies. The probabilistic method begins with the identification of uncertain variables and the assignment of appropriate distributions for those variables. Those parameters are then sampled using a stratified method (Latin Hypercube Sampling) to ensure complete and representative sampling from each distribution. Models of performance, reliability, and/or cost are then simulated multiple times using the sampled set of parameters. The results yield a cumulative distribution function that can be analyzed to quantify the probability of achieving a particular metric (e.g., net energy output or levelized energy cost) and to rank the importance of the uncertain input parameters.     

Life Cycle Assessment of a high temperature molten salt concentrated solar power plant

Realizing and installing renewable energy plants have an environmental “footprint” that has to be evaluated to quantify the real impact of renewable technologies on the environment. Nowadays, the most important tool to evaluate this impact of a product is the Life Cycle Assessment (LCA).The aim of this work is to present a Life Cycle Assessment of an innovative solar technology, the molten salt concentrating solar power (CSP) plant combined with a biomass Back-Up Burner, developed by Italian Research Centre ENEA and able to produce clean electricity by using solar energy. The Life Cycle Assessment was carried out by means of the SimaPro7 software, one of the most used LCA software in the world.In the second part of the study the environmental performance of the CSP plant was compared with these of conventional oil and gas power plants.     

Selection of metal hydrides for a thermal energy storage device to support low-temperature concentrating solar power plants

Metal hydrides have become more and more significant both as hydrogen storage devices and as basic elements in energy conversion systems. Besides the well-known rare earth hydrides, magnesium alloys are very promising in the field of thermal energy storage for concentrating solar power plants. There is interest in analysing the performances of such materials in this context; for this purpose, a numerical model to describe hydrogen absorption and desorption processes of a metal hydride has been connected to a model elaborated with the help of Cycle-Tempo software to simulate a CSP plant operation. The integration of this plant with four metal hydride systems, based on the combination of two low-temperature hydrides (LaNi₅, LaNi_4.8Al_0.2) and two high-temperature hydrides (Mg, Mg₂Ni) has been studied. The investigation has taken into account CSP overall performances, transfer surfaces and storage efficiencies, to determine the feasibility of designed plants. Results show that the selection of the optimal hydrides must take into account hydride operation temperatures, reaction enthalpies, storage capacities and kinetic compatibility. In the light of the calculated parameters, a solar ORC plant using R134a as the working fluid is a valuable choice if matched to a storage system composed of LaNi₅ and Mg₂Ni hydrides.     

Simulation of a solar concentrating dish for steam generation

This research work aims to design theoretically through computer programming a solar concentrating dish using flat mirrors as reflectors to be fixed in pieces on a steel framed dish. The simulation program determines design dimensions, economical factors and thermal performance, relating them to each other and to be controlled through specific preliminary inputs. A model of concentrating dish having 1?m diameter was constructed and tested to achieve design optimisation of such types of systems. A prototype of 8?m diameter was also constructed and tested to verify the reliability of the program and workability of the system to be used for steam generation.     

Thermal energy storage technologies and systems for concentrating solar power plants

This paper presents a review of thermal energy storage system design methodologies and the factors to be considered at different hierarchical levels for concentrating solar power (CSP) plants. Thermal energy storage forms a key component of a power plant for improvement of its dispatchability. Though there have been many reviews of storage media, there are not many that focus on storage system design along with its integration into the power plant. This paper discusses the thermal energy storage system designs presented in the literature along with thermal and exergy efficiency analyses of various thermal energy storage systems integrated into the power plant. Economic aspects of these systems and the relevant publications in literature are also summarized in this effort.     

The potential of metal hydrides paired with compressed hydrogen as thermal energy storage for concentrating solar power plants

Concentrating solar power (CSP) plants require thermal energy storage (TES) systems to produce electricity during the night and periods of cloud cover. The high energy density of high-temperature metal hydrides (HTMHs) compared to state-of-the-art two-tank molten salt systems has recently promoted their investigation as TES systems. A common challenge associated with high-temperature metal hydride thermal energy storage systems (HTMH TES systems) is storing the hydrogen gas until it is required by the HTMH to generate heat. Low-temperature metal hydrides can be used to store the hydrogen but can comprise a significant proportion of the overall system cost and they also require thermal management, which increases the engineering complexity. In this work, the potential of using a hydrogen compressor and large-scale underground hydrogen gas storage using either salt caverns or lined rock caverns has been assessed for a number of magnesium- and sodium-based hydrides: MgH₂, Mg₂FeH₆, NaMgH₃, NaMgH₂F and NaH. Previous work has assumed that the sensible heat of the hydrogen released from the HTMH would be stored in a small, inexpensive regenerative material system. However, we show that storing the sensible heat of the hydrogen released would add between US$3.6 and US$7.5/kWh_th to the total system cost for HTMHs operating at 565 °C. If the sensible heat of released hydrogen is instead exploited to perform work then there is a flow-on cost reduction for each component of the system. The HTMHs combined with underground hydrogen storage all have specific installed costs that range between US$13.7 and US$26.7/kWh_th which is less than that for current state-of-the-art molten salt heat storage. Systems based on the HTMHs Mg₂FeH₆ or NaH have the most near term and long term potential to meet SunShot cost targets for CSP thermal energy storage. Increasing the operating temperature and hydrogen equilibrium pressure of the HTMH is the most effective means to reduce costs further.     

Thermodynamic investigation of a concentrating solar collector based combined plant for poly-generation

The detailed thermodynamic evaluation for combined system assisted on solar energy for poly-generation are studied in this paper. This poly-generation cycle is operated by the concentrating solar radiation by using the parabolic dish solar collector series. The beneficial exits of this integrated plant are the electricity, fresh-water, hot-water, heating-cooling, and hydrogen while there are different heat energy recovery processes within the plant for development performance. A Rankine cycle with three turbines is employed for electricity production. In addition to that, the desalination aim is performed by utilizing the waste heat of electricity production cycle in a membrane distillation unit for fresh-water generation. Also, a PEM electrolyzer sub-component is utilized for hydrogen generation aim in the case of excess power generation. Finally, the hot-water production cycle is performed via the exiting working fluid from the very high-temperature generator of the cooling cycle. Moreover, based on the thermodynamic assessment outputs, the whole energy and exergy efficiencies of 58.43% and 54.18% are computed for the investigated solar plant, respectively.     

Optimal time-invariant operation of a power and water cogeneration solar-thermal plant

Conceptual design, system-level models, and optimization of operation are presented for a cogeneration solar-thermal plant. The solar-thermal energy collected and concentrated in a salt pond is used in a regenerative Rankine steam cycle with an extraction turbine to produce electricity and process steam. The desalination system is based on reverse osmosis (RO) and multi-effect distillation (MED). An equation-oriented modeling environment is used for the development of time-dependent system-level models required for optimization of the plant. A meteorological radiation model is used to estimate the hourly distribution of beam radiation as a function of time (day and hour), location, and local weather (mainly visibility and humidity). A recently developed model is used to estimate the field efficiency, including projection losses and shading/blocking for a given heliostat layout. Time-invariant optimal operating conditions are presented for a summer day, considering Cyprus as a case study. Seawater desalination processes, RO and MED, are modeled by adapting and extending models from the literature. A control-volume model is developed for the steam cycle based on the first and second law, with given isentropic efficiencies, turbine leaks, and a detailed model for thermodynamic properties of steam/water. This model is validated and allows for optimization over a wide range of operating conditions, e.g., various extraction pressures. The optimization problem is formulated as a nonlinear program (NLP) with dynamics embedded and a heuristic global optimization approach is used. The sequential method of optimization is used, decoupling the simulation from the optimization. The results show that for the plant size considered (4 MW_e equivalent nominal capacity) and the MED design chosen based on the literature and industry practice, RO is preferred over MED from an energy point of view. In addition, under the current feed-in tariff (FiT) and water prices in Cyprus, extracting steam for MED is not recommended. In contrast, if current market prices for electricity and water in Cyprus are used, i.e., FiT is neglected, with a typical steam cycle design, extracting steam for MED at low pressures yields maximum income. A new process configuration is presented based on the findings from the case studies, resulting in significantly higher income and exergetic efficiencies.     

Technical and economical system comparison of photovoltaic and concentrating solar thermal power systems depending on annual global irradiation

Concentrating solar thermal power and photovoltaics are two major technologies for converting sunlight to electricity. Variations of the annual solar irradiation depending on the site influence their annual efficiency, specific output and electricity generation cost. Detailed technical and economical analyses performed with computer simulations point out differences of solar thermal parabolic trough power plants, non-tracked and two-axis-tracked PV systems. Therefore, 61 sites in Europe and North Africa covering a global annual irradiation range from 923 to 2438 kW h/m² a have been examined. Simulation results are usable irradiation by the systems, specific annual system output and levelled electricity cost. Cost assumptions are made for today's cost and expected cost in 10 years considering different progress ratios. This will lead to a cost reduction by 50% for PV systems and by 40% for solar thermal power plants. The simulation results show where are optimal regions for installing solar thermal trough and tracked PV systems in comparison to non-tracked PV. For low irradiation values the annual output of solar thermal systems is much lower than of PV systems. On the other hand, for high irradiations solar thermal systems provide the best-cost solution even when considering higher cost reduction factors for PV in the next decade. Electricity generation cost much below 10 Eurocents per kW h for solar thermal systems and about 12 Eurocents/kW h for PV can be expected in 10 years in North Africa.     

考虑光热电站参与的新能源热电联供型微网运行优化

针对传统热电联供型微网运行存在的问题,文章引入光热电站,并结合风力发电、光伏发电、电加热器、储能系统构成热电联供型微网,提出了一种计及微网运行成本的新能源热电联供型微网运行优化策略。该优化策略综合考虑与外部电网交互成本、各设备维护成本、储能老化成本及热电功率平衡约束等因素,建立了热电联供型微网运行优化模型,并采用YALMIP工具箱进行求解。结果表明:该模型运行成本降低了6.2%,电加热器配合光热电站可以提高微网的运行灵活性,实现电-热能量的双向流动,光热电站在一定范围内增大了发电规模,可有效降低微网运行成本。     

Thermodynamic evaluation of solar integration into a natural gas combined cycle power plant

The term integrated solar combined-cycle (ISCC) has been used to define the combination of solar thermal energy into a natural gas combined-cycle (NGCC) power plant. Based on a detailed thermodynamic cycle model for a reference ISCC plant, the impact of solar addition is thoroughly evaluated for a wide range of input parameters such as solar thermal input and ambient temperature. It is shown that solar hybridization into an NGCC plant may give rise to a substantial benefit from a thermodynamic point of view. The work here also indicates that a significant solar contribution may be achieved in an ISCC plant, thus implying substantial fuel savings and environmental benefits.     

Theory and performance analysis of a new heat engine for concentrating solar power

The objectives of this paper are to introduce a new heat engine and evaluate its performance. The new heat engine uses a gas, such as air, nitrogen, or argon, as the working fluid and extracts thermal energy from a heat source as the energy input. The new heat engine may find extensive applications in renewable energy industries, such as concentrating solar power (CSP). Additionally, the heat engine may be employed to recover energy from exhaust streams of internal combustion engines, gas turbine engines, and various industrial processes. It may also work as a thermal‐to‐mechanical conversion system in a nuclear power plant and function as an external combustion engine in which the heat source is the combustion gas from an external combustion chamber. The heat engine is to mimic the performance of an air‐standard Otto cycle. This is achieved by drastically increasing the time duration of heat acquisition from the heat source in conjunction with the timing of the heat acquisition and a large heat transfer surface area. Performance simulations show that the new heat engine can potentially attain a thermal efficiency above 50% and a power output above 100 kW under open‐cycle operation. Additionally, the heat engine could significantly reduce CSP costs and operate in open cycles, effectively removing the difficulties of dry cooling requirement for CSP applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Liquid-based high-temperature receiver technologies for next-generation concentrating solar power: A review of challenges and potential solutions

To reduce the levelized cost of energy for concentrating solar power (CSP), the outlet temperature of the solar receiver needs to be higher than 700 °C in the next-generation CSP. Because of extensive engineering application experience, the liquid-based receiver is an attractive receiver technology for the next-generation CSP. This review is focused on four of the most promising liquid-based receivers, including chloride salts, sodium, lead-bismuth, and tin receivers. The challenges of these receivers and corresponding solutions are comprehensively reviewed and classified. It is concluded that combining salt purification and anti-corrosion receiver materials is promising to tackle the corrosion problems of chloride salts at high temperatures. In addition, reducing energy losses of the receiver from sources and during propagation is the most effective way to improve the receiver efficiency. Moreover, resolving the sodium fire risk and material compatibility issues could promote the potential application of liquid-metal receivers. Furthermore, using multiple heat transfer fluids in one system is also a promising way for the next-generation CSP. For example, the liquid sodium is used as the heat transfer fluid while the molten chloride salt is used as the storage medium. In the end, suggestions for future studies are proposed to bridge the research gaps for > 700 °C liquid-based receivers.     

Evaluation of operational control strategies applicable to solar chimney power plants

Numerical simulations are carried out to study the performance of two schemes of power output control applicable to solar chimney power plants. Either the volume flow or the turbine pressure drop is used as independent control variable. Values found in the literature for the optimum ratio of turbine pressure drop to pressure potential vary between 2/3 and 0.97. It is shown that the optimum ratio is not constant during the whole day and it is dependent of the heat transfer coefficients applied to the collector. This study is a contribution towards understanding solar chimney power plant performance and control and may be useful in the design of solar chimney turbines.     

Economic opportunities resulting from a global deployment of concentrated solar power (CSP) technologies—The example of German technology providers

Several energy scenario studies consider concentrated solar power (CSP) plants as an important technology option to reduce the world’s CO₂ emissions to a level required for not letting the global average temperature exceed a threshold of 2–2.4 °C. A global ramp up of CSP technologies offers great economic opportunities for technology providers as CSP technologies include highly specialised components. This paper analyses possible value creation effects resulting from a global deployment of CSP until 2050 as projected in scenarios of the International Energy Agency (IEA) and Greenpeace International. The analysis focuses on the economic opportunities of German technology providers since companies such as Schott Solar, Flabeg or Solar Millennium are among the leading suppliers of CSP technologies on the global market.