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.     

Analysis of CSP plants for the definition of energy policies: The influence on electricity cost of solar multiples,capacity factors and energy storage

The effect on the cost of electricity from concentrating solar power (CSP) plants of the solar multiple, the capacity factor and the storage capacity is studied. The interplay among these factors can be used to search for a minimal-cost objective that can serve as a technical criterion to guide in the design of economic incentives for CSP plants. The probability-density function of irradiation is used in conjunction with screening models to evaluate the performance characteristics and costs of concentrating solar power plants. Two technologies have been analyzed in this study: parabolic-trough and tower plants. The results provide information to define the optimal operational range as a function of the desired objective. Thus, it is possible to derive a technical criterion for the design of CSP plants which optimizes the solar electricity produced and its generation cost. The methodology is applied to Spain, and the analysis of the results shows that a solar energy production of 37 kWh/m²/year for tower plants and 66 kWh/m²/year for parabolic-trough ones define the approximate optimal working conditions for the mean DNI in Spain.     

CRS4-2: A numerical code for the calculation of the solar power collected in a central receiver system

The analysis of the solar power collected at the receiver in solar tower systems requires the use of efficient and accurate numerical codes. This paper presents a new Fortran computer program, CRS4-2 (an acronym for Crs4 Research Software for Central Receiver Solar System SimulationS), for the simulation of the optical performance of a central receiver solar plant. The implemented mathematical algorithm allows for the calculation of cosine, shading and blocking effects for heliostats arbitrarily arranged in the solar field. Special attention has been given to ensure the maximum flexibility concerning the number, dimension, shape, and position of the heliostats. In the present implementation, the solar field can be composed of both square and circular heliostats possibly mixed together, each one of them characterized by the size and height from the ground. The modular design of CRS4-2 allows the extension to heliostats of arbitrary shape with only minor modifications of the code. Shading and blocking effects are computed by a tessellation of the heliostats: therefore, the numerical accuracy depends only on the refinement of the tessellation. The application to actual systems has shown that the approach is stable and general.     

Assessment of different configurations for combined parabolic-trough (PT) solar power and desalination plants in arid regions

The combination of desalination technology into concentrating solar power (CSP) plants needs to be considered for the planned installation of CSP plants in arid regions. There are interesting synergies between the two technologies, like the possibility of substituting the condenser of the power cycle for a thermal desalination unit. This paper presents a thermodynamic evaluation of different configurations for coupling parabolic-trough (PT) solar power plants and desalination facilities in a dry location representing the Middle East and North Africa (MENA) region. The integration of a low-temperature multi-effect distillation (LT-MED) plant fed by the steam at the outlet of the turbine replacing the condenser of the power cycle has been simulated and compared with the combination of CSP with a reverse osmosis (RO) plant. Furthermore, an additional novel concept of concentrating solar power and desalination (CSP+D) has been evaluated: a LT-MED powered by the steam obtained from a thermal vapour compressor (TVC) using the exhaust steam of the CSP plant as entrained vapour and steam extracted from the turbine as the motive vapour of the ejector. This new concept (LT-MED-TVC) has been analyzed and compared with the others, evaluating its optimization for the integration into a CSP plant by considering different extractions of the turbine.     

Hybridizing concentrated solar power (CSP) with biogas and biomethane as an alternative to natural gas: Analysis of environmental performance using LCA

Concentrating Solar Power (CSP) plants typically incorporate one or various auxiliary boilers operating in parallel to the solar field to facilitate start up operations, provide system stability, avoid freezing of heat transfer fluid (HTF) and increase generation capacity. The environmental performance of these plants is highly influenced by the energy input and the type of auxiliary fuel, which in most cases is natural gas (NG). Replacing the NG with biogas or biomethane (BM) in commercial CSP installations is being considered as a means to produce electricity that is fully renewable and free from fossil inputs. Despite their renewable nature, the use of these biofuels also generates environmental impacts that need to be adequately identified and quantified. This paper investigates the environmental performance of a commercial wet-cooled parabolic trough 50 MWe CSP plant in Spain operating according to two strategies: solar-only, with minimum technically viable energy non-solar contribution; and hybrid operation, where 12% of the electricity derives from auxiliary fuels (as permitted by Spanish legislation). The analysis was based on standard Life Cycle Assessment (LCA) methodology (ISO 14040-14040). The technical viability and the environmental profile of operating the CSP plant with different auxiliary fuels was evaluated, including: NG; biogas from an adjacent plant; and BM withdrawn from the gas network. The effect of using different substrates (biowaste, sewage sludge, grass and a mix of biowaste with animal manure) for the production of the biofuels was also investigated. The results showed that NG is responsible for most of the environmental damage associated with the operation of the plant in hybrid mode. Replacing NG with biogas resulted in a significant improvement of the environmental performance of the installation, primarily due to reduced impact in the following categories: natural land transformation, depletion of fossil resources, and climate change. However, despite the renewable nature of the biofuels, other environmental categories like human toxicity, eutrophication, acidification and marine ecotoxicity scored higher when using biogas and BM.     

Setting a fostered energy network by decarbonizing the grid: Hybridization,control, and future solutions upon storage

According to recent energy scenario, the abundancy of noncarbonaceous resources (NCRs) is capable of satisfying the energy demand of residential, commercial, and domestic in near future. This paper portrays hybridization of these sources, along with its control and hence presenting a novel framework for finding the operational hours of the storage device. This in turn will help in developing a fostered energy network (FEN) across the globe. Instead of connecting the NCRs concurrently, the proposed system is integrated in a segment fashion that yields three subsystems like solar PV‐wind, wind‐fuel cell, and solar PV‐fuel cell. The controller thus designed for the voltage source converter (VSC) has its own uniqueness in operating at any system combination under healthy as well as various fault conditions. The electrolyzer is used for storing the surplus energy generated by the system and supplying energy during energy crisis and operates on a bidirectional controller. The reliability of the controller is tested by examining its operation for healthy as well as faulty conditions such as single line to ground (SLG) and three phase fault. Finally, the useful lifespan of the electrolyzer is estimated by using the probability approximation method. It relies upon obtaining the number of electrolyzers that will work for stipulated time period and how many of them will be discarded among all the installed. The system under study is modeled, simulated, and validated in MATLAB/SIMULINK environment.     

Modeling, design and thermal performance of a BIPV/T system thermally coupled with a ventilated concrete slab in a low energy solar house: Part 2, ventilated concrete slab

This paper is the second of two papers that describe the modeling and design of a building-integrated photovoltaic-thermal (BIPV/T) system thermally coupled with a ventilated concrete slab (VCS) adopted in a prefabricated, two-storey detached, low energy solar house and their performance assessment based on monitored data. The VCS concept is based on an integrated thermal-structural design with active storage of solar thermal energy while serving as a structural component - the basement floor slab (∼33 m²). This paper describes the numerical modeling, design, and thermal performance assessment of the VCS. The thermal performance of the VCS during the commissioning of the unoccupied house is presented. Analysis of the monitored data shows that the VCS can store 9-12 kWh of heat from the total thermal energy collected by the BIPV/T system, on a typical clear sunny day with an outdoor temperature of about 0 °C. It can also accumulate thermal energy during a series of clear sunny days without overheating the slab surface or the living space. This research shows that coupling the VCS with the BIPV/T system is a viable method to enhance the utilization of collected solar thermal energy. A method is presented for creating a simplified three-dimensional, control volume finite difference, explicit thermal model of the VCS. The model is created and validated using monitored data. The modeling method is suitable for detailed parametric study of the thermal behavior of the VCS without excessive computational effort.