Conventional Concentrated Solar Power Research Articles

Comparison of Parabolic Troughs and Solar Photovoltaic as Solar Field Technology in Dispatchable Solar Power Plants

The use of thermal energy storage (TES) technologies, as means to provide dispatchability to thermally driven solar power production, has long stood as the main argument for the interest and potential competitiveness of Concentrated Solar Power (CSP) when compared to other non-dispatchable alternatives. Whereas reductions of the Levelized Cost of Electricity (LCOE) are observed for CSP in recent years, the notable LCOE reduction observed along this decade in large-scale solar photovoltaics (PV) plants is set to break the taboo of "power-to-heat-to-power" approaches, as its potential economic performance outcasts the associated thermodynamic inefficiency. The possibility of using available resistive heating technologies and components in PV-TES combinations, renders the configuration of a conventional CSP plant suitable for the replacement of a thermal conversion solar field by a photovoltaic field presenting further the possibility of delocalization and/or spatial distribution of the solar field (e.g. on a Carnot Battery configuration). As dispatchability no longer stands as an exclusive argument in favor of CSP over PV, the present article addresses the boundary conditions for the competitiveness of each technology as the champion of dispatchable solar power fields. The impact of both land and electrical heater costs variation in the variation of LCOE for PV-TES plants is much more modest than that observed for the impact of CSP solar field cost variations in the variation of LCOE for CSP plants, which leans for the latter and at present costs, towards better competitiveness for plant designs with a storage capacity in excess of 10.0 FLH (for GHI values in excess of 2100-2200 kWh∙m-2∙year-1).

Experimental study of erosion in heat exchangers immersed in fluidized beds

Fluidized beds can be used as solar energy receivers in beam-down concentrated solar power plants. The fact that solid particles can withstand temperatures over 1,000°C is promising because it would mean higher thermal efficiencies than conventional concentrated solar power plants (CSP, that use molten salts, whose maximum operating temperature is limited to about 560°C). Nonetheless, immersed heat exchangers are exposed to erosion because fluidized particles impinge on their surfaces. The multiple variables of a multiphase flow and the uncertainties of the material detachment process make erosion a complex problem that stills not fully solved.The aim of this study is to conceive an experimental procedure to measure erosion on cylindrical probes immersed in a lab-scale high temperature fluidized bed (able to operate up to 1,000°C and atmospheric pressure), simulating a tube of a heat exchanger in a fluidized bed working at expected temperatures in CSP applications.Preliminary results at ambient temperature are presented in this study. Silica sand particles were fluidized with air and erosion was measured on cylindrical probes made of aluminium 5027. Silica sand was characterized with a microscope before and after each test to determine its size distribution and shape. Several parameters (diameter, mass, and circumferential profile) of each probe were also studied before and after each test. Different fluidization velocities were implemented to assess the influence of the flow rate on erosion.

Environmental and economic impacts of photovoltaic integration in concentrated solar power plants

This study conducted an environmental and economic assessment of an innovative hybrid energy generation system, a CSP+ plant, which integrates photovoltaic (PV) panels in a concentrated solar power (CSP) setup. The CSP+ concept uses a beam splitter that transmits part of the incident solar spectrum towards the PV cells for electricity generation and reflects ultraviolet and infrared light to the receiver tube for heating. This system allows more efficient use of solar radiation in a compact system with optimal efficiency.The environmental impacts were assessed using the life cycle assessment (LCA) methodology, focusing on the climate change impact category. The economic impacts were calculated using the levelized cost of electricity (LCOE) and the levelized cost of heat (LCOH). Both assessments considered a cradle-to-grave perspective in three scenarios (SC). SCI considered only electricity generation, while SCII involved the combined production of electricity and heat. These scenarios were compared to conventional CSP and PV technologies (SCIII) and benchmark values from the literature.The LCA results showed SCII was the most preferable: the impacts on climate change were reduced by up to 83% for electricity production and up to 97% for heat production compared to benchmark values. In SCII, the LCOE and the LCOH in the CSP+ plant were lower than the average benchmark values, with reductions of up to 70% for electricity and 40% for heat. The sensitivity analysis showed that the environmental performance was strongly influenced by the operating lifetime. For economic performance, the weighted cost of capital was the most influential factor.

Efficient turbomachinery layout design and performance comparison of supercritical CO2 cycles for high-temperature concentrated solar power plants under peak-shaving scenarios

The supercritical CO2 (S–CO2) cycle with high operating temperature for the next-generation concentrated solar power (CSP) technology are constructed. The turbomachinery layouts are designed and operating parameters are optimized to efficiently and flexibly respond to part-load operating conditions. The thermodynamic performance advantages of CSP plant based on S–CO2 cycle with high temperature and optimized turbomachinery layout under peak-shaving scenarios are clearly indicated. Results show that compared with the cycle with split shaft layout, the optimization of cycle turbomachinery layout can improve the part-load efficiencies of the cycle by 0.47%–2.33 %. The cycle connecting the turbine and main compressor is recommended to be adopted for deep peak-shaving scenarios, and its efficiency at 30 % rated load is only reduced to 86.3 % of the rated value. While the cycle connecting the turbine and re-compressor maintains superior efficiency performance when the load exceeds 60 % of the rated value. Furthermore, the increase of operating temperature to 750 °C and optimization of cycle turbomachinery layout can improve the efficiency of CSP plant to 21.60 % under PV-CSP peak-shaving scenarios, which is 0.55 % higher than that of the system based on cycle with split shaft layout and 2.18 % higher than that of the conventional CSP plant with 550 °C operating temperature.

Modeling of a hybrid power system integrating solar radiation and syngas combustion energy

AbstractThis study aims to model a hybrid power system that can continuously generate power by switching between two possible thermal sources: solar radiation and combustion energy from synthesis gases. The system comprised a hybrid energy receiver, solar dish, Stirling generator, fluidized‐bed gasifier, boiler, and water tank. The solar dish was a dual‐reflection solar collector that used two mirrors, namely the main and subordinate concentrators, to concentrate a broad expanse of solar radiation onto a hybrid energy receiver. The fluidized‐bed gasifier was employed for the production of synthesis gases. The synthesis gases were combusted to provide an auxiliary heat source for the Stirling generator when solar radiation was insufficient. Solar radiation or combustion energy was alternatively introduced into the hybrid energy receiver and converted to power by a 1‐kW‐scale beta‐type Stirling engine. In this manner, the Stirling generator could serve as a base‐load power plant regardless of solar conditions. In this study, a complete quantitative model was developed for a demonstration plant by incorporating thermodynamic and dynamic models of the beta‐type Stirling engine, a ray‐tracing model for the dual‐reflection solar dish, an energy model of the hybrid energy receiver, and experimental data for the fluidized‐bed gasifier. The performance response of the system during switching between solar radiation and combustion energy was predicted. The modeling results indicated that switching can result in a continuous power output ranging from 600 to 1200 W. With synthesis gas combustion as the auxiliary heat source, the hybrid Stirling power system can be operated continuously, and the overall power output is increased by 109.82% compared to a conventional concentrated solar power system that only uses solar radiation.

Thermal performance optimization of rectangular cavity receiver for cross linear concentrating solar power system

ABSTRACT A thermodynamic analysis was performed on a newly developed concentrated solar power (CSP) technology known as the Cross-Linear (CL), which addresses the issue of cosine loss in conventional CSP technology. The analytical model has been developed and validated using experimental data collected at the experimental site situated in Bhopal, India. The analysis was performed under direct normal irradiance of 775 W/m2 with the key objective to determine the optimum inlet condition of the heat transfer fluid (HTF) considering three optimization parameters: HTF outlet temperature, energy, and exergy efficiency of the receiver. Also, the exergy of the solar field is investigated depending on the available solar irradiation throughout the day for three different configurations of the heliostat field. After a comprehensive analysis of the results, the optimal air inlet temperature range was observed to be between 373 and 423 K, and the optimal air mass flow rate was overserved to be 0.0925 kg/s (333 kg/h), which provides energy and exergy efficiency values within 50% to 60% and 28% to 34%, respectively. The maximum electrical exergy efficiency for 30 kW plant capacity is observed to be around 70% at solar noon with a cosine factor of around 0.9 for 4-hour duration.

Combined direct oxy‐combustion and concentrated solar supercritical carbon dioxide power system—Thermo, exergoeconomic, and quadruple optimization analyses

For the global future energy systems, concentrated solar power (CSP) and direct CO2 capture systems are of the most important key technologies, however, each of these systems has shortcomings. This study addresses the solar intermittency and power control complexity of the CSP systems and the substantial energy penalty of the direct oxy-combustion (DOC) supercritical carbon dioxide (sCO2) power systems by integrating both systems. Herein, innovative power cycle configurations that integrate the CSP tower system with DOC sCO2 power cycle are introduced. The configurations include two basic cycles for comparison and validation purposes and three integrated cycles. The basic configurations are: an intercooled sCO2 power cycle driven by DOC system (S1), and a stand-alone basic CSP tower system (S2). The integrated configurations are: CSP/DOC system where the CSP works as a preheater (S3); CSP/DOC system where the CSP works as a reheater (S4); and CSP/DOC system where each system heats part of the working fluid to drive its high-pressure turbine (S5). The hybrid configurations reduce the fuel and the parasitic power consumptions of the basic DOC systems (S1) and reduce the capital cost associated with the conventional CSP systems (S2) by eliminating the need for thermal storage. Over practical ranges of operational parameters, comprehensive thermoeconomic, exergoeconomic, and optimization analyses for the proposed configurations are performed. Compared to the conventional CSP system, the LCOE of the hybrid system is lower by 50%. Among the hybrid configurations, the energetic and exergetic performances of S4 are the best with the lowest LCOE. According to the optimization analysis, S4 has a thermal efficiency of 55.29% at LCOEs of 7.705¢/kWh. S3, S5, S2, and S1 have thermal efficiencies of 52.90%, 48.72%, 45.56%, and 40.54% at LCOE of 7.970, 8.138, 7.864, and 6.351¢/kWh, respectively.

Recent advances of hybrid solar - Biomass thermo-chemical conversion systems

Solar biomass hybridization is a promising energy technique for efficient utilization while mitigating the disadvantages associated with both biomass and solar energy source. In conventional concentrating solar power (CSP) systems, the contribution of solar energy is relatively low, merely supplementing the system with low/medium temperature air/steam. This paper aimed to emphasize the improvement of solar heat share, particularly in the topping cycle of the hybrid system. The solar aided processes, either directly generating superheated air/steam or direct gasification are thermodynamically favorable at very high temperatures, in excess of 800 °C. Unfortunately, this temperature is unattainable in conventional CSP systems using molten salt. Accordingly, the integration of solar power tower (SPT) with solid particle fluidized system in a beam down configuration has been proposed for the hybrid solar-biomass systems. Studies of such integration system presented challenges in terms of operating temperature, continuous supply/syngas production and scaling of reactor, particularly for circulating fluidized bed (CFB). The selection of solid particle and gas flow rate are among the governing parameters for high operating temperature and effective utilization of solar heat. The development of high temperature hybrid solar-biomass system is anticipated for higher solar-to-fuel conversion efficiencies, minimizing the direct combustion of biomass and reduce the emission of greenhouse gas (GHG) emissions.

Effect of Tube Size on the Thermal Stress in Concentrating Solar Receiver Tubes

AbstractHigh-level thermal stress in the receiver tubes is detrimental for the integrity and safety of concentrating solar power (CSP) plants and is a major concern in CSP design. One important factor affecting the thermal stress is the tube size. However, conventional CSP designs mainly focus on heat transfer efficiency and pumping loss when considering the tube size effect. Investigations into the influence of tube wall thickness and diameter on the thermal stress profile are still lacking. In this paper, we bridge this knowledge gap by conducting a coupled fluid-thermal-structural simulation. The results demonstrate that the peak thermal stress correlates linearly with both the tube diameter and thickness. In comparison, the increase in thickness raises thermal stress more profoundly than the tube diameter does. Further analysis also reveals a shift in the axial thermal stress distribution by decreasing thickness or enlarging tube diameter. Notably, the axial stress on the tube front section's inner surface is inverted from tension to compression at small thicknesses or large diameters. This change is found to be attributed to the diminishing of the radial temperature gradient. These findings are beneficial in CSP receiver designs for mitigating the high-stress risks and extending its operational lifespan.

A Cost‐Performance Analysis of a Sodium Heat Engine for Distributed Concentrating Solar Power

AbstractA sodium thermal electrochemical converter (Na‐TEC) generates electricity directly from heat through isothermal expansion of sodium ions across a beta″‐alumina solid‐electrolyte. This heat engine has been considered for use with conventional concentrating solar power (CSP) systems before. However, unlike previous single‐stage devices, the improved design uses two stages with an interstage reheat, allowing more economical and efficient conversion up to 29% at a hot side temperature of 850 °C. Herein, a cost‐performance analysis for this improved design assesses opportunities for distributed‐CSP in the context of micro‐combined heat and power systems. A high‐level techno‐economic analysis (TEA) is presented that explores four scenarios where a Na‐TEC is used as the heat engine for a distributed‐CSP system. Overnight capital cost and levelized cost of electricity (LCOE) are estimated for a system lifetime of 30 years, revealing that overnight capital costs in a range from $3.57 to $17.71 per We are feasible, which equate to LCOEs from 6.9 to 17.2 cents kWhe−1. This analysis makes a significant contribution by concurrently quantifying the efficiency and unit costs for a range of multistage configurations, and demonstrating that a Na‐TEC may be a promising alternative to Stirling engines for distributed‐CSP systems at residential scale of 1–5 kWe.

Thermal Energy Processes in Direct Steam Generation Solar Systems: Boiling, Condensation and Energy Storage – A Review

Direct steam generation coupled is a promising solar-energy technology, which can reduce the growing dependency on fossil fuels. It has the potential to impact the power-generation sector as well as industrial sectors where significant quantities of process steam are required. Compared to conventional concentrated solar power systems, which use synthetic oils or molten salts as the heat transfer fluid, direct steam generation offers an opportunity to achieve higher steam temperatures in the Rankine power cycle and to reduce parasitic losses, thereby enabling improved thermal efficiencies. However, its practical implementation is associated with non-trivial challenges, which need to be addressed before such systems can become more economically competitive. Specifically, important thermal-energy processes take place during flow boiling, flow condensation and thermal-energy storage, which are highly complex, multi-scale and multi-physics in nature, and which involve phase-change, unsteady and turbulent multiphase flows in the presence of conjugate heat transfer. This paper reviews our current understanding and ability to predict these processes, and the knowledge that has been gained from experimental and computational efforts in the literature. In addition to conventional steam-Rankine cycles, the possibility of implementing organic Rankine cycle power blocks, which are relevant to lower operating temperature conditions, are also considered. This expands the focus beyond water as the working fluid, to include refrigerants also. In general, significant progress has been achieved in this space, yet there remain challenges in our capability to design and to operate high-performance and low-cost systems effectively and with confidence. Of interest are the flow regimes, heat transfer coefficients and pressure drops that are experienced during the thermal processes present in direct steam generation systems, including those occurring in the solar collectors, evaporators, condensers and relevant energy storage schemes during thermal charging and discharging. A brief overview of some energy storage options are also presented to motivate the inclusion of thermal energy storage into direct steam generation systems.

Hybridizing a geothermal power plant with concentrating solar power and thermal storage to increase power generation and dispatchability

Geothermal power plants often deploy less than their full power capacity due to declining geothermal resources. Integrating heat from a concentrating solar power (CSP) collector field increases the power output at low cost. This article considers five methods of solar heat addition in a double-flash geothermal plant. The most promising solution converts solar heat into electrical work with an efficiency of 24.3%. The economic feasibility and optimal sizing of the solar field and thermal stores are evaluated. A hybrid plant that increases power generation from 22 to 24 MWe has a Levelized Cost of Electricity (LCOE) of 0.07 ± 0.01 $/kWhe. Adding three hours of storage increases the LCOE to 0.08 ± 0.01 $/kWhe. Photovoltaic systems are considered to be a low-cost renewable technology, but an equivalent photovoltaic system with battery storage costs 0.15 ± 0.07 $/kWhe due to the high cost and replacement rate of batteries compared to thermal storage. The hybrid plant also has a lower LCOE than a conventional CSP plant. If the dispatchability that thermal storage provides is rewarded with higher electricity prices, calculations indicate storage becomes an attractive investment when discharged power receives 1.75 times the typical price of electricity.

FEASIBILITY STUDY OF HYBRID THERMOELECTRIC PLANTS USING CSP TECHNOLOGY AND FOSSIL FUEL: SIMULATION SCENARIOS

Due to the rapid advance in technology, a new generation of power plants has emerged: the concentrated solar power (CSP). It is a renewable energy system that can be combined with large-scale energy storage systems. CSP holds many promises for the countries with high direct solar radiation, as Brazil. However, there are many problems regarding the viability of these plants in the emerging countries such as high capital costs, lack of national technology and qualified professionals. Hybridization of existing power plants with solar energy could be a possible gateway for the technology deployment. This paper presents the technical and economic feasibility analysis of a steam super-heater plant powered by CSP for electricity production. Such hybridization permits the reduction of CO2 emissions and retrenchment in the long term. In this context, the performances of four different systems of thermoelectric power generation were compared: (i) solar reheating - superheated steam generated by boiler and it expansion in the first turbine using CSP for reheating second expansion turbine; (ii) solar superheater - generating saturated steam in a boiler and superheating it using CSP; (iii) supercritical solar heater - saturated steam production in a boiler and heating at supercritical steam in CSP and (iv) conventional cycle and CSP working in parallel. The direct irradiation data available at the Brazilian solar atlas were analyzed, looking for the best location of power plant installation. In addition to the solar resource data, other criteria as economic, environmental and availability of transmission lines were taken into account. The decision matrix with performance indicators helped in the decision-making process of location selection. Comparing to others scenarios the obtained results showed several advantages of scenario (iv) - conventional cycle and CSP working in parallel using solar power towers without thermal storage. Research result as well revealed Santa Maria da Vitória town, Bahia region, as a better place for plant construction using the selected scenario. The total capacity was determined to be 30 MWe in accordance with the incentives offered by 481/2012-ANEEL (Brazilian Agency) resolution.

Design of a thermosyphon-based thermal valve for controlled high-temperature heat extraction

Conventional concentrated solar power (CSP) is a reliable alternative energy source that uses the sun’s heat to drive a heat engine to produce electrical power. An advantage of CSP is its ability to store thermal energy for use during off-sun hours which is typically done by storing sensible heat in molten salts. Alternatively, thermal energy may be stored as latent heat in a phase-change material (PCM), which stores large quantities of thermal energy in an isothermal process. On-sun, the PCM melts, storing energy. Off-sun, the latent heat is extracted to produce dispatchable electrical power.This paper presents the design of a thermosyphon-based device with sodium working fluid that is able to extract heat from a source as demand requires. A prototype has been designed to transfer 37kW of thermal energy from a 600°C molten PCM tank to an array of 9% efficient thermoelectric generators (TEGs) to produce 3kW of usable electrical energy for 5h. This “thermal valve” design incorporates a funnel to collect condensate and a central shut-off valve to control condensate gravity return to the evaporator. Three circumferential tubes allow vapour transport up to the condenser.Pressure and a thermal resistance models were developed to predict the performance of the thermal valve. The pressure model predicts that the thermal valve will function as designed. The thermal resistance model predicts a 5500× difference in total thermal resistance between “on” and “off” states. The evaporator and condenser walls comprise 96% of the “on” thermal resistance, while the small parasitic heat transfer in the “off” state is primarily (77%) due to radiation losses.This simple and effective technology can have a strong impact on the feasibility, scalability, and dispatchability of CSP latent storage. In addition, other industrial and commercial applications can benefit from this thermal valve concept.

Comparative LCA Between Current and Alternative Waste-Based TES for CSP

Alternative thermal energy storage (TES) materials are needed for the expected worldwide deployment of concentrated solar power (CSP) plants, and they should meet related criterion of technical, economical and ecological performances. This paper aims to quantify the environmental footprint of an alternative recycled ceramic made from industrial wastes by performing a comparative life cycle analysis. Compared to the conventional CSP TES technology based upon the two tank molten salt technique, the environmental impacts of the storage unit using recycled ceramics from industrial wastes are reduced by 40 % in terms of potential climate change, 30 % in primary energy demand and 60 % in water consumption. Those impacts are calculated for a scope of recycled ceramics promoting the use of secondary raw material and for which the inerting process is attached to the upstream lifecycle. If included, the energy payback time of the storage remains below 3 years before about 25–30 years of expected use. Such a low payback time represents a strong advantage toward further encouraging high added-value recovery, an issue which is often strongly constrained by its economical and environmental concerns.

Environmental Assessment of a HYSOL CSP Plant Compared to a Conventional Tower CSP Plant

The aim of this paper is to evaluate the environmental performance of a Concentrating Solar Power (CSP) plant based on HYSOL technology. The plant under investigation is a solar tower system with 14hours thermal energy storage using biomethane as auxiliary fuel and using a 100 MWe steam turbine and a 80 MWe gas turbine in the combined cycle (Brayton and Rankine) characteristic of the HYSOL technology. The results evidence that HYSOL technology performs significantly better in environmental terms than conventional CSP. This evidence is particularly relevant in the climate change category where HYSOL plants presents 43.0kg CO2 eq /MWh. In contrast, the hybrid CSP plant operating with natural gas emits 370kg CO2 eq /MWh. This difference is attributable primarily to the nature of the auxiliary fuel (biomethane in HYSOL and natural gas in conventional CSP), but also to the higher thermal efficiencies achieved in the HYSOL configuration, which prevents the emission of 106kg CO2 eq /MWh. The environmental significance of the additional components and infrastructure associated with the Brayton cycle in the HYSOL technology (gas turbine, Heat Recovery System and Low Temperature Energy Storage) are negligible.

Biomass Resources to Hybridize CSP with Biomethane: Potential of Horticultural Residues and Drought-tolerant Crops.

HYSOL technology allows the hybridization of Concentrated Solar Power (CSP) technology with biomethane for the efficient generation of clean and sustainable electricity in a firm and dispatchable manner. Biomass from horticultural residues and drought-tolerant crops is a promising feedstock for biomethane production in areas with high solar radiation. This paper investigates the biomass potential of these two resources in Spain by considering the volume of horticultural residues generated, availability of suitable land for dedicated prickly pear plantations and its methane generation capacity. Experimental biomethane yields have also been determined for different substrates mixtures of overripe tomatoes and prickly pear cladodes. Potential biomethane and electricity production are then calculated, as well as the number of conventional CSP and HYSOL plants that could be supplied with this energy. Results show that a significant number of CSP plant could be methane-supplied by the studied resources: up to 45 conventional CSP or 4 HYSOL plants.

Development of a Concentrating Solar Power System Using Fluidized-bed Technology for Thermal Energy Conversion and Solid Particles for Thermal Energy Storage

Abstract Concentrating solar power (CSP) is an effective way to convert solar energy into electricity with an economic energy-storage capability for grid-scale, dispatchable renewable power generation. However, CSP plants need to reduce costs to be competitive with other power generation methods. Two ways to reduce CSP cost are to increase solar-to-electric efficiency by supporting a high-efficiency power conversion system, and to use low-cost materials in the system. The current nitrate-based molten-salt systems have limited potential for cost reduction and improved power-conversion efficiencywith high operating temperatures. Even with significant improvements in operating performance, these systems face challenges in satisfying the cost and performance targets. This paper introduces a novel CSP system with high-temperature capability that can be integrated into a high-efficiency CSP plant and that meets the low-cost, high-performance CSP targets. Unlike a conventional salt-based CSP plant, this design uses gas/solid, two-phase flow as the heat-transfer fluid (HTF); separated solid particles as storage media; and stable, inexpensive materials for the high-temperature receiver and energy storage containment. We highlightthe economic and performance benefits of this innovative CSP system design, whichhas thermal energy storage capability for base-load power generation.

Night time performance of a storage integrated solar thermophotovoltaic (SISTPV) system

Energy storage at low maintenance cost is one of the key challenges for generating electricity from the solar energy. This paper presents the theoretical analysis (verified by CFD) of the night time performance of a recently proposed conceptual system that integrates thermal storage (via phase change materials) and thermophotovoltaics for power generation. These storage integrated solar thermophotovoltaic (SISTPV) systems are attractive owing to their simple design (no moving parts) and modularity compared to conventional Concentrated Solar Power (CSP) technologies. Importantly, the ability of high temperature operation of these systems allows the use of silicon (melting point of 1680K) as the phase change material (PCM). Silicon’s very high latent heat of fusion of 1800kJ/kg and low cost ($1.70/kg), makes it an ideal heat storage medium enabling for an extremely high storage energy density and low weight modular systems. In this paper, the night time operation of the SISTPV system optimised for steady state is analysed. The results indicate that for any given PCM length, a combination of small taper ratio and large inlet hole-to-absorber area ratio are essential to increase the operation time and the average power produced during the night time. Additionally, the overall results show that there is a trade-off between running time and the average power produced during the night time. Average night time power densities as high as 30W/cm2 are possible if the system is designed with a small PCM length (10cm) to operate just a few hours after sun-set, but running times longer than 72h (3days) are possible for larger lengths (50cm) at the expense of a lower average power density of about 14W/cm2. In both cases the steady state system efficiency has been predicted to be about 30%. This makes SISTPV systems to be a versatile solution that can be adapted for operation in a broad range of locations with different climate conditions, even being used off-grid and in space applications.

Life cycle assessment of greenhouse gas emissions, water and land use for concentrated solar power plants with different energy backup systems

Concentrated solar power (CSP) is unique among intermittent renewable energy options because for the past four years, utility-scale plants have been using an energy storage technology that could allow a CSP plant to operate as a baseload renewable energy generator in the future. No study to-date has directly compared the environmental implications of this technology with more conventional CSP backup energy options. This study compares the life cycle greenhouse gas (GHG) emissions, water consumption, and direct, onsite land use associated with one MWh of electricity production from CSP plants with wet and dry cooling and with three energy backup systems: (1) minimal backup (MB), (2) molten salt thermal energy storage (TES), and (3) a natural gas-fired heat transfer fluid heater (NG). Plants with NG had 4–9 times more life cycle GHG emissions than plants with TES. Plants with TES generally had twice as many life cycle GHG emissions as the MB plants. Dry cooling reduced life cycle water consumption by 71–78% compared to wet cooling. Plants with larger backup capacities had greater life cycle water consumption than plants with smaller backup capacities, and plants with NG had lower direct, onsite life cycle land use than plants with MB or TES.