HPS2 - Demonstration of Molten-Salt in Parabolic Trough Plants -Simulation Results from System Advisor Model

High-Performance-Solar-2 (HPS2) is a parabolic trough demo project that is being built by a European consortium of research institutions (German Aerospace Center DLR, University of Évora) and companies (TSK-Flagsol, Rioglass, innogy SE, Steinmüller Engineering, Yara, eltherm) on the Evora Molten Salt Platform (EMSP). The purpose of this plant is to demonstrate the viability of using molten salts as heat transfer fluid in parabolic trough power plants, while performing research and development on such technology. Commissioning of the power plant is foreseen for the end of 2020. Meanwhile, a theoretical study consisting of an annual simulation with NREL’s System Advisor Model (SAM) has been performed to support consolidate the test plan of the platform with possible operation strategies to avoid freezing of the salts

Modeling and experimental characterization of a parabolic trough solar loop integrating a thermocline energy storage system

Comme les autres technologies liées aux énergies renouvelables, le solaire à concentration souffre des problèmes liés à l’intermittence de la ressource. La technologie thermocline est une solution prometteuse qui réduirait le coût du stockage thermique dans les centrales solaires de ce type. Cependant, aucune étude n’a jusqu’ici porté sur l’impact de la variation de la température en sortie du réservoir de stockage de type thermocline sur les autres composants de la centrale. Ce travail de thèse a pour but d’améliorer les connaissances sur ce sujet, grâce à l’utilisation d’une mini boucle solaire cylindro parabolique intégrant un stockage thermocline.En premier lieu, la compatibilité entre le fluide de transfert de la centrale (huile synthétique) et les potentiels matériaux de garnissage de la cuve de stockage (Cofalit, briques de cendres volantes, alumine) est vérifiée. Puis les performances de chacun des composants de la centrale (cuve de stockage, collecteurs solaires, générateur de vapeur) sont analysées expérimentalement et numériquement. Enfin, le comportement du système global est étudié, avec un accent porté sur l’impact de la variation de la température de sortie de la cuve thermocline sur les autres composants.Il a été montré qu’avec un dimensionnement et une stratégie de contrôle appropriés, la technologie thermocline diminue très peu les performances de la centrale solaire par rapport à la technologie conventionnelle à deux cuves (maximum 3 4 % de diminution de la production électrique).Like other renewable energy technologies, concentrated solar power (CSP) suffers from resource intermittence. Thermocline technology is a promising solution to decrease cost of thermal energy storage in CSP plants. Thermocline behavior has thoroughly been studied in the past years and its behavior is considered well known. However no study treated of thermocline tanks integrated in CSP plants. Thus, the impact of the varying outlet temperature of the thermocline storage has not been assessed yet. This work aims to fill this lack of knowledge by studying a mini parabolic trough power plant integrating a thermocline tank as storage.First, the compatibility between the heat transfer fluid of the plant (synthetic oil) and various potential filler materials (Cofalit, coal fly ash bricks, alumina) of the storage tank is verified. Then, some performance studies are performed on the three main components of the power plant (energy storage tank, solar collectors, steam generator). Finally, the behavior of the whole system is assessed, with a focus on the impact of the varying fluid temperature at the outlet of the thermocline tank on the other components.It has been shown that, with a proper sizing and an appropriate control strategy, thermocline technology induces very low decrease of the solar power plant performance in comparison to the conventional two tank technology (maximum 3-4% of electrical power production difference)

Modélisation et caractérisation expérimentale d’une boucle solaire cylindro-parabolique intégrant un stockage de type thermocline

Like other renewable energy technologies, concentrated solar power (CSP) suffers from resource intermittence. Thermocline technology is a promising solution to decrease cost of thermal energy storage in CSP plants. Thermocline behavior has thoroughly been studied in the past years and its behavior is considered well known. However no study treated of thermocline tanks integrated in CSP plants. Thus, the impact of the varying outlet temperature of the thermocline storage has not been assessed yet. This work aims to fill this lack of knowledge by studying a mini parabolic trough power plant integrating a thermocline tank as storage.First, the compatibility between the heat transfer fluid of the plant (synthetic oil) and various potential filler materials (Cofalit, coal fly ash bricks, alumina) of the storage tank is verified. Then, some performance studies are performed on the three main components of the power plant (energy storage tank, solar collectors, steam generator). Finally, the behavior of the whole system is assessed, with a focus on the impact of the varying fluid temperature at the outlet of the thermocline tank on the other components.It has been shown that, with a proper sizing and an appropriate control strategy, thermocline technology induces very low decrease of the solar power plant performance in comparison to the conventional two tank technology (maximum 3-4% of electrical power production difference).Comme les autres technologies liées aux énergies renouvelables, le solaire à concentration souffre des problèmes liés à l’intermittence de la ressource. La technologie thermocline est une solution prometteuse qui réduirait le coût du stockage thermique dans les centrales solaires de ce type. Cependant, aucune étude n’a jusqu’ici porté sur l’impact de la variation de la température en sortie du réservoir de stockage de type thermocline sur les autres composants de la centrale. Ce travail de thèse a pour but d’améliorer les connaissances sur ce sujet, grâce à l’utilisation d’une mini boucle solaire cylindro parabolique intégrant un stockage thermocline.En premier lieu, la compatibilité entre le fluide de transfert de la centrale (huile synthétique) et les potentiels matériaux de garnissage de la cuve de stockage (Cofalit, briques de cendres volantes, alumine) est vérifiée. Puis les performances de chacun des composants de la centrale (cuve de stockage, collecteurs solaires, générateur de vapeur) sont analysées expérimentalement et numériquement. Enfin, le comportement du système global est étudié, avec un accent porté sur l’impact de la variation de la température de sortie de la cuve thermocline sur les autres composants.Il a été montré qu’avec un dimensionnement et une stratégie de contrôle appropriés, la technologie thermocline diminue très peu les performances de la centrale solaire par rapport à la technologie conventionnelle à deux cuves (maximum 3 4 % de diminution de la production électrique)

Solar_Power_Plants_with_storage_performance_and_LCOE

Code of the article "Making solar electricity dispatchable : a technical and economic assessment of the main conversion and storage technologies", published in iScienc

Pressure drops, heat transfer coefficient, cost and power block structure for a direct storage parabolic trough power plant running molten salts

Direct circulation of molten salts in the solar field of parabolic trough solar power plants may be a possible breakthrough to decrease their levelized cost of electricity. While prototypes are being erected around the world, this study addresses the main concerns and changes that are related to the replacement of thermal oils by molten salts, i.e. pressure drops, heat transfer coefficient, anti-freezing solutions, cost and power block design. It combines: 1) an analytical comparison of both technologies with respect to pressure drops and heat transfers; 2) simulations of a 50 MWe/7.5 h-of-storage power plant, using NREL’s SAM software, providing details on the dynamics of the outputs and parasitics. It has been observed the following: 1) pressure drops in the solar field are smaller running molten salts instead of thermal oil, thanks to higher operating temperature ranges; 2) HitecXL molten salt leads to lower electricity consumption than Therminol VP-1 oil and Solar Salt (parasitics); 3) a 6.3% reduction of the levelized cost of electricity when running HitecXL, ~14.80 c€/kWh, instead of Therminol VP-1, ~15.80 c€/kWh; 4) simpler power block designs can be considered for the higher operating temperatures of molten salts, resulting in higher efficiencies and/or cheaper power blocks

Making solar electricity dispatchable : a technical and economic assessment of the main conversion and storage technologies

The techno-economic performances of five different solar-electricity conversion technologies (photovoltaic, solar tower, parabolic trough as well as two hybrid PV/CSP systems) associated with three energy storage means (electrochemical, thermal, thermophotovoltaic) are evaluated thanks to representative models applied to four representative sites around the world. The evaluation is based upon the ability to dispatch the power production throughout the year, the ability to maximize energy injection in the electrical grid, and the levelized cost of electricity. It is found that increasing the dispatchability of solar power plants will necessarily lead to the emergence of additional energy losses and important LCOE increase, either because of low round-trip efficiency of the storage system, or because of its high cost of energy capacity. Despite lower energy production for a given collecting area, combination of PV power plants with electrochemical storage or thermal energy storage surprisingly seem to be the most promising paths

Multi-criteria optimization of an experimental system for the production of domestic hot water

International audienc

Nasal vaccination of six squirrel monkeys (Saimiri sciureus): Improved immunization protocol against Toxoplasma gondii with a nanoparticle-born vaccine

Toxoplasma gondii is an intracellular protozoon found worldwide, which completes its life cycle between felids (its definitive host) and other warm-blooded animals. While the infection rarely leads to severe complications in humans, many animal species are very susceptible to this infection, for example the squirrel monkey (Saimiri sciureus) which is the subject of this study. Toxoplasmosis is lethal for 80% of cases in this species, and fatal outbreaks are frequently reported in zoological parks.No efficient treatment exists, but a new vaccine prepared with maltodextrin nanoparticles containing killed T. gondii antigens has been tested recently in French zoos. The animals were immunized through heterologous administrations, with two nasal doses at one-month interval, followed by nasal/subcutaneous boosts thereafter. No death has been reported since the beginning of this vaccination campaign, but we felt the protocol could be simplified.Here, an improved and less-invasive immunization protocol was evaluated on 6 Saimiri sciureus in the French zoo La Palmyre. It consisted of two nasal administrations at one-month interval, followed by a nasal boost at 6 months. A specific memory T-cell immunity was observed by ELISPOT after two administrations in all the animals, without humoral responses. The results suggest that 2 nasal administrations induce a protective immune response against T. gondii infection and might be sufficient to induce a strong Tcell memory, further improving immunity

Predicted direct solar radiation (ECMWF) for optimized operational strategies of linear focus parabolic-trough systems

Day-ahead forecasts of direct normal irradiance (DNI) from the Integrated Forecasting System (IFS), the global model of the European Centre for Medium-Range Weather Forecasts (ECMWF), are used to simulate a concentrating solar power (CSP) plant through the System Advisor Model (SAM) to assess the potential value of the IFS in the electricity market. Although DNI forecasting from the IFS still demands advances towards cloud and aerosol representation, present results show substantial improvements with the new operational radiative scheme ecRad (cycle 43R3). A relative difference of approximately 0.12% for the total annual energy availability is found between forecasts and local measurements, while approx- imately 10.6% is obtained for the previous version. Results of electric energy injection to the grid from a simulated linear focus parabolic-trough system shows correlations coefficients of approximately 0.87 between hourly values of electric energy based on forecasted and measured DNI, while 0.92 are obtained for the daily values. In the context of control strategy, four operational strategies are given for different weather scenarios to handle the energy management of a CSP plant, including the effect of thermal energy storage capacity. Charge and discharge operational strategies are applied accordingly to the predicted energy availability

Short-Term Forecasts of DNI from an Integrated Forecasting System (ECMWF) for Optimized Operational Strategies of a Central Receiver System

Short-term forecasts of direct normal irradiance (DNI) from the Integrated Forecasting System (IFS) and the global numerical weather prediction model of the European Centre for Medium-Range Weather Forecasts (ECMWF) were used in the simulation of a solar power tower, through the System Advisor Model (SAM). Recent results demonstrated that DNI forecasts have been enhanced, having the potential to be a suitable tool for plant operators that allows achieving higher energy efficiency in the management of concentrating solar power (CSP) plants, particularly during periods of direct solar radiation intermittency. The main objective of this work was to assert the predictive value of the IFS forecasts, regarding operation outputs from a simulated central receiver system. Considering a 365-day period, the present results showed an hourly correlation of ≈0.78 between the electric energy injected into the grid based on forecasted and measured data, while a higher correlation was found for the daily values (≈0.89). Operational strategies based on the forecasted results were proposed for plant operators regarding the three different weather scenarios. Although there were still deviations due to the cloud and aerosol representation, the IFS forecasts showed a high potential to be used for supporting informed energy dispatch decisions in the operation of central receiver units