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New StOrage Latent and sensible concept for high efficient CSP Plants

Periodic Reporting for period 3 - NewSOL (New StOrage Latent and sensible concept for high efficient CSP Plants)

Reporting period: 2019-07-01 to 2021-07-31

The storage of energy harvested from renewable energy sources – whose availability presents daily and seasonal fluctuations – is paramount for their use befitting the load profiles of the energy system. NEWSOL addresses the challenge of increasing the efficiency of solar energy harvesting by means of advanced materials and architectures in line with those specified in SET-plan. Its main objective is to develop advanced materials for innovative storage media concepts for Concentrated Solar Power (CSP) up to the validation of their performance after lab scale and demonstrator prototypes. To this end, the project aimed at delivering an innovative concrete based thermal energy storage design. The material developments envisaged in the project include:
• two different new high thermal performance concrete
• a new ternary Molten Salts mixture
• a Filler Material selected after a recycling/reuse concept.
The combination of the most suitable materials into the two different storage concepts stood for their test at a lab-scale and for the design of up-scaled demonstrators. The technical-economic assessment of the storage concepts withstood the following conclusions:
• the concrete solid sensible storage concept is not suitable for Molten Salt driven CSP Plant integration, as it cannot compensate the costs required with the construction of drainage volume necessary for maintenance purposes. Its use is possible for e.g. industrial waste heat applications, yet its low energy density stands for a possible hindrance;
• the need for a inner steel liner in the Thermocline design, in view of the failure of the tested coatings in preventing salt incrustations undermining long-term durability assurance, stood for LCOE results 1.5% in excess of those observed with the reference 2-Tank technology;
• Despite the concrete coating solutions tested failed to achieve good performance regarding salt incrustations, further investigation on coatings present the potential of LCOE reductions standing for a TES related LCOE reduction in excess of 10% of its overall potential (i.e. when considering TES CAPEX = 0).
These results have shown:
• a concrete based Thermocline architecture presents the potential of LCOE cost reductions and competitiveness with the current SOA 2-Tank technology, regarded a full substitution of steel is achieved;
• a market uptake strategy, dependent on measurable LCOE cost reductions, entails further research on suitable concrete coatings enabling long-term durability assurances,
thus leaving the developed solutions still on a TRL 5/6 stage.
Whereas materials developments and testing leading to the optimal design of the storage solutions envisaged in the project have been achieved along Reporting Periods 1 and 2, the works developed in Reporting Period 3 entailed the construction and testing of theThermocline demonstrator, together with the technical-economic assessment of both Concrete Module and Thermocline solutions.
In view of the delays suffered in the construction process – the need for a demonstrator relocation and redesign as a “stand-alone” infrastructure and the severe procurement and supply disruptions stemming from the COVID-19 pandemic – the project failed to present, at this stage, due testing experience enabling a full-fledged exploitation of results.
Notwithstanding, the technical-economic assessment enabled already a due assessment of both storage solutions, concluding for the need of further specific research fulfilling the observed potential for LCOE cost reductions.
Material development activities had a strong laboratorial component, namely at high performance concrete, molten salt and filler material levels, including experimental test of their compatibility under the prescribed operating conditions.
Developments at Design, Sensoring and Monitoring level included setting up numerical models for optimal designs for Thermocline and Concrete module configurations, embedded sensor development and system monitoring.
The preparation of the EMSP facilities for the construction and testing of the Thermocline prototype entailed the development and implementation of construction procedures, commissioning procedures, and the development of due control procedures for the development of specific testing following the requirements of KPI assessment.
The conclusive procurement and construction experience gathered along the final Reporting Period enabled, moreover, a technical-economic assessment of the storage solutions developed in the project.
A commercialization roadmap entails, at this point, further R&D activities aiming at improved competitiveness of the NEWSOL TES concepts.
In spite of LCOE reductions paving the way for an higher TRL 7 not being achieved, several results present the potential for immediate exploitation, e.g.:
• High Thermal Performance concrete and Insulating concrete products;
• Fiber Optic Sensors to be embedded in different materials (concrete, molten salts) to monitor high temperatures and corrosive environments.
The dissemination plan considered dissemination trough peer-to-peer information (communications in congresses and publications in peer reviewed journals) and participation in relevant standardization activities (IEC TC 117 - Solar thermal electric plants). Activities related to ethics in the project have been achieved after NEC and EPQ Requirements.
Several technological areas have reached significant results that go beyond state of the art:
• CAC and OPC+FA concretes with thermal aggregates demonstrated high thermal stability up to 550ºC and thermal fatigue resistance for suitable for CSP use
• Salt incrustations observed upon interaction with molten salts imply further coating research as to provide assurance of long-term durability;
• High thermal insulation foam concretes of CAC and OPC+FA withstood thermal cycles up to 200ºC;
Molten Salts:
• Innovative low-melting point (131ºC) and high stability (up to 525ºC) Molten Salt ternary have been investigated: NaNO3 – KNO3 – Ca(NO3)2;
• "NaNO3 – KNO3 – Ca(NO3)2" safety sheets produced from the laboratorial tests;
• A novel Li-salt system, LiNO3-NaNO3-KNO3 obtained at lab scale stable up to 490ºC has been characterized.
• Slag re-usage has been validated to be used as a heat storage material.
Sensor Development
• Fiber Optic Sensors to be embedded in different materials (concrete, molten salts) to monitor high temperatures and corrosive environments have been successfully developed and embedded into concrete tested up to 500ºC;
• A new multiplexer module that extends the sensor channel capability of the interrogator products;
• A new peak detection algorithm has been enhanced in order to enable the correct measurement of the wavelength peak for the special femto-FBG.
Thermocline construction and commissioning:
• development and implementation of construction procedures, including the due incorporation of concrete delivery, pouring and drying requirements;
• development and implementation of commissioning procedures, including due Thermocline pre-heating following suitable concrete dehydration curves and salt mixture melting procedures, including all due requirements to salt mixture control, melting rates and water evaporation stages.
Newsol Logo
Newsol demonstrator site at EMSP
Newsol demo construction
Newsol Thermocline design