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Water Saving for Solar Concentrated Power

Periodic Reporting for period 3 - WASCOP (Water Saving for Solar Concentrated Power)

Reporting period: 2019-01-01 to 2019-12-31

Although deserts present great opportunity of solar energy resource, compared to conventional power plants, solar thermal plants operation consume large amounts of water (up to 3000 m3/GWh) in areas with high water scarcity. In CSP plant, the water is used to ensure the steam generation (4 - 8%), the cooling of the power-block (82 - 94% in case of wet cooling) and the cleaning of the solar field collecting solar thermal energy (2 - 10%). Excessive water need, desertification and increasing ambient temperatures are serious impediment for developing solar thermal sustainable energy. Considering that highly irradiated areas are usually water deficient together with high water prices (up to 10 €/m3, with water transportation costs for some regions), the profitability of CSP plants may be questionable. Saving water is so a key issue to ensure a financially competitive position of CSP and its sustainable implementation, as well as being a humanitarian and environmental consideration.
In WASCOP, the consortium will develop and validate a flexible and adaptive integrated solution named “toolbox” encompassing different innovative technologies and optimized strategies for both the cooling of the power-block and the cleaning of the solar field optical surfaces. This holistic solution will provide an effective combination of technologies adaptable to any solar field and power-block type and CSP plant location. WASCOP will allow a significant reduction in water consumption (up to 70% - 90%) and a significant improvement in the water management of CSP plants. The project approach is a three step strategy :
• Limitation of inconveniences: Reducing the amount of heat to be removed from the power block by conventional water cooling (with heat recover during hottest hours and delayed heat exhaust at night) and reducing the amount of soiling to be removed from the optical surfaces by conventional water cleaning (with dust barriers and antisoiling coatings for protection of the optical surfaces);
• Optimization of remedial strategies: Developing flexibility in order to manage the operating strategy for cleaning (with the real time monitoring of the soiling level inside the field), and cooling in line with external environmental conditions (with the optimization of hybridized wet/dry cooling management).
• Optimization of remedial means: Increasing the efficiency and sustainability of the cooling and cleaning devices and systems (with the development of innovative low water consumption cooler and cleaners).
The first period aimed at settling the basis for accurate demonstrators. It comprises activities as agreement on requirements between all project stakeholders to define specifications, interfaces and testing conditions. Once done, works on specific and global modelling of the toolbox components both for cooling and cleaning, as well as preliminary lab experiments have been performed to support the design of the technological solutions and their test platforms.
During the second period, designs of the final prototypes have been achieved for all technologies to be developed, as well as the preparation of the different test benches for the operational tests. Finally, the realization and the integration of demonstrators have been partially completed, with some delays to be noticed dues to longer stages for test benches modifications or material provision. In parallel, activities related to the analysis the water consumption of CSP plant have been performed. A successful dedicated workshop with 28 stakeholders including plant owners and EPC companies, and including a sister project team, has been organized in last 2016 in Almeria to collect feedback.
Results have been reported in a public deliverable for the benefit of the CSP community. In addition, environmental and economic analysis of the toolbox have started. During this first period, the increase of the public awareness on water savings technologies potential, has been ensured through a dedicated project website, leaflet and fact sheet. Furthermore, the consortium has achieved strong relations the CSP community building links with a sister projects. In addition, 41 peer and not-peer scientific publications have been raised and several members of the consortium participated to Solar Paces 2016, 2017 and 2018 conferences where apart the oral presentations and posters, Consortium organised a successful workshop in Water Consumption for CSP Plants. Definition of the exploitation strategy has also been conducted with a preliminary identification of the exploitable project results, and updates realized in end 2018. This activity has been supported by the SSERR to help partners to identify and exploit their results.
The WASCOP project aims at demonstrating from the functional prototypes currently designed that solutions for the reduction of the water use in CSP plant can be achieved.
On the cooling operation side, from the modelling activities already done, a preliminary assessment of the interest of the technologies has been achieved. Technologies are delayed heat exhaust through different kind of heat storage methods, hybridized wet/dry cooler and an innovative versatile cooler (air cooler with additional water spray avoiding full evaporation system). For each of those technologies, functional prototype will be realized during the second period of the project and then assessed in relevant environment. Numerical models will then be fitted to be able to predict the water (and energy) saved from each technology with the associated economic parameters, and this for any kind of plant location and configuration. Expected impacts are both the reduction down to 10 % of the water traditionally consumed by power block cooling operation, but also the increase of the dry cooled plant performances under high temperature environments.
On the cleaning operation side, different kind of lab prototypes of soiling sensors have shown promising results achieving respectively accurate soiling information levels. This information, coupled with the preparation of the soiling and dew model to be developed will help plant owners to schedule in a more convenient way the cleaning cycle operations and so save water while avoiding unrelevant ones. In addition, dust prevention technologies comprising both dust barriers for the solar fields, anti-soiling coatings for absorber glasses and reflectors have also, from preliminary lab experiments, shown interesting effects that must be confirmed on out door or simulated operational conditions. Water cleaning operation for CSP plants integrating those technologies are expected to be 2 time less frequent than without, saving human resource besides water. In addition, as the preliminary tests seems to confirm it, novel cleaning method using US effect will achieve a very good recover of the mirror reflectance with hardly any water (less than 10% of the water normally used for cleaning operations).
Finally, the toolbox encompassing model, will provide, from each technology development, a global assessment of the total gain expected for specific location and configuration, leading to optimization of CSP plant operation and maintenance.
Besides the technological and economic impacts of water savings on CSP stakeholders, the project expects to demonstrate that CSP can be beneficial to local communities, taking care of the water resource preservation while supporting sustainable local wealth creation.
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