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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - MinWaterCSP (MinWaterCSP - Minimized water consumption in CSP plants)

Teaser

Summary

The predominant water consumers at CSP plants are cooling system evaporation, drift and blow-down losses as well as the cleaning of mirrors. The objective of the MinWaterCSP project is therefore to reduce the annual water consumption of a CSP plant through a number of complementary measures while at the same time maintaining or improving overall plant performance and reducing the levelized cost of electricity. A holistic combination of next generation technologies in the fields of hybrid dry/wet cooling systems, wire structure heat transfer surfaces, large-diameter axial flow fans, mirror cleaning, optimized mirror cleaning strategies and comprehensive water management plans form the basis of the overall water consumption initiative.
The first objective of the project was to develop a novel hybrid dry/wet cooling system which reduces water evaporation losses by 75 to 95%, compared to wet-cooling systems, without compromising performance. A further objective was to increase the net power output of a dry-cooled CSP plant by up to 2% without increasing capital cost through the use of a hybrid cooling system. In addition the reduction of power consumption by axial flow fans was pursued, by improving fan static efficiencies from the current levels between 55 and 60% into the range of 65 to 70%.
The main objective related to mirror cleaning was to reduce the cleaning water consumption by 25%. In the cases of parabolic trough and heliostat collectors the focus was on the development of improved spray and brush technologies, while in the case of Fresnel collectors the use of a cleaning robot was introduced.
Comprehensive water management plans were developed for CSP plants, including the employment of water treatment technologies with the ultimate aim to achieve zero liquid discharge, in order to make CSP plants less dependent on sites with high quality water sources.
The impact of the newly developed technologies were assessed through overall CSP plant simulation by making use of a comprehensive plant performance simulation software tool.

Work performed

A hybrid dry/wet cooling system was developed, where deluge cooling technology was integrated into existing air-cooled condensing technology. Detailed engineering design was carried out for the new cooling system complete with a 3D CAD model to support constructability studies and more detailed capital cost calculations. Performance modelling equations for thermal performance, auxiliary power consumption and water consumption were derived.
A new axial flow fan for a CSP plant was developed and designed based on duty point specific aerodynamic optimization. Noise level reduction techniques were investigated as part of the development process. A scale mode magnetic gearbox was developed and tested, aimed as a potential replacement of state-of-the-art gears in the fan drive train.
A further work package covered the development of compact heat exchanger technology based on wire structure heat transfer surfaces for potential use in large-scale cooling systems. Design and optimization was carried out with the support of CFD analysis. Sample heat exchangers making use of wire structures were subsequently manufactured and tested for heat transfer and air-side pressure drop.
Truck-based spray- and brush-type mirror cleaning systems were developed for parabolic and heliostat collector fields, where the focus of the improved technology was on cleaning water consumption reduction. A cleaning robot was designed for Fresnel collector applications. New cleaning strategies based on collector reflectance spatial monitoring and cleanliness threshold values were developed.
Water management and water treatment were further focus areas. A concept for designing a water management plan for a CSP plant based on steady-state mass balances was created and a new MinWaterCSP approach towards water use and management was defined. The overall water mass flows were reduced through the new technologies and as a result the capacity of water treatment units and annual treatment costs were reduced.
Scaling and fouling as found during deluge cooling was investigated. A test rig simulating actual heat transfer and operating conditions was constructed and operated at Green Energy Park in Benguerir, Morocco.
A full-scale axial flow fan of 30ft diameter was designed, constructed and tested at Matimba Power Station, South Africa. This work package also included the construction of a full-scale 24ft diameter axial flow fan and deluge cooling water functional test facility at the University of Stellenbosch, South Africa, as part of the hybrid cooling system development initiative.
CSP plant simulation software ColsimCSP was further developed to include all water and wastewater streams found throughout a CSP plant. Various CSP plant simulations dealing with state-of-the-art CSP reference plants and new CSP plant designs incorporating the MinWaterCSP developments were carried out as part of benchmarking and optimization studies.
Two work packages dealt with communication, dissemination and exploitation. Two conference events were arranged in Marrakech, Morocco, and Stellenbosch, South Africa, where project results were presented and an international audience was reached. A large number of stakeholders were reached through the MinWaterCSP website, press releases, newsletters, blogs, social media and site visits. Several exploitation workshops were held and exploitable results were identified. Business plans were generated for selected exploitable results.

Final results

Overall CSP plant simulations have shown that hybrid-cooling system can result in a marginally improved LCOE compared to wet-cooling, but at the same time reduces annual water consumption by 78%. Further simulations demonstrated that the hybrid cooling system leads to an increased net annual power output of the plant beyond 2%, compared to dry-cooling, while meeting the project objective of saving 75% to 95% of water use compared to wet-cooling and maintaining capital investment. The LCOE for CSP plants with hybrid cooling systems was also consistently lower compared to dry-cooled plants.
The reference axial flow fan showed a reduction in auxiliary consumption of approximately 15% compared to a state-of-the-art commercially available axial flow fan.
A total of reduction in cleaning water consumption of 25% for spray tools and 35% for brush tools by the development of a truck-based cleaning process (parabolic trough and heliostats) was achieved, in relation to state-of-the-art solutions. The water consumption during mirror cleaning of linear Fresnel system could also be reduced by 85% through the development of a cleaning robot which replaces manual cleaning. Changing collector cleaning from state-of-the-art fixed interval cleaning to a variable cleanliness threshold strategy contributes a further saving of mirror cleaning water consumption of 25%.
As a result of these developments, potential impacts expected include significantly improving technology performance, reducing life-cycle environmental impact, strengthening the European industrial technology base, creating new component manufacturing opportunities, decreasing operation costs and contributing to solving the global climate and energy challenges.