WATERLEAU ‘s & Fraunhofer ISE’s main task within the MinWaterCSP project is to elaborate a water management program and suggest the best concepts and designs for the sustainable water utilization within CSP projects (WP6), that would allow all partners in the project to quickly have access to all related water matters for their several products.
This would also help end users and constructors of new CSP parks in their decision making, hopefully leading to more sustainable and environmental friendly projects for all research partners and end-users.
To get a clear picture on the needs, facts and figures WATERLEAU did several study tours to sites in EU and Morroco.
In April 2016 they visited the 20 MW Gemasolar Torresol Energy Tower CSP plant close to Sevilla in Spain, a park that was designed and built by Sener Ingenieria and partners and partly subsidized by EU funds and operational since 2011 (see picture below). (The experiences have been used for the development of new larger projects in Morocco, e.g. NOOR III).
In this plant 304.750 m2 total reflective area (195ha solar field) in the form of 2.650 Heliostats eliostats concentrate the solar power towards a 140 meter high tower with central receiver, through which a molten salt HTF (heat transfer fluid) transfers the solar heat finally via heat exchangers towards a high pressure steam that drives a steam turbine. The system also allows the storage of molten salt, extending the electricity production after sun set (24 h).
WATERLEAU linked their tour with a meeting of the MinWaterCSP research partner ECILIMP termosolar (WP5 leader), a cleaning services supplying company from Ecija which takes care for the mirror cleaning services of the Torresol Heliostats park with their already very advanced mirror cleaning trucks (see picture on the left).These cleaning trucks are using cleaning wiper-arms with either brushes and/or pressurized water (preferred by clients, no abrasion risk) to clean each mirror up on demand. The partnership with ECILIMP means that the research part of the consortium receives the practical information on the specific water consumption for mirror cleaning.
Where do water losses occur?
The current status is that the spray water (demineralized water) is not reused and leaking away in the soil below the heliostats. This is one important topic in the project that is studied as the spray water ‘drippings’ potentially could be collected and treated for reuse by simple sedimentation and/or more advanced filtration steps.
Next to the mirror cleaning, water is mainly needed for the steam turbine process, actually for cooling in the condenser before entering again the next closed loop cycle towards feed pump, the heat exchanger and steam turbine.
The Torresol plant uses recirculated Wet Cooling and thus has as consequence a high water consumption.
Based on the information from Sener the total daily water consumption is 100 m3/h, from which 90 m3/h is used for the cooling purpose, after conventional coagulation, flocculation, sand filtration and disinfection steps.
Sources of water can be…
The Torresol CSP park has a (rain) water storage lagoon that contains approximately 300.000 m3 that is filled up during the winter period and provides all the water needed throughout the year (see picture).
The rest 10 m3/h (a small fraction of water is also used for potabilization) water production is carried out with Reverse Osmosis (RO) treatment to produce demineralized water that is used as boiler make-up water, mirror cleaning water and other smaller demin-water users.
As such the visit was very useful as this plant can serve ideally as basic reference for water treatment and consumption for CSP plants in general and for the research partners MinWaterCSP new concepts specifically (compared to hybrid cooling).
In August WATERLEAU visited the research park of Iresen in Ben Guerir (Morocco) to gain further knowledge about the several options for CSP technologies and the implications for the water utilization.
The site shows several new lab and research facilities, including PV, parabolic through CSP coupled to an ORC turbine and several other test set-ups (e.g. a Linear Fresnel collector set-up) (see pictures below).
Just to get an experience on a soiled mirror the following pictures show a mirror soiled with mainly sandy dust.
The site also recently has installed a 10 m3/h water treatment plant that is consisting of a combination of RO and Membrane Distillation desalination systems using solar energy to reduce brine discharge and increase overall permeate recovery (see picture on the left).
Finally in November WATERLEAU participated in the joint workshop at the Almeria PSA research site (Plataforma Solar de Almeria), exchanging information between the WASCOP and MinWaterCSP consortia, while also visiting the site showing several CSP research projects related to the optimization of knowledge about mirror soiling, CSP performances of central receivers and PT and also water consumption and reuse, one important example being the Solar Desalination Unit using Multi-Effect Distillation technology using solar thermal energy.
How did WATERLEAU benefit:
Primarily they found basic information about water qualities, quantities needed for all the critical steps in CSP.
With Torresol they identified the perfect reference for the MinWaterCSP concept (rainwater use, state of the art water treatment, but with wet cooling application and no reuse of water).
And further they also found typical examples of solar driven alternative water solutions in Iresen (the membrane distillation set-up) and at PSA the multi effect distillation.
WATERLEAU was created in 2000 by five entrepreneurs with many years of experience in the water and wastewater technology. The track record of the founders resulted in new water projects as from the early start. WATERLEAU’s rapid growth (500 engineers & worldwide presence) has led to a complete portfolio of environmental services and solutions to both industry and municipalities in the fields of water, air and waste treatment as well as in new energy recovery.
(c) Notice to pictures of Torresol: Gemasolar Plant, property of Torresol Energy ©SENER, Cleaning Technology property of ECILIMP