Objective
This project aims to demonstrate the feasibility of exploiting solar energy as the prime energy source for seawater desalination using a multiple effect evaporator. Fresh water production will be ca.12 000 m3 per year or 40 m3/day and the expected payback time is 7 years. Successful implementation of this project could lead to it becoming a spring board for similar projects in areas of the Community or the World where there is abundant sunshine and saltwater but shortages of fresh water.
The desalination plant consists of high energy efficiency multiple effect evaporators operating at very low pressure, coupled by way of a water storage and an automatic energy management system to a field of evacuated tube collectors. The distillation process uses heat supplied by the solar collectors and electricity for auxiliaries (pumps, controls, etc). All the heat is used at 70 deg.C.
In order to reduce the possibility of corrosion or blockage, the temperature of the seawater entering the evaporators never exceeds 70 deg.C. This necessitates operation under vacuum and therefore a vacuum pump is required upon start-up and during operation to compensate for air beaks.
With the aim of limiting the build up of deposits in the system a dissolving agent is introduced by a measuring pump, along with the seawater. This should allow continuous production for 6 months to 1 year before cleaning is necessary. Several evaporation stages or effects are stacked inside a vertical cylindricalbody. Heat is introduced into the highest effect by hot water coming from the solar water storage. This heat is released to the seawater across the walls of a horizontal exchanger. A fraction of seawater evaporates and the vapour thus produced condenses to fresh water, at a slightly lower temperature, on the exchanger in the next effect. The heat of condensation is then released to seawater.
This process continues until the final effect where the temperature is close to that of the seawater feed which is pumped to the top of the evaporator. The salt and fresh water are extracted by pumps.
Drinking water is produced by dosing the distilled water with minerals, increasing its pH and adding chlorine.
To maintain continual operation and to control the evaporator inlet temperature a buffer storage of 100 m3 is placed between the collectors and the evaporator unit.
The whole system is controlled and monitored automatically.
The costs of equipment, transport, installation commissioningand training are about 7.5 MFF (ex taxes).
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
78100 ST-GERMAIN-EN-LAYE
France