How can solar energy be used in water treatment plants?

Solar energy via Concentrated solar power ( CSP)with thermal energy storage ( TES)can be utilised for providing cost effective and greener electricity 24x7(Reliable, firm and dispatchable power) to the water treatment plants.( The plants run 24x7 and not only when PV is able to provide electricity). Also the heat and electricity can be used to provide heating, desalination, pumping of water and excess heat and electricity can be sold for process heat to industry or for district heating and cooling ( putting Vapour Absorption Machines :VAM in tandem)or as electricity to the grid. PV and wind can also be used for hybridising with CSP using ERH( Electric Resistance Heaters).

24x7 power can be provided locating CSP ( concentrated solar power)with thermal storage in the locations with suitable DNI ( Direct Normal Irradiance). Also heat can be provided using CST (concentrated solar thermal) part of the application even in locations with annual DNI of 700 or more. The heat can be provided as process heat at various temperature ranges as per the requirement and also for district heating applications even as industrial heat or process steam. The applications can include even laundry, cooking etc and also sterilisation for Hotels, Hospitals etc. This heat can be converted into cooling for district cooling using chilled water at -3 degree Centigrade using VAMs( Vapour Absorption Machines).

The challenge of providing 24x7 electricity can be addressed using Thermal energy storage. The medium for heat storage can be Molten salt (Eutectic mixture of KNO3 and NaNO3). The heat can be stored using solar fields of CSP or by ERH utilising PVs and can also be supplemented using HHO ( Oxyhydrogen Browns gas) produced via electrolysers using the treated water.

The land required for CSP systems is not more than PV. Actually we should consider the total energy produced in kWh and should not see only the capacity. The PV systems can generate only intermittent variable power that too when Sun is shining and the power produced fluctuates a lot during the day as per Sunlight. Lesser power is produced during the morning hours say during Sunrise and in the evening hours when Sun starts to set. PV systems have a CUF of only around 20% and footprint is 4-5 acre per MW. For 5 MWh electrical energy generation, 5 PV plants of 1 MW capacity will be required and the area required will be 20 acre(4x5 ). CSP can provide 24x7 firm and dispatchable power with a footprint of 15 acre per MW, using storage.

The heat part of CSP can provide desalination in a cost effective manner. It can be utilised 24x7 using Thermal energy storage (TES). Also the power can be produced 24x7 RE RTC( round the clock) that too firm and dispatchable (even during the nights) using CSP with TES for desalination or for green power to the water treatment plants. The water requirement for Power generation can be reduced if Air cooled Condensers are used in a closed cycle. Also water requirement can be minimised by deploying Brayton cycle using air and thermoacoustic engines or Heat-to- electricity systems instead of generating steam and deploying steam turbines working on low efficiency Rankine cycle. These measures can result in minimising use of water.