Activated carbon-cement composite coated polyurethane foam based solar thermal evaporator
The disclosure provides a solar evaporation substrate for recovering water from a solution. The substrate includes a porous support and an activated carbon-cement composite. The disclosure also provides a solar thermal evaporation apparatus based on a novel substrate. The apparatus includes an open tray, a solution, a solar evaporation substrate, an enclosure and a plurality of collectors. The disclosure further provides a method for preparing the substrate from activated carbon-cement composite coated porous support and that is used to heat the solution by harvesting solar energy. The apparatus and method is chemical free, cost effective and gives a high evaporation rate of 2.4 kg/m 2 h under one-sun illumination with zero carbon footprint.
1 . A solar evaporation substrate for recovering water from a solution, comprising:
a porous support of polyurethane foam of thickness 10-25 mm, configured to imbibe and wick a solution to be purified; and
an activated carbon-cement composite configured to absorb solar energy for evaporation;
wherein the activated carbon-cement composite is coated at a predetermined thickness of 0.5-1 mm on an upper surface of the porous support.
2 . The substrate as claimed in claim 1 , wherein the activated carbon-cement composite includes powdered activated carbon and cement at a ratio in the range 2:1-3:1.
3 . The substrate as claimed in claim 1 , wherein the substrate attains a maximum surface temperature of 62° C. under one sun illumination for 1 hour.
4 . The substrate as claimed in claim 1 , wherein the substrate has a working life ranging from 2 to 8 months.
5 . A solar thermal evaporation apparatus for purification of an aqueous solution or separation of a solute therefrom, including the solar evaporation substrate as claimed in claim 1 , further comprising:
an open tray configured to hold a layer of the solar evaporation substrate on the solution;
an enclosure configured to cover the tray, wherein the enclosure admits solar energy to facilitate evaporation of the solution followed by condensation to form a condensate; and
a plurality of collectors attached to the enclosure and configured to collect the condensate.
6 . The apparatus as claimed in claim 5 , wherein the solution comprises salt water, wastewater or impure water.
7 . The apparatus as claimed in claim 5 , wherein the enclosure comprises a solar still configured to maintain a closed environment with an ambient temperature for facilitating condensation within the enclosure.
8 . The apparatus as claimed in claim 7 , wherein the enclosure comprises a condenser placed on a top of the solar still and configured to enhance a rate of vaporization and condensation.
9 . The apparatus as claimed in claim 5 , wherein the apparatus provides an evaporation rate of 2.4 Kg/m 2 h or more under one-sun illumination.
10 . The apparatus as claimed in claim 5 , wherein the apparatus provides an increase in surface temperature of the substrate from 29.9 C to 41.° C. in one minute under one-sun illumination.
11 . A method for preparing a solar evaporation substrate for use in solar thermal evaporation, the method comprising steps of:
mixing powdered activated carbon in cement to form a mixture;
adding double distilled water to the mixture to prepare a paste of activated carbon-cement composite;
providing pre-treated polyurethane foam;
layering the paste on an upper surface of the pre-treated foam to a predetermined thickness, forming a composite structure;
drying the composite structure at 60° C. for 10 hours.
12 . The method as claimed in claim 11 , wherein the mixing comprises mixing the powdered activated carbon and cement at a ratio of 2:1-3:1.
13 . The method as claimed in claim 11 , wherein providing the pre-treated polyurethane foam comprises washing the pre-treated polyurethane foam with distilled water followed by drying for 2 hrs at 55° C.