Research Project Information

Research Project Summary Information

Solar Water Treatment for Cooling Towers Employing UV Photocatalytic Oxidation (ST10626-1)

Steven Winter Associates, Inc.


HVAC cooling tower water is continuously exposed to airborne organic materials, resulting in the buildup of microorganisms that present hazards to the tower system and to human health. Chemicals and other water purification techniques are used to combat biological growth problems. Ultraviolet germicidal irradiation (UVGI) is being increasingly used for air and water disinfection. Ultraviolet photocatalytic oxidation (UVPCO) has been shown to eliminate most microorganisms, organic pollutants, and some inorganic pollutants in water and air. UVPCO technology can use solar UV radiation rather than artificial UV radiation, and thus eliminate the need for electrical energy use. TioxoClean, Inc. is a New York-based company that produces a water-based suspension of nano-sized particles of photoactive titanium dioxide. Tioxo has teamed with Steven Winter Associates to develop the Solar UVPCO System (SUVPCO System) for cooling tower water treatment through pre-prototype experiments.

Map Error

Project Description

A pre-prototype SUVPCO System will be designed and built for water treatment. The pre-prototype SUVPCO System will be tested to measure its effectiveness for breaking down common organic pollutants in the water, destroying microorganisms, and to determine effect of solids such as calcium carbonate on the photo reactor. Test results will be analyzed to develop mathematical models to predict and optimize the performance of SUVPCO system.


It is crudely estimated that cooling towers operating in New York State consume as much as 50 billion gallons of water annually. The proposed technology could reduce this consumption by as much 20%.

Project Results

A theoretical analysis estimated that a cooling tower with 1,000 gallons of water (100 to 200 tons of cooling capacity) can be treated with no more than 20 SUVPCO collectors measuring 7ft by 5ft. SWA designed and built two different flat-plate (non-concentrating) collectors measuring 8ft by 4ft with absorber plates coated with titanium dioxide. Tests demonstrated that 50 gallons of water can be disinfected by a 8ft-by-4ft SUVPCO collector in less than three hours indicating that the actual number of collectors needed for a cooling tower may be even smaller than predicted by the theoretical analysis (< 20 collectors/1,000 gallons). Based on simple calculations, a conventional flat plate solar collector, and a June day in New York City at noon, the collected solar energy by the SUVPCO system would increase the cooling load to the cooling tower by 4%. A more appropriate collector for this SUVPCO application can be designed with a cover sheet that blocks the infrared portion of the solar spectrum and its heating effects. Therefore, the impact of solar heat gain during the SUVPCO reaction can be significantly reduced with simple design changes to the collector.


Steven Winter Associates, Inc.
61 Washington St
Norwalk, CT 06854

Principle Investigator

Ravi Gorthala

Universities Involved


Project Type:

Product Development

Technologies Types:

Waste Management and Pollution Prevention
Water/Wastewater treatment systems

NYSERDA Contact Information

Robert Carver


R&D - Buildings Research

Contract Details

Start Date: 1/11/2010
Project Status: Active
Contract Number: ST10626-1

Last Updated: 3/8/2012 2