There are three main avenues for improving the efficiency of cooling towers while reducing a plant or facility’s carbon footprint. The first opportunity for change comes before a single drop of water or process fluid is cooled. The design and construction of an individual cooling tower has a tremendous impact on both longevity and performance. While traditionally made of galvanized or coated steel and other metals, towers made of plastics, such as molded high density polyethylene, last decades longer and do not require chemical treatments to prevent corrosion or rust. This eliminates potential water and air contamination while reducing maintenance and even disposal costs as the plastic towers can be recycled should they become obsolete.
Cooling tower design also plays a role on the second venue for savings, energy efficiency. While powerful fans are often used to facilitate the flow of materials through a tower, these incur substantial drains on energy sources. Natural draft cooling towers, however, are specially designed for use without electric fans, instead relying on gravity and natural convective airflow. Although the most efficient option available, natural draft requires that a cooling tower be very large, larger than would be required by many applications. For this reason and others, many applications require mechanical or forced draft. This does not eliminate all hope of environmental and economic savings as manufacturers can easily install direct-drive motors in place of electric motors. Direct-drive options deliver more horsepower as well as significant reductions in energy expenditures.
Similar to energy efficiency, the final avenue for savings is partially reliant on the initial design of a given cooling tower system. Although water use is one of the most environmentally challenging aspects of cooling towers, simply using counterflow designs which work with gravity rather than crossflow to cool process streams requires significantly less water. Improving cycles of concentration (COC) is also important as even small changes, for example moving from two to four COC, offer as much as 67% improvements in blowdown. The economic use of water reduces costs at both the front and back end of industry as utility and wastewater treatment often encompass large portions of a company’s total budget. Lower water usage therefore means lower cost as well as lessened impact.