AWWA SOURCES55662

The availability of recycled water may create a collateral benefit by serving as a heat sink or source for cooling and heating for commercial and industrial applications. Previously, the concept of using water sources as non-consumptive heat sinks has been utilized with a variety of water sources (e.g. potable water, groundwater, and geothermal fluids). However, risk of drinking water or environmental contamination and the unavailability of sources due to physical, environmental, legal or economic reasons have limited this use of water sources. Because recycled water is generally not utilized for potable purposes and may be already delivered to a site for consumptive uses, it avoids many of the drawbacks of other water sources. This study evaluated a water-recycling concept of using municipal reclaimed water systems for once through, non-consumptive cooling as a replacement for the conventional cooling tower systems. Use of reclaimed water as a heat sink in cooling systems can result in significant energy conservation due to elimination of cooling tower fans, and improvement in chiller performance due to lower temperatures of reclaimed water. Additional benefits of this application include pollution prevention (elimination of cooling tower chemicals) and salinity reduction (elimination of blowdown discharge). Preliminary economic evaluation of the proposed system to serve buildings of 60,000 square foot to 450,000 square foot indicated an estimated annual cost savings (amortized capital and O&M Cost) ranging from 10% for smaller units to 25% for the larger units. Market potential for the proposed system was evaluated in Southern California Edison (SCE) service area. The key limitations to retrofit potential customers included costs for installation of long pipe reaches to connect cooling systems, and increase of the reclaimed water temperature in the distribution system. Therefore, only those customers along the alignment of reclaimed main were considered for retrofitting the proposed system. In addition, potential customers were limited so that the reclaimed water temperature did not rise above 6 degrees C. Under the existing reclaimed water systems, approximately 29 cooling units were projected that can be potentially retrofitted with once through reclaimed water-cooling system. This will result in conservation of 150 acre feet (AF) of potable make up water and 1,300 MWh of power per year. In addition, it will eliminate salinity loading into the sewer system by about 115 tons per year. This application will also eliminate the use of cooling tower chemicals resulting in a savings of $125,000 per year. Reclaimed water systems in SCE service area are currently undergoing expansion. Upon completion of expansion, a total of 45 units can potentially be retrofitted with the proposed cooling system. If all 45 units are brought on-line, it will result in conservation of 250 AF of potable make up water and 2,200 MWh energy per year. In addition, this will reduce salinity loading of about 190 tons into sanitary sewers and eliminate use of cooling tower chemicals, resulting in a saving of $210,000 per year. Includes reference, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

01/01/2002

Number of Pages:

15

File Size:

1 file , 300 KB