Thermal storage can also be incorporated to transfer electric consumption
off-peak. A producer of copper, copper alloy, and aluminum tubing has a casting
shop containing melting furnaces, turning copper, scrap, etc., into billets fed
into extrusion presses used in the production of the base tubing. Both these
operations have requirements for large volumes of cooling water to keep the tube
dies from overheating. The return water from the equipment is at a temperature
of between 90 and 95°F and has to be cooled to 80°F before it can be reused
for cooling.
Lubrication for the tubing during the drawing step is provided by dipping the tubing into a 2,800-gallon hot water tank containing lubricants. This "soap tank" requires water at 130°F. A tube finning operation also makes use of hot water, both for lubrication and washing.
Previously, the return cooling water was sent directly to a cooling tower, where its temperature was lowered to required levels for further cooling of the equipment. The 5 million-Btu/hr heating needs were taken care of by steam boilers.
The steam system was converted to a 150°F hot water loop, a heat pump used to produce the heat by reclaiming waste heat, and a 12,000-gallon storage tank was used so the heat pump could be turned off during peak electric demand hours. Thus, the system can operate at a 4.3 COP, and the 341-kW added electric load does not contribute any additional demand.
