|Cooling water (chilled and cool) is a major hidden cost for plastics processors and in most sites, cooling water air is approximately 10-15% of the total energy use.
Minimise the demand
Reduce Heat Gains
Insulate chilled water piping wherever possible to reduce parasitic heat gains. The temperature that counts is the temperature at the point of application not the temperature at the point of generation.
Good insulation reduces parasitic heat gains and allows increased generation temperatures with no effect on the process. Typically insulation projects will have a payback of less than 1 year. If you can see condensation on pipes during summer then it is obvious that there is a need for insulation on the piping.
Increasing water temperatures will reduce energy costs. For a chiller system (chillers are basically compressors), a 1°C increase in the flow temperature will decrease the generation costs by M 3%. Sites should find out what the flow temperatures are and ask why they are set at this level. Increasing the flow temperature by 4°C will decrease chiller operating costs by > 10%.
Optimise the Supply
Reduce Cooling Costs
For cooling water (16°C to 30°C), cooling towers are widely used and offer good opportunities for energy saving through low-cost actions such as VSDs for fan control. The total cost of cooling when using cooling towers is often increased substantially because of the need for Legionella controls. Many modern sites use air blast or free cooling to remove the need for cooling towers and the associated testing.
For chilled water (5°C to 16°C), chillers are almost always used to produce the chilled water. If the flow temperatures are high enough (> 12°C) it is possible to use air blast or free cooling to act as pre-cooling for the return water. In this case, when the external temperature is < 9°C the pre-cooler will provide the complete cooling load and the chiller will not operate. This arrangement will reduce cooling costs dramatically and have a payback of less than 2 years.
Reduce Distribution Costs
Most sites use fixed speed pumps for distribution of the cooling and chilled water. This is a perfect application for VSDs. A VSD can be used to control the speed of the pump based on the temperature of the return water from the process - as the water gets warmer the pump slows down to adjust to the needs of the process. VSDs in this type of application often generate paybacks of less than 6 months.
Download the Booklet
Click here to download