Among the larger energy consumers on board vessels are seawater cooling pumps, chilled water pumps and engine room ventilation fans. These applications are often over-dimensioned to handle the most extreme conditions. In addition they operate at full capacity even when demand is not high. Any flow control is often through mechanical devices such as bypass valves and air dampers which are inefficient and costly to maintain.
By installing a variable-speed drive to adjust the speed of these motors according to demand, can reduce the energy consumed by around 50 percent with payback on equipment and installation, from fuel savings alone, in less than one year.
Lowering energy consumption helps to reduce carbon dioxide (CO2), sulphur oxides (SOx) and nitrogen oxide (NOx) emissions. “A single seawater cooling pump can save $29,000 and 117 tons of CO2 per year,” says Stuart Melling, manager for harbour cranes and merchant vessel service. “When applied ship-wide and fleet-wide these savings can be tremendous.
“There is a large potential for retrofitting existing ships with new fuel-reducing technologies. For example, only around 2 percent of the global fleet is currently equipped with variable-speed drives for their seawater cooling pumps, which means that 98 percent of the fleet is missing an opportunity for high fuel savings and environmental rewards.”
ABB’s marine energy appraisal aims to identify the motor-driven applications that can benefit from the use of variable-speed drives. Once the applications have been identified, the energy appraisal is undertaken and a value proposal for implementing improvements is presented. If accepted an installation site survey is carried out before the actual engineering and commissioning is completed. A final report verifies the results including a return on investment.
