WP4 Energy Efficiency and Heat Recovery

The purpose of this WP is to identify and analyse existing methods and methods under development for improving energy efficiency, energy preservation and heat recovery in ship machinery and outfitting systems.

Areas for potential future development to be identified and ways to achieve this described.

A vessel has machinery and outfitting systems that consumes energy. The electric energy needed is typically generated by diesel generators or shaft generators which effects the fuel oil consumption. To some extent systems are powered by recovered energy e.g. tank heating. By reducing the systems energy consumption and increase the energy recovery the energy available for ship propulsion can be increased.

The intended methodology includes an inventory of all onboard energy consumers with regards to possible means and measures to reduce the energy consumptions taking into account energy savings and pay-back time.

The overall mechanical efficiency of a diesel engine today is less than 50%. This means that there is a considerable potential in efficiency improvement by energy recovery. The main sources for recoverable energy are found in the exhaust gases and the cooling water. The key components to recover energy are the heat exchangers. Depending of the source different kinds of heat exchangers are used. Shell and tube or plate heat exchangers are used for cooling water energy recovery,and exhaust gas boilers are used for exhaust gas energy recovery. With more energy to be recovered the size and capacity of the heat exchangers have to increase. For exhaust gas recovery the physical size of the heat exchanger, i.e. the exhaust gas boilers will become a limitation if conventional designs are used. Improved technology and design will be developed and proposed.

Almost all marine fuel today contains sulphur and if the exhaust gases are cooled below the dew point the sulphur in the exhaust gases condensate into sulphuric acid and give corrosion in the exhaust pipe. Therefore,only a part of the heat in the exhaust gases can be recovered. However, with a sulphur free fuel more energy can be recovered as a lower exhaust gas temperature can be obtained.

mproved technology including alternative design and material are needed in order to increase the potential for energy to be recovered.