Dr Juan Perez Torreglosa | eCCoSHIP: A New Heat Recovery System to Reduce the Carbon Footprint of Shipping

The team’s project, called eCCoSHIP, proposes the use of direct-current electrical networks on ships alongside a heat recovery system based on the ‘organic Rankine cycle’ – or ORC. The operation of an ORC system is similar to that of a thermal power plant, in which steam is generated and passed through a turbine to produce electricity. However, the system utilises an organic liquid that evaporates at a much lower temperature than water, making it more efficient.

The ORC system can be used on ships with electric propulsion systems. In electric propulsion systems, a diesel engine drives an electric generator. The generator supplies electricity to a network connected to electric motors that drive the ship’s propellers. Using an ORC system, the electricity harnessed from the diesel engine’s exhaust gases could be injected back into the ship’s propulsion system.

However, one problem with connecting an ORC system to a ship’s electrical network is that the alternating currents generated by the diesel engines must be synchronised with each other. This is why the eCCoSHIP team proposes the use of direct current rather than alternating current networks. The use of direct current means that synchronising the generators is not necessary.

Direct current also has many other advantages, including reduced power supply problems and easy integration of renewable energy and storage systems. Notably, direct current networks consist of much lighter electrical components, meaning that the whole ship would be lighter, requiring less energy for propulsion.

Studies have estimated that the use of electric propulsion based on direct current can achieve fuel savings of up to 30% compared to their alternating current counterparts. Integrating an ORC system can reduce the consumption of diesel in ships by a further 10%. As such, the combined use of direct current and an ORC system could drastically reduce the greenhouse gas emissions of global shipping.