The HEME project will develop a highly optimised hybrid energy system for vessels up to 50m in length. To deliver the maximum reduction in fuel consumption, such a system needs to include all areas of energy consumption, notably the propulsion and house loads.
HEME’s main method for achieving fuel economies is to use a large battery bank to smooth out peaks and troughs in the electrical load, and as an energy buffer that enables dynamic manipulation of the mechanical load on both the generator and propulsion diesel engines. This ensures that the diesel engines only operate when they must, and only at the most efficient possible point on the fuel map.
Three main methods are proposed to deliver this dynamic load control:
• Managing the battery bank such that the generator only runs when the engine load is optimal
• Managing the way in which power is applied to the propeller shaft by adding and subtracting torque using a dedicated motor/generator coupled to the diesel engine, driving an ‘oversized’ propeller for optimized propeller efficiency
• Managing the shaft load by dynamically altering the pitch of the propeller blades
A number of complementary technologies are needed to ensure that the life of the batteries is not compromised and that reliable, holistic communication and control is provided. Wherever possible, low power and renewable energies will be added to the mix including fuel cells, solar and regeneration.