Two long-term visions determine the research activities at Imtech Marine: to develop the unmanned ship and to create the zero-emission ship. Research projects suggested by the company engineers or clients are evaluated by their contribution to one or both of these goals.
”At Imtech, we have taken a leading position in hybrid propulsion with, among others, the Energy Management System, EMS, that controls the most efficient power source for ship propulsion and onboard equipment, based on the variety of power sources installed and the operational status of the vessel.” Walter van der Pennen, consultant at the Competence Centre Energy Systems of Imtech Marine tells about recent developments in smart propulsion automation with enthusiasm. ”In a hybrid configuration there is more than one power source, for instance a combination of batteries and diesel generators. Given a certain power demand, smart automation can help the captain to control the power supply balance between the battery and diesel generator optimally. In order to do so the exact performance characteristics of the power sources is a necessity. For example, if the optimisation goal is to reduce the fuel consumption, the different efficiency characteristics are the input data for the EMS.”
Energy Management System
”This performance data is key in the development of smart propulsion automation, therefore we execute extensive measurement tests on all of our recent hybrid projects. Allowing various power sources, such as batteries, diesel generators, fuel cells, to be operated in their peak efficiency regions given a specific operational goal, for example fuel/ emission reduction, reduction in wear and tear, increased performance, etcetera. The energy balance is actively adjusted to the current load situation without operator interaction according to two different strategies.”
Van der Pennen continues: ”In case ofan a-priory known time schedule, for example ferries, actual position and speed, daily voyage energy consumption data and possible scheduled charging times are all used to actively influence the energy balance between different power sources. Without an a-priory known schedule the energy balance is actively controlled on the basis of power source efficiency properties. Both strategies use a self-learning scheme to, during the lifetime, adapt to actual vessel and power component conditions.”
It was with the two ferries Lochinvar and Hallaig for ship owner Caledonian Maritime Assets Ltd. that Imtech first completed the EMS. These ferries are operated by Caledonian MacBrayne (CalMac) in Scotland. “Now, we are at the forefront of intelligent propulsion automation”, Van der Pennen states. “To get the most out of a hybrid power supply, it is better to use smart automation that takes decisions based on the data input, advising the helmsman at the bridge. If a decision must be made about switching from diesel generator power to battery power, experience from other projects points out that fuel reduction will be less, even a lot less, than an automated system can achieve. Another advantage is that the captain and the helmsman can focus on his primary task.”
The ferries connect islands in the Irish Sea to the Scottish main land over modest distances and are operated by the Clyde and Hebrides operator CalMac. They are propelled with electric motor driven Voith Schneider propulsion (cycloidal propulsors) that is powered from a 400 volt switchboard by small diesel generator sets and a battery bank of 700 kWh. The generators are laid out to always run on optimal rotation speeds. As all required power is provided by an engine running in optimal load, the fuel is burnt with the least possible pollution and the highest efficiency. If less power is required, the batteries provide energy. Also, at peak loads during acceleration or de-acceleration of the ferry in front of the quay, the batteries provide the extra power temporarily needed. To further reduce fuel cost and emissions, the batteries are charged during the night stops at the island quays, using electricity generated by wind turbines. “This results in a 28 per cent fuel saving,” says Van der Pennen, “while the energy management system further reduces fuel consumption with ten per cent. The overall saving in fuel and emissions is 38 per cent with this power system.”
”With ferries and workboats that have an operational profile with varying load demands for sailing short distances and that all have shore contact at least on a daily basis, it is possible to achieve big fuel savings with hybrid propulsion”, Van der Pennen explains. “It is a lot harder with cargo ships that are out at sea for weeks with constant speed and power demand. For such ships, we need to look at other possibilities to generate power besides the generators, as charging batteries with shore power is no option here. At Imtech, we are investigating new solutions. However, we are not engine manufacturers. We design and install everything between the power source, being a generator for example, and the propulsion or deck equipment. Our software helps improving fuel efficiency, so engine potential – aiming at the lowest pollution possible – is at least benefited to the most.”