In recent weeks there have been a number of reports of new electronic propulsion systems and designs for tugs, so it seems like a good time for another look at battery-powered propulsion.
I was always sceptical about batteries for use on tugs in very busy ports, because nobody could assure me that they would have sufficient energy to keep a tug running for hours on end without recharging. Similarly, I did not see the point of having batteries and diesel propulsion combined because it seemed like an expensive way of building a tug and not a very efficient way of reducing emissions.
All that seems to be changing, though, and batteries seem to be getting bigger and better. For example, Swedish company Echandia Marine recently obtained type approval for a lithium titanium oxide (LTO) battery system based on Toshiba battery cells and said to provide high performance and safety, and to have a service life of at least ten years of heavy operation without service interruptions. A spokesman pointed out that tugs will need to be recharged quickly and in operation for long periods, and claimed their system can be recharged in a matter of minutes. Echandia is already working with Damen, so I expect we will soon see how good they are.
“Reputable designers and builders are offering to work with potential clients to calculate the optimum size of the battery array, and tabulate costs, savings and emissions reductions for specific ports.”
Meanwhile, Robert Allan has been promoting a new range of battery-powered tugs under the trade name ElectRA, and HaiSea Marine has ordered a trio of 70-tonne bollard pull newbuildings. With the local grid supplying electricity from hydro-electric sources, it is intended that the tugs will perform a majority, if not all jobs on batteries alone, and with zero emissions throughout.
It is claimed these three new tugs will each eliminate approximately 1,700 tonnes of CO2 per annum, so together they will eliminate the equivalent of the emissions from 1,000 cars (or three tugs, presumably).
The new designs can be customised to suit the needs of individual customers, and to ensure the battery capacity meets the energy needs of a specific port, without resulting in excessive cost. This is good, although I have not been able to find any information on the emissions reductions in countries where the electricity is generated from coal-fired power stations rather than from hydro-electric sources. What is important is that reputable designers and builders are offering to work with potential clients to calculate the optimum size of the battery array, and tabulate costs, savings and emissions reductions for specific ports. I really can’t see why any tug owner who cares about the environment would not at least investigate the possibilities.
However, there is a drawback with electric tugs which has not been mentioned – they will not make much noise.
“Perhaps we need a small loudspeaker wired into the engine controls to emit a deep growling noise whenever the power comes on.”
I had not realised how much we rely on our sense of hearing until my former company won a contract to build some small containerships for government. We came up with a hatchcoverless design, so placed the accommodation forward to help shelter the cargo spaces from waves and sea spray. The engines, of course, remained aft.
All went swimmingly until we embarked upon sea trials when, after casting off, we engaged the engines and nothing appeared to happen. We, the owner’s representatives, milled around wondering why the engines had not started, and were soon accosting the shipyard staff and asking them what was wrong. They looked startled at our reaction, and were soon clustered around us trying to understand why we were all getting so upset.
While we were all thus engaged, the ship sailed rapidly ahead and straight towards a floating dock which was in the way. Only a last-minute intervention reduced the impact to a glancing blow, and no major damage was done.
It turned out, of course, that the engines had started but we were expecting to hear them and became concerned when we did not hear the mighty roar that all tug people love. The shipyard staff, on the other hand, knew they had started and became concerned when the owner’s representatives showed signs of alarm for reasons they simply could not fathom.
It could have been a disaster, and I can see the same thing happening on electric tugs as they silently leap into action whilst their crews are still waiting for an audible indication that power is being applied. Perhaps we need a small loudspeaker wired into the engine controls to emit a deep growling noise whenever the power comes on. It should be simple enough to rig on an electric tug, and might prevent potential disasters.
Alan Loynd is a master mariner with extensive seagoing and shore experience, especially in the areas of salvage and towage. He is the former General Manager of the renowned Hong Kong Salvage and Towage company. He now runs his own marine consultancy and was chairman of the International Tugmasters Association.