Electric engines are designed to be a direct replacement for a traditional diesel engine both in size and cost. Already several 48 volt DC electric motors, designed to replace small diesel engines are available for boats up to 10 metres and larger canal craft. Companies are manufacturing and marketing marinized chargers and inverter/chargers which, when working alongside lead acid and lithium batteries, complement and facilitate the use of electric motors to drive water jets and conventional propellers.
The efficiency of these new style drives means that there are new tenders emerging onto the market that offer an excellent range as well as being easy to service and maintain on board the mothership. Without the need of water cooling systems or gearboxes and with their direct connection to shafts, electric tenders are, right now, at the cutting edge of technology. Several are now beginning to emerge onto the market that feature motor direction, throttle and navigation controls in one digital colour touch screen display that really look like the future has already arrived.
For those looking to reduce both noise and emissions, the affordable electric option offers really efficient and reliable electric that are sensible alternatives to the traditionally powered superyacht tender.
Rim-driven and brushless motors capable of delivering more torque using less energy are becoming available to boat builders and with new lithium batteries capable of storing a higher charge from deep cycle charging which crucially can be repeatedly undertaken without damage, the electric boat scene is gathering momentum. One of the most recent breakthroughs in the world of electric motors, comes from Siemens who have designed a motor for the aeronautical industry that could well be adapted they say, for marine use. With a weight of just 50kg the motor delivers a continuous 260kW (348hp), at just 2,500rpm which is about five times more power than equivalent systems.
With a new generation of digital controllers, managing the ebb and flow of energy with predictive intelligence and the fast development of battery technology, things are looking up. The Dutch manufacturer Mastervolt pioneered full-size 12 and 24 volt lithium-ion batteries for marine use. Their second generation, Ultra range are one third of the weight of an equivalent lead-acid design and come with a claimed life cycle of at least 2,000 deep discharges. Complex electronic circuitry connecting each cell ensures perfect charge and discharge balancing, and guards against the risk of overcharging.
Batteries employing the use of oxygen as one of the reagents are in development and could, be made for a fifth of the price and a fifth as light as lithium, and offer operation times five times longer. Graphenano based in Spain has developed a graphene polymer battery called the Grabat, which it claims is 33 per cent the weight of lithium ion and four times the energy density. These batteries can recharge 33 times faster than lithium ion, and retain over 80 per cent of their capacity.
When it comes to powering yachts by electricity it would seem that the future is not far away. But what we do know is, that some of the electric tenders on offer are also pushing the boundaries of design aswell.