POWERED BY WATER
Energy Observer is the first boat to cruise round the world using hydrogen extracted on board from seawater
The remarkable boat that generates its own hydrogen fuel from sea water
The problem with electric boats is not the lack of speed or power, it’s the size and weight of the batteries needed to give them a decent range. In simple terms the energy density of
1kg diesel is around 100 times greater than that of a lithium ion battery. Even taking into account the relative thermal efficiency of an electric motor (90%) compared to a diesel engine (35%), you would still need to carry almost 30 tonnes of lithium-ion batteries to match the equivalent power/range of 1,000 litres of diesel.
To match the energy density of diesel what you really need is a means of storing power in another form that is lighter, denser and immune to the slow power leakage which all batteries suffer from. The solution which former offshore sailor Victorien Erussard and maritime explorer Jerome Delafosse settled on was hydrogen. Hydrogen is the most abundant element in the universe (mostly in the form of water), has exceptional energy density (three times greater than diesel) and can either be burnt or converted back into electricity via a fuel cell while emitting nothing but pure water.
To demonstrate hydrogen’s potential as a fuel of the future, they decided to build a boat that was not only powered by hydrogen but also extracted it from the very water it was cruising on. Since its launch in June 2017, Energy Observer has already cruised 18,000nm and visited over 25 countries extracting hydrogen from the sea, using a combination of solar and wind power, and converting it back to electricity to power its twin electric motors.
We caught up with the crew at a stopover in London to discover the secrets behind Energy Observer’s technology and how that could translate to the world of leisure boats.
The starting point for the project was a former offshore sailing catamaran designed by Nigel Irens. Removed of its rigging this provided a stiff, low drag platform to house the systems needed to produce and store hydrogen.
The first stage of the process involves generating sufficient electricity to split the water molecules (H2O) into hydrogen molecules (H2) and oxygen atoms (O). This is done with the aid of 326 bifacial solar panels which harvest direct and reflected energy from the sun. Together they cover an area of 168m² and generate a peak of 28.5kw.
POWER POINTS
The second power source are two 12m high wing sails known as Oceanwings. These drive the boat like a traditional sail but also generate electricity by turning the propellers as the boat moves through the water. The crew also experimented with kites but found them too difficult to operate in high winds.
The electricity generated is initially fed into a 106kwh bank of lithium ion batteries for short term storage, while any surplus is used to generate hydrogen. Before sea water can be turned into hydrogen it first has to be desalinated by reverse osmosis then passed through two special membranes to create 100% pure de-ionised water. This is then transferred to an electrolyser where an electrical current is passed through it, splitting the water into hydrogen and oxygen at a rate of up to 4nm³ of hydrogen per hour. It takes around 40kwh of electricity to produce 1kg of hydrogen.
Although hydrogen’s energy density is very high, the gas itself is very light and therefore takes up a lot of space at atmospheric pressure so the hydrogen is passed through two compressors raising it to 350 bars. This is stored in eight carbon-fibre gas tanks of 322 litres each for a total capacity of 62kg where it can be kept until needed.
When the time comes to turn it back into electricity, the hydrogen is passed through a 20kw fuel cell generating electricity, heat and water. Compared to a combustion engine, which turns about 65% of the diesel’s energy into heat and only 35% into power, a fuel cell turns about 50% of it into heat and 50% into power. Energy Observer also recovers much of this waste heat to warm the boat. The electricity generated is then used to power two motors delivering up to 41kw (55hp) each at 3,000rpm for a top speed of 12 knots.
THE FUTURE
Having proved and refined Energy Observer’s systems over two years and 18,000nm in all different seas and weather, Jerome and Victorien are confident that the technology is robust but they are well aware that it is currently too restrictive and expensive to fit to production leisure boats – even turning the kettle on slows the boat’s progress by a knot to use its energy more efficiently.
Their mission is not to sell hydrogen-powered boats but to demonstrate hydrogen’s viability as an alternative fuel and a means of storing excess electricity wherever and whenever it is generated. That could be from large scale solar or wind farms or multiple smaller units. For instance every road or dockside fuel station could generate its own hydrogen, then dispense it to cars and boats as quickly and efficiently as it would diesel.
They acknowledge it will take considerable time and money to develop a network large enough to cope, and maintain that whatever the outcome we will all have to use energy more sparingly in the future. In the meantime, unless there is a dramatic breakthrough in battery technology, hydrogen may well be our best hope for a cleaner, quieter motor boat with the same speed and range as the current petrol and diesel models. www.energy-observer.org