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An Electric Experience

There are more positives than negatives when it comes to battery-powered propulsion afloat, says Kathy Mansfield.

Just a few miles from where Kenneth Grahame’s Ratty expounded to Mole that there was “...nothing half so much worth doing as simply messing about in boats,” a group of people gathered at Emrhys and Linda Barrell’s Thames Electric Launch Co at Goring-on-Thames to investigate the reality and the potential future of electric propulsion systems afloat.

Certainly, they ought to have a rosy future in this more ecologically aware era and anyone with a petrol or diesel powered craft, especially those on inland lakes or waterways, should consider electrical power as a viable alternative. Electric propulsion systems are smooth, quiet and reliable, and the low voltages used, usually 12 to 36 volts, are comparatively safe. Electric motors themselves do not pollute the local environment although the power required for overnight charging of their batteries may cause pollution one step removed at the power station but at a much lower level. But even this can be reduced through use of solar panels, wind or water generators for keeping the batteries up to strength.

Electric engines have been fitted into canoes, skiffs, narrowboats, launches of all sizes and materials, workboats and sailing boats, and they can be retro-fitted into your existing craft of any type or vintage, taking up far less space than a petrol or diesel engine. The batteries can be fitted under the seats or thwarts or even worked into the keel to provide extra stability. This has been successfully done on some of the sailing boats on the Norfolk Broads, one of which, a gaff rigged traditional Broads yacht, is available for hire from Camelot Craft of Wroxham, Norfolk.

Cruising speeds under power in these craft are slower but compatible with the speed limits already in place on most inland waterways. Some countries, notably the Netherlands and Austria, have already imposed a ban on non-electric engines on some inland waterways, and this is also being considered for Coniston Water where electric boats are proving cost effective.

A Fascinating History

But of course we have been here before. In 1882 the 26’ (7.9m) Electricity was taken on trials down the tidal Thames, and a 36’ (11m) galvanised steel boat named Volta, with 70 batteries connected to two motors, crossed the Channel in 1886, something which hasn’t been done since. By 1889, there were eight recharging points along the Thames sponsored by the electric boat hire companies who could advertise silent and vibrationless propulsion, lack of pollution, ease of operation, and extra space gained by a smaller engine, all advantages which hold just as true today. Edward VII, then Prince of Wales, hired the Viscountess Bury regularly from 1888. She was a 65’ (19.8m) long, 10’ (3m) beam, electric launch capable of carrying 80 passengers at up to 7mph - and is still afloat in Ely, awaiting restoration.

Electric boats were to be seen as far north as Edinburgh in 1890, and before the turn of the century they had been exported to Australia, the Netherlands, Turkey, Russia and India, mainly for sultans, maharajahs, czars and other potentates, but they were increasingly available to the middle class in Britain. However, the internal combustion engine transformed boating of all descriptions in the early 1900s, going farther and faster than steam or electric propulsion, but soon afterwards, WW1 put an end to leisure pleasures. The story is a fascinating one, and for those wishing to delve further into the history of electric boating, turn to Edward Hawthorne’s Electric Boats on the Thames 1889-1914, reviewed here.

Today’s Systems

So where have we come to now, and what is needed to go afloat electrically? The basic battery technology has changed little in 100 years, with most craft still using lead-acid cells, but reliability and life have increased immeasurable, and it will be some time before more sophisticated cells replace them. Products on the market today include the Lynch inboard motor, systems from London Innovation, the American Minn Kota electric outboards for canoes and dinghies, and the Dutch heavy duty Combi outboards or sail/drive systems, all sold and installed by the Thames Electric Launch Co who also offer their own Electron outboards.

You can start electric boating for less than £1000 with an Avon inflatable, or about £300 if you already own a canoe or a dinghy, either of which could be propelled by a Minn Kota electric engine and one battery. Fitting an electric propulsion system into an existing boat is possible, and the rewards are instant in simple and quiet propulsion. The Thames Electric Launch Co also offer a range of electric boats from a 16’ (4.9m) GRP dayboat fitted out in mahogany and pine or a 16’ or 18’ (4.9 or 5.5m) GRP river cruiser with canvas canopy, and will advise on conversions to electric or diesel/electric propulsion. There are superb traditional river craft, suitable for electric power units, built by Peter Freebody, John Williams and others. Sadly the Steam and Electric Launch Co was recently wound up, but some of their boats are set to re-emerge shortly.

Apart from the engine itself, in anything apart from a smaller dinghy or canoe using a single motor attached to an outboard drive unit, there are some other necessary components that need to be allowed for both in terms of space and cost. In order to be able to control the direction and speed of the output, a sophisticated controller is needed. This will cost in the region of £250 - £450, and will incorporate circuit protection and cut outs as well as a single lever control for speed and direction. A specialised charger unit to convert standard mains power of 240V AC to 12V or up to 72V DC is also necessary once banks of batteries are involved. These can cost from £250 for an overnight charger with automatic cut-off for a smaller bank of batteries, up to £800 for the largest bank.

Batteries themselves are a separate item, and although the lead/acid, deep discharge traction battery is reliable and one such should be sufficient for a canoe or small dinghy for 3 to 4 hours cruising at up to 4 mph, a bank of batteries to power a medium sized cruising boat represents a serious outlay in both finance and weight. A four berth yacht of 21’ (6.4m) waterline length may use eight 6V batteries, at a cost of about £100 each which, if properly maintained should last for 8 to 10 years. Sadly, the extra power of the expensive lithium battery or the sodium/sulphur battery (which delivers 150Wh/kg compared to lead/acid’s 35 Wh/kg, but needs to operate at a temperature of 350°C) will not be a viable option for the foreseeable future. The cost is not much more than a full installation of a diesel engine including electrics, exhaust and fuel tank, and should come down as demand rises. Running costs of overnight charging when needed, say weekly or more often in the summer season, work out at less than 50p per charge for a smaller bank of batteries.

The National Rivers Authority, who already have two Selectric electric/diesel combinations in the patrol boats Lambourn and Colne, where the diesel is only used for emergencies or driving fire pumps, are laying cables for a series of charging points on the Thames once a standard charging post has been agreed. At present there is only one, at Benson Lock. The Norfolk Broads already have 8 charging points installed by Eastern Electricity, and the Broads Authority have just taken delivery of their own 31’ (9.45m) patrol boat with Telco’s Selectric system. Midlands Electricity also installed charging points which are now in the control of local marinas. And in practice, boatyards and pubs are usually willing to plug in your extension lead: “13 amps and a pint, please,” could become the accepted norm!

How much power?

Electric boat engine horsepowers are lower than for internal combustion engines, but some surprising data is available. For instance, it is claimed by London Innovations that only about 1 horsepower is needed to drive a typical four berth sailing boat or cabin cruiser at 5mph, but the power requirement will rise rapidly as hull speed is approached at around 6mph. This means that four or five times as much power may be needed without much increase in boat speed. The average internal combustion engine actually wastes significant amounts of energy through mechanical losses, particularly through gears and bearings, as well as through propeller losses.

A 7hp internal combustion engine may drive the boat at 5mph, but possibly 20hp will be needed to get it up to 6mph. An electric engine achieves much greater efficiencies and at 5mph a 1.6kW engine (ie 2.1hp) could be adequate for a job for which a much more powerful petrol or diesel engine would need to be used. Bigger and lighter propellers, can also be used with electric power units. Upgrading a 12” (300mm) prop on a 21’ (6.4m) daysailer to an 18” (457mm) folding prop made of plastic or hard rubber for example, could increase energy efficiency significantly. Once the hull drag is accurately

measured, the mechanical and propeller efficiency losses estimated and minimised, the desired speed and range required by the owner assessed, and the size and use of the boat taken into account, the appropriate engine and battery system can be selected and installed.

Greater horsepower in electric engines (746 watts = 1 horsepower) means more lead/acid batteries, and hence more weight. Britain captured the World Speed Record for an electric boat in 1990 when An Stradag achieved 51mph, so the electric motor has no inherent problem with speed, but the banks of batteries needed, using existing battery technology, are more than the average boat owner is going to need or want. This means in practical terms that the average daysailer on the sea, using an electric inboard or outboard to return to harbour when the wind dies in late afternoon, is going to have to use tide, or current, or else have sufficient batteries to ensure that a short burst of higher speed can be relied upon. Electric power would be no problem on an inland waterway, but great care would have to be exercised at sea, where the fact that a gallon (4.5l) of petrol can deliver 150 times more energy for a similar weight could prove pivotal, especially if there is a need to fight against any kind of wind or sea.

In Practice

I tried out a skiff with a Minn Kota engine, the actual motor underwater in a pod, directly driving the propeller for energy efficiency, and though the engine handled like any other, the silence and lack of vibration was surprising and very pleasant. The wooden dinghy Ample was converted from a petrol engine to an inboard electric with six 6V batteries under the main thwart, and starts and stops with a turn of a key. Later I wafted up the Thames in the 30’ (9.1m) Edwardian style river cruiser Wagtail, powered by a 3kW electric inboard with two banks of twelve 6V batteries under the seats (weighing about a ton) capable of pushing us along at 6mph. At 5mph we could have had a range of 50 miles (80km), or at 3.5mph, a range of 140 miles (225km), a full week’s cruising. The controls were smooth and responsive. The only noise as we swept along at 4mph using 12 amps was a whispering sound of the brushes on the commutator, and the slap of the waves on the hull. I’ve rarely seen so many kingfishers, suddenly surprised by our presence.

Electric boating is back to stay. Hopefully the Electric Boat Association, the Thames Electric Launch Company and others in the field can help us re-experience the acceptance it enjoyed fully a century ago, now we realise the need to reduce our energy profligacy. It could greatly reduce noise and pollution throughout our inland boating waterways, and who can argue with that?


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