Edward Hawthorne, Hon. vice-president of the Electric Boat Association, outlines the history of electric propulsion on the Thames and describes present trends.

During 1898 electric boat activity on the River Thames was growing apace. The Immisch Electric Launch Co. and the Thames Valley Launch Co. each had about sixty electric launches for hire, there were about the same number in private ownership and most of the large boatbuilders had experience in building, fitting out and hiring electric boats.

In Austria electric ferries carry up to 200 passengers on trips across lakes where petrol or diesel engines are banned. It is interesting that the original electric boats on the Thames were designed as ferry boats for use in the Pool of London. Recently Hammertons of Twickenham opened the first Thames electric ferry since the end of the last century.

The main components of an inboard electric propulsion system (DIY kits are becoming available for those who wish to do their own installation or conversion) are:

Batteries: The batteries of 1896 were lead-acid 2-volt single cells with removable plates and with a typical capacity of 30 watthours/litre. Today's batteries store 100 watthours/litre in a sealed 6 volt monobloc containing 3 cells. Liquid electrolyte is the most common in use but gel electrolyte cuts out the need to top up, although at some slight loss in performance. Batteries can be the most costly item in the electrical system and users are therefore acutely interested in the life which can be expected. Most industrial battery applications are rated at a life of 1500 cycles equivalent to 5 years of normal industrial usage, but the lower usage of most boats means that, if properly treated, modern batteries should last at least seven years and lives of 10 to 15 years have been quoted. The golden rule is never to overcharge and try not to discharge more than 80 per cent of capacity.

Motors: Until recently, the motors used in boats were standard industrial DC series types with axial armatures and run at speeds at which they could be directly coupled to the propeller. A typical 1.4kw motor would have dimensions of 11in x 10in diameter, a weight of l00lb and an efficiency of about 80 per cent. Motor size can be reduced by increasing motor rpm and fitting a gearbox as in the Brimbelow E drive system. However, during the last ten years the radial armature motor reinvented by Cedric Lynch has been developed and is increasingly being used. Not only is such a motor much smaller (eg a 5" x 8" diameter motor will provide 1 to 8.5kw continuously and weigh 241b) but the efficiency is 90 per cent, thereby adding 11 percent to the boat's range. One snag is that these motors run at 2000 to 4000rpm and have to be geared down to the propeller.

Controllers: The Curtis pulse modulated controller based on solid state technology is fitted in many electric boats and provides infinitely variable forward and astern speeds. This probably enhances the reliability of batteries and motors by providing smooth changes in speed although there are a few percentage points of loss. The traditional switch system, usually giving up to four forward and two astern speeds is now very reliable, cheaper and quite satisfactory for the smaller boats. There are no losses in the switch but corrosion and arcing can occur and may reduce life.

Chargers: For dinghies and small boats fitted with only one or two batteries it is usual practice to take the batteries out and charge them on the land. If enough time is available, trickle charging can be used but it is always better to use an automatic charger in order to avoid any risk of overcharging. Traditional chargers are transformer types, but the new high frequency switching technology can reduce charger size and weights by up to 80%. Most boats larger than dinghies carry their chargers onboard with a normal 13 or 15 amp cable carrying the mains supply to the boat. Many pubs and the like are prepared to allow boat-owners to plug in - "a pint and a charge, please", as Lord St. Davids used to say to the landlord. Virtually any powered leisure boat can be electric but it is important to match the electrical system to the boat's operational requirements, the essence being to reconcile speed and range. Batteries are limited in capacity (i.e. ampere-hours); speed is a function of power which at a given voltage is itself a function of current flow (i.e. amps). Therefore the higher the amps the higher the speed but the lower the running time. A 21ft open launch may require a current of 50 Amps at 48 volts to reach a speed of 6.5mph with a range of 36 miles, whereas at 5 amps and a cruising speed of 3 mph a corresponding distance of about 170 miles could be achieved. For example, the EBA 24-hour Endurance Record on a single charge for a battery powered 31 ft saloon launch is 116 miles at an average speed of 4.8mph. Contrary to popular belief, electric boats can go fast. Lady Arran established the world speed record of 50.8 mph in 1989 only to have the Americans capture it at a speed of 70.6 mph in 1996.

(The above article appeared in "The Boater" magazine, June 1998)

Electric boating is currently enjoying a worldwide revival, yet at the turn of the
century there were 100 electric launches on the Thames alone.

1834 IMPERIAL RUSSIA:
German physicist Moritz Hermann Jacobi presents a paper to the St. Petersburg Academy of Sciences about electromagnetism as applied to machines. Four years later Tsar Nicholas I grants Jacobi enough money to design and build an electric motor to be fitted to a ten-oared shallop.

The engine Jacobi built comprised electromagnets to drive two paddlewheels (propellers were as yet unheard of). The general arrangement proved successful and the electric paddle-boat began to voyage up the River Neva, applauded by the Tsar and his Court. But the motor gave out as much nitrous fumes as smoke from a steam train. The brave pioneers, choked and asphyxiated by these sickening and suffocating fumes, were obliged to stop their observations. The following year Jacobi tried another experiment with the same boat. It was worked by a battery a fifth the size of the previous one. Following the recent formula published by British physicist William Grove, it was charged with concentrated nitric and sulfuric acid. The vessel attained an average speed of 3 mph with some 12 or 13 passengers aboard.

In August 1848 an electric boat was demonstrated on the private lake of Penllergaer near Swansea, Wales. It was propelled by a motor developed by Benjamin Hill, sponsored by John Dillwyn Llewelyn, again deriving its energy from a Grove cell.

Twenty years were to elapse before a certain Monsieur de Molins launched his electric paddleboat in the Bois de Boulogne lake. Despite her strong electric batteries (developed by Robert Bunsen and using carbon electrodes instead of platinum) the boat started slowly, disappeared behind the island which forms the centre of the lake, and did not reappear.

Disinterest continued over this promising form of motive power until a Parisian electrical precision instrument maker, Gustave Trouve, arrived on the scene. In May 1880 he patented a small 11lb (5kg) electric motor and described its possible applications (Patent N°136,560). Trouve suggested using two such motors, each driving a paddle wheel on either side of the hull. Later he progressed to a multi-bladed propeller. Modifications to this master patent date from August 1880, then March, July, November and December 1881. To quote: “It is the rudder containing the propeller and its motor, the whole of which is removable and easily lifted off the boat…”

With this invention, Trouve could not only lay claim to the world’s first marine outboard engine but, in taking the same motor and adapting it as the drive mechanism of a Coventry-Rotary pedal tricycle or velocipede, Trouve also pioneered the world’s first electric vehicle.  On 1 August 1881 Trouve made his benchmark report to the French Academy of Sciences, stating: “I had the honour to submit to this Academy, in the session of 7th July 1880, a new electric motor based on the eccentricity of the Siemens coil flange. By suggestive studies, which have allowed me to reduce the weight of all the components of the motor, I have succeeded in obtaining an output which to me appears quite remarkable.

A motor weighing 5kg [11lb], powered by 6el of Plante producing an effective work of 7kgm per second, was placed, on the 8th April, on a tricycle whose weight, including the rider and the batteries rose to 160kg [352lb] and recorded a speed of 12km/h.

The same motor, placed on the 26 May in a boat of 5.5m long by 1.2m beam [18 x 4ft], carrying three people, give it a speed of 2.5m [per second] in going down the Seine at Pont-Royal and 1.5 m [8 & 5ft] in going back up the river. The motor was driven by two biochromate of potassium batteries each producing 6el and with a three-bladed propeller.

On the 26th June 1881, I repeated this experiment on the calm waters of the upper lake of the Bois de Boulogne, with a four-bladed propeller 28cm [11 ¼in] in diameter and 12el of Ruhmkorff-type Bunsen plates, charged with one part hydrochloric acid, one part nitric acid and two parts water in the porous vase so as to lessen the emission of nitrous fumes. The speed at the start, measured by an ordinary log, reached 150m [490ft] in 48 seconds, or a little more than 3m [10ft] per second; but after three hours of functioning, this had fallen to 150m in 55 seconds and after five hours, this had further fallen to 150m in 65 seconds.

One bichromate battery, enclosed in a 50cm [20in] long case, will give a constant current of 7 to 8 hours. There is a great saving of fuel and cleanliness.”

During the 15 years that followed, it is estimated that over 100 Trouve electric motors were installed in pleasure launches. Some of these were fitted with his electric headlights and klaxons. There was, for example, the Sirene, a charming electric boat which he built for Monsieur de Nabat, arranging it so that her owner could change at will from propeller to paddles. This boat, whose owner used her three times a week during long periods, measured 29ft 6in long by 6ft beam (9 x 1.8m) and cruised regularly at between 8 ½ and 9 ½ mph (14-15km/h), her propeller turning at between 1,200 and 1,800 rpm.

To show the speed with which an electric boat could move in a race situation, on 8 October 1882 a Trouve craft was launched onto the River Aube and steered onto the race circuit only five minutes before the start. It left at gunfire and spectators noticed, not without astonishment, that in this famous race the boat covered more than 2 miles (3.2km) in 17 minutes, averaging 7mph (11km/h) and slowing down to make four turns around the buoys!

In September 1888 a Trouve boat was sent to China to fight against opium smuggling on the China Sea. 49ft (15m) long and steel-hulled, it weighed some 8 tons and the bronze prop had a diameter of about 20in (500mm). One can but wonder at the electric power necessary to shift her along.

The idea had caught on elsewhere. The iron-hulled 25ft (7.6m) Electricity, designed by the brilliant Austrian-born Anthony Reckenzaun, was built for the Electric Power Storage Company at Millwall, London, to accommodate 12 passengers. Power came from 45 Plante accumulators, modified by Messrs Sellon and Volchmar to total 96 volts and supply power for six hours at 4hp to two Siemens D3 dynamos with regulators and reverse gear, belt-driving a 20in screw propeller of 3ft pitch (500mm x 0.9m) at 350 rpm. Either or both motors could be switched into circuit at will. On 28 September 1882 Electricity made a pioneering trip on the River Thames to London Bridge.

Two years later a race took place between Electricity and the electric launch Australia from Millwall to Charing Cross Bridge and back to Greenwich. There is no record of which boat won, but apparently Australia was very slightly ahead at Charing Cross on the way upstream!

The accumulators were manufactured by the Electric Power Storage Company to drive Immisch motors of from 1.5hp up to 12hp, at 65, 95 and 120 volts, and give with certainty a run of 30 miles at 6mph, half upstream and half downstream, on one charge.

In 1888 there were half-a-dozen charging stations on the Thames, but by 1902 there were over 20 on land and two floating barges. At Maidenhead alone, seven electric hireboat operations jostled for business. During the same period, over 50 British boatbuilders are known to have built one or more electric launches. Most of these were Thameside yards. Launches were also exported to Venice, Ceylon and South Africa, while Eastern princes and rajahs received sumptuously fitted-out vessels.

The Thames Valley Launch Company of Weybridge, Surrey, offered 29 launches for hire, many of which were fitted with feathering propellers. Messrs Andrews & Sons of Maidenhead had a fleet of 12 electric launches, each one named after a freshwater fish, with an additional flagship called the Angler. It was on the Angler that King Edward VII, Queen Alexandra and a royal party enjoyed the pleasures of the Thames.

Elsewhere, British electrical boat pioneer Anthony Reckenzaun and his brother Frederick, emigrated to the USA and settled in Newark, New Jersey. Using experience gained with the cross-Channel Volta and other vessels, they built for their own use a 28 ft (8m) launch which they named Magnet, with a 2.5hp, 420lb (191kg) Reckenzaun motor powered by two banks of accumulators made by the Electric Accumulator Company of Newark. The vessel was reviewed by Thomas Martin, Editor of The Electrical Engineer, who described a voyage of 50-60 miles without recharging, so supporting the Reckenzauns' claim of 60-70 miles over 10 hours.

It was in 1891 that the fabulously wealthy WK Vanderbilt became the first American to order an electric boat. It was built at Charles L. Seabury's yard, measured 30ft (9m) in length and was called Alva. In terms of length, US millionaire John Jacob Astor sported the largest privately-owned electric launch in the world: the 72ft (22m) Utopia had two motors each developing around 25hp and was luxuriously fitted out like a miniature Titanic. The largest electric passenger boat in the world, however, was the 93ft (28.4m) Victory, designed by William S. Sargeant in 1904 and licensed to carry 350 passengers above Westminster Bridge.

The main reason for the decline of the quiet and clean electric launch in subsequent decades was the development and ease of refueling of the more powerful diesel engine. Since the late 1970s, however, there has been a revival of interest in electric boats for pleasure boating on the inland waterways around the world. Better underwater hull designs, lighter glass-fibre construction, improved motors and batteries and electronic control and recharge systems have given birth to a new generation which is already contributing more environmentally friendly pleasure boating for the 21st century.

Electric offshore: time to plug in?

The past may have been electric, but electricity could also save us from a polluted, fossil-fuelless future. In fact diesel and petrol engines are to be banned in Friesland before too long. Electric boats are becoming commonplace on Britain's inland waters, Broads and rivers, but no-one seems to have taken electric power seriously as a direct alternative to diesel engine in an offshore cruising yacht. Yet the technology, arguably, is so nearly there.

Back in April 1998 we ran an article entitled 'The quiet revolution' about an American invention that could just be that. Developed at a cost of $ millions by NASA to power its Mars Rover, the Electric Wheel would seem ideal as a marine engine. As we write there's a 50ft (15.24m) wooden Herreshoff-type being fitted with a derivative of the space buggy's propulsion system in a traditional South Coast boat yard. A yacht that once had a 45hp diesel will make do with a 10kW Wheel, her existing Fischer Panda 15kW generator topping up a hefty bank of 10, 220amp/hour carbon fibre batteries. There'll be solar panels and a wind generator too.

Dave Tether of Solomon Technologies, which is developing the system, fitted the prototype to his 33ft (10m) heavy displacement cruising yacht to replace a 22hp diesel. From a bank of ten deep-cycle marine batteries weighing 500lb (226.7kg), the 50lb (22.7kg) Electric Wheel, rated at just 4.5kW, the equivalent to 6hp, could move the 9-ton Seaward at 6 knots for six hours. Uncoupled from its shaft he also uses it to haul his boat up the slip at season's end…

So how come a 6hp electric motor can do the job of a 22hp diesel? Simply speaking, diesels only develop maximum torque near the top of their revs; electric motors do so from start-up. To put it in perspective, a 20kW Wheel puts out as much torque (150ft/lb) as a Ford Mondeo's 2-litre petrol engine.

Eighteen months later Tether reports that, although he has a small 1.5kW Kawasaki petrol generator on board Seaward and charging facilities at the dock, he has never had to recharge the batteries. Why? Because, when she's under sail, the Wheel works in 'reverse' as a dynamo, turned by the trailing propeller, topping up the juice extracted by the device in propulsive mode. Clever, huh (as the Americans would say). "It's an 80 per cent efficient generator," says Tether. Apparently it will, in nanoseconds, switch from power to charge mode while the yacht is motoring, ie. slide down a wave, and it will start charging. And given that the ratio of sailing to motoring time of the average sailing yacht is, perhaps, 4:1 that gives plenty of time for charging. "But for Pete's sake don't use the word perpetual motion," says Tether. There's no magic involved.

The Wheel (incidentally, it's waterproof, so will live quite happily in a dank, wet bilge) is still in pre-production stage; the price for a 4kW model (equivalent to an 18hp diesel) is currently $7,500. But next year Tether is predicting a price of $5,500 and $4,500 the year after. A typical, high-revving Japanese 18hp diesel currently costs around $6,500. And that's without the tank, fuel system, exhaust and sterngear.

Clearly the costs will need to drop considerably before the Wheel - whether you fully believe its claims or not - stacks up directly against a conventional diesel installation, especially in small yachts. But what about more conventional electric motors, such as Brimbelow's E-Drive and the various Lynch motors that currently power a host of river craft, such as Creative Marine's Firefly and Frolic, Swancraft's Mayflower, John Williams Bros' Dearest and even the National River Authority launches? Could a 5kW electric motor power a 25ft (7.6m) long-keeled, heavy displacement cruising yacht, bearing in mind that it would primarily be used to get her into and out of harbour? How many batteries would she need, and how many hours of motoring at what speed could we expect?

Jim Keating, past chairman of the Electric Boat Association and managing director of DesignEta, believes it is just feasible. He suggests marrying a 5kW Lynch motor, with a bank of six, 12V Chloride leisure batteries, providing 36V x 160a/hrs and calculates that, in flat water, just 1kW (1.5hp) of the available 5kW would be sufficient to propel her at about 4 knots. "There would be 4kW of additional power available for use in heavy weather, maneuvering, towing or high speed dash to 6 knots, maximum," he says.

The drive would be by toothed belt to the shaft, geared down to turn at an efficient 960rpm at full power (600rpm/1kW would give 4 knots). The batteries would be mounted as low as possible, and positioned to trim the boat correctly. "Then maybe the ballast weight could be reduced," says Keating.

At 6 knots, Keating expects 1.5 hours of silent running (not much, admittedly but enough to get a cruising yacht out of trouble, perhaps), 2.5 hours at 5 knots or 5 hours at a more realistic 4 knots. At this speed a small 30lb (13.5kg), 1kW 230V AC petrol generator running in the fo'c'sle or cockpit locker and linked to a high output 'smart' battery charger (not a household trickle charger) could, in theory, 'keep pace' with the motor. Its 2.3 litres of fuel would last up to eight hours. Flat out, generator running, would eke out your endurance to, perhaps, 3 hours, but all these scenarios presuppose some sort of small (and possibly pricey) box between alternator and battery terminals to sense battery state.

The efficiency of such a 'hybrid' system might only be around 35 per cent, but diesels are no better than 30 per cent. "And a generator running at a constant speed is more efficient than the conventional engine," says Keating. Apart from the whir of the motor and the hum of the generator, concealed in its soundproof box up forward, such a system would be mercifully quiet and vibration-free. "If you anticipate low use of battery power, then consideration could be given to using a wind generator or solar cells," says Keating. To fully recharge our batteries would take the little AC generator 8-12 hours, or a tank full of fuel.

A viable alternative might be a DC generator, as fitted to Whitbread yachts. A 1.8 kW diesel generator, charging a bank of three 190a/hr deep cycle carbon fibre batteries at 50 amps, would replenish them in about 12 hours from dead flat.

"The key to it all," says naval architect John Perryman, "is to dispense with the generator and exploit the self-generating properties of a DC motor such as the Wheel being 'driven' by a variable pitch propeller when the yacht is sailing." At its simplest this could be of the Swedish type, whereby a rod is manually moved to alter the pitch until the optimum charge rate is reached, then feathered when the batteries are full.

"Fit a Kort-type nozzle around the prop," John adds, "and you could improve thrust by as much as 40 per cent, which also means 40 per cent improvement in battery duration."

It all sounds tantalizingly close. Jeremy Freeland of Bossoms Boatyard, which builds a 4.2 ton displacement, long-keeled cruising yacht currently fitted with a 9hp diesel, is more cautious. "The positive factors," he says, "are quiet and pollution-free running, better weight distribution and less space than a diesel, especially if batteries are used as ballast. The best place for them would be under the floor, to augment about 1.3 tonnes of encapsulated lead shot ballast, as opposed to 2 tonnes. And they'd need to be well vented."

But no small electric motor, he reckons, would punch a 4-knot tide; running time from the battery bank, unless it was huge, would be short and the cost would be about 1,300 pounds more than a 9hp diesel. "In a nutshell, the standard diesel can not be replaced by an electric motor on a sailing craft where a similar performance is required," he concludes. "Electric power is suited to inland use where better hull shapes and still water is more the norm."

New technologies could change all this, the most exciting being the so-called 'fuel cell'. Zemar's electrochemical engine (ECE) combines hydrogen (carried in a fuel tank) and oxygen (from the air) to produce electricity and water, storing the energy in batteries for use by the electric motor. The only bi-product is pure water. Noiseless and cheaper to run than a conventional engine, the ECE is claimed to be "the marine power of the millennium". No moving parts, running on a fuel that is safer than petrol or LPG (forget the Hindenberg; hydrogen can be safely stored these days) the ECE's only drawback is a current cost of 7,500 pounds for 5kW.

Victron Energie's new Sterling engine, patented by a Scot in 1816 and best described as an 'external combustion engine', is another idea waiting its time. Used to drive a generator, it is said to be 90 per cent efficient. Noise levels are that of a fridge.

Again, it's too expensive for the owner of our little cruising yacht. Perhaps an ECE/Wheel combination will one day provide the solution. But even with the technology available now, the argument of diesel vs electric is not as one-sided as it once looked. If the sound of your diesel is getting on your nerves, the answer may lie in a hybrid system and, more pertinently, a commitment to doing it wherever possible under sail - the ultimate energy-saving device, invented over 5,000 years ago.

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