News

Hybrid power for London’s floating cinema

Mon, 18 November 2013

If you visit Limehouse Basin in London after dark you might well find yourself smiling at a boat lit up like a Christmas tree.

It’s actually as odd as it seems. The vessel is a floating cinema with enough room for a show, a talk or even a stand-up comedy act.

However, behind the scenes the boat, named UP-And-A-Wave, is kitted out with a fairly smart piece of hybrid engineering. Alongside the boat’s diesel is a battery bank and electric motor which can provide around 12hp for propulsion, and it’s this that usually powers the 25m craft almost silently through the canal waters of inner London, allowing for just a few moments of tight manoeuvring when the diesel engine is engaged. 

The reason for its design was that although for an initial trial period a narrow boat was hired by the arts group Up Projects to give them a small, floating event space, “people couldn’t hear properly over the noise of the diesel”, says Simon Cummin of Up. The racket proved ruinous for the impact of a dramatic moment or delivery of a punchline.

So, a quieter alternative was sought, and Hybrid Marine on the Isle of Wight came up with an all-round sustainable solution.

The boat’s 45 hp Beta Marine engine, which is only used around 5% of the time, can charge the battery bank alongside its ‘straight through’ mechanical connection with the propellers. With the power take-off to the hybrid disengaged, this also allows for the most efficient propulsive power configuration and gives the boat a turn of speed and extra redundancy if needed. In case the engine isn’t used for long enough to give a decent charge to the wet-cell lead acid batteries, these also get a top up from an ordinary shoreside electrical connection during the night.

The engine itself can be powered by pure rapeseed oil or 100% biodiesel “provided by a local company that manufactures it from waste cooking oil from the local chippies”, says Mr Cummin.

None of these elements are particularly new, being established, mature technology says Gerry Jones, the boat’s skipper: “It’s all tried and trusted. We didn’t really need anything too sophisticated like lithium ion batteries as they are very expensive and wouldn’t actually benefit us that much.” He adds the kind of power draw the floating cinema needs is quite within the capability of the normal lead acid batteries. The bank gives 400Ah at 48V, with a provision to double that to 800Ah if needed later on.

This means that, after the propulsion is accounted for, there is enough left to run projectors, PA systems, video streaming and even occasionally popcorn machines, “which need more energy than anything else onboard”, says Mr Cummin.

Interestingly, the tender that won the design for the internal space and superstructure was not from a boatyard at all, adds Mr Cummins, although architects Duggan Morris did bring in Tony Tucker of Tucker Engineers to add the necessary marine expertise. “It was a good, simple idea which was very much in keeping with the needs of a cinema, not so much curved as square.” Usefully, the cinema is designed so it can also project outside the boat to a landside screen.

Still, although the propulsion, power and superstructure design had been developed as far as possible, one basic element was missing. There was still no hull. Worse, time was running out for the allocated funding. After a number of frustrating months attempting to locate a hull in good enough condition to warrant the necessary extensive repair and refit, Turks Shipyard in London came up with an alternative, build it from scratch. “I’m rather glad they did,” says skipper Gerry Jones. “It’s built like a tank and I am much more confident about what we are relying on to stay afloat.”

However, marrying all of these disparate elements together has of course had its impact further down the line. Mr Jones explains: “Part of it has been that we’ve relied on old data, and I do mean very old data, that told us the bridge clearance would be fine for an airdraught of just over 2m. True enough if you have a slim boat that can fit under the highest point of these old arched bridges, not so true if you have a floating box like this one.” So, changes were required, included more ballasting and lowering the interior floor of the auditorium to compensate, leaving the airdraught at 1.93m.

More ballasting was distributed on the starboard side too he explains, as the half tonne of battery bank and other equipment fitted on the port side was unexpectedly heavy and gave the vessel a distinct list.

And finally, even the ‘Christmas tree effect’ that turns so many heads doesn’t actually take up much energy. It simply works by refracting light from LEDs through a hollow pattern inside the toughened windows which run along the length of the boat.

By Stevie Knight

Source: http://www.maritimejournal.com/news101/power-and-propulsion/hybrid-power-for-londons-floating-cinema

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