Free electricity for Christmas?

I've been approached by a local group who are interested in putting on some 'green' Christmas lights in the High Street this year using pedal power.
I was sent a document outlining the idea but, unfortunately, it seems to be based on a lot of press reports of other schemes which I suspect have cost a lot more than their nothing pence target ...
Now my background is electronics, so I've never had any dealings with generators other than the Miller dynamo on my mum's old bike (pre-war, 28" wheels, cast iron frame, no gears) which was handed down to me over half a century ago. Oh yes! There was also the little motor from my Trix construction set when I was about 10 which could be made to light a 2.5V torch bulb - just!
I've stripped out all the 'why we should do this' and so on bits out and a lot at the end - which does mention the H&S aspect, by the way. What follows are the sections I've commented on - including my comments, of course.
What does the team think? Has anybody ever got involved with anything like this before? And is my car alternator idea worth pursuing?
The originator already confesses to having zero electrical knowledge, so I don't think that point needs further elaboration!
============================================================ ] PRECEDENTS OF PEDAL POWERED LIGHTS
I do so love it when journalists get involved with technical matters – they can be a constant source of mirth unless, of course, anybody makes the fatal mistake of taking them seriously!
] - Belsize Park, London ] <http://www.hamhigh.co.uk/news/belsize_eco_boys_put_pedal_to_the_metal_1_ 727643>
Doesn't say they managed it - just an appeal for bits. "We are currently looking for an old exercise bike, a small 12volt generator and a battery ..."
] - Chorlton, Greater Manchester ] <http://menmedia.co.uk/southmanchesterreporter/news/s/1183002 _celebrating_a_pedalpowered_christmas>
Better, but "The turbine costs £500 ..." etc.
] - Copenhagen - UN Climate Summit: ] http://news.bbc.co.uk/1/hi/world/europe/8387187.stm
Hardly sounds like one 80V 300W generator (see below) ... "a number of bikes are (each) connected to a different section of the tree ..."
] - Video of Copenhagen (larger-scale than ours will be - but same principles) ]
http://www.youtube.com/watch?vYJYRyzSfz4

Unfortunately, you don't see what they are using for generators!
] - Make Your Own Xmas - Rob and Roberta Smith at Tate Britain ] http://www.tate.org.uk/britain/exhibitions/makeyourownxmas/default.shtm
Reading between the lines, this was all done commercially (see last paragraph) at an undisclosed cost. The only thing free about this is the cycling!
] - Electric Pedals bicycle generator: <http://electricpedals.com/shop/bicycle - generator/>
300W ...? One horsepower = 746W so 300W is nearly ½ hp! 300W is actually 0.4hp but this is assuming 100% efficiency! If 80% efficiency could be achieved, the physical input would be ½ hp.
I note they have a ‘shop’ but no pricing or any way to place the order ... Weird?
Delving further, we find: http://electricpedals.com/shop/bicycle-generator /
Ah! This bit mentions "a 10m high tree with 2400 LED lights powered by the public using 10 bikes and generators ..." So that's 240 LEDs per bike - but no mention of the power demand of each LED ...
There is some further info on the Tate tree, though: "an 11m high tree with 30 halogen bulbs powered by 8 bikes ..." but, again, no details of the bulbs' consumption but if we assume 12V 10W bulbs, that's approx. 4 per bike, so 40W per bike. Finding suitable bulbs in weatherproof enclosures won't be cheap, though ...
Perhaps this will help? http://electricpedals.com/how-it-works /
At last, some more realistic figures! "An average human can maintain 40 to 50 watts for an hour or more ..." - a tad short on the previous 300W then! Oh yes, the generators: "Recycled 250 watt electric-scooter motors work a treat ...". Have you got a source for these ...?
] TECHNICAL SPECIFICATION FOR PEDAL POWERED LIGHTS
] - Motor - expect 0 to 80volts (the faster you pedal, the higher the voltage); ] can generate over 300watts.
Rubbish! No way can you expect an average person/bike to expend ½ hp continuously (See above) As for 80V, I’d expect a 12V motor (under load) to generate something more like 12V! You might also like to look into the H&S aspects of generating anything above, I think, about 40V – bearing in mind that this is outside and almost certainly in wet/damp conditions! ] - If we want to store power, need a diode, DC/AC inverter and a battery
What is the inverter for? Assuming the generator voltage is matched to the battery, a diode simply stops the battery attempting to drive the motor/generator in the absence of physical energy (from the bike). If an AC generator is used, it also rectifies the AC to produce DC to charge the battery but note that this is a very simplified explanation though.
] - LED lights
I note that no specification is given for these! However, as the intention is to use whatever is freely or cheaply available, this comes down to Hobson’s choice, anyway ...
Environmental and physical constraints probably rule out any idea of building anything with sufficient mechanical strength from component parts – which would also be extremely time consuming.
LEDs are intrinsically low voltage devices (2 – 3V typical) but care has to be taken to limit the current through them or they can (and will!) instantly self- destruct!
Adapting available lights will depend on how they are designed to work in the first place. Low voltage lights (intended to be driven from a ‘wall-wart’) should be the easiest to match to the generator.
Mains driven strings might be a problem as it could be very difficult to sub- divide them into lower voltage strings without causing considerable physical damage. Each sub-string will then need to have its own current limiter added as there is unlikely to be more than one in the original.
It may be easier to use a DC/AC inverter here to feed the string/s with 230V AC. Note that most inverters are designed to work on 12V DC only. 24V and 12/24V types are available but less common. This has a bearing on the choice of generator.
Provided thick low voltage cables are used to minimise energy loss, inverters could be mounted high up out of reach (for safety purposes).
* Alternator alternative
If a suitable automotive expert is available, how about using a car alternator, rather than a DC generator. A scrap car can supply a complete alternator/regulator/battery set-up. (Virtually any old car battery should do – most get replaced because they can’t start a car but are still good enough for the current purpose – if you’ll pardon the pun ...)
As an alternator, as its name suggests, generates AC, rather than DC, which would ease the problem of producing a range of voltages, if required, using suitable transformers.
] NECESSARY RESOURCES - (I've deleted this section except for one paragraph I ] added:)
* Protective earth. Even a small DC generator can generate some nasty peak voltages if inadvertently run unloaded. Overall, we’re looking at a fair bit of power here, so a PE may be mandatory, even if everything is kept to 12V. Can be a bit awkward on a large paved area. Would the council let you lift one of the paving slabs ...?
] COSTS
] The aim is that they should be free, with materials obtained through ] Freecycle or donations. ] Paul Allen says there may be a small cost. LED light strings cost c. £10 for ] 50.
--

Terry

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Terry Casey wrote:

<Snip>
Exercise bike, either find one that the owner's bored with or through freecycle, longish v-belt from a local supplier, (Probably FOC if you out a plate on saying "Some parts supplied by...."), car dynamo and regulator (Not an alternator) from a scrappie, a couple of pulleys and an old car battery. If labour's free, you could even modfiy an old pushbike without too much trouble. You'll need a roof of some sort to keep the rain (And, hopefully, snow, if we get a White Christmas) off the pedaller (And, incidentally, the delicate bits), too.
Protective earth via a spike made from a length of 6mm threaded rod between a couple of slabs, as they're mostly just laid on a sand bed in pedestrian areas. The hardest thing is going to be fastening it all down so it doesn't "walk". Even that could be done with a couple of Fischer fixings into a 2 metre by 1.2 metre by 100mm thick slab just laid on the floor. You'd need to borrow a lorry with a Hiab or equivalent to position the slab. Again, a "sponsored by" plate nay get it FOC.
--
Tciao for Now!

John.

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John Williamson wrote:

God, I hate this keyboard....
--
Tciao for Now!

John.

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The freecycle pushbike (rear tyre removed to use as a pulley) is already in the plan. Interested that you prefer a dynamo to an alternator. Any particular reason? I thought dynamos had been out of favour for so long that it would be difficult to find one these days - how old does the scrappie have to be?
I like the slab anchor idea!
--

Terry

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Terry Casey wrote:

I bought a brand new dynamo and regulator ex-stock at my local Lucas agent for my Land Rover last year for under fifty quid, no exchange needed. Or speak to a scrappie that deals with old Land Rovers or Army vehicles. Some of them have 24 Volt dynamos fitted, so you have a choice of voltages.
I suggested a dynamo as they are self exciting, so will charge a totally flat battery, and don't *need* the same warning light and associated switchery as car alternators do. Just get on and pedal....
It's also easy to adjust the maximum current output to match the likely energy levels of the participants and protect the mechanical bits from overloading.

K.I.S.S. You could also potentially just crane the lot away afterwards and store it somewhere for next year as a unit.
--
Tciao for Now!

John.

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Terry Casey wrote:

1) Nick a Boris Bike (they have the genny built in);
2) Jack it so back wheel off the road;
3) Add one tree hugger;
4) Hang PV FIT contract exactly 3ft in front of treehugger's nose;
5) When treehugger expires, replace and start at 4)
Oops - not really in the spirit of Xmas???
But I'd pay to see it on youtube!
--
Tim Watts

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Tim Watts wrote:

some being a number greater than one, but in this case, less than 3.
A TOP cyclist can probably crank out 20W for an hour or so.
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The Natural Philosopher wrote:

Nearer 200W for a few hours.
Have a look at this near the bottom of the page, two of these bikes ran the sound system all night, The rear wheel jacked up and the tyre driving the 250W electric scooter motor into 2 one farad capacitors with a green led indicating how hard to pedal. Even I maintained a constant 100W.
http://energycafe.wordpress.com/category/generating-power-off-grid /
BTW if anyone comes across the horsebox with its hand made kitchen let the girls know as it was stolen in July. With it went some bright leds donated by a pv sceptic on this group and I suspect my panaflow fans ( where can I get these now Dorothy Bradbury seems to have stopped trading?).
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On 15/08/2011 21:10, andrew wrote:

Make that about 50 watts for the average shopper or commuter though. Whitt and Wilson's book /bicycling science/ is the bible on such matters.
--
Andy

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We were somewhere around Barstow, on the edge of the desert, when the
saying something like:

She's on ebay. url:http://feedback.ebay.co.uk/ws/eBayISAPI.dll?ViewFeedback2&userid=dorothybradbury&ftab=AllFeedback
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If you mean 10W halogen bulbs, possibly though, in the example quoted, the number worked out to 4 per generator.
However, the stated intention is to use LEDs which increases the numbers considerably.
If the performance of the 7 LEDs in my 3 x AAA cell torch is anything to go by, that would be very considerably ...
Of course, there is a vast variety available and it all depends on what LEDs can be sourced in suitable physical form ...
--

Terry

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Yes there was a bit on the telly last Christmas of where a group of cyclists tried to power an average family home for the day, seemed it needed some 60 or more of them to run an electric kettle;!..
I remember in the science museum downstairs in the domestic section there is a handle to crank and light up a 30 watt IIRC bulb and thats bloody hard work for any length of time;!...
--
Tony Sayer



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I remmebr that I thought it was 80 cyclists when the pout the otaster on too i.e breakfast time.

True the thing is that this energy isn;t free, people tend to forget that, if you have these cyslists cycling they need food water to enable them to continue and with the price of food nowadays well........
Why can't we run off politicians hot air or lies, surely those sources would be truely endless ;-)
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Closer to 400W. http://www.sportsscientists.com/2009/07/tour-de-france-2009-power-estimates.html http://www.nytimes.com/2005/06/14/science/14cycl.html http://en.wikipedia.org/wiki/Bicycle_performance#Energy_efficiency
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+0100 (BST)

http://www.sportsscientists.com/2009/07/tour-de-france-2009-power-estimates.html
Hardly relevant unless you've got a way of attracting the world's top cyclists to the local High Street to keep the illuminations going!
"Armstrong can ride up the mountains in France generating about 500 watts of power for 20 minutes ..."
Hardly relates to Christmas shoppers and enthusiastic children, does it?
"...something a typical 25-year-old could do for only 30 seconds ..."
So, brilliant lighting for 30 seconds - then nothing. It's a bit like a firework display with one firework - momentarily brilliant but disappointing overall ...
--

Terry

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wrote:

It was relevent to TNP's "A TOP cyclist".
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The Natural Philosopher

http://www.sportsscientists.com/2009/07/tour-de-france-2009-power-estimates.html
A casual look around would indicate that you are correct.. an electric bike with a 250 watt motor will run at about 10-15 mph, a top cyclist would be able to manage more than that indicating that they generate around 400+ watts. I doubt if I could manage 250 watts for an hour though and I doubt if there are any cycle dynamos that generate more than about 20 watts. i wonder how much power they generate on the hill sections of that toure in France (or was it Germany?).
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On Tue, 16 Aug 2011 13:45:37 +0100, dennis@home wrote:

In the TdF, even over undulating terrain, they'll do ~25mph for 5h+.

Most are 3W; some are 5W. I don't know about modern hub dynamos - mostly 5W I think.
--
Peter.
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Almost all are nominally 2.4W for front light only, or 3W for front and rear, but the hub dynamos are actually roughly constant current devices which will deliver 6W at reasonable cycling speeds if you give them twice the load. http://en.wikipedia.org/wiki/Bicycle_lighting#Output_and_optics
There are secondary dynamo lights designed to be switched in at speed (with the switch shorting across them when not used), but there's less point with modern LED lights. http://www.sjscycles.co.uk/schmidt-e6-zb-secondary-dynamo-headlamp-with-black-reflector-rim-includes-90-cm-cable-and-special-connectors-prod11200 /
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On 16 Aug 2011 18:43:42 +0100 (BST), Alan Braggins wrote:

All of mine are 3W, usually run as 2.4W and O.6W, and most are modded systems to have LED rear and 3W front.
My only hub dynamo was a Sturmey-Archer, built back-to-back with a hub brake and with a Campag. rear QR axle all in the front wheel of a trike. Bloody good light front and rear! Modern hub dynos are much better. My Father had a Miller 12V dynamo on his tandem in the late '30s - cars used to pull in and stop as their headlights just weren't competitive!

http://www.sjscycles.co.uk/schmidt-e6-zb-secondary-dynamo-headlamp-with-black-reflector-rim-includes-90-cm-cable-and-special-connectors-prod11200 /
--
Peter.
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