Solar Powered Tandem Recumbent - Solar Pedal Assist

[launchpad]

Is there a better beast to convert to fully solar?

Starting base: Greenspeed GTT. We have had this baby for about 10 years. Done lots of kms including a couple of 600 km tours.

If people can carry canoes on their H-bars, why can't we carry solar panels?

Current Configuration:

Greenspeed GTT (including SS couples - packs away in a bike box - seats in a bag)
240W Solar Panels on custom made frame.
Genasun GV Lithium Boost MPPT controller to get maximum juice out of cells
Sky RC Watt Meter to measure power going into battery
Cycle Analyst 3 - to monitor power consumption and manage torque pedal assist. Speed limited to local laws of course. CAv3 = best thing since sliced bread
Thun Torque sensor on front crank - this is a true pedal assist and greatly extends battery life while keeping us honest
Golden Motor Magic Pie 3 - the solid aluminum casted wheel good for this trike.
Current 36V 16A LiFePO4 battery (about to be replaced by 20A).

Total weight with 2 riders, about 200 kg.

Does it work? Damn right it does. On our first couple of 40km - 60km rides, we have returned with a full battery (still with tired legs). Gets us up hills at a respectable 15km/h (about double what we did before solar assist).

 

[swbluto]

How many watts you getting?

 

[launchpad]

How many watts you getting?

Winter here currently, but we are peaking about 170 W of max 240W. Still to work out the watt hours, but our consumption and production during normal trips are equal.

Now doing some hill trials and will post some numbers shortly.

 

[swbluto]

How many watts you getting?

Winter here currently, but we are peaking about 170 W of max 240W. Still to work out the watt hours, but our consumption and production during normal trips are equal.

Now doing some hill trials and will post some numbers shortly.

Oh wow, you have some really nice winter weather! That's pretty cool. Pretty good wattage! That's capable of going like 25kph on the flats?

I think your design is pretty neat. The length of the tandem design makes it easy to put a lot of solar panels on it, while the recumbent trike style is pretty aerodynamic. I'd want to build something like that if there was a good place to put it on USA's roads.

 

[launchpad]

That's capable of going like 25kph on the flats?

Correct. As a pedal assist, we are cruising at 25km/h on the flat using about 80W. So battery remains topped up for those "dang" hills. On an average grade we are pushing at 20km/h using around 300 - 400W. Interestingly, the torque sensor cannot pickup the stoker as she is only on my left pedal so is seen as a constant torque. However the cycle analyst is good enough to compensate and gives a fabulous kick as we hit the inclines.

 

[Danny Mayes]

I love this!

What a cool ride. Congratulations on your achievement

D

 

[bowlofsalad]

I love the concept of pairing solar with an ebike, I am a little envious. It might not always pay off, but when it does, it's good news. Speaking comparatively, the cost of more batteries with their weight versus the weight of the panels and their cost, which do you feel is worth it? I have put a lot of thought into solar panels and their pros and cons, clouds, rain, night and things like that really put a damper on the concept of solar for myself. I often imagined putting the panels on a trailer of some kind. In addition to that, I often imagined affixing flexible solar panels to some kind of framing to make a mild form of fairing or something to that degree.

What tires are you using? How is the ride? The tires look pretty fat but they look like marathon tires.

What is the weight without the riders?

How did you decide on the height of the solar panels? They look a bit high, but it's hard to know for sure. It's a little hard to tell how those panels are attached to the bike. Attaching the posts for the solar panels can seem like both a great and bad idea. The worry I have in my mind is imagining a great gust of wind either flipping the trike, breaking the seat, or some or all of the solar panels simply ripping/breaking off. Though, not incredibly common, I have heard of recumbent seats having issues with cracks and breaks here and there. I imagine that attaching the panels to the seats might add a lot of stress to the structure of the seats.

Personally, if it were me, I'd make a bike/trike out of square tubing and weld the posts (if I was going to have the panels over head as you did) for the panels to the frame itself. I am sure you've really thought out lots of those stuff yourself, I hope you aren't offended by these suggestions, a different perspective can be worth a sealed lead acid batteries weight in gold.

The pictures look like you are lacking a front light. I can't tell for sure though. That tricycle seems unusual to me in that it looks like it lacks a front derailleur mount. Maybe it's there and I am simply missing it, but that might mounting certain things a little tricky. Anyway, what I did for the light as I got a 30 dollar 12w LED light from ebay that is discussing in http://endless-sphere.com/forums/viewtopic.php?f=31&t=35095&start=150 this thread. I plugged the light into my cycleanalyst (CA 2.3) through the plug that came with the CA and a female plug (mentioned in linked thread) I got at radio shack. Very worth it, very excellent.

 

[swbluto]

I love the concept of pairing solar with an ebike, I am a little envious. It might not always pay off, but when it does, it's good news. Speaking comparatively, the cost of more batteries with their weight versus the weight of the panels and their cost, which do you feel is worth it? I have put a lot of thought into solar panels and their pros and cons, clouds, rain, night and things like that really put a damper on the concept of solar for myself.

I get the feeling he's in the land down under, mate. I get the feeling that changes the solar calculus a bit.

Don't know where you live, but I'm guessing somewhere near the pacific northwest. Somewhere... I understand sunny days seem to be mostly in the summer time. I'm still waiting for "the perfect day" for my solar recumbent trip, lol.

 

[veloman]

Reminds of SolarShifts trike.

Good job

 

[launchpad]

I get the feeling he's in the land down under, mate. I get the feeling that changes the solar calculus a bit.

Yes, sunny Queensland, Australia. State motto used to be "Beautiful one day, perfect the next". Lack of sunlight tends not to be the issue. The photos above were taken around the winter Solstice.

I hope you aren't offended by these suggestions, a different perspective can be worth a sealed lead acid batteries weight in gold.

Never. I don't claim to have any answers, only lots of questions..." What answers I do have I have listed below:

Let me preface below by pointing out this is a Greenspeed Tandem (GTT). It is a limo of tandems including 5xSS couples, Schlumpf mountain drive, magura light automotive disc brakes, SRAM dual drive, etc. Its not a cheap trike to start with but the build quality is exceptional. I have tended to go for the most efficient options with price a lesser consideration.

Cost of batteries vs Solar Panels:
1) Battery: 36V x 16AH. Cost $ 615. Single most expensive component.
Weight: 8kg
2) Solar cells (light weight semi flex) 4 x 50W ($90 each) + 2 x 20W ( $36 each). Add shipping - see http://www.eco-worthy.com
Weight 50W @ 1.85kg each 20W @ 0.95kg each
Rack (steel not aluminium) 4 kg.
Don't forget your electrics - wires, connectors etc.
3) NEED MPPT controller. This gives the most efficient power into the battery from the solar cells. My research showed the Genasun was likely the best. Not cheap at $300 but we take the longer term view.

Total weight overhead = 9.3kg (+ wires). Additional battery - 8kg. The solar cells are cheaper but slightly heavier , but the extra battery won't charge itself...

Lights: We have 6 front lights (tioga, cateyes) mounted front and 3 red tiogas mounted back. (1/3 on the trike, 2/3 on the rack) All independent powered.

Tyres: Good observation. 3 x Marathon plus - near puncture proof. They need to be able to take our total weight of about 200kg. (Were Big Apple).

Trike Weight (sans riders): About 62kg

Height of Panels. We are using the standard H-bars that came with the trike. The panel is easily removed by one or two persons - slides in or out. The height is 47cm above the seat tops (about 117 cm off the ground). The height is excellent for entering and exiting the bike. It does raise the C.O.G and we avoid going sideways on steep slopes. We have yet to experience strong buffeting winds - something we need to consider and test.

I would recommend removable panel rack above. It means on those moonlight nights we can ride and see the stars or elect to put on the rack and use our extra lights. On our shopping runs - we may or may not have on the panel as they are well within pedal assist battery range. Also, I can set the solar rack up adjacent to the trike and adjust its angle perpendicular to the sun for maximum W.

We will monitor the stress on the bike seats (which themselves are fully removable/replaceable). The panels are all bolted to the square steel frame and bolted to themselves. I don't think they will be dislodged but you point about tipping in strong winds is valid. However, down hill at 50km/h showed no handling difference except the steering being a bit heavier (not surprisingly).

No front derailleur on the tandem. Pedals captain vs stoker are 90deg out of phase so that someone is always in the power stroke. Confused the hell out of the thun torque sensor on the front - remedied by CAv3 custom torque setting.


Regards, PW

 

[iowadoc]

Any updates or changes to the GTT and solar panel or pedal assist? I am interested in converting one of my 2 GTTs into a solar powered tandem and find your information extremely valuable. Any info would be greatly appreciated.