Solar panels idea

[Andy]

I've got a charger question running in another thread - this is another idea I've got for my bike

Would I be doing more harm than good if I stuck some solar panels on my bike to keep it trickle charging when I'm out using it?

Also What if I tried to run the whole bike that way, with very slow, constant voltage from solar panels rather than a jolting charge every now than then? Would that break the batts quicker, or make them last longer?

(The batteries are 3 x 12v, 15ah, sealed lead-acid Panasonics from Powabyke btw)

 

[keithhazel]

solar pannals on bike

i have no idea whether its any good andy but check this one on e-bay that has got solar pannals..
140230772076

 

[flecc]

In general Lead Acid batteries don't mind a trickle charge, but it doesn't suit some other types. So you wouldn't do any harm, but you'd need to spend a large amount of money to get any appreciable charge in our climate even in Summer.
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[frank9755]

I think I remember reading that the Henshaws of AtoB magazine run their Lafree using entirely solar power. The panels aren't mounted on the bike but trickle charge some old SLA's which then are used to recharge the bike battery.

I don't know if solar panels have yet got to the point where mounting on the bike is feasible. Anyone know how many Watts can be generated, assuming a sunny day, per sq m and/or per kg of solar panel?

 

[Jeremy]

It's certainly possible, but the charge rate from even fairly large on-board solar panels will be very low, most probably only about 5 watts or so. Solar panels only usually give around 1/3 to 1/2 of their rated power at best, due to the vagaries of British sunshine levels and less than perfect alignment with the sun.

Most electric bikes will use around 20 to 40 watt hours per mile, which equates to about 4 to 8 hours solar charging time per mile, assuming bright sunshine. Charging a flat 10Ah 36V battery would take at least 72 hours for a 5 watt panel in bright sunshine (assuming 100% charge efficiency). In practice, charging time would be probably be double this.

The best bet for solar charging is to set up a big solar panel at home, charging a large storage battery that is then used to charge the bike. This would work well, but would be fairly expensive to set up.

Jeremy

 

[flecc]

A to B's setup was two very large solar panels on the roof of a shed, and from memory I think they cost around £360.

I think solar power in this country is pushing environmentalism a bit too far, since they cost resources to mine materials and manufacture, don't last for ever, and give such a poor return. In the present state of the technology I think they belong in permanently sunny regions.
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[prState]

The simplest incarnation is to tow around a solar panel and charge up your portable battery devices or whatever. See here:

YouTube - Towing the solar wagon

If you searched youtube long enough, you could probably find something interesting to do.

 

[john]

Britain receives around 60% of the of the solar energy received at the equator and about 50% compared to the sahara desert. So solar energy is certainly not out of the question here.

Solar energy is likely to be the cheapest form of energy in only a few years due to recent developments Nanosolar - Wikipedia, the free encyclopedia although lack of manufacturing capacity and high demand will likely keep prices fairly high.

 

[ElephantsGerald]

The best bet for solar charging is to set up a big solar panel at home, charging a large storage battery that is then used to charge the bike.

Using solar panels to charge a battery bank which you then use to charge your bike battery is rather inefficient and expensive. You need panels, a battery bank, a solar charge/controller (to manage the charge process) and an invertor to get useful mains power back out of the battery bank.

If you're serious about solar you'd be better off permanently installing solar panels and a grid-tie invertor at home. You'll still need plenty of money, but the end result is better .

A piece of kit like the Mastervolt Soladin Grid Tie Invertor will allow you to connect up to 600Watts of panels into your household mains supply. This item only costs about £400, so its a (relatively) cheap way to get started with solar.

With a grid-tie invertor the electricity supplied by the panels/invertor goes directly into the mains and is used to run household appliances (e.g. a bike battery charger) plugged into your normal ring-main sockets. If the panels/invertor aren't supplying enough electricity, the shortfall is taken from the national grid. If the panels/invertor are supplying too much electricity then it goes back into the national grid and your energy supplier will pay you for it. Marvellous!!!

Unfortunately panels aren't cheap; you could start with a single panel (e.g. a Kyocera 130Watt Panel for £550), then buy a couple more when you're feeling flush. Its also possible to get grants for solar installations.

Bear in mind that the rating of a panel assumes ideal conditions (not something that happens much in the UK). This PV calculator helps estimate how much power you can realistically expect to generate in various latitudes/longitudes around Europe.

Using the calculator I could expect a yearly output of 114KwH from my (theoretical) £950, 130W installation in rural Herefordshire (obviously you get more in summer and less in winter). On that basis you're going to have to really want to use solar because its going to take years (decades even) to recoup the investment. Roll on cheap solar panels!!

 

[john]

Here is the kind of setup you would need to charge on the move:

 

[flecc]

Britain receives around 60% of the of the solar energy received at the equator and about 50% compared to the sahara desert. So solar energy is certainly not out of the question here.

Solar energy is likely to be the cheapest form of energy in only a few years due to recent developments Nanosolar - Wikipedia, the free encyclopedia although lack of manufacturing capacity and high demand will likely keep prices fairly high.

These sort of things have been said for years now, but the fact is that solar power in the UK is horrifyingly expensive and cannot begin to make economic sense, and it isn't likely to within decades. The percentage proportions of sunlight have little value when the panel efficiencies are so low still, needing to run at peak input to be any good.
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[john]

These sort of things have been said for years now, but the fact is that solar power in the UK is horrifyingly expensive and cannot begin to make economic sense, and it isn't likely to within decades. The percentage proportions of sunlight have little value when the panel efficiencies are so low still, needing to run at peak input to be any good.
.

If you install a solar PV system on your house today (in the UK), the cost of electricity will be about twice what you would pay from the grid (mainly fossil fuel based). The developments of Nanosolar and others will improve this considerably. These are not just "things said", Nanosolar are now in production.

 

[flecc]

As I said John. I rate something costing double as hopelessly uneconomic.
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[Jeremy]

Using solar panels to charge a battery bank which you then use to charge your bike battery is rather inefficient and expensive. You need panels, a battery bank, a solar charge/controller (to manage the charge process) and an invertor to get useful mains power back out of the battery bank.

If you're serious about solar you'd be better off permanently installing solar panels and a grid-tie invertor at home. You'll still need plenty of money, but the end result is better .

A piece of kit like the Mastervolt Soladin Grid Tie Invertor will allow you to connect up to 600Watts of panels into your household mains supply. This item only costs about £400, so its a (relatively) cheap way to get started with solar.

With a grid-tie invertor the electricity supplied by the panels/invertor goes directly into the mains and is used to run household appliances (e.g. a bike battery charger) plugged into your normal ring-main sockets. If the panels/invertor aren't supplying enough electricity, the shortfall is taken from the national grid. If the panels/invertor are supplying too much electricity then it goes back into the national grid and your energy supplier will pay you for it. Marvellous!!!

Unfortunately panels aren't cheap; you could start with a single panel (e.g. a Kyocera 130Watt Panel for £550), then buy a couple more when you're feeling flush. Its also possible to get grants for solar installations.

Bear in mind that the rating of a panel assumes ideal conditions (not something that happens much in the UK). This PV calculator helps estimate how much power you can realistically expect to generate in various latitudes/longitudes around Europe.

Using the calculator I could expect a yearly output of 114KwH from my (theoretical) £950, 130W installation in rural Herefordshire (obviously you get more in summer and less in winter). On that basis you're going to have to really want to use solar because its going to take years (decades even) to recoup the investment. Roll on cheap solar panels!!

You can make a viable, simple (but less efficient) system along the lines I suggested for a lot less money, though.

As an example, it's quite easy to get hold of old car batteries for next to nothing, which although pretty rubbish for starting cars will still be OK for making a simple ebike charging system. A fairly hefty photovoltaic panel to charge these, plus a series/parallel switch to allow a 12V charge, but higher voltage arrangement to run a custom bike DC charger, can be had fairly cheaply.

Overall I think it would be quite possible to build a viable budget solar charging system for around £100 - £150, with a bit of scrounging and a good bit of ingenuity.

Sure it won't be very efficient, but as the purchase cost is quite low that doesn't really matter too much. The only bits that will need regularly replacement will be the battery bank, but with luck these might be obtainable for free. Even so, the repayment time would be quite lengthy. It would take around 2500 to 3500 "free" bike charges just to recover the purchase price.

I would think that, to be viable, a solar charging system should cost no more than the value of around 1000 charges, which is probably around £40 or thereabouts. We're a long way off that sort of price yet, mores the pity.

Jeremy

 

[Footie]

I found this site yesterday and though it was a nice example of theory put into practice - about a chap who lives off grid and has an electric scooter running on solar power.

PVScooter

Not sure it would be practical for an electric bicycle - looks rather heavy to me

Indecently, I found my solar charger (£50 from Maplin) was able to recharge my campervan leisure battery in two days (just bright days with a little bit of sun) reading before charge 10.5 volts – after charging for two days 12.7 volts.
So solar charging does work reasonably well in the UK, even if we don't have sun all the time
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[Chris_Bike]

John's photo makes the point perfectly. A 36 v charging system would use 54 5in x 5in cells (I think - I have a 24V charging system that uses 36 cells in series - you need to overspec to get a charge voltage reliably greater than the batteries).

However, you could have an offgrid system to re-charge your bike batteries - this is what we have.

Chris

 

[Footie]

My solar charger puts out 20.4 volts in sunlight and 13.3 volts on overcast days - so well able to recharge a 12-volt battery.
So respectively, three together could out put 61.2 volts in sunlight and 39.9 volts on overcast days - I would have thought that's enough "overspec" to manage a 36-volt battery.
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[john]

small panel = low power

A solar cell puts out roughly a constant voltage irrespective of it's size. To increase voltage you connect several cells in series. You can therefore create a solar panel with high voltage that is quite small. However, a small panel will only produce a low current and hence low power. That is why you need a fairly large panel to supply the power requirements of recharging an e-bike battery.

 

[Chris_Bike]

Thanks John, that's the point I should have made more clearly yesterday - I should have also noticed the second page of posts!! Jeremy has made all the points I was trying to summarise. It's true that PVs are currently an expensive source of power vs the grid. However, they are green and have already become much cheaper in the 12 years or so I have used them. For those of us who live (in my case, part of the time) off grid, they are an essential part of the mix. I get about 33% of my needs from PVs at this time of year (will be 50% when I fit the Chinese panel awaiting connection) - the rest comes from a wind generator. I've only just got our Treks, but intend to charge them via the inverter which, at 90+%, is probably as efficient as any DC switch mode voltage converter I would manage to cobble together!

Chris