Power from Pedaling

[Warpspeed]

Sixty watts for an hour for an average healthy person, sounds about right.

But how about (say) six watts average from a solar panel for ten hours instead ?

A solar panel of that power might be roughly 200mm square. (eight inches square).
That ain't exactly enormous.

And one hour per day of sweat on a bike, requires some serious commitment.

I know which I would rather be doing.

 

[Nigel Goodwin]

Sixty watts for an hour for an average healthy person, sounds about right.

But how about (say) six watts average from a solar panel for ten hours instead ?

A solar panel of that power might be roughly 200mm square. (eight inches square).
That ain't exactly enormous.

And one hour per day of sweat on a bike, requires some serious commitment.

I know which I would rather be doing.

So you can get 6W average over ten hours per day from an 8 inch solar panel?.

Just did a quick random check, a panel rated at only 10W is 397 x 278mm (and £100), and that probably wouldn't get anywhere near 6W average.

I'm not suggesting using bikes, just that 'small' solar panel falls well short.

 

[tcmtech]

So you can get 6W average over ten hours per day from an 8 inch solar panel?.

Just did a quick random check, a panel rated at only 10W is 397 x 278mm (and £100), and that probably wouldn't get anywhere near 6W average.

Here is what I found in a quick search. Twelve 1.8 watt cells for $29.50 including shipping.
3" x 6" .5 volt 1.8 watt cells. **broken link removed**

My math says thats 1.5 sq feet of solar panels putting out 6 volts at 21.6 watts peak.
So I suspect that they could easily top that 60+ watt hour mark in an average day with considerable time to spare.

 

[Nigel Goodwin]

Here is what I found in a quick search. Twelve 1.8 watt cells for $29.50 including shipping.
3" x 6" .5 volt 1.8 watt cells. **broken link removed**

My math says thats 1.5 sq feet of solar panels putting out 6 volts at 21.6 watts peak.
So I suspect that they could easily top that 60+ watt hour mark in an average day with considerable time to spare.

I think you probably have a wildly ambitious idea of how much power solar cells provide - their rated power is generally pretty theoretical, even for high quality ones, never mind for cheap Chinese ones off Ebay

 

[Warpspeed]

Well if you wish to be pedantic about how many watts an "average" person can continuously sustain on an exercise bike over long periods, and the size and efficiency of photovoltaic cells, then I believe the exact figures for both might be rather elastic.

I based my figures on what I know from my own personal experience of using and measuring both.

The cost of a bike, suitable gear train, and a generator, might be fairly comparable to an array of photovoltaic cells.

The fact that a bike requires a huge physical effort, and solar none, makes it a no contest in my view.

 

[tcmtech]

I am not a solar panel person so I have no clue as to what is a normal or realistic power output for any given size.
Even at a half a watt per cell these could produce 60 watt hours in a 10 hour day.

Several other auctions have the same solar cells listed with Germany as the manufacturing source.

I have some old 1 foot square solar panels that can produce about 3 watts per square foot and they are probably 15 - 20 years old.
If two of them can still produce 60 watt hours on a good day I would assume that far newer solar cells can produce considerably more power in the same size range.

 

[Nigel Goodwin]

You're simplifying the maths FAR too much - the cells will produce maximum power for only a short time per day (and thet's likely to be considerably less than their rating), the rest of the time they will produce even less, and very much less five hours each side of maximum.

There are certainly panels that will manage 60W per day, in the right country, under the right circumstances - but it's not as simple as you make out.

Try reading the huge numbers of posts on here from people who have bought solar panels and then found the reality of them.

An obvious point is that you can charge from a bicycle when it's raining!

 

[transistor495]

The Element X

Today, on a mad time, I was thinking about lots of mad ideas and finally came up with this one.

It is an answer to all power problems..you just need to find the so called 'the Element X'...I dunno I lost it somewhere sometime..let me know plz if you find it.

Thank you.

 

[Oznog]

You're simplifying the maths FAR too much - the cells will produce maximum power for only a short time per day (and thet's likely to be considerably less than their rating), the rest of the time they will produce even less, and very much less five hours each side of maximum.

There are certainly panels that will manage 60W per day, in the right country, under the right circumstances - but it's not as simple as you make out.

Try reading the huge numbers of posts on here from people who have bought solar panels and then found the reality of them.

Look up "average insolation" for your city. You can find the average for a given month or over a whole year. Also the really good charts list the different orientations, like fixed-angle vs changing the plate angle with the season vs "sun tracking" the longitude of the sun over the course of a day.
The official basis for the cell rating is 1KW/m^2 insolation at 25C.

Like in Austin, Tx, we get about 4.8KWH/m^2 per day. A 6W panel would produce 28.8WH per day over the course of a year, and I believe that's for a panel fixed at an optimum angle for the entire year. That figure includes winter vs summer and all the rainy weather days averaged in.

What the figure does NOT include is whether the panel's actually 6W. The panel's output will drop significantly at high temps and increase at lower temps. But, there's not a lot of sunlight at lower temps so that's kind of a dead end. Dust on the panel will derate it a lot. And- here's a biggie- the rating seems to often be from the cells themselves. Well, the cover glass will glare off some of the sunlight and such. Thus the cells' ratings when installed in a panel will be lower than on the lab bench.