Can I turn my theory into reality? Fossil fuel free, 100% off grid, but modcons

[reg]

5 hours ago, ditchcrawler said:

There use to be a boat moored up near Anderton with the cabin side covered in solar panels.

Yes I have seen similar elsewhere however the op was on about temporarily moving the panels to the cabin side for short periods which I would envisage being a great faff fir little gain.

 

[DerekB]

On 04/11/2021 at 07:23, MtB said:

 

This strikes me as spectacularly narrow minded and pointless.

 

The naysayers are the one who will highlight and draw your attention to the areas of particular technical difficulty, where 99% of your effort will need to be concentrated in developing solutions. 

 

My own naysaying contribution in this vein is to point out that your plan of 3-4kW of solar on a narrowboat is difficult due to the sheer area of panel this involves*. I presume therefore, you are getting a widebeam but you don't say. The beam of your boat will also turn out to be important I think, not only for the extra roof area it gives for the solar panels, but the space for all the gubbins you are planning (heat pump especially) will eat into your living area.

 

* Unless you have access to new technology panels that harvest more than the approx 200w per square metre that current tech delivers. 

I've just been looking at solar systems this last week. Your 200w/square meter figure is pretty accurate. The 1.8kw system i'm looking at will require 10 square meters of roof space. So upping that to the 3.5-4kw would be about 20. Even with a wide beam this would be tricky unless it was designed with all the vents, centre line cleat etc in the right places. 

3 hours ago, reg said:

Yes I have seen similar elsewhere however the op was on about temporarily moving the panels to the cabin side for short periods which I would envisage being a great faff fir little gain.

 

There are some interesting developments in solar film tech so, potentially, you could cover both sides of the cabin to augment the roof panels....i wouldn't want to be shifting panels around if i could help it.

[peterboat]

8 minutes ago, DerekB said:

I've just been looking at solar systems this last week. Your 200w/square meter figure is pretty accurate. The 1.8kw system i'm looking at will require 10 square meters of roof space. So upping that to the 3.5-4kw would be about 20. Even with a wide beam this would be tricky unless it was designed with all the vents, centre line cleat etc in the right places. 

There are some interesting developments in solar film tech so, potentially, you could cover both sides of the cabin to augment the roof panels....i wouldn't want to be shifting panels around if i could help it.

I have 4.6 kw on my widebeam it requires the use of the wheelhouse roof and needs to be 12 foot wide so you are right. 

Edited November 7, 2021 by peterboat

[DerekB]

2 minutes ago, peterboat said:

I have 4.6 kw on my widebeam it requires the use of the wheelhouse roof and needs to be 12 foot wide 

and a shoehorn? 🙂

[peterboat]

Just now, DerekB said:

and a shoehorn? 🙂

I could possibly get more on now with the bigger panels that now cheaply available 

[DerekB]

5 minutes ago, peterboat said:

I could possibly get more on now with the bigger panels that now cheaply available 

Fingers crossed on this but i'm hopefully about to buy first boat, 10' widebeam, and i'll be up on the roof taking measurements to figure out a solar layout that leaves walkways to the sides and avoids things sticking out of the roof

[peterboat]

2 minutes ago, DerekB said:

Fingers crossed on this but i'm hopefully about to buy first boat, 10' widebeam, and i'll be up on the roof taking measurements to figure out a solar layout that leaves walkways to the sides and avoids things sticking out of the roof

Measure twice fit once! 300watt panels should fit in 2 rows, one down each side I picked some more up earlier this year cheap as chips 

[MtB]

9 minutes ago, DerekB said:

Fingers crossed on this but i'm hopefully about to buy first boat, 10' widebeam,

 

Very sensible choice, if you must have a widebeam. 10ft boats feel at least twice as wide inside as a 7ft narrowboat but are far more nimble and cruisable than the 12ft and 13ft behemoths. 

 

The severe limitations on cruising range will grind you down eventually though, if you get the wanderlust. 

[DerekB]

11 minutes ago, peterboat said:

Measure twice fit once! 300watt panels should fit in 2 rows, one down each side I picked some more up earlier this year cheap as chips 

i'm thinking one row down the centre to keep sides clear to walk down

 

2 minutes ago, MtB said:

 

Very sensible choice, if you must have a widebeam. 10ft boats feel at least twice as wide inside as a 7ft narrowboat but are far more nimble and cruisable than the 12ft and 13ft behemoths. 

 

The severe limitations on cruising range will grind you down eventually though, if you get the wanderlust. 

it's going to be full time liveaboard and my shoulders need the extra space 🙂

[reg]

Has anyone any experience with these bifacial solar panels ?

https://www.bimblesolar.com/index.php?route=product/product&product_id=2542

 

[MtB]

8 minutes ago, DerekB said:

i'm thinking one row down the centre to keep sides clear to walk down

 

it's going to be full time liveaboard and my shoulders need the extra space 🙂

 

Honestly, if living alone a narrowboat is fine. If there a two of you though, a NB will drive you demented unless you are stick insects.....

[DerekB]

2 minutes ago, MtB said:

 

Honestly, if living alone a narrowboat is fine. If there a two of you though, a NB will drive you demented unless you are stick insects.....

i viewed a narrowboat and had to turn totally sideways in sections and my chest and back were both dragging along the walls.....i'm built for widebeam 🙂

[MtB]

1 minute ago, DerekB said:

i viewed a narrowboat and had to turn totally sideways in sections and my chest and back were both dragging along the walls.....i'm built for widebeam 🙂

 

 

I don't like books.

 

I know this because I read one once. I didn't like it.

[David Mack]

15 minutes ago, MtB said:

 

 

I don't like books.

 

I know this because I read one once. I didn't like it.

 

[Graham Davis]

2 hours ago, peterboat said:

Measure twice fit once! 300watt panels should fit in 2 rows, one down each side I picked some more up earlier this year cheap as chips 

 

Where from, Peter? Looking for one or two for my daughter's new caravan.

[IanD]

2 hours ago, reg said:

Has anyone any experience with these bifacial solar panels ?

https://www.bimblesolar.com/index.php?route=product/product&product_id=2542

 

 

Not experience, but read the small print about how they get the extra output and you'll realise they won't do this on narrowboats -- you need a white/reflective surface underneath and gaps between the panels so that light that misses the panels bounces back up onto the rear, this doesn't work on a boat roof which is pretty much covered in panels.

[peterboat]

36 minutes ago, Graham Davis said:

 

Where from, Peter? Looking for one or two for my daughter's new caravan.

I will have a look Graham, I bought 4 with a boat mate from York, they are good panels monos and seem well made 

[Graham Davis]

9 minutes ago, peterboat said:

I will have a look Graham, I bought 4 with a boat mate from York, they are good panels monos and seem well made 

Thanks for that. She's just setting up an 18' caravan for off-grid living and does have some experience from her camper van but knows she will need a decent set-up. Atleast she's already got a few batteries.

[reg]

2 hours ago, IanD said:

 

Not experience, but read the small print about how they get the extra output and you'll realise they won't do this on narrowboats -- you need a white/reflective surface underneath and gaps between the panels so that light that misses the panels bounces back up onto the rear, this doesn't work on a boat roof which is pretty much covered in panels.

Thanks for that. Might work in my case as I have a mat white roof, primarily to reduce winter glare, and also I only have 2 largish panels at the front end of the roof which gives me circa 60% clear roof space.

I'm not sure if it is  currenyky worth it financially to swap these 2 out for the bifacial but if I ever do need to then the bifacial  would certainly be a strong contender mainly for the better low light performance in winter.

Edited November 8, 2021 by reg

[IanD]

7 hours ago, reg said:

Thanks for that. Might work in my case as I have a mat white roof, primarily to reduce winter glare, and also I only have 2 largish panels at the front end of the roof which gives me circa 60% clear roof space.

I'm not sure if it is  currenyky worth it financially to swap these 2 out for the bifacial but if I ever do need to then the bifacial  would certainly be a strong contender mainly for the better low light performance in winter.

I've never seen any convincing explanation about "better low light performance in winter" claims, a solar panel just converts a given fraction (about 20% for mono panels) of whatever light hits them into electricity.

 

Unless it's the same reason as for the bifacial claims, where light that misses the panels bounces back off a reflective surface underneath. In which case they've already claimed that benefit -- you can't double-count it...

[Alan de Enfield]

6 minutes ago, IanD said:

I've never seen any convincing explanation about "better low light performance in winter" claims, a solar panel just converts a given fraction (about 20% for mono panels) of whatever light hits them into electricity.

 

I've mentioned this before - I bought 'low light' panels from Bimble, on asking what was 'low light' about them they explained that they were ex-Scandinavian panels and have been designed to pick up light at lower angles of incidence (not 'low light' levels - dusk or dawn etc) found in the higher latitudes and in 'our' latitudes during Winter.

 I have no idea if this is achived by having the panels built at different (lower) angles or if it is some technology.

 

Certainly seem to have more output that standard panels did, but no longer have any 'old' panels to compare them to.

 

120 volt, 170 watt panels, this was a single 170w panel on a fine February day, batteries virtually full but still putting 3.3 amps (47 watts) in, and 10.8 amps (151 watts) in June

 

 

 

 

[Jen-in-Wellies]

40 minutes ago, Alan de Enfield said:

 I have no idea if this is achived by having the panels built at different (lower) angles or if it is some technology.

No idea either. Possibly a glass cover sheet with a lower proportion of the light reflected from the surfaces at low angles? Might be a property of the glass itself, or a coating on the glass, in which case, how long may it survive with cleaning etc?

[IanD]

27 minutes ago, Jen-in-Wellies said:

No idea either. Possibly a glass cover sheet with a lower proportion of the light reflected from the surfaces at low angles? Might be a property of the glass itself, or a coating on the glass, in which case, how long may it survive with cleaning etc?

 

Solar panels are simply flat bits of silicon that absorb light and convert a fixed fraction of it into electricity (about 20%), with some covering over them. For rigid panels this is a sheet of glass, for flexible ones it's some kind of polymer. The only way to get higher output at low levels of incidence is to cut down on reflection, and most of the ways that are claimed to do this (non-gloss surface, little hemispherical "bumps" don't actually do this, all they do is convert specular reflection (like a mirror) to non-specular (fuzzy) by scattering the reflected light, but this *doesn't* change the amount that gets through to the panel -- the laws of physics say this is only affected by the refractive index and the angle the light hits at.

 

The only thing that would increase the amount of light reaching the panel is an anti-reflective coating like is used on lenses; the problem is that a single coating only works at one optical frequency (light colour), so lenses use multiple layers, which are expensive to make and prone to damage -- and *nobody* does this on conventional solar panels, it would increase the cost several times over even if the factories had equipment to do it -- which they don't.

 

Just like in many other areas, there are a lot of dubious marketing claims made for solar panels which are not backed up by the science or any evidence. If anyone finds any that are -- not just a good-sounding claim by the seller but with actual data to show that it works -- then I'll change my mind, but physics tends to win over BS every time... 😉

 

[yes I studied optics as part of my degree...]

Edited November 8, 2021 by IanD

[reg]

Some good info and explanations here, thanks. Would be nice if anyone has any practical experience of these but I think that probably requires its  own thread rather than have it buried deep in this one.

My current setup gives more than adequate for most of the year but often in winter just falls short of providing a high enough voltage to do any charging. My thinking is that even a marginal percentage improvement may just give an extra hour or 2 of charge in winter. Without side by side comparison it's unclear whether this could be achieved.

Anyway it will have to, fir me, remain speculation at the moment as changing out to find out makes no economic sense.

Appreciate all the inputs.

 

Edited November 8, 2021 by reg

[IanD]

20 minutes ago, reg said:

Some good info and explanations here, thanks. Would be nice if anyone has any practical experience of these but I think that probably requires its  own thread rather than have it buried deep in this one.

My current setup gives more than adequate for most of the year but often in winter just falls short of providing a high enough voltage to do any charging. My thinking is that even a marginal percentage improvement may just give an extra hour or 2 of charge in winter. Without side by side comparison it's unclear whether this could be achieved.

Anyway it will have to, fir me, remain speculation at the moment as changing out to find out makes no economic sense.

Appreciate all the inputs.

 

 

If you're not getting enough voltage to charge in winter, you need more panels in series going into the MPPT controller to make sure the panel voltage is always bigger than the battery voltage.

 

Don't forget that even with this, power yield in winter is a tiny fraction of that in summer, typically 6x lower in midwinter... 😞