Solar panel setup

[Alan de Enfield]

2 minutes ago, Slow and Steady said:

Good answer! 

So... higher voltage panels for the win? Are their any downsides that you're aware of?

 

I have never found any, but I think someone did suggest that shading (of trees) etc may have more impact on series wired panels.

 

 

[Slow and Steady]

12 minutes ago, Alan de Enfield said:

 

I have never found any, but I think someone did suggest that shading (of trees) etc may have more impact on series wired panels.

 

 

In that case, which I'm aware of, I think I'd be looking for higher voltage panels in the first place rather than wiring low voltage panels in series... if they even exist - the mass market does seem to be aimed at smaller installations. I'm still at the pre-planning stage myself and I'm glad not to have jumped earlier as no doubt I'd have ended up with low volt panels and LA batteries.

Looks to me like High volts and Lithium is the way to go. I'm more interested in the practical usefulness than the initial cost, I like to run a fridge, computers and powered speakers all of which are constant drains and need 240v AC so there is the conversion and standby losses there too. Laptops are not powerful enough for my use and the ones that approach it, the batteries last about 30 minutes so in effect they are mains powered, noisy and hot. None of my uses are high power consumers like a microwave, kettle, washing machine etc but the hours add up to a substantial daily total.

Edited June 25, 2022 by Slow and Steady

[Tony1]

48 minutes ago, Slow and Steady said:

In that case, which I'm aware of, I think I'd be looking for higher voltage panels in the first place rather than wiring low voltage panels in series... if they even exist - the mass market does seem to be aimed at smaller installations. I'm still at the pre-planning stage myself and I'm glad not to have jumped earlier as no doubt I'd have ended up with low volt panels and LA batteries.

Looks to me like High volts and Lithium is the way to go. I'm more interested in the practical usefulness than the initial cost, I like to run a fridge, computers and powered speakers all of which are constant drains and need 240v AC so there is the conversion and standby losses there too. Laptops are not powerful enough for my use and the ones that approach it, the batteries last about 30 minutes so in effect they are mains powered, noisy and hot. None of my uses are high power consumers like a microwave, kettle, washing machine etc but the hours add up to a substantial daily total.

 

If your budget will stretch a bit, I'd recommend the Victron MPPTs. They can be remotely controlled using your phone with the victron app, and its really easy even for a numpty like me to understand and to use. 

I use one 50 amp MPPT for the front panels (660 watts) and one for the rear set (750 watts).

I think the highest power I've seen so far from the rear set of panels was around 700 watts, but that was in absolutely ideal conditions, and its usually 500-600 watts in summer.

I had a Tracer unit previously, and although they are good quality units, the PC software was clunky and difficult for me to work through. They do sell a bluetooth dongle-type thing to link to your phone so you can control the MPPT remotely. I tried it out, but their phone app was hard to get to grips with, when compared to the victron app. 

If you are singlehanding and at the tiller, and you want to manually stop the solar charging for some reason, you can switch off the MPPTs using your phone (or adjust the charging voltage, etc).  

 

[agg221]

1 hour ago, Slow and Steady said:

My impression is that he's looking for some rather basic info on the difference the panel voltage makes to the expected output in various, but particularly low light conditions. I agree with him that this basic element of panel choice is rarely if ever discussed and I also wonder why that is.

 

Maybe it's because it actually doesn't make much difference apart from high voltage/low amp panels not requiring such beefy cabling as low volt/high amp panels. If that's the case you could infer that the higher the output, the more gain to be had from high volt/low amp panels in terms of less bulky/expensive cables and losses in the cables.*

 

*I'm armchair at this, a grownup will be along to clarify hopefully.

I think that information may not be so basic.

 

If a manufacturer decides it's a USP then they may choose to measure under a series of conditions but if not then it would be quite a major undertaking to look for example at the influence of angle, flux and random partial shading under a variety of conditions against a control. You wouldn't for example want to just run it outside and hope - you would need controlled environmental conditions for a definitive answer. If you wanted to run that as an experimental set-up across various scenarios then unless there is a recognised standard which different manufacturers would apply, the trials would need to be run by an independent body, so they would need to have a reason to invest in doing so. That would typically mean external third-party funding since there are not many bodies which would directly benefit from generating the data and if funded by a single manufacturer the data is likely to be accused of bias. That means it is most likely to be derived from public funding so you would find the results in the academic literature - not something I would expect to find from a solar panel shop, or something I would expect them to review. The alternative is anecdotal data but, unless you get a large body of consensus, this is always prone to error. It would be hard for a shop to state what the actual expected output would be under a very specific set of conditions and certainly would be difficult for them to guarantee it. I suspect it ends up being an 'it depends' answer with too many variables to give any sensible commitment.

 

In the end, I was happy because I didn't have to consider this too much!

 

Coincidentally, my background includes running such independent verification trials although this is mainly for paints and surface preparation methods, not for solar panels, but exposure factors have a similar bearing in both cases, hence I do have a fair understanding of why it rapidly becomes very involved.

Alec

Edited June 25, 2022 by agg221

[Slow and Steady]

17 minutes ago, agg221 said:

The alternative is anecdotal data

I'm happy with anecdotal + some tech reasoning to make sense of it like Alan's "not enough volts = no charging" example above. That's useful information despite not being a laboratory controlled experiment.

[agg221]

40 minutes ago, Slow and Steady said:

I'm happy with anecdotal + some tech reasoning to make sense of it like Alan's "not enough volts = no charging" example above. That's useful information despite not being a laboratory controlled experiment.

It is, and a forum such as this is ideally placed to provide it. You can reasonably decide who is likely to have credible information and who may not. However, that's more difficult for a shop as they may get held to it ('but you said...') so I wouldn't expect them to provide it, although there are some shops of course which were set up by real enthusiasts who may well have enough experience to provide data with confidence, however they don't tend to make much money as they spend too much time giving advice for free rather than selling product!

 

Alec

[Slow and Steady]

1 hour ago, agg221 said:

It is, and a forum such as this is ideally placed to provide it. You can reasonably decide who is likely to have credible information and who may not. However, that's more difficult for a shop as they may get held to it ('but you said...') so I wouldn't expect them to provide it, although there are some shops of course which were set up by real enthusiasts who may well have enough experience to provide data with confidence, however they don't tend to make much money as they spend too much time giving advice for free rather than selling product!

 

Alec

I think we're all different too - some are happy to blindly follow advice and some of us need to understand it first. If you're in the second variety forums are good, if you're in the first then heaven help you!

[Tony Brooks]

26 minutes ago, Slow and Steady said:

I think we're all different too - some are happy to blindly follow advice and some of us need to understand it first. If you're in the second variety forums are good, if you're in the first then heaven help you!

 

And that is what concerns me when we are not given the info we think we need to give a decent answer. In the first case I would expect it to be forthcoming, in the second the OPs are likely to pick an answer they like and thrash on - correct or incorrect.

Edited June 25, 2022 by Tony Brooks