Upgrading system

[Kathymel]

Hi all,

I currently have a small system on my narrowboat that I bought cheaply about 10 years ago. I recently moved aboard full time and quickly realised I need to upgrade. The current set-up is 3 x 80w unbranded panels and 4 x 110ah batteries. I’ve already upgraded the CC to a 40a Epever and I have a 2.5kw Mastervolt inverter (too big imo, but came with the boat).

I have a few questions. The first is about my current panels. In full sun (considering their age and price) they do surprisingly well, producing nearly 260w on occasion. However, in anything other than full sun they seem pretty poor. I’m not sure how to really measure output in relation to light levels without a light meter. All I can say is that, when the sun is still faintly visible through thin cloud, I’m getting about 60w and under full cloud it’s about 20w. What would people expect a new, efficient panel to behave like under low light (not partial shade).

Secondly, I’d be grateful for some recommendations as to what make panels to buy. I’m looking at a 400-500w total but they have to have a good low-light efficiency. I’ve looked at countless websites and the more I learn it seems the less I know. There are some unbelievably cheap options on Bimble but I’m always suspicious of things that sound too good to be true.

Thirdly, do folk think it’s worth trying to incorporate my old panels into the new system? I know it won’t be realistic to put them on the same CC, but I’m considering putting them through the old cheap PWM I have on to the same batteries or even having a separate system at the other end of the boat on some old batteries I have just to run the telly (avoiding flattening the main bank should I fall asleep in front of it).

Thanks in advance for your suggestions.

Kathy

 

[svetz]

Welcome to the forums!

... I’m not sure how to really measure output in relation to light levels without a light meter...

What I do is to cheat. I find a near by weather station on Weather Underground that reports solar irradiance (not all do). You have to pick a day when its not likely that you or the station will have different conditions (e.g., not a cloud covering either).

Panels are rated at 1000 Watts per meter squared at standard temperature and conditions (77°F/25°C, air mass of 1.5, etc.). Panels have an efficiency, so the power they generate is the watts per meter square times the efficiency times their area. That is:

watts generated = watts available/m^2 x area x efficiency(T).​

​

The area doesn't change and efficiency changes slowly with temperature, so as long as the temperature doesn't change much their product is a constant (K), that is K = area x eff. That simplifies the equation to:

​

watts generated = watts available/m^2 x K​

Since they're not branded and don't have data, you'll need to solve for K. So, get the irradiance from the weather station, the power from the panels and calculate K. If K is the same over different times of the day they're probably okay. Note that this isn't perfect as the panel's efficiency is actually based on ambient temperature, but it should get you reasonable close. Note also that once the irradiance falls below 200 W/m^2 all bets are off.

Hope that helps!

...Thirdly, do folk think it’s worth trying to incorporate my old panels into the new system?...

I suspect you'll be limited by space, and therefore want to upgrade to the best you can get per square meter.

 

[ianganderton]

Where about in the UK are you?

Assuming it’s the UK. Only place I know of where the term narrow boat would be used ?

 

[tictag]

What would people expect a new, efficient panel to behave like under low light (not partial shade).

If your 240W array is producing 260W then it's fine! Better than fine! If you want to get more power at lower light levels, swap to an MPPT solar controller. You can expect up to around 30% increase in output power in low / changeable light conditions compared to a PWM. I would recommend a Victron SCC, their BlueSolar/SmartSolar 75|15 would be a good option for around £80/100, respectively.

Secondly, I’d be grateful for some recommendations as to what make panels to buy.

Suggest you visit Will's website (https://www.mobile-solarpower.com/solar-panels.html) for some tested suggestions. I tend to buy my panels cheap off eBay but if you want quality, Sunpower always seem to come up.

Thirdly, do folk think it’s worth trying to incorporate my old panels into the new system?

No point wasting them but you will be doing yourself a disservice if you connect differing specs panels together. Two SCCs connected to the same battery bank is absolutely fine.

 

[Kathymel]

Thanks for the detailed reply. I’ll try to get my head round the maths and have a look.

I suspect you'll be limited by space, and therefore want to upgrade to the best you can get per square meter.

The boat is very long so space isn’t an issue. ?

 

[Kathymel]

If your 240W array is producing 260W then it's fine! Better than fine! If you want to get more power at lower light levels, swap to an MPPT solar controller. You can expect up to around 30% increase in output power in low / changeable light conditions compared to a PWM. I would recommend a Victron SCC, their BlueSolar/SmartSolar 75|15 would be a good option for around £80/100, respectively.

Suggest you visit Will's website (https://www.mobile-solarpower.com/solar-panels.html) for some tested suggestions. I tend to buy my panels cheap off eBay but if you want quality, Sunpower always seem to come up.

No point wasting them but you will be doing yourself a disservice if you connect differing specs panels together. Two SCCs connected to the same battery bank is absolutely fine.

Producing 260w would be fine if it did that all the time. I forgot to mention I live in North Wales in the UK though, where full sun is a rarity. I see 20w way more than I see 260w, or even 160w. I’m already using an MPPT CC, an Epever 40a.

I need to edit my original post to say I’m in the UK and need recommendations for UK panel makes but can’t see how. ?

 

[Kathymel]

Where about in the UK are you?

Assuming it’s the UK. Only place I know of where the term narrow boat would be used ?

Yep. You’re right. I can’t see how to edit my original post to say that though. ?

 

[tictag]

North Wales, huh? Have you considered wind...

 

[Kathymel]

???

In all seriousness, I have, but all those who’ve tried it say it sucks on a narrowboat.

 

[tictag]

Never bought PV from these guys but everything else I've bought from them has been of good quality: 12VPlanet

 

[svetz]

Okay... had to google Narrow boat.... and now I want to see pictures!!!!

Don't do what these guys did... flexible panels... from what I've heard (no actual experience) they break down in a few years. Regular panels are glass and slippery when wet, but generally pretty tough. There are ones with "security" glass that can take a brick if you have to go on top and worry about them breaking from tools or people. I've heard of semi-rigid non-slip panels for boats, but don't know anything about them.

If aesthetics are important, polycrystalline are generally blue, and monocrystalline generally black. A 200 W panel of either will be the same power, but the polycrystalline will be a bit bigger.

 

[ianganderton]

If you are living aboard full time you are going to need to go through the following process to make any good decisions

Power audit - the job no one wants to do. It’s a tedious shlep but without doing it you won’t have good info to make good decisions.

Next you need to look at your power source/charging options

I’m assuming by north wales you are probably Llangollen way. The solar insolation tables I use don’t have anything in that area (actually north wales at all) so I’ve used Stoke because it’s on about the same latitude. See attached

They are simple to use. Times the wattage of your solar panel by the number to give an estimated daily watt hour output

The yearly average for the world is about 5. The table is showing less that one for your uk winter months. 0.5 average for December.

You will quickly see the relationship between the power you can generate and the power you want to use.

What other charging sources do you have the option to use?

Your boats alternator? A small generator? Shore power?

To live full time on an energy self sufficient narrow boat In North Wales is going to take a bit of planning I’m afraid.

 

[tictag]

I do like how they have hidden their wires!!

No narrow boats in the states? The UK has lots of canals, used to ferry goods around the country during the industrial revolution. Some of them can be decadently furnished on the inside - like palaces.

 

[ianganderton]

Okay... had to google Narrow boat.... and now I want to see pictures!!!!

Don't do what these guys did... flexible panels... from what I've heard (no actual experience) they break down in a few years. Regular panels are glass and slippery when wet, but generally pretty tough. There are ones with "security" glass that can take a brick if you have to go on top and worry about them breaking from tools or people. I've heard of semi-rigid non-slip panels for boats, but don't know anything about them.

If aesthetics are important, polycrystalline are generally blue, and monocrystalline generally black. A 200 W panel of either will be the same power, but the polycrystalline will be a bit bigger.

My hypothesis for the failure rates I’ve seen with flexible panels is people mount them permanently super flat with no air gap. This causes over heating. The combination of heat and plastic doesn’t stand a chance

 

[ianganderton]

@Kathymel - one thing for sure is if you provide the info needed to plan your system to the folks on here you will definitely get the help you need ?

 

[svetz]

My hypothesis for the failure rates I’ve seen with flexible panels is people mount them permanently super flat with no air gap. This causes over heating. The combination of heat and plastic doesn’t stand a chance

Will had a video on why he didn't like them... thought it had something to do with UV fogging/yellowing the plastic and destroying the efficiency... I might have it all mixed up though. They're probably okay if you can get a 25 year warranty like with regular panels.

 

[ianganderton]

Will had a video on why he didn't like them... thought it had something to do with UV fogging/yellowing the plastic and destroying the efficiency... I might have it all mixed up though. They're probably okay if you can get a 25 year warranty like with regular panels.

I think as with everything they have their place. For me one example would be applications that use their low weight and durability to knocks and bumps. Eg Portable solar suitcase style designs.

 

[svetz]

I'm going to take back everything I said about flexible panels... the Renogy flexible panel warranty:

25-year power output warranty: 5 year/95% efficiency rate, 10 year/90% efficiency rate, 25-year/80% efficiency rate
5-year material and workmanship warranty

100W for 4.2 lbs that I could glue down somewhere and is 21% efficient at $1.89/W? This paves the way for a few more solar projects....
We sure do live in interesting times!

 

[PHoganDive]

I'm going to take back everything I said about flexible panels... the Renogy flexible panel warranty:



100W for 4.2 lbs that I could glue down somewhere and is 21% efficient at $1.89/W? This paves the way for a few more solar projects....
We sure do live in interesting times!

The company also has to be around in 25 years to honor that warranty. Company I used to work for bought flexible panels from a company called Xunlight. Panels work well, but Xunlight is no longer around, as is any warranty they might have had. You can see some of them coiled up in the aluminum storage tub.

 

[tictag]

You can see some of them coiled up in the aluminum storage tub.

The bend radius for the flexible panels I have experience of should not exceed 30%. Something tells me that those panels should not be relied upon.

I can concur with the earlier comment that flexible panels do not age well. My first set lasted maybe 2 years and the front polymer started to turn opaque and eventually begun to peel off. But then, I did buy cheap.