Jump to content

Solar setup


Featured Posts

Hi there,

 

So I am fitting out a 1940s 50' x 10' Dutch barge. Have had it out of the water and plating work done, inside is sprayfoamed, that's as far as we've got! So a blank canvas as far as everything else goes!

 

It will be a liveaboard boat, and it is a dumb barge, so will be permanently on the mooring. We do not have mains electric on the mooring. We currently live aboard a 43' narrowboat on the same mooring, so I have a fair idea of our lifestyle, and how it works to be in this location. Solar is our friend, we currently have 330w on the narrowboat, feeding a 345AH 12v battery bank. I'd like the new boat to be quite a bit more substantial, as we currently have to run the genny quite a bit more than we'd like, and we turn the fridge off in winter.

 

I have two significant avenues of investigation, which I would appreciate the forum's thoughts on:

 

1) The mooring is in the shadow of a large oak tree and loses direct sun between about 1pm and 4pm. I am thinking of having at least two PV arrays, one focussed for the morning/midday sun, and a second to catch the afternoon rays. My thinking here is that the batteries would like a small current over a long time period, so best to give them as many hours of input as I can, rather than loads of Amps until 1pm, and then have the panels completely at the wrong angle in the afternoon. In the morning we have direct sunlight from the moment the sun rises, so there is a school of thought that says a third array (perhaps just a single panel) angled to pick up this early sun, might be beneficial as well, but I don't know if the sun at that time of the day strong enough to make a worthwhile difference?

 

2) I am hoping to have at least a 600AH battery bank (early calculations, I can somewhat tailor the devices on board to fit the capacity). It is my understanding that large battery banks like this are much more economical if set up in 24v. Thoughts on this? If I have my facts straight, 24v means twice as much battery needed, but half the current in the cables, so less copper (or less voltage drop in the same sized copper). My only thought here is what about the prevalence of 12v devices (car stereo, computer chargers, etc etc) can I have 24v/12v step downs and keep using these devices? Obviously lights and pumps can be run on 24v (are 24v pumps more expensive???)

 

So, your thoughts and experiences are welcome...

Link to comment
Share on other sites

If one panel gets shaded when the other doesn't you would be better off with a dedicated MPPT solar controller for each panel. That way the shaded panel won't throttle the unshaded one. I find that in the winter my panels can on some days only put out about 5% of their rated output, so to minimise generator running fill the roof with panels, even then some days you will need the gennie.

Remember what ever the size of your battery bank you need to put back a bit more than you use so more batteries won't necessarily be better.

Can't comment on 24V as I have no experience with it.

 

Top Cat

Link to comment
Share on other sites

Old Oak tree likes copper nails.

 

........... take year or three unsure.png

 

 

 

 

2) I am hoping to have at least a 600AH battery bank (early calculations, I can somewhat tailor the devices on board to fit the capacity). It is my understanding that large battery banks like this are much more economical if set up in 24v.

just to clarify, are you proposing 600AH with 12V (7.2KWH) or 600AH at 24V (14.4KWH)?

Link to comment
Share on other sites

Methinks the order of calculations is wrong here.

 

1. Perform an energy audit.

2. Calculate how you will replace 120% of 1.

 

If 2. is much less than 1. then keep re-jigging until they balance.

 

Once they balance then (and only then)...

3. Choose battery bank approx three times the size of 1.

  • Greenie 1
Link to comment
Share on other sites

Thanks all... Some good, and some less useful, thoughts.

 

 

Chop the tree down.ninja.gif

 

The tree is older, more valuable and more beautiful than me, or my boat will ever be. It makes my mooring special in a way that I cannot describe. Clear winter nights, when I look out of the roof hatch over my bed and see the moon through the bare branches, are one of the most special times I have experienced. I believe there is also a tree preservation order on it.

 

 

just to clarify, are you proposing 600AH with 12V (7.2KWH) or 600AH at 24V (14.4KWH)?

 

Aha! This is valuable insight for my limited technical mind! I was proposing 600AH @ 12V, so I guess I would in fact only need 300AH at 24V.

 

 

Methinks the order of calculations is wrong here.

1. Perform an energy audit.
2. Calculate how you will replace 120% of 1.

If 2. is much less than 1. then keep re-jigging until they balance.

Once they balance then (and only then)...
3. Choose battery bank approx three times the size of 1.

Thanks, clearly put. I do understand the order of events. However, I am aware that my solar system is limited, and I want to establish what sort of figure I can achieve for 2, before I start going too crazy with 1! I am at the early stages of the fit out, so I can somewhat choose how much power I use, by choosing what I put on the boat.

 

For example: My better half would like a freezer running all year; this could be a small, top loading, 12v unit or a 240v under counter unit with an inverter running 24/7, or I might well have to tell her that we can't have a freezer and she should keep visiting ice cream vans as she does now, but all of these things very much depend on how much power I think I can get from PV.

 

If one panel gets shaded when the other doesn't you would be better off with a dedicated MPPT solar controller for each panel. That way the shaded panel won't throttle the unshaded one. I find that in the winter my panels can on some days only put out about 5% of their rated output, so to minimise generator running fill the roof with panels, even then some days you will need the gennie.
Remember what ever the size of your battery bank you need to put back a bit more than you use so more batteries won't necessarily be better.
Can't comment on 24V as I have no experience with it.

Top Cat

 

Yes, this is my thinking, when I speak about separate arrays. I propose that each array (facing into the sun for that time of day, and positioned as best possible so that none will be in shadow) have it's own MPPT charger.

 

Some questions:

 

1) I understand there is some logic to having 2 or 3 panels in series running into an MMPT controller, can anyone explain this further? There is more to it than just saving cable runs, isn't there?

 

2) What would the difference be between say, a 20A controller with two 100w panels and two 10A controllers with a single 100w panel on? Obviously there is a cost difference, and as indicated by Top Cat, there would be a difference if one panel were shadowed, but would there be any other difference?

Link to comment
Share on other sites

Hi there,

 

So I am fitting out a 1940s 50' x 10' Dutch barge. Have had it out of the water and plating work done, inside is sprayfoamed, that's as far as we've got! So a blank canvas as far as everything else goes!

 

It will be a liveaboard boat, and it is a dumb barge, so will be permanently on the mooring. We do not have mains electric on the mooring. We currently live aboard a 43' narrowboat on the same mooring, so I have a fair idea of our lifestyle, and how it works to be in this location. Solar is our friend, we currently have 330w on the narrowboat, feeding a 345AH 12v battery bank. I'd like the new boat to be quite a bit more substantial, as we currently have to run the genny quite a bit more than we'd like, and we turn the fridge off in winter.

 

I have two significant avenues of investigation, which I would appreciate the forum's thoughts on:

 

1) The mooring is in the shadow of a large oak tree and loses direct sun between about 1pm and 4pm. I am thinking of having at least two PV arrays, one focussed for the morning/midday sun, and a second to catch the afternoon rays. My thinking here is that the batteries would like a small current over a long time period, so best to give them as many hours of input as I can, rather than loads of Amps until 1pm, and then have the panels completely at the wrong angle in the afternoon. In the morning we have direct sunlight from the moment the sun rises, so there is a school of thought that says a third array (perhaps just a single panel) angled to pick up this early sun, might be beneficial as well, but I don't know if the sun at that time of the day strong enough to make a worthwhile difference?

 

The two sets of panels would need to be totally separate systems otherwise they will adversely affect each other.

Assuming 50% SoC, at the start of charging, batteries will take charge much more quickly 50% to 80% than after they reach say 80%. From 80% to 100%, assuming the current levels needed are available for the earlier charging, it will take as longer to charge the last 15/20% than it took to charge the first 30%. Thus I would suggest the higher charge current you can have at the beginning the better.

 

2) I am hoping to have at least a 600AH battery bank (early calculations, I can somewhat tailor the devices on board to fit the capacity). It is my understanding that large battery banks like this are much more economical if set up in 24v. Thoughts on this? If I have my facts straight, 24v means twice as much battery needed, but half the current in the cables, so less copper (or less voltage drop in the same sized copper). My only thought here is what about the prevalence of 12v devices (car stereo, computer chargers, etc etc) can I have 24v/12v step downs and keep using these devices? Obviously lights and pumps can be run on 24v (are 24v pumps more expensive???)

 

24V stuff is marginally more expensive but there will be a good saving in the copper cables as they need to be only half the size. My last canal boat was 24V and there were no problems and wiring etc was cheaper by a long way. Yes it is easy to get 24/12V step down for things like radios etc. A lot of phone stuff etc is happy on 24V.

 

So, your thoughts and experiences are welcome...

Edited by Geo
Link to comment
Share on other sites

Hi there,

 

So I am fitting out a 1940s 50' x 10' Dutch barge. Have had it out of the water and plating work done, inside is sprayfoamed, that's as far as we've got! So a blank canvas as far as everything else goes!

 

It will be a liveaboard boat, and it is a dumb barge, so will be permanently on the mooring. We do not have mains electric on the mooring. We currently live aboard a 43' narrowboat on the same mooring, so I have a fair idea of our lifestyle, and how it works to be in this location. Solar is our friend, we currently have 330w on the narrowboat, feeding a 345AH 12v battery bank. I'd like the new boat to be quite a bit more substantial, as we currently have to run the genny quite a bit more than we'd like, and we turn the fridge off in winter.

 

I have two significant avenues of investigation, which I would appreciate the forum's thoughts on:

 

1) The mooring is in the shadow of a large oak tree and loses direct sun between about 1pm and 4pm. I am thinking of having at least two PV arrays, one focussed for the morning/midday sun, and a second to catch the afternoon rays. My thinking here is that the batteries would like a small current over a long time period, so best to give them as many hours of input as I can, rather than loads of Amps until 1pm, and then have the panels completely at the wrong angle in the afternoon. In the morning we have direct sunlight from the moment the sun rises, so there is a school of thought that says a third array (perhaps just a single panel) angled to pick up this early sun, might be beneficial as well, but I don't know if the sun at that time of the day strong enough to make a worthwhile difference?

 

2) I am hoping to have at least a 600AH battery bank (early calculations, I can somewhat tailor the devices on board to fit the capacity). It is my understanding that large battery banks like this are much more economical if set up in 24v. Thoughts on this? If I have my facts straight, 24v means twice as much battery needed, but half the current in the cables, so less copper (or less voltage drop in the same sized copper). My only thought here is what about the prevalence of 12v devices (car stereo, computer chargers, etc etc) can I have 24v/12v step downs and keep using these devices? Obviously lights and pumps can be run on 24v (are 24v pumps more expensive???)

 

So, your thoughts and experiences are welcome...

 

Not realy. Same batts but wired diferently but Matty is on the money.

 

Fit a woodburner and you have electricity and fuel for next winter.wink.png

 

Ed for not refreshing screen before posting. Late again.

Edited by Taslim
Link to comment
Share on other sites

Hi

I have a motorhome on a 24 v vehicle and run a 24 v domestic battery system with a solar array. The system works very well and I run as much as I can at 24v. Fridge, Webasto, water pump R3626 344 here http://www.mackengineering.co.uk/product_downloads/FLOJET%20R3426.pdf

I use one of these http://alfatronix.com/assets/Uploads/1610-PV-EN.pdfPV24s to run a 12 v system for lights and other things I can't get in 24 v

Hope the links help

Phil

Link to comment
Share on other sites

Regarding the idea of having two or more panels going into an MPPT controller it all depends on the voltage of the panels vs your battery voltage. You need the panels to be running somwhat above your battery voltage.

So for example on my system which is 12V.

Originally I has a single nominally 12V 130 W panel feeding a Victron 75/15 controller. That panel has a max power voltage of about 17V and an open circuit of 21V. The controller will only start charging if the panel output is more than 5V above the batteries and needs battery voltage plus 1 to continue. Other controllers may differ.

Assuming we start the day at 12.4V then we need 17.4V out of the panel to start charging which is just above the max power point also with low sun the panel will be well down on output. I found that the panel did not start to give meaningful power till quite late in the day even under good conditions and if it was cloudy sometimes not at all.

Then I replaced it with a 190W , 24V panel this has a max power point of 35V and open circuit of 42V. To my surprise I found I got not the expected 1.5x power but twice as much because the panel hit battery voltage plus 5V much earlier and in poorer conditions.

 

So the key thing is ensure your panel voltage exceeds you battery voltage by quite a bit to get best efficiency, whether that's by panels in series or higher voltage panels doesnt matter other than the shading issue.

 

Also with higher voltage panels your current is less so you loise less power in the inevitable long cable runs.

 

So for a 12V boat I would use a 24V panel per controller, for a 24V boat I would use two 24V panels in series per controller.

 

Top Cat

Link to comment
Share on other sites

I have 3 x 250W sanyo panels feeding one MPPT controller. The other 1 x 250W panel feeds a seperate MPPT controller.

 

Initially, the 4 panels were connected together in a Series-Parrallel arrangement, but due to shading of one panel by a nearby tree, I decided to separate them out a bit, which resulted in a marked improvement.

 

The larger MPPT controller also requires a certain Voltage to power-up (I can't remember off hand what it is), which it may not achieve on one panel alone.

 

As Topcat suggests, try and get the voltage as high as possible from the panels (below the max input limit of the controller). Connecting the panels in series at a higher voltage will require smaller/less cable.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.