Another clueless solar power post (sorry)

[Starcoaster]

Solar panels, wow the whole thing is doing my head right in. The more I read and try to learn, the less I get it. But I am trying to work out what I need and I'd appreciate some fresh pairs of eyes and opinions on it.

Please please don't make it technical, my brain will just disconnect. I won't be fitting the panels myself, so I don't need to know the dark science of it all, just if I am heading in the right direction in terms of what I need and how to budget for it.

 

As I understand it, I need the panels themselves, an mppt controller unit thingy, appropriate wiring for the panels, and for them to be affixed to the roof. Have I missed anything obvious?

 

My electric usage looks something like this:

One laptop computer (a regular average one, not an energy saving one or anything) in use on average 10-12 hours a day.

Water pump and whale gulper for daily shower and washing up.

Charging of small items such as phone and kindle.

Two lights on at any time, which alongside of getting solar, I will swap for LED's unless the cost is prohibitively expensive as I have to change the fittings or something.

that's all off the 12v power direct.

I would like ideally to be able to run a printer and small 300w twin tub from an inverter once a week, but could live without this.

 

 

So I don't really use masses of stuff, I don't think; The laptop is the only real issue, and it is vital that I can power that.

Also, not sure if this is worth mentioning or not, but at the moment I have two batteries only; that's two batteries total, both connected and acting as joint leisure and starter, which is obviously crap. Along with getting solar, I wish to have the starter separated and run a total of three leisure batteries, which I hope should be enough.

 

I am thinking to get a total of either 300w or 320w of panels (ie, three 100w panels or four 80w panels) either of which should just about fit my available roof space as I don't keep masses on it. Realistically I can't fit any more than that on the roof, nor am I likely to be able to fund the purchase of more, should I even get as far as buying this set up!

 

So I suppose my 'how long is a piece of string' question is, assuming I got around 300-320w worth of panels in total up and running, roughly (and I know it would be very rough!) how much of my power usage could I expect the panels to provide for, in summer and in winter? Or is there a way I can go about finding out reasonably easily (ie, I can do maths but ask me to understand what a kw it and how it relates to an amp or an ohm and all I hear is "10amps plus 8kw times solar divided by kittens= Tomato, because narrowboats are blue." Or something that makes even less sense).

 

Thank you!

Edited March 1, 2013 by Starcoaster

[lexicon]

Hi star

 

AIUI with 320w of panels you will get a max of around 26 from the panels. So cut that in half most summer days (English summer) and times by hours of sun,

In winter maybe 2-3 Amps times a lot less hours.

[Starcoaster]

Hi star

 

AIUI with 320w of panels you will get a max of around 26 from the panels. So cut that in half most summer days (English summer) and times by hours of sun,

In winter maybe 2-3 Amps times a lot less hours.

 

 

Ok, great! Just a couple of questions though!

AIUI is..?

A max of around 26 what?

I guess I need to know the answer to that first to know why I would need to cut whatever it is in half for summers days?

I don't actually know what an amp is/means in relation to the panels in real terms, so the last bit means nothing to me. I see that an amp is a unit of electrical current, but without context for what that means in real terms and in relation to the panels, I am none the wiser. All I know about electric is how to wire a plug, not to use a hairdryer in the bath, and not to piss on an electric fence.

Like if I blow a 13amp fuse I know to replace it with a 13amp fuse and why a fuse is needed, but not what an amp does or why there are 13 of them!

 

Thanks for trying though.

I was not kidding when I said I didn't know how kw, amps and ohms and whatever all relate to each other. All I basically need to know at this point is if, as the end user, the setup I am considering will fit my needs or not, because I am unlikely to understand anything more!

Edited March 1, 2013 by Starcoaster

[Paul C]

As above, really. On a sunny summer's day, you'll have excess power from them 320W panels, on a winter's day you might get 10% on a nice day, during the daylight hours. So you need to generate power during the winter too, from something other than solar. Without doing a complete power audit (need to know the power requirement of the laptop and do a spreadsheet of it all, etc) 320W seems about right, possibly overkill, based on a hunch.

 

No TV?

 

No fridge?

[Starcoaster]

Cheers.

Is there an easy way to find out the laptop power? Like is there somewhere its likely to be written on it, or is that too simple?

No tv, and a threeway fridge that will run on gas (after MB has fixed it...)

So this theoretical winter 10%, thing, 10% of what? The power I got in the summer? Of 320 watts? I am trying to translate these sums into real terms... So if in winter I get this '10%' (of whatever it is?) what does that mean in terms of my power usage? Does it mean I will get a couple of hours of use per day powered by the panels? A couple of minutes? How do I know what it is in real terms, or how can I find out before I buy?

 

I understand that in the winter (or possibly summer too) I will also to run a genny or the engine; I get that solar won't provide enough energy for everything I need in winter.

Edited March 1, 2013 by Starcoaster

[Paul C]

yes, 10% of what you'd get in the summer. The summer sun is 10 times as strong as the winter sun.

 

I imagine your power usage will go UP in winter too, due to lights needing to be on for longer.

 

Laptop - it will charge the battery, then it will be fully charged, so its power consumption will vary. Easiest way to find it would be to measure it.

[kevinl]

First get rid of the light bulbs. They'll be between 10 and 25 Watts each you can replace them with LED strips, I bought 2 x 3 foot strips from Ikea at £10 each easily as good as the 2 x 20 Watt bulbs they replaced and at 3 watts each it's 40 Watts down to 6 Watts just in the living area. Tried it out by plugging them into a cigarette lighter socket (don't have 240V)and stuck them in place with double sided tape.

Next forrage for electricity, the stuff on charge under my desk at work keeps my legs warm all day, find a seat in a pub next to a plug socket, nobody I've asked has said no when I've asked if they mind me charging my phone for 10 minutes (or longer).

Fill the shower tray before you turn the pump on rather than running it all the time you're in there, better still have the switch for the pump in the shower, turn the water and pump off while you're shaving your legs and things saves water and power.

Keep looking for solar panels, something will turn up at the right price when you least expect it, e-bay is good boat/boot sales, the longer they're around the more you'll see for sale. Someone one here got a system for £1 per Watt, I've not come close to that yet but it gives you an idea of what can be done if you get lucky.

[Starcoaster]

Sure, I get you with the lights in winter, but I am of the understanding (though I may be wrong) that LED lights draw very negligible power?

The laptop, it will charge the battery, and then be fully charged but as I am using it constantly, it will never stay charged! I run the laptop plugged in. How might I measure the power consumption of the laptop?

Edited March 1, 2013 by Starcoaster

[Homer 123]

Hi Star,

Thanks for this post, it has covered just about all my questions! I'm still looking for the answers to the laptop power one and also mobile phone unless I missed it?

Thanks again for asking the questions!

[Biggles]

Hi Star

 

AIUI as i understand it.

 

If your plan it to live entirely on solar your won't do it with a 320w panel. In fact I doubt you have enough roof space to get all you need especially in winter.

 

At best its a supplemental power source in this country. In the summer you might get an excess but what you gonna do with that?

 

My 500w gets me this time of year am maximum reading of 12amps but this is no way continuous. In the summer I have seen a max of 36amp but again not continuous.

 

The main I have them is in preparation for France so the batteries get a conditioning charge.

 

I don't think you will see the returns you want for the money its going to cost.

[MtB]

Rule of Thumb: The laptop draws 5 Amps all the time it is turned ON.

 

This has the potential to turn into a 500 post thread all of it's own.... but ultimately, I'm right

 

 

MtB

[Starcoaster]

First get rid of the light bulbs. They'll be between 10 and 25 Watts each you can replace them with LED strips, I bought 2 x 3 foot strips from Ikea at £10 each easily as good as the 2 x 20 Watt bulbs they replaced and at 3 watts each it's 40 Watts down to 6 Watts just in the living area. Tried it out by plugging them into a cigarette lighter socket (don't have 240V)and stuck them in place with double sided tape.

Next forrage for electricity, the stuff on charge under my desk at work keeps my legs warm all day, find a seat in a pub next to a plug socket, nobody I've asked has said no when I've asked if they mind me charging my phone for 10 minutes (or longer).

Fill the shower tray before you turn the pump on rather than running it all the time you're in there, better still have the switch for the pump in the shower, turn the water and pump off while you're shaving your legs and things saves water and power.

Keep looking for solar panels, something will turn up at the right price when you least expect it, e-bay is good boat/boot sales, the longer they're around the more you'll see for sale. Someone one here got a system for £1 per Watt, I've not come close to that yet but it gives you an idea of what can be done if you get lucky.

 

Thanks Kev.

 

As mentioned, I am going to get LED lights.

I do not have 'stuff on charge under my desk all day' I run a laptop all day, and charge my phone once a day; That's the lot. I don't use a lot of power.

I do not and will not be going to the pub on a daily basis (may I one day be so rich)! nor anywhere else I can nick someone else's power, much less to the extent that it will make any dent in what I use.

My shower tray is 1cm deep, filling it on one side is the job of a few seconds.

I am aware of how best to conserve water in the shower, although the Paloma constantly trying to find the right temp each time I turn it on and off makes life hard.

I've been living aboard nearly 18 months now and I have established very well what I use, what I didn't need, where I can save power and where I cannot.

I am really just trying to find out specifically about solar panel suitability vs. my usage as outlined, rather than ways of saving energy (I have been doing so for some time now in the ways that fit my lifestyle!) or where to buy panels.

 

Hi Star

 

AIUI as i understand it.

 

If your plan it to live entirely on solar your won't do it with a 320w panel. In fact I doubt you have enough roof space to get all you need especially in winter.

 

At best its a supplemental power source in this country. In the summer you might get an excess but what you gonna do with that?

 

My 500w gets me this time of year am maximum reading of 12amps but this is no way continuous. In the summer I have seen a max of 36amp but again not continuous.

 

The main I have them is in preparation for France so the batteries get a conditioning charge.

 

I don't think you will see the returns you want for the money its going to cost.

 

Thanks Biggles.

I don't plan to live entirely on solar-never did- I very much doubt that would be possible in the Winter, even in a house.

 

I can't make this clear enough- when you say "My 500w gets me this time of year am maximum reading of 12amps but this is no way continuous. In the summer I have seen a max of 36amp but again not continuous." I don't understand the slightest part of what you just said. What 12amps is or does, if that is a reading that one would be happy with, what 36amps is/does/ relates to panel size/ amount of sun, what is meant in this context by continuous.

 

I would be happy if the panels covered most of my usage in summer. I would like to know if this is likely with a 300w or 320w system. So far I get the impression that it may even be slightly oversized.

I am interested to get an idea if they will provide any noticeable help in winter. I do not expect them to make any significant difference in winter.

This is the kind of information I am looking for. Very theoretical non technical simple yes, no, maybe. I really appreciate everyone's help and comments but as I said before, I just want a layman's yes or no, go bigger, go smaller, yes you are right about what you need, no, you forgot 'xxx'.

 

What returns do you think I want from them, that makes it not worth it?

Edited March 1, 2013 by Starcoaster

[jodansgang]

Hi Star, I fit 12v dc solar panels/regulators all the time at work (I build Motorhomes) and I also maintain them when they go wrong (which they never often do) and my advice to you would be buy a compass or at least check out your stretch of navvy for coverage. Remember that an over hanging tree or high wall even broken shadow will dramatically reduce the amount of current given to your battery bank from your 1-2 or three panels. Good, unobstructed sun, summer or winter should power your needs with the small amount of consumption you have described. Make sure your batteries are in good fettle as well. Hope this helps.

[Grace and Favour]

Starry - - -To determine whether solar would be a financially sound proposition - - I did my sums for Solar this way

 

My engine charging costs me, say, 1tr of fuel per hour, (I'll ignore engine servicing/maintenance in the costs just to keep it simple for this example)

Assume I had to run the engine for 3hrs per day for 6 days, and 7 hours on the 7th day - (£25 per week)

 

So - If I get an acceptable amount of power to provide my requirements for just 100 days per year, it saves me spending £357 per year on fuel

The solar panels should last at least 15 years

 

 

(and they are an awful lot quieter than my engine!)

[Starcoaster]

Thanks for your input everyone. I don't think this thread is really going to get me to where I am looking for though.

I'm not trying to establish if solar is a good option financially, where to buy it or how to take a shower; I really just wanted to know approximately how much of my energy requirements 300w-320w or solar would provide for me, in the summer, and in the winter.

That really is all I was trying to establish, literally. Apart from maybe mention if I had missed something from the list of what would be needed, ie, panels, wiring, controller and fixings.

I get the impression now that 300w-320w might even be more than I need in the summer, which is useful to know. Thanks all!

 

I appreciate you all offering input and advice on other aspects of things, but I don't think I'm going to be able to find the complete answer I was looking for here; perhaps it is not even possible to answer with an educated guess based on the info I can give and my level of understanding. Thanks for trying peeps!

Edited March 1, 2013 by Starcoaster

[Skye]

Starcoaster I'll keep it simple because you have asked us to do so, you recognise that you need more batteries (energy storage devises) and to split them domestic / starting.

how do you currently charge your batteries? (I mean the boats, not a pint or two at the local).

 

Do you run out of electricity now? If not your energy conservation is good (you). Keep that regime going and you may not need much additional input devices for the new additions.

 

Here I'm going to leave myself open to criticism, there are alternatives like wind power, but that depends on where you are moored up. Leeds Liverpool 'top a moor' you won't even have to start your engine, you'll use more energy bolting the bugger down, but tucked away in some secluded spot it aint going to be any good.

 

Let us know the answers to above and I'm sure the dark magic will be done and your answers will appear.

 

Edited to add MtB is right with the about 5A for lappy

Edited March 1, 2013 by Skye

[ditchcrawler]

Rule of Thumb: The laptop draws 5 Amps all the time it is turned ON.

 

This has the potential to turn into a 500 post thread all of it's own.... but ultimately, I'm right

 

 

MtB

That is about right for mine, bit more while the battery charges and a bit less once its fully charged. Now I tend to charge the laptop while travelling and use it plugged in when we are stopped in the evening to maintain the charge. I have heard it suggested that it would use less power with the battery removed completely.

[Ange]

Hey Starry

 

Your power requirements sound very similar to ours. We went for 390 watts of panels which Dave figured would be over the top for summer use but might give us something in the winter. We've had to run the engine over the winter, but during the warm spell we had recently we didn't have to run it. During the summer we have the fridge on which would put our usage well over yours, and the solars kept up - we didn't have to run the engine for months which was bliss! The whole cost of our set up including panels, MPPT controller, cables and connectors was less than £600. Before we had the panels we had to run the engine for 3-5 hours every day, I think they'll pay for themselves in no time just in diesel savings, let alone engine maintenance costs.

 

Jodansgang's point about unobstructed sun on the panels is an important one. Where we're moored at the moment is next to a big hedge, and that greatly reduces the power we get.

 

Hope this helps - give us a shout if you need any more information

 

ETA crossed posts with you

Edited March 1, 2013 by Ange

[kevinl]

Simple enough then buy as much as possible Wattage for as few pounds as you can, forget all the numbers and go out on a bargain hunt. As I said before someone here said they bought their system for £1 per Watt, see how close to that you can get for the amount of money you want you spend.

Best I can find is about £2 per Watt so a 100 Watt panel for £200 have a shop around and see what you can find and just get the best value for money accepting as you said you do it won't be enough to be self sufficient.

Typically the 2 lights you have on now are 2 x 20 Watt and the lappy (if I'm right MtB) 5 amps x 12 volts = 60 Watts so right now you're using 100 Watts, so for every hour you spend on here (at night) you probably need 3 hours of reasonable daylight to break even assuming you buy a 100 Watt panel and it's an average day i.e. your 100W panel would only be producing 30W.

I wouldn't worry too much about an expensive controller as a 100 Watt panel at full sunlight is probably only the same as you when your engine is running so it's not likely you'll over charge the batteries even in summer, monitor the battery level and take the panel out of ther sun if they read full (won't happen too often though).

[LoneWolf]

 

...

I would be happy if the panels covered most of my usage in summer. I would like to know if this is likely with a 300w or 320w system. So far I get the impression that it may even be slightly oversized.

I am interested to get an idea if they will provide any noticeable help in winter. I do not expect them to make any significant difference in winter.

This is the kind of information I am looking for. Very theoretical non technical simple yes, no, maybe. I really appreciate everyone's help and comments but as I said before, I just want a layman's yes or no, go bigger, go smaller, yes you are right about what you need, no, you forgot 'xxx'.

 

What returns do you think I want from them, that makes it not worth it?

 

 

I think you'll get by on 200w & 2 leisure batteries (maybe 3 due to the laptop not having an effective battery)

Whatever you choose you'll need to run the engine in the winter & you'll have surplus in summer

 

This answer is not based on any calculations at all

[ditchcrawler]

Hey Starry

 

Your power requirements sound very similar to ours. We went for 390 watts of panels which Dave figured would be over the top for summer use but might give us something in the winter. We've had to run the engine over the winter, but during the warm spell we had recently we didn't have to run it. During the summer we have the fridge on which would put our usage well over yours, and the solars kept up - we didn't have to run the engine for months which was bliss! The whole cost of our set up including panels, MPPT controller, cables and connectors was less than £600. Before we had the panels we had to run the engine for 3-5 hours every day, I think they'll pay for themselves in no time just in diesel savings, let alone engine maintenance costs.

 

Jodansgang's point about unobstructed sun on the panels is an important one. Where we're moored at the moment is next to a big hedge, and that greatly reduces the power we get.

 

Hope this helps - give us a shout if you need any more information

 

ETA crossed posts with you

What surprised me was that a fridge and a lap top are very similar in power requirements.

[Chris Pink]

how much of my power usage could I expect the panels to provide for, in summer and in winter? Or is there a way I can go about finding out reasonably easily (ie, I can do maths but ask me to understand what a kw it and how it relates to an amp or an ohm and all I hear is "10amps plus 8kw times solar divided by kittens= Tomato, because narrowboats are blue." Or something that makes even less sense).

 

Thank you!

 

Options; 250W house panel with MPPT. £300

 

3 x 100W MPPT £420

 

3 x 100W 20A PWM controller £320

 

The tomatoes you need to worry about are called Amp Hours (not Amps, Ah). This is a measure of how many tomatoes you make rather than how fast you eat them.

 

The daily consumption you describe is around 40-50 tomatoes. Possibly a bit less.

 

Important factor; you use power for the computer as you make it, making your solar setup quite efficient.

 

You will generate, with the options above all your power march to September. With a fair amount of waste in June-August.

 

In periods of grey weather you'll need a bit of a topup from engine / generator once a week or so.

 

Oct to mar. You will keep your batteries in good nick and make some of your power (10-50%) but should really think of this time as primarily generating power with fossil fuels. Charging 2-3 times per week with a decent charger.

 

Increasing or decreasing the number of panels won't affect this very much because the amount of sunlight is a sine wave over the year. When it is changing (now, September) it is changing fast. The effect of this is that most of the time your solar gives you too many tomatoes or too little and only matches briefly during the time of change.

 

The specifications above are on the high side and will increase your summer tomatoes by only a few weeks over the 200W I would consider matched to your use.

 

Obviously all this is subject to the vagaries of English weather so there is no smooth set of data. Good winter days and grotty summer ones will affect your tomatoes unseasonably.

 

You would be wise to budget for a pair of 6V batteries £250 as your domestic and use the best of your existing ones as the start battery.

 

With 300W you could consider the use of a fridge or 12V water heater in the mid-summer.

[MtB]

As I understand it, I need the panels themselves, an mppt controller unit thingy, appropriate wiring for the panels, and for them to be affixed to the roof. Have I missed anything obvious?

 

Nope, other than some wires. The y-joints for the wires are not cheap and you'll need four for three panels and six if you get four panels. Think £15-ish each IIRC. And a meter to display what the panels are doing is nice to have, like, so you can find out what the panels are doing, like, when you start wondering what they are doing...

 

 

My electric usage looks something like this:

One laptop computer (a regular average one, not an energy saving one or anything) in use on average 10-12 hours a day.

Water pump and whale gulper for daily shower and washing up.

Charging of small items such as phone and kindle.

Two lights on at any time, which alongside of getting solar, I will swap for LED's unless the cost is prohibitively expensive as I have to change the fittings or something.

that's all off the 12v power direct.

I would like ideally to be able to run a printer and small 300w twin tub from an inverter once a week, but could live without this.

 

I'd say the laptop is the big user, along with the non-led lights. Everything else is background noise, as it is in use for only short periods of time.

 

Lets's do some calcs. (DON'T LISTEN!) Laptop is 5 amps x 12 hours = 60 AmpHours. Two non-led lights are say 2 amps each, for ten hours = 40 AmpHours. Total demand 100 AmpHours per day. Assuming 50% charge/discharge efficiency in the batteries, this means you need 200 AmpHours per day from your panels to (roughly) supply all your leccy needs.

 

Now the panels. Lets start with a hot summer's day, with the panels constantly tipped up and angled towards the sun. 200 ampHours are needed from say 12 hours of bright daylight. The panels under these conditions will be supplying close to their rated output, so 200 divided by 12 = 16.66 Amps output needed. This equates to the nominal maximum output from a 200w panel, coincidentally.

 

Now lets assume a cloudy summer's day. Output is halved, roughly. So for a cloudy summer's day you need a 400 watt panel.

 

Now for a cold dull winter's day. Output is down to 10%, and hours are down to 8 per day. Now you need 3000 Watts of solar panel to keep up. OR, supplement with engine or genny.

 

 

{

So I don't really use masses of stuff, I don't think; The laptop is the only real issue, and it is vital that I can power that.

 

Basically, in summer, yes, with 400w of panels. Or less with a bit of genny back-up. In winter, no. Get a mreeena mooring, or use the genny a LOT.

 

And yes your plan of 320w will be fine for summer if you get all LED lamps.

 

I'm going to sleep now....

 

 

MtB

 

Chrsi, you have overlooked the fact that Coasty is approximately nocturnal. Her use of the lappy occurs mostly between 6pm and 6am, so most of the power for it is drawn from batteries.

 

 

MtB

Edited March 2, 2013 by Mike the Boilerman

[Starcoaster]

Chris, that's brilliant and exactly what I was hoping for, thanks.

 

Sounds like the 250w house panel and MPPT at £300 is the best bet, as well as the cheapest. Assuming the panel is not too wide for the roof, which I haven't looked into yet as I didn't consider getting one big panel until now.

I only have a paloma water heater, no 12v option for hot water, and the fridge is a threeway so would be better on the gas than 12v anyway, so that won't be a consideration.

 

Regarding the batteries, I think Jenlyn has suggested 6v ones to me when we have talked before, due to them being smaller and the space under the deck being oddly partitioned, ie, it would be easier to fit in two 6v batteries than one 12v one in any given space, because of the different configuration options. Other than this, is there a reason why 6v batteries would be better?

I would like to have three 12v leisure batteries or a total of 36v leisure altogether (when funds permit) as the best scenario.

My current two batteries are in pretty good nick, so I think adding another two 12v/ four 6v/ some combination, and using the best 12v one overall as the starter would be a safe bet?

 

I understand that in winter and sometimes in spring/fall and on grey days I will have to run the genny or the engine regularly to keep the batteries good, this is what I expected.

 

The only possible incongruency in how my usage will match the solar production in the warmer months is where you said "Important factor; you use power for the computer as you make it, making your solar setup quite efficient."

With my work and the hours I keep, I tend to use my laptop from around midday until the wee hours, so may be 'wasting' hours of light in the mornings by not using the laptop during these times, but using it later on when it has got dark.

[Chris Pink]

Ok, forget the fridge, you'll not have so much surplus. You'll only lose a bit, the battery inefficiency.

 

It's a suck-it-and-see situation, with the 20A MPPT options you can go up to around 500W - not in theory but in practice, in England - and the tracers have a meter so you can begin to equate kittens and amp hours.

 

I would still caution against too much solar, it's a matter of hitting some averages that are impossible to measure. Start with less and add more. The house panel will have size issues check this.

 

Get LED lights. Very important and will save you a dozen tomatoes each day.

 

The 6V batteries are a good match to a mid range solar system and don't suffer so much from the cycling demands, they can go down to 30% charge without costing you much more than any other routine and will help to smooth out your diurnal usage.

 

Mike's point about connectors is a good one, allow £50. Each extra panel will cost another £5 in connectors. You can, easily, wire this yourself, and save £100 on labour charges.

 

Ps I think Mike's 200ah is out by a factor of three assuming LED lights. . I have the same usage as you and I run it in summer from 120W though I will double that this year I will only expect modest improvement (in spring autumn and overcast summer). You will get most of your power from some point after equinox but you won't shift that break even point easily. The 10x summer winter ratio is true but the rate of change at this time of year is huge.

Edited March 2, 2013 by Chris Pink