Going Solar- Know nothing

[Tony B]

I will be adding Solar Power to my boat this winter. My objective is to use the generator for Air Conditioning only. We will be on a 3 or 4 month cruise from Galveston Bay to the northern part of Ky Lake, Ky.
I have many questions:

1). I have a small crane in one corner of my Aft Cabin hard top. It runs at an angle and is probably no more than 3 or 4 feet above the hard top where the panels will go. How much or how often will its shadow affect the out put and to what extent? The crane can be rotated out of the way.

2). I will be cruising the ICW for several hundred miles then will be mostly inland rivers and interconnecting lakes. I really dont expect all that many hours of direct sun because of trees, etc. casting shadows during the morning and evening hours. My Rooftop will be about 8' square (rough guess) How many square feet of panels will I need considering we are not 'high usage' people? Our trip will not be a race so many days will be just spent at anchor.

3) We currently have 2 starting batteries - one for each engine. These will not be part of the Solar Charging system. We also currently have 2 house batteries. The house batteries will be part of the Solar charging system. In reality, how many house batteries should I have?

4) Will the solar panels require some kind of of regulation? I currently have budgeted myself for around $1K for the solar system. This does not include more batteries. That will be a separate issue. I am not looking for top-of-the-line equipment but am also not looking at bargain systems. On a scale of 1 to 10, probably about a 7 or 8 in quality. What would be a decent system in this price range?

As a side note, we are used to anchoring out and roughing it on our sailboat. We are getting older (66 and 72) so we would like some creature features like unlimited use of fans, TV and the likes. I will be replacing the electric stove, hot water heater with propane and the lights with LEDS and fluorescent.

What would be some of your ideas for a solar set-up in the $1K range?

[Pete7]

Tony, I think most yacht owners would die for an 8 x 8' flat surface to mount solar on. Shadows from the crane will be a problem but if it can be swung out of the way then great.

I think the first thing you need to do is calculate your daily amp hour consumption at anchor or tied to a river bank without shore power. The rest of the time you will have an engine running so it won't be a problem. It's what happens if you stop in the middle of nowhere for several days without running the engines that count. from that figure you can then both spec the amount of solar you need and the size of the battery banks required so you don't discharge below 50%.

The good news is there is a host of information on CF how to do this. It really would be worth spending a couple of evenings reading back through the forum before you start to spend those dollars.

Pete

[s/vPainkiller]

Tony,
I've recently gone through this process myself. I've made my decisions and purchased my setup but have not installed it yet. You are starting off by asking a lot of the right questions. Let me first respond by saying that there is a TON of information already in the archives that will answer a lot of your questions. Many of these topics have been covered in great detail previously. Spend some time searching and reviewing the old threads. There is no one right answer, only the one that works for you and your budget.

In short, the amount of solar and battery capacity you need is determined by your usage. Go through your electrical demands and determine your daily AH requirements. That's the first place to start. Yes, you probably will need regulation, although there are those that do not use it. Yes, shading will definitely impair the optimal output of the panels. How much is really hard to say without making some assumptions on what percentage, and how many hours per day.

Good luck.

Scott

[Pete7]

Tony, I wouldn't rule out cheap solar panels either. We have been using an 80w e bay special panel this summer and combined with another gives us 125w of solar. This feeds a 220 AH house bank which in full sun during the summer is kept full. However, we only use 30 - 40 AH a day (fridge, lights and laptops etc) which is very low, you may use much more.

A day recently spent at the UKs largest boat show revealed the e bay buget solar panel looked identical to the much more expensive ones, made in the same chinese factories perhaps? Only time will only tell if it was the right choice but it could be the cost effective solution partcularly as solar technology moves forwards over the next decade with much greater efficiencies.

Pete

[denverd0n]

Best website I have found for educating yourself on these issues...
HandyBob's Blog

There's a lot to read there, but it is worth the time to go through it all. The whole matter of off-the-grid living is not overly complicated. It does, however, take some time, effort, and thought to do it right. The alternative is to risk spending a whole lot more than you have to, or ending up with a system that doesn't meet your needs.

[noelex 77]

If you have an area 8feet X8 feet=6 sqm (I think better in metric).

With the medium efficiency panels that gives you room in theory for about 870w.
With mounting space between panels it means in practice say 700w.i am not up with current solar prices, but this will probably go a bit over budget, but not much for cheaper ebay panels with a controller and low mounting costs.

I don't know the ICW but with the shadowy conditions you describe that will give you something like 125-175AHrs per day with 700w

Now you need to do some energy calculations to see if this will meet your demand.

Most yachts live on 100-175AHrs day, but power boats are often set up with less energy efficient gear. Some generator equipped boats use much more, so you need to determine your consumption.

[Cotemar]

Tony B,

You may want to look at SunPower panels.
They have been installed on a lots of boats with great success.
They are the most powerfull, lightweight & smallest panels you can buy.
SunPower makes a 240 & a 327 watt panel.

You will need a MPPT controller, which is the brains of the Solar panel system and takes what ever power the panels put out and brings it down to 12 volts

[Carraiadimare]

Hello,

I moved to solar pamels only this year as I was waitning for a good solution and for tecnology to be available.
In fact I bought a single cells panel wich allows charge even when partially under shadow.
I now have 2 115 watts solar panels from solbian, the same that enabled Mr Soldini to go alone in the world cross with no generator. They are expensive, abouto 1000 euros each including the electronic regulator that I agree is important.
They are very light and, including the alluminium structure that holds them and is in the price, has a weight of only 3 kg!!
They were enough to keep my two 90 ampere service batteries charged, and serve the fridge, nav instruments, autopilot and device charge.
If you are interested I can send a foto of them. Otherwise just check at www.asseaboat.com.
Sorry for my English, I'm from Italy and actually writing from Florence.

[Dsanduril]

Originally Posted by Cotemar

Tony B,

You may want to look at SunPower panels.
...
They are the most powerfull, lightweight & smallest panels you can buy.

They are the most powerful/efficient only when the positive pole is grounded, which is tough to do on most boat installations. Without the positive pole grounding the silicon will polarize, and what you end up with is a panel that is average in efficiency and power, but that cost you more.

Here is Sunpower's own research paper on the subject:

Sunpower Paper - Polarization

They make a great product, but one of the reasons (besides their profit goal) that they don't cater to DIY is that there are very specific installation requirements to prevent polarization and loss of efficiency (and loss of efficiency means unhappy customers and loss of reputation).

If you want to use them anyway, the installation manual (with the discussion of positive grounding) is here:

Sunpower Installation Manual

[djmarchand]

Given your situation: trawler with a generator, never a long time on the hook and high amphour usage; I wouldn't install solar panels. I would upgrade my shore power charger and perhaps your batteries though. Let me tell you why.

Let's assume that you use 200 amp hours a day. That is high but not unreasonable. Given your $1000ish budget you can probably buy two 200 watt panels and a suitable MPPT controller for about that much. That 400 watts of panels will supply about 130 amp hours of energy on a full sun day. The long term average will be maybe 2/3 of that depending on where you are. So solar is not going to cover all of your power needs if you are just sitting on the hook long term.

But it didn't sound like you are going to do that. Running your propulsion engine for several hours (or less if you upgrade to a high output alternator with external regulator) will recharge your batteries. And running you genset will recharge them as well. But most boats have smallish shore power chargers (powered by the genset).

So increase your shore power charging capacity so you don't have to run your generator for so long. IOTA makes very efficient, low cost chargers. Add at least a 75 amp unit to your existing charger to give you a minimum of 100 amps of charging capacity.

To use that capacity without harming your batteries you will need either 400 amphours of flooded cell capacity or 200 amp hours of AGM capacity to stay within their charging parameters. I would prefer 4- 6V golf cart batteries wired series/parallel.

The whole charger/battery upgrade can be done for about $500.

David

[Bash]

I'm going to disagree with djmarchand. It's a lovely thing to be able to sit in an anchorage for days on end without having to start up an engine to recharge the house bank. This is doubly true for the summer months, when running even a generator will heat up the cabin.

Up in the Delta we'll often sit in one anchorage for an entire week without running an engine. We're never in a situation where we have to worry about running the stereo all day, or about having left the anchor light on until noon, et cetera. With 200 gallon tankage, I'll run out of water before I ever need to worry about charging.

With 270 watts of solar (backed up by 200 watts of wind) I get by with a 420 AH house bank just fine.

[Dsanduril]

+1 on Bash's take, I love being able to hang on the hook for days/weeks at a time without running anything.

I do however, get David's argument, and to the OP I would ask "how often do you think you'll run the AC when on the hook?" If you think you'll be running it every 2-3 days during most of the season then you'll be running the genset anyway and David wins (as long as your genset is big enough to run both the AC and the battery charger at the same time).

[Bluewaters2812]

Forgive my ignorance but I wonder if there is anyone here who knows of a 40foot or bigger sailboat with all the bells and whistles not having to run a generator because they have enough in the way of solar panels, wind generators?

I am also wondering whether 800watts of solar panels will be sufficient to negate the need to run a generator? I am not suggesting do away with a generator because we don't have 365/365 days of sunshine. I am merely trying to see how one can reduce running costs.

I have read a number of posts that are quite helpful but are also very technical. I suppose the bottom line answer would be to know how many watts minimum would be required to run a 40ft plus sailboat with all the bells and whistles without having to regularly run the generator?

[Pete7]

Originally Posted by Bluewaters2812

I have read a number of posts that are quite helpful but are also very technical. I suppose the bottom line answer would be to know how many watts minimum would be required to run a 40ft plus sailboat with all the bells and whistles without having to regularly run the generator?

I think you have answered your own question, take a little while to do the calculation. However, 800w of panels is a huge amount you could run a small town on that, well perhaps not but certainly a large yacht.

The other point is that solar works very well in the UK during the summer, long day light hours and lower temperatures all help. Of course from now onwards during the UK winter things will be completely different unfortunately.

Pete

[Bluewaters2812]

Originally Posted by Pete7

I think you have answered your own question, take a little while to do the calculation. However, 800w of panels is a huge amount you could run a small town on that, well perhaps not but certainly a large yacht.

The other point is that solar works very well in the UK during the summer, long day light hours and lower temperatures all help. Of course from now onwards during the UK winter things will be completely different unfortunately.

Pete

Thanks Pete, appreciate the feedback. One of the reasons we will be leaving the UK to go to the Caribbean is exactly that ... the weather! We don't ever want to return lol. I was born in and grew up in South Africa so have spent the last 6 years hating this damp cold. We can't wait to get back to the sea again and in a warmer climate. (Another small piece of furniture went today, so a tiny bit closer to our dream. Have spent the morning ruthlessly going through the garage but will need at least another week for that task lol.

I agree, I will do my best to go through each piece of equipment in an attempt to calculate electrical/battery consumption and then install enough to power the battery banks at all times hopefully. I am hoping that 800watts of solar panels will definitely be the answer and will also cater for future additions if any?