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laika · 23-05-2015, 10:09

There is a very intriguing wind gen being built and sold thru marinebeam.com that has me rethinking my strictly solar install..The best marine wind generator - MarineKinetix

FWIW

socaldmax · 23-05-2015, 11:17

Quote:

Originally Posted by monte

We have 1150W of solar and on passage average about 20Ah as well. Battery bank is 840Ah
Ok for a week or so but then we have to run the engine for 1hr at night. I don't think more solar is the key for passage making. Next long passage we will reduce power consumption as much as possible. Watt and sea type hydro generators might be a better option. We found the sails shaded the panels a lot heading east to west in the northern hemisphere. We also had 2 fridges and laptop, plotter,radar, etc running full time so there's definitely room to cut back on usage

Shading is a huge problem. You really weren't getting anywhere near 1150w out of the panels due to the shading. 300w produces 20 A, so you were losing 850w due to shading.

**newhaul** · 23-05-2015, 11:30

Quote:

Originally Posted by socaldmax

Shading is a huge problem. You really weren't getting anywhere near 1150w out of the panels due to the shading. 300w produces 20 A, so you were losing 850w due to shading.

Sorry but according to most manufacturers of small 100 watt panels 300 watts is not 20 amps out its more like 17 amps tops and real world only about 15 amps depending on panel temps

**newhaul** · 23-05-2015, 11:34

And I bet the 20 ah was a typo and supposed to be 200 ah

socaldmax · 23-05-2015, 11:49

Quote:

Originally Posted by Jaymannyc

My current solar panel set up is:

2 x 85 watt 12.5% efficient by Solartech (40 inches by 26 inches on the dinghy arch with zero shading)
4 x 55 watts, 13.2% efficient by Solartech (25 by 25 inches each built into hard top)
Total wattage: 390 watts
Solar controller is MPPT by Victron.

I am looking at replacing the panels with 4x 110 watt by Solara to increase wattage by only 50 watts BUT efficiency from 13% to 22%.

Here is my question. The new panels are the same surface area as the old panels and the efficiency is almost double then why are the panels almost the same wattage? Will I just get the same output and have wasted money? My hope is they would produce more during the non peak hours. Two panels with the same wattage and different efficiencies should have different surface areas (just a mathematical fact)?

I placed an amp clamp every hour on the input to my solar controller to give measure the output of the panels. I am in Grenada in May. This was done on a day without clouds.

7am 6 amps
8am 13 amps
9am. 19 amps
10am. 22 amps
11 am. 24 amps
Noon. 24 amps
1pm 22 amps
2pm 18 amps
3pm 15 amps
4pm 9amp
Almost 170amps for the day.

THANK YOU FOR ANY ADVICE!

The answer is...

the Solara panels are not 22% efficient, that is their cell efficiency, their panel efficiency is much lower. As you noticed when you compared size vs output, they aren't much more efficient than the panels you currently have.

Since you're producing 24A at midday with only 390w of panels, I can see you're getting very little shading, the theoretical limit for 390w of panels is 26 A, and you're not far off, especially for this time of year. Actually, for this time of year your output is very good!

IMHO, the only panels worth trading up for are Sunpower E series, 327w panels at 20% efficiency (Solara isn't in the same league.) However, they're big, 61.4"x 41.2", fairly expensive, and require a controller capable of taking 65Voc, which leaves out a lot of the lower end/lower priced controllers.

I'm not familiar with Victron, but units like Morningstar, Midnite Solar, Xantrex, Outback, etc can all take 150Voc, none of them are cheap.

Considering how well your system is working, if your Victron can take more current, I'd simply add 2 more of the 85 watt panels on the dinghy arch, for a total of 560 w producing about 35 A, under these conditions. I'd expect just over 37 A in the summer. You're very fortunate with so little shading! I wouldn't spend a ton of money buying more expensive panels and trying to make them fit and possibly changing out controllers (if you want to run some in series) unless you really want to go big, like 981w, 1,308w, or higher.

Depending on whether you're running a 12v or 24v battery banks, it looks like you could run up to 700w (12v) or 1400w (24v) into most of the Victron line, possibly more if you have a higher power model.

socaldmax · 23-05-2015, 12:11

Quote:

Originally Posted by newhaul

Sorry but according to most manufacturers of small 100 watt panels 300 watts is not 20 amps out its more like 17 amps tops and real world only about 15 amps depending on panel temps

20 A out of the controller. I should have been more specific: theoretical output.

Let's take an example, Grape solar 100w panel. (The math works with any brand of panel.)

18Vmp, 5.56A, 100w. The math makes sense, 18x5.56 = 100.08w

Now we pump that into an MPPT controller. 100w converted down to 14.8v = 6.757A.

Since 100 = 1/3 of 300w, let's multiply by 3.

6.757 x 3 = 20.27A. Yup, the math works.

More importantly, it agrees with all of my observations on both of my solar system MPPT controllers in the summer sun. That's a theoretical amount, but it's not too far off from observed. You might lose .2A or so due to inefficiency of the controller, and another 1.5A due to panel temp. but you're certainly not going to lose over 5A.

If so, you might consider finding a better quality controller, or remount your panels for better cooling.

Also, you might want to tell the OP his ammeter is reading too high, since he was producing 24A out of a max of 390w in May. According to my math, his theoretical absolute max. output was 26 A, and he was only 2 A off of that.

Either his ammeter is wrong, or he's fibbing, plus I'm wrong, or....

somebody else was misled.

socaldmax · 23-05-2015, 12:19

Quote:

Originally Posted by newhaul

And I bet the 20 ah was a typo and supposed to be 200 ah

The correct unit is Amps, and no, 1150w of panels has a theoretical max output of 77.7A at 14.8V. That's with sun directly overhead, cool day, MPPT controller, batteries that will take the current, no shading, etc.

Is this a calculator issue, or do we need to go over the math?

**newhaul** · 23-05-2015, 12:57

Quote:

Originally Posted by socaldmax

The correct unit is Amps, and no, 1150w of panels has a theoretical max output of 77.7A at 14.8V. That's with sun directly overhead, cool day, MPPT controller, batteries that will take the current, no shading, etc.

Is this a calculator issue, or do we need to go over the math?

The op stated 20 ah not amps so I would bet that he meant to type 200 ah not 20 amps he also stated he could run a week with solar alone prior to needing a top off of an hour with the mains or Genny so I would assume he is getting far better than 20 ah per day.
On other fronts the only issue I find was you were talking theroretical to controler and I was talking real world to batteries.

Matt Johnson · 23-05-2015, 13:17

Monte was saying he uses 20 amps an hour while cruising.

Matt

**Bulawayo** · 23-05-2015, 13:36

Monte, with so much solar you still didn't have enough energy? We have 3x 340watt Kyocera panels and 2x 110w panels plus 2x D400 wind gennies and never have an issue. The two smaller panels are on the bimini and one is often shaded. We have 3x Rolls lead acid batteries (12 md 375), new in early 2014, giving 1125A. We swear by these batteries but, boy, are they heavy. I believe that two (750A) would have been adequate.
We also run a chart plotter, three lots of refrigeration, VHF full time, autopilot, a 12v water maker and the usual other stuff. We often run our radar at night or in poorer weather, otherwise it is usually off. We did change all our lights to LED.

**newhaul** · 23-05-2015, 13:38

That's a lot of power works out to be 480 ah per day. We use less than 50 ah when underway but also just paper charts and a handheld GPS to take positions with every few hours

**Bulawayo** · 23-05-2015, 13:53

You are absolutely right but when it comes to power and water we like to have enough. Our battery bank can tide us over on the rare occassions of an overcast day (the panels are still generating even on a cloudy day) and when the breeze dies or we are anchored in an especially protected location. It is a nice feeling.

socaldmax · 23-05-2015, 13:57

Quote:

Originally Posted by newhaul

The op stated 20 ah not amps so I would bet that he meant to type 200 ah not 20 amps he also stated he could run a week with solar alone prior to needing a top off of an hour with the mains or Genny so I would assume he is getting far better than 20 ah per day.
On other fronts the only issue I find was you were talking theroretical to controler and I was talking real world to batteries.

I think funjohnson is correct. The post above Monte's post mentions USING 20ah, and Monte says "20ah as well" so it looks like he meant they consumed 20ah.

I'm not going to assume he left off a 0, he can correct that if it's true.

As for my calculations, no, those are Amps into the batteries - as evidenced by 14.8V, = charging voltage, not solar panel output voltage. But it should be very close, most decent MPPT controllers are 95% efficient or better.

Sure, panel output will drop as temp increases, there are line losses, you'll lose a few % through the controller, but many people on here have reported solar harvests closer to 18-19A per 300w of solar, and the OP is also in that group, even though it's only May.

How much current are you getting out of your solar array?