Solar Panel efficiency - Should I upgrade

[svlamorocha]

Originally Posted by funjohnson

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

Matt

The units in your statement don't make sense. It may sound pedantic, but it is just necessary to get units right of you want to get the right answer. Equipment uses amps, each of which represent a certain number of electrons per second. It does not make sense to talk about amps per hour.

Sent from my GT-I9192 using Cruisers Sailing Forum mobile app

[newhaul]

Originally Posted by redsky49

"...In the case of the Sunpower 327w panel, if it's connected to a good MPPT controller, in perfect conditions you'll see close to 21-22A going into the batteries, much higher than the current posted right on the back of the panel...".

You mention Sunpower frequently.

I am not very knowledgeable on photovoltaics, but I thought that Sunpower panels were not marine approved by manufacturer. Don't they also only sell to vendors/installers, and not directly to users?

And what is the $100 MPPT controller you mention?

Please pardon the thread drift.

Thanks!

I would also like to hear where the 100 buck mppt controller is available.

[socaldmax]

Originally Posted by redsky49

"...In the case of the Sunpower 327w panel, if it's connected to a good MPPT controller, in perfect conditions you'll see close to 21-22A going into the batteries, much higher than the current posted right on the back of the panel...".

You mention Sunpower frequently.

I am not very knowledgeable on photovoltaics, but I thought that Sunpower panels were not marine approved by manufacturer. Don't they also only sell to vendors/installers, and not directly to users?

And what is the $100 MPPT controller you mention?

Please pardon the thread drift.

Thanks!

There are a few people on the forum who have those panels on their boats. IIRC, they were assured that the warranty would be honored regardless of where they were mounted.

You could mount panels on a house in Seattle and they could be subjected to more rain and standing water than on a boat in the Caribbean, so I wouldn't worry about it.

Most of the panels are sold through distributors to installers, but there was someone here on the board who either sold them some, or found a dealer willing to sell to the public. I've been using them as an example because they are the most efficient panels available to the public (for now) and since space is at a premium on a boat, they're a logical choice. Why mount 3x100w panels when one 327w panel produces more in heat, more when partially shaded and takes up less space?


The $102 controller is from Eco-worthy.com. Although the site says it needs to calculate shipping, it's still free. It's a nice little controller with a lot of display info (watts in, current out, battery voltage, kwh accumulated, time) and fully adjustable absorption and float voltages in .1v increments. This gives you more flexibility than just selecting a battery type, check your battery mfr website for correct absorption and float voltage settings.

A friend of mine was going to buy a Morningstar 45 MPPT, with the display, it was going to cost him a little over $600 with tax and s&h. He bought 2 of these, connected one to each panel, and probably gets (very) slightly more power since each controller can track one panel more closely than 2 on the same string. Plus there's a bit more redundancy, with 2 separate solar systems - 1 controller or 1 panel fails, you still get full power out of the other.

[mitiempo]

Originally Posted by newhaul

I would also like to hear where the 100 buck mppt controller is available.

I'm not sure which controller redsky49 is referring to but the Victron Bluesolar 75/15 MPPT is available for $110 here Victron BlueSolar Charge Controller MPPT 75/15 - 15A at 12/24 Volts

[socaldmax]

Originally Posted by mitiempo

With a good quality MPPT controller I would expect 21-22 amps @14.4 from any quality 327 watt panel.

Absolutely! I was just using that as an example. I am partial to Sunpower for boat applications, since they're currently the most efficient panel on the market and thus take less room per watt.

[hellosailor]

Reading the power output (amperage) from any MPPT controller into the batteries should be taken with a grain of salt. Your ammeter will be set to measure DC, real DC. But the output from an MPPT controller will always be *pulsed* DC (PWM DC) so it will never actually be quite the same as a pure continuous DC output.


That's not to slam MPPT, just to say "buyer beware" unless you're real intimate with your ammeter and have a way to correct for that. If the MPPT output has a 90% pulse width duration...that's still going to be 10% less power than it may read on a DC meter that can't tell it is reading pulses.

[socaldmax]

Originally Posted by newhaul

I would also like to hear where the 100 buck mppt controller is available.

This is it: ECO-WORTHY 20A MPPT Solar Charge Controller 12V/24V |Eco-worthy

It's $102, delivered. Good build quality, gold plated connectors, lots of nice features - like load control based on timer, or sunlight, full adjustability of absorption voltage, etc.

[nimblemotors]

I've seen no actual technical information on how SunPower cells can magically do what no other cell can do regarding shading, nothing about it in the literature except marketing claims. The sunpower cells used in other panels perform no magic and have exactly the same shading problems as all cells do.

They could use bypass diodes on every cell on their own panels, (you know, the ones that nobody can actually buy). This adds substantial cost.
The ideal diodes with very little voltage drop now available cost more than the cells do, so using one per cell would at least double the cost of a panel.

Regarding shading, the major problem is when a cell is fully shaded. Partial shading of a cell still has a big effect, but it is much less severe.
The older larger less-efficient Amorphous silicon cells are less effected simply because they are larger and have more material in parallel.

I repeat what I've been saying for years yet again, that using smaller panels in parallel using a MPPT controller for each panel is the best configuration when there is any shading.

[newhaul]

Originally Posted by socaldmax

This is it: ECO-WORTHY 20A MPPT Solar Charge Controller 12V/24V |Eco-worthy

It's $102, delivered. Good build quality, gold plated connectors, lots of nice features - like load control based on timer, or sunlight, full adjustability of absorption voltage, etc.

OK thanks for the link here's my personal problem with going mppt I have 2 100 watts monocrystaline panels with a 30 amp pwm controller. I know a shop locally that I can get a 100 watt aleko moncrystalline panels for 125 each. Will adding an mppt controller to existing 200 watts give me over 5 additional amps potential?

[socaldmax]

Originally Posted by nimblemotors

I've seen no actual technical information on how SunPower cells can magically do what no other cell can do regarding shading, nothing about it in the literature except marketing claims. The sunpower cells used in other panels perform no magic and have exactly the same shading problems as all cells do.

They could use bypass diodes on every cell on their own panels, (you know, the ones that nobody can actually buy). This adds substantial cost.
The ideal diodes with very little voltage drop now available cost more than the cells do, so using one per cell would at least double the cost of a panel.

Regarding shading, the major problem is when a cell is fully shaded. Partial shading of a cell still has a big effect, but it is much less severe.
The older larger less-efficient Amorphous silicon cells are less effected simply because they are larger and have more material in parallel.

I repeat what I've been saying for years yet again, that using smaller panels in parallel using a MPPT controller for each panel is the best configuration when there is any shading.

In order to see it, you must pay attention.

I posted a video in this thread, dramatically showing exactly how much a normal panel loses vs a Sunpower panel.

Here it is again:

https://www.youtube.com/watch?v=dlZSL4C0VYQ

Notice at 1:04 in the video, the sunpower panel is producing 267.3w vs the larger panel producing 189.6w. I'm assuming they're both rated at 327w.

When they shade one cell on each of the 2 panels, the Sunpower drops to 237.1w, the other panel drops to 124.9w. The Sunpower panel produces 1.9x the output of the slightly larger panel.

As for the technical explanation, they claim it's all in how the cells are connected, allowing the panel to bypass any cells that are shaded.

[socaldmax]

Originally Posted by newhaul

OK thanks for the link here's my personal problem with going mppt I have 2 100 watts monocrystaline panels with a 30 amp pwm controller. I know a shop locally that I can get a 100 watt aleko moncrystalline panels for 125 each. Will adding an mppt controller to existing 200 watts give me over 5 additional amps potential?

No, you're not going to get 5 amps more out of your system with MPPT. You're already getting a surprisingly good amount of power out of your existing PWM controller. You might get 1.5-2 amps more under certain conditions, like cool weather, early in the morning, etc. but at the end of the day, or over the course of a week, it all adds up.

I hope you're not like me, I'll lay awake one night agonizing over 15 electrons I didn't get harvested, and in the morning, I'll go online and order an MPPT controller. It's not a wise decision financially, but it's the only way I can sleep.

[newhaul]

Originally Posted by socaldmax

No, you're not going to get 5 amps more out of your system with MPPT. You're already getting a surprisingly good amount of power out of your existing PWM controller. You might get 1.5-2 amps more under certain conditions, like cool weather, early in the morning, etc. but at the end of the day, or over the course of a week, it all adds up.

I hope you're not like me, I'll lay awake one night agonizing over 15 electrons I didn't get harvested, and in the morning, I'll go online and order an MPPT controller. It's not a wise decision financially, but it's the only way I can sleep.

Nope I'm a retired navy mechanical engineer. ( hull tech)
It was always my job to " make it work" not spend optar
My lack of sleep is due to much different reasons

[newhaul]

Here's one for ya right now with overcast skys I'm seeing almost 8 amps out of my 200 watts ( side note the panels are windy nation made with sun pro mono cells)
Weather | Personal Weather Station: MTCNW1 by Wunderground.com | Weather Underground this station is less than a mile from the boat and showing a UV index of 3

[LeaseOnLife]

Originally Posted by nimblemotors

....

They could use bypass diodes on every cell on their own panels, (you know, the ones that nobody can actually buy). This adds substantial cost.
The ideal diodes with very little voltage drop now available cost more than the cells do, so using one per cell would at least double the cost of a panel.

...

I think you are on to something: look at the Vmp for a Sunpower X-series SPR-X21-255 panel: 42.8V. Looks to me as all cells are connected in series, traditionally worst case for shading resistance.

Then I found this tidbit @ http://www.energyplussolar.com/s/Pro...iency-ocir.pdf

SunPower cells have built-in diode protection, so partial-shading has much
less impact
• For these shade conditions:
E-Series is about 2x better than Conventional
X-Series is about 4x better then Conventional

Now, just where can I buy a couple SPR-X21-255 in the US

Dirk

[mitiempo]

Originally Posted by newhaul

.....here's my personal problem with going mppt I have 2 100 watts monocrystaline panels with a 30 amp pwm controller. I know a shop locally that I can get a 100 watt aleko moncrystalline panels for 125 each. Will adding an mppt controller to existing 200 watts give me over 5 additional amps potential?

You might get 2 or 3 amps more with MPPT.

If you have the space get the extra panel. If you have the budget add MPPT later to maximize the array.