Solar panel wattage VS size, discussion !

Jaahn · Guru

Solar panel wattage VS size, discussion !

Whenarewethere · Guru

I think some of the problem is various companies give you efficiency for the actual cell, probably with no glass in front.

For my situation the actual cells use only 72.7% of the overall area of the panel. On this point alone there is a substantial drop in watts per square metre of the overall panel.

_MG_1837 (3).jpg

_MG_1837-73percent (2).jpg

Whenarewethere · Guru

Jaahn wrote:
My comparison panel 200W size 1580 x 810 mm. Some offered were 1480 x 680, or 1476 x 670, some 300w panels 1330 x 990.

Looking at the 300w @ 1330 x 990 panel.

That's 300 / 1.3167 m² = 227w/m².

On a fabricated panel allowing for aluminium frame, cell spacing, glass, wiring resistance, controller inefficiency.

I will but polite, 227w/m² is BS!

Jaahn · Guru

Whenarewethere wrote:
Jaahn wrote:
My comparison panel 200W size 1580 x 810 mm. Some offered were 1480 x 680, or 1476 x 670, some 300w panels 1330 x 990.
Looking at the 300w @ 1330 x 990 panel. That's 300 / 1.3167 m² = 227w/m².
On a fabricated panel allowing for aluminium frame, cell spacing, glass, wiring resistance, controller inefficiency. I will be polite, 227w/m² is BS! ( spelling corrected)

Hi smile

I continued to look at panels and sizes. I found some from a supplier that listed a series of 24V panels that were a good size for 'my' situation. 1330 x 990. An extra row of cells to increase the width and thus shorter length. Great ! However on looking further at their online store, that supplier has 4 panels on offer all the same dimensions but different wattages ?? 200W, 250W, 300W , 350W. The voltage are similar at about 37-39 Vmp so that's OK. The Imp amps are 5.45, 6.60, 7.79, 9.50. HMMMMMMM interesting. The difference seems to be the claimed brand of the cells used; none, Q, Kyocera, Sharp. Does that make such a big difference. cry Noted this statement

"Certified by German TUV, IEC61215, IEC61730-1, IEC61730-2, CE,C-tick;" what ever that means ?

Hmm almost worth buying some to test them. Cheap at less than $200 with free freight. I would be interested to see what is the variable if they do not produce as described, the voltage is unlikely because that is largely dependent on the cell number, so the current I guess. But possibly if the top one puts out about 200+ W it would be OK for most people to use.

Has anybody bought any of these panels and wants to report. aww Down in Melbourne so I will not be going for a look-see currently. disbelief

https://www.ebay.com.au/sch/m.html?_ssn=3a-power&LH_PrefLoc=&_from=R40&_trksid=p2499338.m570.l1311&_nkw=24v+solar+panel&_sacat=0

Jaahn

Alijac · Member

"[...] ...voltage setup...[...]"

Where energy outputs from solar panels, inter alia., are concerned, it's quite often a $etup in more ways than one.

It's always best to roundly ridicule those commercial operators who promulgate false/misleading statistics about their - what are often highly over-priced - products. Like these companies (not forgetting myriad those retailers who wouldn't know, or care, zip about whether the risibly-adverti$ed $tatistic$ will be of valid benefit in actual use by their customers) boasting that their ignition coils whack out 80,000-100,000 volts, but then neglect to mention that their ignition coils won't ever reach such high voltages unless you detach a sparkplug lead from its spark plug when the engine's running and keep its end well away from an earth return (like the engine block), because under normal operation of your engine, the ignition coil will have easily delivered its electrical energy across the relatively tiny spark plug gap at around only 20,000-30,000 volts; not forgetting that if you DO (it's best you DON'T!) pull a spark plug lead off of its sparkplug when the engine is running and keep it too far away from an earth return, it'll stress the damaging-daylights out of your helli$hly over-priced ignition coil (given there's only some copper wire and iron inside 'em!) as the voltage across the coil's secondary winding inside climbs astronomically trying to find a way to expend its pent-up energy and will then take the easier route of breaking-down the insulation and arcing-over inside, rapidly rendering the coil u$ele$$, and then you'll, $urpri$e, $urpri$e, be up for a new one.

*Light*-fingered *Shady* retailers who aren't too bright shouldn't be allowed to off-load their crappy solar panels onto s_unsuspecting customers so that they can shut-up shop early and just coil_up under the $un somewhere at our expense.

dorian · Guru

ISTM that most of what you see on the Net is BS, at least where solar panels are concerned.

I examined this eBay listing:

https://www.ebay.com.au/itm/24V-350W-MONO-SOLAR-PANEL-CARAVAN-HOME-OFF-GIRD-24V-BATTERY-CHARGING-36V-MODULE/283891924757

Voltage at MPP = 38.7V

Current at MPP = 8.96A

So 38.7V x 8.96A = 346.8W, which is close enough.

There are 3 references to the solar cells:

Model: 2020

Solar Technology: Monocrystalline

High conversion efficiency Grade A Q-Cells

Cell Grade: Grade A

They're claimed to be SHARP cells, but they're also claimed to be Grade A Q-Cells. Something is not right here.

AFAICT, here is the web site for Q-Cells (datasheet page):

https://www.q-cells.com/en/main/service/download/datasheets~datasheets~.html

I have picked two datasheets at random:

https://www.q-cells.com/dam/jcr:dd4261e0-b97e-42aa-84b8-f55e7ccdbbce/Q_CELLS_Data_sheet_Q.PEAK_DUO-G5_QD_315-335_Global_2020-02_Rev01_EN.pdf

https://www.q-cells.com/dam/jcr:f0be21ec-fd73-4776-bc6e-8d919c5c2d5b/Q_CELLS_Data_sheet_Q.PEAK_DUO-G8+_340-360_2020-01_Rev01_EN.pdf

These datasheets show two panels with two different sizes. Each panel has 5 power ratings, the difference being due to efficiency. The first panel is rated for 315W, 320W, 325W, 330W and 335W. The second is rated for 340W - 360W in steps of 5W.

The efficiency of the first panel varies from 18.7% to 19.9%.

The efficiency of the second panel varies from 19.0% to 20.1%.

So who are Q-Cells?

https://www.q-cells.com/en/main/about/our_location~our_location~.html

Q CELLS is headquartered in Seoul, South Korea. Our headquarters for Technology & Innovation is located in the Solar Valley in Thalheim, Germany, where we develop our product portfolio "Engineered in Germany". Excellent scientists and engineers make continuous improvements to existing technologies in our in-house research center developing new innovative product generations.

Our products are manufactured in our international facilities in China, Malaysia, USA, and South Korea. The products and services are sold via our worldwide sales network, spanning photovoltaic markets in Europe, North America, Asia, Australia, South America, Africa and the Middle East.

If you're getting 20% efficiency from this panel, then its expected power output would be 1.33m x .99m x 200W/sq m = 263W.

-- Edited by dorian on Monday 5th of October 2020 07:45:32 PM

Jaahn · Guru

Hi Dorian smile

Doing a bit of good research. Yes the cheap solar and retail is full of BS. Fake news even yawn Come in punters ! confuse

Just a comment on the list of panels with the 5W steps. I understand the normal practice in manufacture is to assemble similar tested output cells into each panel. Then the finished panel is tested with a standard light source and rated for actual output. The panels then have their sticker put on.

Thus the panels are rated in 5 W steps for the same nominal physical size. Obviously the best are worth a bit more. It has been done that way forever. I have a BP solar panel spec sheet received with my house panels 10+ years ago which show that clearly in all sizes. aww

Jaahn

Hmm I though I would look up ISTM as I was an associate member of the forth one in this list ??

Acronym	Definition
ISTM	It Seems To Me
ISTM	International Society of Travel Medicine
ISTM	Irish Society of Travel Medicine
ISTM	International Society for Testing Materials
ISTM	International School of Tactical Medicine (Palm Springs, CA)
ISTM	International Semi Tech Microelectronics, Inx (defunct Canadian holding company)

Hmmm alijac ?? Not so sure the relevance but keep interested !

-- Edited by Jaahn on Tuesday 6th of October 2020 12:36:08 PM

dorian · Guru

Sorry, I probably should avoid acronyms in this forum. This acronym was common practice in text based forums about 20 years ago, along with AFAIK, AFAICT, AFAICS, IIUC.