Latest Solar Field Test.

Jim,
From memory your battery is a 100A/hr AGM. Is that correct?

Geoff.

That's interesting Jimbo

I'm sure I read somewhere that panels actually perform better in sunny cold weather than sunny hot.

Cheers cob

We went away for 8 days last week and set up the solar panels on arrival. We have 2 x 80w and they charge the batteries (2 x 105amp DC ) on the CT. Not once during the trip did the Batteries get under 12.8amp on the Volt meter. They were running a 60litre Evacool, 18litre Waeco and assorted lights. Fairly happy to say the least.

Jimbo,

What's up with the Terracan Forum ?

Just a few comments.

All solar modules convert light energy not heat energy.

All except amorphous modules lose about 0.5% output for every degree C over a CELL temperature of 25 degrees C. This is generally misunderstood however as being over 25 degrees ambient. The 25 degrees C cell temperature actually corresponds to about 5 degrees C ambient. (The makers do spell this out, but in techo-gabble, on the panel at the rear of the module).

All such modules have therefore lost about 10% of their output at 25 degrees C ambient and a lot more where I live in the Kimberley.

There is also a power matching loss that results in a further typical loss of 15-20%.

In practice a typical 120-watt module produces about 89 watts in most places. Most makers claim a typical 57-59 watts for their '80-watt' modules. In my experience this is accurate.

Amorphous modules (of which there are about six makers - of which the best-known is Uni-Solar) gain output very slightly as temperature rises.

Up here, my 28 by 64-watt Uni Solars produce much the same as my 80-watt Solarex once over 35 degrees C. The downside is that they are over twice the area per watt of other modules. That's why I use Uni-Solar for our big home system and others on my OKA.

If you want to know more about solar there's heaps on my website. Address as above except replace collyn@ by www.
Collyn Rivers

Jim

Pretty much spot on.

Most modules lose 50% or more output if shaded by 5%-7% of their surface - and close to all of it if shaded by more than 30-40%.

By contrast an amorphous module loses output in proportion to about 10-20% more than the area shaded. Thus 10% shading of a 64 watt module is likely to reduce output by about 11%-12%.
Collyn Rivers

Mainey

This is a common effect and happens often where I live (about 400 metres from the Indian Ocean north of Broome. It is particularly common when the cloud is low, white and scattered - and even more so close to sea - or lightish colour ground.

What is happening is that the sunlight is being reflected back from the earth's surface and bounced down again from the clouds. The max occurs when the sun shines through a gap in the clouds.

It is common for my system (now 32 by 64-watt modules) to put out close to 40 amps into the 48-volt system when this happens - this is about 25% over the theoretical maximum.
Collyn Rivers

Jimbo - all modules behave as I described above (ie when light is reflected to and from the earth's surface and low white clouds).

But all amorphous (only) modules also have another characteristic that increases output - that I'll get to in a moment.

Firstly - no modules exceed their 'theoretical limit' as such. What they may exceed is what the makers claim for them.

Their output is proportional to the intensity of light. Their claimed output is measured at a high but closely defined light level (and also defioned atospheric losses). If that level is exceeded (via reflected light) thent the output will increase - - sometimes, but usually only for a short time, to way beyond the maker's claims.

That's what happens if the light gets bounced back again on to the modules.

In other words the modules do as predicted theoretically.

Amorphous modules have another characteristic (that results in vast confusions around campfires!) is that amorphous modules produce 10-15% more output (than claimed in the test specs) for their first few months. They then gradually drop back to the claimed test levels.

Depending on what you are selling (or which side of the river you are shouting from!) this effect causes one set of people to claim that Uni-Solar etc produce more than claimed - and another lot to claim they lose output over time.

Both arguments are thus true - and both substantially irrelevant!

Uni-Solar are excellent where you have ample space and temperature is commonly 30 degrees C plus, and/or partial shade performance is vital. Their big drawback in applications where space is limited is that they are twice the area of recent mono- and poly-crystaline modules for the same wattage output in the same conditions)

In my view, mono/poly-crystalline modules are an all round better bet where compact size is important and/or where average tempearture is coolish. - The colder it is the better they work.
Trust this helps (all this stuff is in my books!)
Collyn Rivers