Solar Power Feedback

There is some confusion in the article on a couple of points.
1. A solar panel produces various voltages depending on the incident sunlight and source a current dependent on the load at that voltage. The point of a switching solar regulator is to produce the desired voltage (e.g. 13.8V) at maximum efficiency at any input voltage as long as the load power requirements can be met. That is why it is valid to give a power rating to the solar module for its peak unregulated conditions. A good switched mode regulator/charger would usually be more than 90% efficient. Losses due to "heat" are fairly small.
2. There is some confusion in units here. An Amp/hour unit is fairly a meaningless unit. I think the author means Amp Hour which is a unit of charge (as used in battery capacity). A Watt/Hour is similarly meaningless and I think the author means Watt Hour which is a unit of energy.
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Reply By: Member - Ed C (QLD) - Wednesday, Mar 10, 2010 at 22:46

Wednesday, Mar 10, 2010 at 22:46
OK then, if you say so......................

;-))
Confucius say.....
"He who lie underneath automobile with tool in hand,
....Not necessarily mechanic!!"

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Follow Up By: Priscillian - Wednesday, Mar 10, 2010 at 22:52

Wednesday, Mar 10, 2010 at 22:52
...and LED lights are up to 4 times more efficient than Fluoro's.
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Reply By: Rockape - Wednesday, Mar 10, 2010 at 23:00

Wednesday, Mar 10, 2010 at 23:00
Priscilla, you asking or telling
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Follow Up By: Priscillian - Wednesday, Mar 10, 2010 at 23:03

Wednesday, Mar 10, 2010 at 23:03
I ,Priscillian, am just pointing out some things in the article that are confusing and stating why they are.
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Follow Up By: Rockape - Wednesday, Mar 10, 2010 at 23:08

Wednesday, Mar 10, 2010 at 23:08
Sorry, what article do you mean
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Follow Up By: Priscillian - Wednesday, Mar 10, 2010 at 23:10

Wednesday, Mar 10, 2010 at 23:10
http://www.exploroz.com/Vehicle/Electrics/Solar.aspx
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Follow Up By: Rockape - Wednesday, Mar 10, 2010 at 23:26

Wednesday, Mar 10, 2010 at 23:26
Now we know what you mean.

There are a couple of people on this site that will answer your question.

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Follow Up By: Mandrake's Solar Power- Thursday, Mar 11, 2010 at 12:40

Thursday, Mar 11, 2010 at 12:40
Rockape - I don't think there was a question - Just a complaint .

Rgds

Steve
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Follow Up By: Priscillian - Thursday, Mar 11, 2010 at 12:50

Thursday, Mar 11, 2010 at 12:50
No, I'm not complaining about anything. I was just making an attempt to give more accuracy to the article. No offence intended.
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Reply By: Lex M (Brisbane) - Thursday, Mar 11, 2010 at 13:18

Thursday, Mar 11, 2010 at 13:18
1. A solar panel produces various voltages depending on the incident sunlight and source a current dependent on the load at that voltage.

I think you'll find it more accurate to say a solar panel produces current depending on the incident sunlight and the voltage depends on the load.
(Otherwise the short circuit current rating does not make much sense.)

By a switching solar regulator do you mean a MPPT or just a PWM?

2. Quite amazing that the well known and respected author of that article stuffed up the units. Just shows we're all human.
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Follow Up By: Priscillian - Thursday, Mar 11, 2010 at 13:44

Thursday, Mar 11, 2010 at 13:44
Of course you are correct, I was assuming there would be a load attached.
If there were no load only the voltage would vary with sunlight. If there was a short circuit only the current would vary. In between these limits they both vary according to the IV curve of the particular cell or panel.

a MMTP is a PWM circuit but a PWM controller does not necessarily have an MMTP function (they all should because it adds not a lot of cost or complexity) . I was talking about a simpler non tracking regulator/charger using a buck-boost switcher circuit.
It is unfortunate that the unit amp-hour is used instead of the basic unit of charge- the coulomb. Similarly the unit Watt-hour is used for energy instead of Joule. This is an historical thing I think.
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Follow Up By: Lex M (Brisbane) - Thursday, Mar 11, 2010 at 14:58

Thursday, Mar 11, 2010 at 14:58
"a MMTP is a PWM circuit but a PWM controller does not necessarily have an MMTP function"

If you mean MPPT (maximum power point tracker) then you will find most MPPT controllers are not PWM as such. They are programmable DC-DC Converters with microprocessor control.

PWM controller with MPPT. I don't think so unless you put the old analogue MPPT controllers in that category.

Don't know about a buck-boost controller. Terminology doesn't fit solar controllers.

On the market there are three broad classifications of solar regulators.
1 A hysteresis switch. Switch on at X volts, switch off at x+y volts. repeat.

2 A PWM controller, usually three or more stage. Stage one, switch on until battery reaches programmed voltage 1. Stage 2, PWM function to hold voltage at programmed voltage 2. Stage 3 PWM function to hold voltage at programmed voltage 3.

3 A MPPT controller. Stop DC-DC converter, apply various load conditions to ascertain maximum power point of panel under current conditions of light, heat, etc........................
Program DC-DC converter to load solar panel at that point and output appropriate voltage/current to battery for the current state of the charging regime and start converter. Repeat procedure periodically to test for change in light conditions etc....

"It is unfortunate that the unit amp-hour is used instead of the basic unit of charge- the coulomb. "

I agree. It would avoid a lot of confusion amongst those unfamiliar with the terminology. But I don't know if I could carry a 360000 Coulomb battery. A 100 Ah one is heavy enough.

(For anyone unfamiliar - 1 Ah = 3600 coulombs)
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Follow Up By: Priscillian - Thursday, Mar 11, 2010 at 15:40

Thursday, Mar 11, 2010 at 15:40
Yep I've got my Ms, Ps and Ts all mixed up there. Brain shutting down.

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Reply By: Nomadic Navara - Friday, Mar 12, 2010 at 12:34

Friday, Mar 12, 2010 at 12:34
Priscillian - you said "That is why it is valid to give a power rating to the solar module for its peak unregulated conditions. A good switched mode regulator/charger would usually be more than 90% efficient. Losses due to "heat" are fairly small."

Solar panels were rated by their peak power point because in the early days the panels were used for water pumping. The motors on the pumps were constructed to make use of all the available power - that is why the PP is used for rating panels.

A PWM regulator may be 90% or more efficient if you consider its input power to the output power. However the PWM regulator does not draw all the power that is potentially available from a panel. That is why MPPT regulators were developed.

PeterD
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