Solar Cell Output

More than you'd ever want to know about solar cells:Solar cell - Wikipedia, the free encyclopedia

Wikipedia was the first place I checked, but it didn't address my question.

"Does the output from a solar cell increase in direct proportion to the intensity of the light source?"

No.

However...

the current source (IsubL) output, shown on the wiki page circuit model, IS considered to be proportional to the incoming photon flux.

If I remember correctly, it does to a degree. Then there is a point at where it hits it's limit of how much energy it can output; at this point increasing the light does not affect the output. There are other factors too, I don't doubt that some are sensitive to certain wavelengths of light. Efficiency was around 25% but 'they' seem to be pushing the 40% level now.

The output from the typical solar cell is not generally a linear function of the light intensity. The relationship will be a curve that asymtotically approaches the maximum output. At lower intensities, however, there will be regions of the output curve that are, for all practical purposes, linear. You may also find that at the lower end there is a step up from zero at some low intensity level- this may have to do with the diodes installed in the system, or may be an artifact of my measurement procedure. The only way to actually determine what you get is to measure it. And, you will find that what you measure is not necessarily in agreement with what the manufacturer claims...

GA

Output is also dramatically effected by temperature.

Having had a bank of 3-44w panels for 20+ years, I would agree with you and post #3. However the diodes are integral within the panels, and any other diodes if properly sized are of no consequence. We're talking millivolts here. I use a 50v, 40amp isolation diode that seems to have no effect on output.

Hi, during the past weeks i'm making lots of inquiry on solar cells, because i'm planning to install one in my house. I'm located in Philippines(mostly sunny all year). I have a terrible electric bill and want to reduce it somehow due to environment concern. (i am actually working as a senior mech. engineer in a big combined cycle power plant.) Question???(inside an ongoing thread, i think is allowed? yes?) 1. How do you manage your loading on 3-44 watts panel(light bulb?,desktop pc? etc), because i'm planning to start with same capacity you have, just to gain an experience. Next year i'm planning to build a new house fully roofed with solarcell. 2.In the US at present how much it will cost you(rough estimate) if you will install a complete 3-44 w set including inverters and good set of baterries.? 3. What nice brands manufacturer of residential solar cells can you recommend? you reply(input) will be very much appreciated..

Hi Meched,

1) Currently I'm using the largest marine deep cycle battery I can lift. That provides backup for lighting, coffee grinder/maker, and laptop as well as full duty as power to a 320 cfm blower to cycle hot air (5-9 hours a day). I have replaced most of my incandescent lights with CFL's.

2) I haven't priced a PV system in years. The gel type deep cycle batteries are a waste of money. Stick with regular marine or golf cart types. When your system gets larger use fork lift batteries.

3) I can't recommend any since I have not kept up with the PV market, but Goggling, will keep you busy for a while comparing manufactures/price. Get hold of a book and a magazine subscription for photovoltaics to find the latest in technology. I will change by the time you get your house built.

Hi Tippycanoe,

Thanks a lot

Cheers

Meched

Hi

I design and install PV/micro-hydro systems. Right now solar panels are the cheapest I've seen them and you can get them in the USA for $3+/watt of panel. I don't know your situation, but I never recommend installing "solar" roofs. If/when the roof fails, it would be a rather expensive fix. 3 panels @ 44 watts is pretty small, my supplier doesn't even carry panels smaller than 175 watts anymore. Inverter cost is pretty variable based on your load demands. I use Outback Systems, but their inverters start at 3kVA. As for batteries, at the very least use the 6 or 8 VDC golf cart type batteries. Better yet are the 'L-16' 6 VDC batteries (fork lift); they are 320+ Ah rated.

Good luck.

Hi!

Thank you very much for the input, i want to gain experience first that's why I want to start on small unit. on my location houses are normally concrete walls and steel roof, that's why i'm thinking of roof design PV. If i will be building separate structure for the panels it will be costly i think.

good day ahead

Hi

I'm not sure if I was clear... in my opinion, it is ok to place PVs on the roof; I don't recommend the PVs as the roof. Make sense?

now its clear, although there are some company who actually design pv as a roof, im not planning to do so.

can you give me rough estimate ($)how much a 3kva PV complete system would cost in the US these days? excluding installation cost.

thank you very much for informations your providing me...

regards

There are quite a few variables, but a rough estimate:

$3-4/watt for PVs

$1/watt for a good inverter

$500 Charge controller with MPPT

$1000 +/- Mounting rack

$???? easily $2000 Batteries (assuming it is a system capable of stand alone, not required in a grid-tie system)

$??? Wiring

So that's $20000 +/- for a 3kVA system (with batteries) with a 3kVA inverter. (parts only)

Great topic!

I'll look forward to the inputs.

A solar plant in I believe Arizona has tracking based on the position of the Sun in the sky. The panels keep pointing at the Sun perpendicular. My panels I have made I just tape them to the inside of a window and I use them to charge batteries and they work pretty good but no tracking.

The answer is yes. The power does increase with the light source, its wavelength, and is affected by the type of cell used.

The increase of light will increase the output voltage, to a maximum level as for the wavelength the cell is absorbing to provide the electron flow. Like any semi conductor there is a small starting point to overcome and there is a saturation point. There are cells being/been developed that use many different wave lengths of light to provide power and these are generally the ones that have close to 50% efficiency.

For the person wanting to check out PV cells for practical use, www.Canadiantire.ca sells a small panel and that is used to keep a battery for your recreational toy charged. its not too expensive and they do sell the inverters and all the required items for this application. The panel is a good way to test your PV ideas and keep costs low. The panel can maintain a charge for a standard 12v battery for use in a boat, 4 wheeler and similar things. I am pretty confident that other DIY stores have a similar item for sale so shop around for your Local Rona, Builders warehouse, Canadian Tire, Walmart or whatever your local version is called.