silicon watts

ws9876 · June 2011

do squares of silicon have the same voltage no matter what the size??? or does the voltage
go up with the size of the square or circle..?? providing the silicon is the same..

mike95490 · June 2011

Re: silicon watts

All PV material shares a common voltage, about 0.55V. As the size (surface area goes up, the amps produced, increases. To get more voltage, cells are wired in series.

BB. · June 2011

Re: silicon watts

All silicon PV material has the ~same voltages. Different materials can have somewhat different voltages.

For example, if I got this right, gallium arsenide solar cells run Vmp~2.1 volts per cell (company: www.spacequest.com).

Solar Cells: Triple Junction GaAs with Protective Covering
Protection: Individual diodes on each cell and attached to each string
Bus Bars and Interconnects:
1 mm cell-to-cell spacing; 3 mm string-to-string
Over 90% coverage per panel area
UV-protected Fiberglass
Substrate: Printed Circuit Board
Honeycomb or other flat substrate material
Efficiency: 26% nominal
Panel Size: 10” X 9”
Mass: As low as 10 grams/cell
Peak Power Voltage: 2.1 Vpp/cell at 28°C
Open Circuit Voltage: 2.5 Voc/cell at 28°C
Current: 420 mA/cell
Output Power: 880 mW/cell
Operating Temperature: -90°C to +90°C
Storage Temperature: -100°C to +100°C

-Bill

Dr. Strangelove · June 2011

Re: silicon watts

The voltage produced by any PV cell is based on the energy band gap of the PN semiconductor junction. Silicon junction bandgap is around 0.55V, while other materials like GaAs or CdTe/ZnTe have different band gap potentials. A bigger cell is like many smaller cells of equivalent total area in parallel, hence more current but same potential (voltage). Because of quantuum mechanics, a photon must have the same or higher energy than the band gap to create an electron/hole pair. Photon energy is proportional to wavelength (or color). So a multi-junction cell can be built, stacked on top of each other, to harvest more photons of different energies. In Bill's extremely expensive satellite PV cells, there are three junctions stacked, with different concentrations of In and P to create different band gaps. While they are very efficient, you don't want to know what a panel of those babies are going to set you back, trust me.

nsaspook · June 2011

Re: silicon watts

The quantum efficiency in first/second generation solar cell is limited by photon to electron/hole conversion but there is another way that deals directly with the EM fields.

http://www.nrel.gov/docs/fy03osti/33263.pdf
http://ecee.colorado.edu/~moddel/QEL/Papers/EliassonThesis.pdf

Improvements in MIM diodes for direct optical rectification.
http://onlinelibrary.wiley.com/doi/10.1002/adma.201002678/abstract

mike95490 · June 2011

Re: silicon watts

BB. wrote: »

All silicon PV material has the ~same voltages. Different materials can have somewhat different voltages..... gallium arsenide solar cells run Vmp~2.1 volts per cell....... -Bill

But is anyone actually installing / affording any of the NEW panels ??

ggunn · June 2011

Re: silicon watts

mike90045 wrote: »

But is anyone actually installing / affording any of the NEW panels ??

Define "new". Multijunction Si modules have been around for a while, but the cost of them is still prohibitive for most applications. There are a lot of "new" thin film modules being made, but their efficiencies are generally significantly less than Si modules, but they are cheaper, so if space is not a problem, they may be the way to go.

mike95490 · June 2011

Re: silicon watts

ggunn wrote: »

Define "new". Multijunction Si modules have been around for a while, but the cost of them is still prohibitive for most applications. There are a lot of "new" thin film modules being made, but their efficiencies are generally significantly less than Si modules, but they are cheaper, so if space is not a problem, they may be the way to go.

new = gallium arsenide solar cells $$$$ thin film hybrids are reasonable, but still only .5v

silicon watts

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