# Solar Panel - Voltage and Current from Spectral Radiance

• Hannah Vioula
In summary: You didn't say.In summary, a beam of light with a wavelength of 600nm, spectral width of 4nm, and spectral radiance of 1300 Wm-2μm-1 can generate a voltage of 2.060 Volts and a current of 3.68 mA. The current would change if the beam width were 5 meV, but the specific change is unknown without further information.
Hannah Vioula

## Homework Statement

i)A beam of light at wavelength 600nm, with spectral width of 4nm and spectral radiance of 1300 Wm-2μm-1, illuminates an area of 10cm2 . What is the voltage this beam could generate if converted to energy?
ii) What current could this beam produce?
iii) How would the current change if the width of the beam were 5 meV?

## Homework Equations

i) Voltage = hf / charge = change in energy / charge = h*c / q*λ

ii)
Spectral Radiance= eλ = hf φλ
Where, Spectral Flux Density = φλ
f=c/λ
Current Density = q * φλ * δλ = I / A

iii) Absolutely no idea what to use.
Maybe, E (in eV)=1.24 / λ (in μm)

## The Attempt at a Solution

[/B]
i)
I need max voltage available, so I ignore spectral width.
Voltage = h*c/ (600*10-9 * q)= 2.060 Volts

ii)
I get flux density first
Spectral flux density = φλ
Rearranging equation -- -- > Spectral Radiance= eλ = hf φλ
φλ = eλ * λ / h*c = 1300 * (600*10-9) / h*c = 4.58*1021
Rearranging equation, Current Density = q * φλ * δλ = I / A
I = q * φλ * δλ * A = 3.68 mA

iii) Not a the faintest of idea of what to do here...

Last edited:
Hannah Vioula said:
I'm puzzled by this statement. Spectral radiance is for the case where light is coming from a surface at some distance. To get the total power we have to consider the area of the emitting surface as well as the solid angle the receiving surface subtends at each point of the emitting surface. I'm guessing this should say spectral irradiance. See e.g. https://en.wikipedia.org/wiki/Radiance.
I assume you meant 1300 Wm-2μm-1
Hannah Vioula said:
Energy of wavelength 602nm = h*c / (602nm) = 3.31*10-19
Energy of wavelength at 598nm = h*c / (598nm) = 3.28*10-19
No point in working those two out separately, just work with the average here.
That's in Joules, right?
Hannah Vioula said:
Voltage = Change in energy / charge = -0.014V
That's not what I get, but I could be wrong. Please post your working.

Thanks, I re edited my original post and I definatly have part 1 and part 2 correct as I checked with my study group who all confirmed they have that answer.

I just don't know where to get part iii

Hannah Vioula said:
Thanks, I re edited my original post and I definatly have part 1 and part 2 correct as I checked with my study group who all confirmed they have that answer.

I just don't know where to get part iii
Given the units, I have to guess that beam width refers to the range of wavelengths. In your original post you calculated the Joules per photon at each end of the 4nm range. The difference would be the beam width in this sense. What was that beam width in units of meV?

## 1. What is the relationship between solar panel voltage and spectral radiance?

The voltage produced by a solar panel is directly proportional to the spectral radiance of the incident light. This means that the higher the spectral radiance, the higher the voltage output of the solar panel will be.

## 2. How does the spectral composition of light affect the current output of a solar panel?

The spectral composition of light has a significant impact on the current output of a solar panel. Different wavelengths of light have varying levels of energy, and the solar panel's efficiency in converting that energy to electricity depends on its spectral response. Therefore, a solar panel will produce a higher current output when exposed to light with a higher spectral radiance.

## 3. Can a solar panel produce electricity without any sunlight?

No, a solar panel requires sunlight to produce electricity. Sunlight contains a wide range of wavelengths, including visible light, ultraviolet light, and infrared light, which are all necessary for the solar panel to function. Without sunlight, the solar panel will not be able to generate any voltage or current.

## 4. What is the difference between voltage and current in a solar panel?

Voltage and current are two important measures of an electrical system's performance, including a solar panel. Voltage is the potential difference between two points, while current is the flow of electrons through a conductor. In a solar panel, voltage is the amount of electrical potential produced, while current is the amount of electricity being generated and delivered to a load.

## 5. How does temperature affect the voltage and current output of a solar panel?

Temperature can have a significant impact on the voltage and current output of a solar panel. As the temperature increases, the solar panel's voltage output decreases, while the current output increases. This is because higher temperatures can decrease the efficiency of the solar cells, resulting in a lower voltage output. However, the increase in current output can help compensate for this decrease in voltage.

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