# Minimum light bulb wattage for solar simulator

#### joey_hanks

Joined Nov 19, 2022
3
I am trying to design a simple homemade PV solar simulator. I have picked metal-halide lamps as my light source.

If the PV panel has an area of 1m^2 and I wanted to achieve spatial uniformity across the irradiated surface with an irradiance of 1000 W/m^2, how do I go about selecting what wattage of lamp I need?

I understand that the solar irradiance is going depend on a number of factors including the number of lamps I use within a given area and the distance of the light source from the test bed. I have read research papers on others using multiple 400W metal halide lamps to achieve the 1000 W/m^2 irradiance but I don't quite understand how that works.

#### BobTPH

Joined Jun 5, 2013
8,958
Instead of trying ti calculate it, why not measure and adjust to get the correct illumination?

#### Ian0

Joined Aug 7, 2020
9,814
A good quality metal halide lamp is about 110 lm/W. If you look on Wikipedia
https://en.wikipedia.org/wiki/Luminous_efficacy
that equates to about 16% efficiency.
So, to get 1000W of light on your square metre, you probably need about 6000W of metal halide lamps (or about 3000W of LEDs), and your solar panel will generate about 200W.

#### joey_hanks

Joined Nov 19, 2022
3
I guess my real question is do I just need to make sure that 1000W of power reaches a 1m^2 surface to achieve an irradiance of 1000/m^2? Putting aside efficiency and diffusion of light, if I had 5 lamps each producing 200W laid out evenly in a 1 meter squared area, does that achieve what I need?

#### Ian0

Joined Aug 7, 2020
9,814
Yes. You have to collect all the light produced by the lamps and reflect it on to your solar panel, using mirrors, lenses etc. but there will be some losses (say 2%) involved whenever it is reflected.
But when you say producing 200W, make sure you don't mean consuming 200W.