# Measuring Infrared Irradiance for Solar Research

#### SIM77

I'm working on research into the feasibility of separating out the infrared rays above 1200 nm in sunlight for solar power generation. Since silicon cells do not effectively harness these wavelengths, we are experimenting with using interference coatings and a wave guide to separate these waves out.

Since we'll need to measure the impact that this separation will have on the available power, I'm wondering how we could measure the power that is separated out? The visible light can simply be measured with the silicon cell, but how can the infrared light be measured? Given our dimensions, I'd expect ~25 W of infrared light leaving through a 40 cm^2 opening. This would mean getting an output 6250 W/m^2.

Ideally I'd be looking to measure either the irradiance or the total power of the infrared light exiting the waveguide. I'd rather measure this directly if possible. I looked at using a pyranometer for this, but our irradiance seems to be too high for this and I'm not very familiar with optics in general.

Anyone have any ideas for measuring devices?

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#### UltrafastPED

Gold Member
You can measure in two steps: measure total irradiance (A) entering your cell, then insert the filters and repeat the measurement (B). Your solar cell then sees the fraction (B)/(A).

Finally you can measure the power generated by the solar cell, (C), giving the efficiency as (C)/(B) for the wavelengths used.

#### SIM77

Oh sorry, I wasn't specific about the configuration. So the infrared and visible would be split such that they travel down different funnels.

The solar cell actually cannot react to wavelengths beyond 1200 nm, so it would not be capable of measuring this infrared light. Thanks for your help though.

#### UltrafastPED

Gold Member
Oh sorry, I wasn't specific about the configuration. So the infrared and visible would be split such that they travel down different funnels.

The solar cell actually cannot react to wavelengths beyond 1200 nm, so it would not be capable of measuring this infrared light. Thanks for your help though.
I was suggesting that you use another type of measuring device (such as a bolometer), then measure a well-defined flux with and then without the filter.

#### SIM77

Ah, well that makes sense. I was actually unfamiliar with bolometers, it sounds promising though. Do you have any other recommendations for measuring infrared power?

#### UltrafastPED

Gold Member
Last edited by a moderator:

#### SIM77

Interesting, I'll have to look through those resources

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