Energy conversion efficiency (Light -> heat)

AI Thread Summary
To calculate energy conversion efficiency from light to heat, one must consider the heat capacity of the materials involved, as it directly affects the temperature change. The formula for efficiency, typically energy output divided by energy input, may not apply directly without accounting for the absorption and reflection of light by the materials. For example, if material 1 heats from 20°C to 30°C and material 2 from 20°C to 40°C under the same light source, material 2 demonstrates better efficiency. The energy required for these temperature changes can be calculated using the heat capacity value of 3600 J/(kg*K). Understanding the definitions and relationships between absorbed energy, heat capacity, and temperature change is crucial for accurate efficiency calculations.
Tah
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Hi, all

I'm seeking advice on how to calculate the energy conversion efficiency, in case of heat from light energy.

I think that one of the general formulas 'energy output/energy input' can not be applied in this problem.

Assuming that light(or laser) has 10W power output and material 1 exposed to the light source generates heat from 20C' to 30'C for a second, while material 2 generates heat from 20'C to 40'C for a second.

In this case, we can say that the energy conversion efficiency is better for material 2, but I want to describe this as a quantitative expression.

Please can anyone help me?
 
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Note: temperature and heat are different things. You need the material heat capacity so you can relate the power delivered by the laser to the rate heat-energy increases.
 
Sorry for that, I didn't realize that.

Heat capacity can be 3600 J/(kg*K)
 
All energy expended by a laser (and most other devices) eventually becomes heat (thermal energy). The only real question is how much is absorbed and how much is reflected.

If the laser is the same and only the material is different, then the difference can either be in how much is reflected or what the heat capacity is (or both).
 
Tah said:
Sorry for that, I didn't realize that.

Heat capacity can be 3600 J/(kg*K)
OK - so can you work out the energy needed to get the temperature changes that were observed?
What is the definition of "energy conversion efficiency"?
 

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