# Entropy calculate from EPW data (theoretical base)

Hello all,

I attempt to calculate and generate Entropy data base on EPW and create an hourly plot (theoretical base).
Below are the two calculation/hypothesis methods:

**Method 1:
Relationship between Enthalpy and Entropy:

TΔs = Δh − vΔp

where:

• T is the temperature (k)
• Δs is the change in entropy
• Δh is the change in enthalpy
• v is the specific volume
• Δp is the change in pressure

In this method, the specific volume v and the pressure change Δp is ignored, which means the direct relationship between Enthalpy (H) and Temperature (T) is only considered. This can be simplified to:

Δs = Δh/T

To calculate the change in entropy ΔS:
Assuming H is the change in enthalpy per unit mass (kJ/kg), and the initial state has a change in enthalpy Δh=16.63 kJ/kg, with the initial state’s entropy being zero (reference state), it can be written as:

ΔS = H/T

**Method 2:
In this method the specific volume v is ignored (assume = 1), Δh and Δp is done by substrate the value of previous hour.

Therefore:
TΔs = Δh − 1 * Δp

Please let me know what you thinks, and if it even make sense!

Entropy.gh (52.2 KB)