Due to different ambient temperatures many would expect that the overall thermal energy consumption in a tannery in a hot climate zone is considerably lower than in a temperate zone. In reality it is somewhat more complex and worth comparing.
In any case, two very important factors, (i) temperature and (ii) humidity of inlet air are often overlooked in estimation of energy required for the crust and/or leather drying.
Chamber drying in (sub)tropical zone benefits from the higher ambient (air) temperature but at the same time it is negatively affected by high relative humidity and consequently much higher volume of fresh air required. However, the fact that the energy required for water evaporation does not change much with water temperature ultimately prevails over parameters such as ambient (air) temperature and air humidity. Accordingly, energy consumption for chamber drying in (sub)tropical zone with average air temperature of 30oC and relative humidity in the span of 50-90 % is only about 5 % less than in the temperate zone.
However, if the solar energy is used to support water heating, the conditions in the tropic zone are substantially more favourable, due to two factors:
efficiency factor (depends on the temperature difference of the final vs. inlet water temperature)
The insolation in the temperate zone (Europe) is approx. 1500 kWh/m2/y (4.1 kWh/m2/d), and in the tropical zone (South India) approx. 2200 kWh/m2/y (6.0 kWh/m2/d), so that the factor of proportionality is 1.5. Since the efficiency ratio case can be estimated as 1.05 it means that the solar based production of thermal energy in a hot climate country is about 1.6 times more favourable than in temperate climate.
The (latent) heat of vaporization is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas. The enthalpy of vaporization is a function of the pressure at which that transformation takes place.