@Jane: Is that for the washing machine or dishwasher Jane? I tend to experiment with laundry products and keep reducing the amount until I reach the point where it still does the job but any less wouldn’t. Water softness needs to be taken into account; i’m sure with soft water you hardly need any detergent at all.

]]>Let take water as an example. How much energy is required to evaporate one kilogramme of water at 15 degree Celsuis (ambient temperature)?

Energy required to evaporate 1 kg= Sensible heating of water from 15 deg C to 100 Deg C (I will assume it is under normal atmospheric pressure and no vacuum is present that will reduce energy consumption + latent heat of vaporistion (energy required to convert 1kg of liquid water to 1 kg of Vapor)

Energy required to evaporate 1 kg= Mass of water*specific heat capacity of water* temperature rise + latent heat of vaporistion

Energy required to evaporate 1 kg= 1*4.186*(100-15)+ 2257

= 355.81+2257= 2612.81 kJ

Not all heat will be transferred from the heating source to the water and if we assume a coil efficiency of 85% will result in an energy requirement of 2612.81/0.85= 3073.89 kJ

If we assume Octane as a means of representing the combustion of petrol then we find that (3073.89/5293.9) =0.5806 moles of octane is required. There are 114.23 grammes per mole and therefore 0.5806*114.23= 66.32 grammes of Octane is required. The density of octane is 0.703g/ml and therefore the volume of octane required to evaporate 1kg is 66.32/0.703= 94.34 mL or in other words 1 litre of octane (petrol) can evaporate 10.6 kg of water aproximately or 94.3 litres of petrol is required to evaporate 1 tonne of water, hardly energy consuming compared to transport is it?

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