Svetlana wrote:why, when we have so much 'free (solar heated) water do we have cold fill washing machines and dishwashers!!!
Because they work better with cold water: in fact, they do not work with how water.
Try this experiment. Take two plates or somesuch, preferably with a rustic matt glaze. Put a few drops of egg white on each and smear it round. Now take one of them and rinse it under the cold tap: hey presto! It's clean. Now take the other and rinse it under the hot tap! An unholy white gooey mess that will not wash off. This is because all proteins are transformed into insoluble matter at temps above ~60°C. Where do you find proteins other than in eggs? In all animal products, including those produced by human sweat glands and in a lot of vegetable ones, as well. So, if you want clothes where organic stains are not washed out or cutlery with food congealed around the fork tines, go ahead and connect your washing machine to the hot tap. If you want clean clothes and food-free crockery/cutlery, then use the cold water. In fact, starting with cold water and
slowly heating it up in the machine is, by far, the most efficient way of cleaning both dishes and clothes, because proteins are often bound with fats and doing it this way can often enhance the micellar effect of the detergent and pull the protein/fat mixtures away from the substrate at the optimum temperature for each combination.
My company in Switzerland used to make washing machines for electronics assemblies, which also had to have strict temperature control because some flux component residues (the stuff we were trying to clean off) contained amino acids (the building blocks of proteins). In order to cut down on the time required for a cleaning cycle, we experimented with injecting hot water after the start of the cleaning cycle with cold water, rather than simply heating the water in the machine. The success was very mitigated; the cleaning quality was poorer and the extra cost of the hot water system plus an electronic controller to have the correct heating profile was nearly the equivalent of £800. We never put that machine into production.