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Solar Hot Water Tank - Potable Water Tank
Solar heating system.
Solar heating system.

The most common application of Solar Heating are systems designed to heat the domestic hot water. A central component of such systems it the hot water tank, used to store the solar thermal energy. A Heat Exchanger tranfers the heat produced in the Collector to the potable water in the well-insulated tank, where it can be hold for hours or sometimes days until it's consumed e.g. providing a bath or shower.

Typical characteristics of a solar hot water tank compared to conventional boilers or hot water tanks are:

- For an household of a given size the volumen – and therefore the storage capacity – of a solar storage tank is significantly higher.

- The structural shape of a solar tank has to be tall and slim, so supporting the thermal stratification in the tank: the solar heat exchanger at the bottom of the tank is working on cold water; the heated water arises in the tank. The outlet is at the top of the tank, where the water is hottest.

- A very strong insulation prevents heat loss and facilitates heat storaging for not only hours, but days.

- At least two heat exchanging units: the first at the bottom of the tank to transfer the solar heat to the tank, the second in the upper part of tank to allow additional heating by another source (e.g. a conventional central heating system) that is activated when the water in this part of the tank falls below a minimum temperature setting. Hence, hot water is always available.

Generally a solar hot water tank will be dimensioned to about the double size of the anticipated amount of consumption per day. Regarding this, the tank for an household with 4 persons and an average consumption of 40 litres hot water per head and day should hold about 300 to 320 litres. To avoid potential hygienic problems in bigger households (more than 6 persons) with an highly vacillating total consumption per day it's often recommended to use Solar Combisystems instead.

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