Hot water systems - Better tanks give quick and clean hot water06 December 2004

Hot water tanks made by a small German company use a patented system to ensure that they deliver hot water soon after heat has been applied to the water. This makes them especially suited to systems fuelled by solar energy.

The same company also has technology to ensure that water for humans is of drinking water quality, unlike most of what comes from the average hot tap.

Carl Capito Heiztechnik is a company with 75 employees and is part of a small group of three companies. Its factory is midway between Cologne and Frankfurt. Founded in 1900, the company started making marine boilers in 1937 but soon turned to making boilers for buildings.

Quick delivery of hot water from buffer tanks is achieved by admitting heated water to the lower part of the tank, which is separated from the rest of the tank by a plate with a hole in it. The hot water then rises through a narrow channel to the top of the tank. This encourages stratification so that the hot water in the top of the tank is truly hot, and can be drawn off hot as required. After prolonged heating, the hot water zone expands downwards until all the water in the tank is hot. Because function depends only on the natural relative buoyancy of hot water relative to cold, no pumps are required. The system is more thermally efficient: with conventional systems, most of the water in the tank must be heated before properly hot water can be obtained. Also, when heat is being derived from a solar source, at a time when not much water is being used, it is possible to accumulate hot water in the bulk of the tank. Heat input from the sun tends to be spread over a long period during the day whereas maximum heat demand from a heating system is likely to be during the evening.

The other technology available to purchasers of Capito buffer tanks is their ability to deliver drinkingquality hot water. General manager Wolfgang Heinzel told Plant Engineer at a 'green' technologies partnering event in London: "If you look inside the average hot water buffer tank, you would definitely not want to shower in what came out of it." For those who want their hot water to be properly clean and hygienic, hot water is supplied from copper coil heat exchangers inside the top part of the buffer tank and not from the tank contents itself. The bulk of the water inside the buffer tank is there to be circulated to central heating radiators.

Capito boilers for solar hot water heating have auxiliary fossil fuel burners and are available in capacities from 480 litres to 840 litres. Buffer tanks without burners are available in capacities from 350 litres to 3,000 litres. Designs are optimised using infrared thermal imaging techniques. The company group also makes pressure vessels, heat exchangers, columns, agitator vessels, wood gasification and wood pellet fired systems, flat solar collectors, tube solar collectors, heating pump systems, wall mounted boilers, wheelbarrows and sack carts. With its wide range of skills, the company is also able to undertake bespoke manufacturing. More information can be obtained from www.capito-gmbh.de or email heinzel@capito-gmbh.de.

SOE

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