238: Thermosyphoning


Is it possible to heat without using electricity from the grid?


Thermosyphoning is a high efficiency/low maintenance method of passive heat exchange, based on natural convection, which circulates a fluid without the necessity of a mechanical pump.

It is used for circulation of liquids and volatile gases in heating and cooling applications such as heat pumps, water heaters, boilers and furnaces. Thermosyphoning also occurs across air temperature gradients such as those utilized in a wood fire chimney or solar chimney.

In thermoelectric refrigerators, the cooling systems that work on the Peltier effect, creating heat flux between the junctions of two types of materials, have a much smaller coefficient of performance as compared to the conventional compressor-style refrigerators, especially when the cooling capacity is large.

Nevertheless, owing to the small size of cooling units, their silent nature, the absence of any moving parts in them or any gases or liquids, and their long life, thermoelectric refrigerators are used in a vast set of applications.

In 1983 Robert Draper of the Westinghouse Electric Corporation obtained a patent for “Thermosyphon coil arrangement for heat pump outdoor unit”. In 2012, Richard Boyle and a team at Naked Energy in Guildford, England used thermosyphoning to develop a hybrid solar panel they called Virtu, capable of generating both electricity and hot water simultaneously.

Reviewing Virtu, the Imperial College London found that the panels they tested can produce up to 46 % more energy than the typical PV panel when the cells are heated to 65ºC. In 2015, Naked Energy teamed up with Jabil in the US to scale up production of Virtu.

Thermosyphon installation accounted for over 55% of global solar water heater market share in 2018. The product finds wide application in residential and small commercial buildings on account of ease of installation, simple design and cost effectiveness features.

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