Direct Solar Water Heating System

There are two main types of water heating system – direct and indirect. In an indirect system fluid such as anti-freeze is heated and then passed through a heat exchanger fitted to the water tank. The heat from the fluid raises the temperature of the water in the tank, and the water in the tank cools the fluid ready to be passed around the system again for further heating. The less complicated option is direct heating in which the water to be heated is itself passed around the system. Such a system can be put together by anyone with an intermediate level of DIY proficiency.

In this article we will look at a very simple direct solar water heating system which can be built using easy to find plumbing and automotive supplies, and a small pump.

Direct Water Heating Schematic

Pictured below is a schematic diagram of a typical simple direct solar water heating system.

Direct solar water heating system schematic diagram

Connecting everything up just requires copper pipe and either solder (or more simply) compression joints. This system can be used year ’round with evacuated tubes, and will work well for 2-3 seasons of the year with a flat panel solar collector – e.g. a radiator painted black.

The only tricky part to implement is sourcing and connecting in a suitable pump and controller (to run the pump when the solar panel is hotter than the water in the tank). For the pump controller we of course recommend our very own solar water heating pump controller. For the pump we recommend the following 12 VDC high temperature water pump.

7W pump for solar water heating system

This pump is brushless so it will be maintenance free and long lasting. It can operate from 9-14 VDCand can be powered directly from a PV solar panel (10 Watt). It is rated at around 7 Watts (0.55 Amps @ 12VDC), it can pump water up to temperatures of 120 Celcius, has a flow rate adjustable from 1-7 litres per minute, and it is virtually silent in operation. The pump creates a head of 2 metres, however do not forget that in this design of solar water heating system this is not relevant since the water moving downwards pulls the water going upwards up by the syphon effect.

This pump is available for less than £25 plus £2.99 postage. Click here to buy this solar pump now.

The pump has a 14.1mm inlet and a 10mm outlet diameter. In order to connect this to standard 10mm or 15mm copper piping it is recommended to use auto radiator hose. It is also possible to use flexible tap connectors available from DIY stores and plumbers merchants. It is usually recommended to use10mm rather than 15mm since the narrower pipe is easier to work with and cheaper per metre length.

Kit to connect pump into a solar water heating system

The vendor of the pump discussed in this article is also willing to put together a full connecting kitwhich is offered for sale in 10mm or 15mm versions for £4.50 including postage if purchased at the same time as the pump.