Panels and cylinders

Collector panels

There are two main types of collector panels for solar water heating systems: flat plate panels, and evacuated tube panels.

• A flat plate panel looks similar to a skylight. It absorbs sunlight and transfers the heat into the water or fluid flowing through the collector panel. The common size for a house is one to three panels, between 2.5 square metres and 6 square metres in total.
  
  
• An evacuated tube panel is made up of a series of glass tubes (between 1.5m and 2m long) sloping lengthwise up and down the roof.
  
  

In New Zealand's temperate climate, both types of panel are equally efficient.

Flat plate panel detail (image from EECA).

Detail of an evacuated tube with heat pipe (image from EECA).

Hot water cylinders

The hot water cylinder can be part of the system on the roof, or it can be mounted separately - in another part of the house.

You can use a conventional hot water cylinder or a specialist solar water heating cylinder. The key difference is that specialist cylinders are larger and they are specially designed to maximise the use of solar energy. If you choose a specialist cylinder the system is likely to perform better. However, it is possible to achieve reasonable performance with a conventional cylinder, through effective system design.

If you choose to use a conventional cylinder, you'll need to have a controller for the supplementary heating.

Conventional hot water cylinders in houses are usually 180 litres or less. This storage capacity is generally too small for a solar water heater to achieve optimal performance for a household of three or more people. Performance can be increased with the use of a controller for the supplementary heating.

If you are planning to get a system that includes a cylinder, check the quotes carefully - a cheap price may mean the cylinder and other components aren't included.

A conventional hot water cylinder (image from EECA).

A specialist solar water heating cylinder (image from EECA).