Solar Heating Information

How do we use solar energy for solar heating systems?

Solar energy is the single most abundant form of renewable energy in the world. Energy from sunlight can reach the earth's surface with a maximum intensity of more than 1000W/m². Solar heating is the process of taking the solar energy and converting it into usable energy for heating water. Solar energy can also be used to generate electricity. If you are wishing to obtain information on generating electricity you should contact the Sustainable Electricity Association of NZ (SEANZ).

What Solar Water Heating Systems are available?

There are a wide range of models of solar water heating systems available in New Zealand but essentially they have the same basic components of collector, hot water storage tank, means of moving water around the system, and a supplementary heating controller. The solar system is designed so that the various components are integrated, so if you are looking for a solar system you should look for a packaged system.

A packaged system is one which has been properly designed for optimal energy performance. Energy performance can be affected by the collector area, way and time in which hot water is used, when the supplementary heating is added and how the components are integrated. Simply purchasing a collector and adding it to your existing hot water storage tank could result in very poor energy performance. A packaged system can have its likely energy performance modelled so that you know what you are buying.

There are two types of solar water heating systems available in New Zealand:

• Thermosyphon systems use the theory that hot water will rise through cold water and thus rely on convection to circulate the water through the system. Therefore the solar panels need to be located below the water storage cylinder to ensure that this convective circulation can occur.
• Pump circulated systems allow more freedom with regards to the positioning of the solar panels and the cylinder due to there being a small electric pump in the system. This pump is used to generate water flow within the system.

There are two ways of getting the heat from a collector panel to the storage container:

• In an open loop system the cold water from the storage container is circulated through the collector and back to the storage container. This can also be called a direct heat system.
• In a closed loop system a glycol type heat transfer fluid is circulated from the collector to the container and back to the collector in a closed loop. The heat is transferred from the loop to the water in the container via a heat exchanger in or associated with the container.

There are two types of solar collector, and a number of design variations are avaiable:

• Flat plate
• Glass tube

A Solar water heating system can be supplied as a packaged system or custom built. Where a solar water heating system is supplied as a packaged system it will be supplied with all components (tank, collector, pump, controllers) which have been designed for complementary and optimal energy performance. Systems supplied and installed as complementary packaged systems can be tested for energy performance as packaged systems with nominated sized and type of containers, and any claimed performance relate to the system as a whole.

 A customised system may be constructed for a special application or be where solar components from a packaged system are connected to an existing hot water cylinder. Such systems should only be put together by Approved Installers from components of packaged systems and connected to other existing components such as a hot water storage cylinder. Where systems are custom built using components, suppliers must be able to provide evidence that the individual components meet the appropriate standard tests, and that the customised system as a whole meets any claimed performance levels by demonstrated similarity of performance to a representative product that meets the requirements of the standard. For more information on solar water heating click here.