There are currently four main ways of preventing freeze damage in solar panels. All are technically viable: * A traditional solution is to use chemical antifreeze at a relatively high concentration of, say, 30%, as in a car radiator. This is the approach of older, conventional solar panels. However, some antifreeze can degrade if not replaced regularly, which imposes a maintenance cycle on the installation. The three remaining solutions are: 1. Fill the panel with air as a heat transfer medium, rather than with water, while also having larger surface areas of heat exchangers in order to allow for the lower heat capacity of air . 2. Automatically drain down the panel completely when it becomes cold, say 5C. 3. Use pipes made of silicone rubber which can simply freeze without cracking. These three newer solutions tend to need less maintenance, since the antifreeze renewal cycle is not required.

Narrow pipes make a difference
A lot of heat can be lost in a conventional solar water heating system because its pipes tend to be 15 mm or 22 mm wide. Issues to consider include both surface area and pipe volume. Reducing surface area means less thermal losses. Using narrow microbore pipes, with an internal diameter of 6mm, plus low flow pumps instead of wider pipes can cut heat loss from the surfaces of pipes by over 50%. Reducing volumes of water contained in pipes by making them narrower means reducing the energy lost in transit between the panel and the cylinder when a pump stops. These “dead leg losses” can be cut by 80% by using microbore pipe.

Variable and slow speed pumping
Slowing the pump down at low light levels tends to produce hotter water sooner in the day than happens in lower cost on-off pump designs, particularly when used in direct solar water heating systems since they stratify (float) the solar hot water over cooler water below.

Future proofing and customer service
Once the installation is complete, installers should take photographic records of installations for quality purposes unless the customer requests otherwise. Photos can include: pipe runs, pump positioning and panel positioning. This way if a query crops up, the company who installed will be able to gain an immediate picture of your installation. In addition, installers should keep complete, accurate and confidential records in compliance with data protection legislation of: customer contacts, installation photos, relevant plans or diagrams, original installation specifications plus any variations from these and written details of significant health, safety and environmental issues including Legionella risk assessment and recommendations. In addition, dates and times of important events such as installations or services need to be recorded and easily available.

Maximise energy gain- start with cool water The cooler your water is when it enters your panel, the more its temperature will rise, and so the more energy it will gain. So from an efficiency viewpoint, is best to design, and to use, solar hot water systems in ways that let the water start the day as cool as possible rather than hot.