Domestic Water Heating
Solar hot water systems can be sized for any level of domestic hot water demand in any type of environment.
Generally the solar thermal system acts as the primary heat source; with a boiler, immersion heater or heat pump etc. automatically raising the water temperature further if required.
An appropriately sized solar water heating system will provide 50% to 70% of the annual domestic hot water demand. 100% of the hot water requirement should be met during the summer months, with typically 20%-30% of the hot water demand being provided during the middle of winter.
A typical solar hot water system will comprise the following components:
• Collectors (Panels)
Vacuum tube or glazed flat plate collectors can be used. Flat plate collectors don’t work as well as vacuum tube collectors when the weather is cold or windy (i.e. most of the UK winter), therefore a larger area of flat plate will usually be required. The cost of flat plate collector is general lower and they can be integrated into a pitched roof covering if required.
Collectors should be mounted on a southerly-facing pitched roof or wall, or a flat roof. They can be installed on an east or west-facing but the total collector area will need to be increased to compensate for the lower energy levels. Shading, aesthetics, roof condition and accessibility will all be considered when selecting a position for the solar collectors.
The number of collectors required can be specified once the domestic hot water demand has been estimated and the collector location identified. As the amount of solar energy available to the collectors is fixed; the greater the collector area the more energy will be absorbed.
• Pipe Work
Copper or flexible stainless steel pipe work will be used to connect the collectors, cylinder and pump station. The pipe work will be sized to maximise the performance of the system. Insulation, and were appropriate mechanical protection, will be applied to all pipes.
• Controls
The solar control system; incorporating a differential controller, pump station and expansion vessel, will usually be installed close to the solar cylinder.
The solar differential controller monitors system temperatures to automatically control the delivery of energy to the cylinder. A display screen indicates how the system is performing. The control settings will be optimised at the time of installation.
The solar pump station incorporates a circulation pump, as well as the flow controls, gauges and valves required for the safe and effective operation of the system.
A suitably sized expansion allows for the expansion and contraction of solar fluid within the system. The solar fluid contains an anti-freeze and corrosion inhibitor.
In larger and more complex systems additional valves, controls, metering equipment and displays may be installed.
The solar heating system control system is usually totally separate to the controls for the other heat sources. Standard timer and thermostatic controls should be used on the boiler and immersion heater etc.
• Cylinder (Calorifier or Buffer Vessel)
A hot water cylinder is always required to store the solar energy that the solar thermal system is producing. The design of the hot water system will influence the way in which the solar heating system is integrated and the type of cylinder installed. The volume of the hot water cylinder will depend on the area of collectors specified.
For a household system we would usually install a cylinder that can be heated by the solar collectors and a boiler/immersion heater. If retro-fitting the solar heating system this would typically involve replacing the existing hot water cylinder and installing a new more efficient model.
Installing a dedicated solar cylinder or buffer to pre-feed the main hot water cylinder is another option that can be considered. This type of system is generally more suited to applications where there is continuous hot water demand during the day.
A thermostatic blender valve will normally be fitted to the output of the solar cylinder to automatically regulate the temperature of water reaching the taps (not required if other thermostatic controls are installed).
System Diagrams
Example system diagrams can be downloaded and viewed by clicking here
Further Information
Call or email us now if you have any questions or would like to discuss a particular project.