The solar collector is designed to be used with pressure up to 8 bar/116psi. This means it is compatible with all low pressure, and most mains pressure domestic hot water systems. In closed loop or sealed (dead water) thermal store systems an expansion vessel is often used to prevent pressure buildup as the water expands. A pressure release valve should also be used as a safety backup.
In areas where freezing is not of concern, open loop systems are often used. Open-loop systems are also appropriate for cold regions when used in combination with a Delta-T controller that incorporates a freeze protection feature. Closed loop systems usually incorporate the use of a heat exchanger, either inside or outside the hot water storage tank. Solar collectors are suitable for both open or closed systems, as long as pressure, heat and freezing are controlled.
The solar collector does not have a built-in tank, in fact the manifold of the 20 tube solar collector only contains about 510ml/1pint of water. A circulation pump is required to circulate the water through the manifold and back to the solar storage tank. Generally a controller is used to control the pump. A flow rate of only 2L/min is required for most domestic installations, and therefore a low wattage pump is sufficient. Larger pumps are only necessary when several solar collectors are connected in series, or when the pump is required to overcome head pressure. The pressure drop at low flow rates is very minimal, only 700 Pa @ 3.3L/min for 20 tube manifold, and so is not a major consideration when sizing pumps.
Thick glass wool surrounds the solar collector's copper header, providing excellent insulation. The piping to and from the collector are however still susceptible to freezing, and therefore traditional freeze protection should be employed (low temp controller setting, or glycol/water closed loop). Solar tubes and heat pipes are able to withstand extremely cold conditions without being damaged..
The advantage of solar tubes is that they insulate the inner tube from heat loss. This means that once heat is absorbed, it is transferred to the water in the manifold, and not lost to the outside environment. This is the key difference between solar tubes and flat plate solar collectors: the insulative properties. Combined with the heat transfer efficiency of the heat pipe, the solar collector can deliver excellent heat output all year round. The IAM (Incidence Angle Modifier) values of the solar collectorsare also very different to solar collectors with flat absorbers. The positive (>1) IAM values mean that the solar collector actually performs best mid morning and mid afternoon, resulting in a more stable heat output throughout the day.
When installing a solar collector on your roof, how it looks is certainly important. The solar collector is designed to be low profile, sitting close to the surface of the roof. The tubes are black and so blend in nicely with most roof colours. The manifold is silver colour aluminium.
Corrosion is always a consideration for any system that involves water and high temperatures. In warm environments, heavily chlorinated water can become a strong corrosive agent. In order to provide maximum corrosion resistance, the solar collector uses high purity (99.93%) copper piping and silver braze for the header. Copper provides excellent corrosion resistance and is commonly used in household plumbing.
If corrosive liquids are to be used in the system, then a closed loop is highly recommended, thus allowing a non-corrosive liquids to be used in the solar collector loop.
If installed in open flow with a dead water thermal store style tank, corrosion and scale are almost eliminated as the system accepts almost no fresh water supply.
The high cost of solar tube style collectors, and in fact all solar collectors, has been a major obstacle to their popularity and wide scale use. The solar collector is a high quality system that provides excellent heat output and reliable operation. As a result of clever product design and low manufacturing costs, solar collectors are now very affordable, providing fast payback times. (Depends on factors such as total system cost, energy costs and solar insolation levels.)
Scale formation is an issue in many regions, as it gradually blocks up plumbing particularly in hot water systems. With the high temperatures that the solar collector produces, scale formation in the manifold may occur.
If water supply is very hard there are some options:
1. Use an electric or magnetic water softener on plumbing
2. Use a closed loop system
3. Use an dead water thermal store configuration. Option 1 may still be required to protect the rest of the system.
A closed loop requires a more complicated system design and added cost. If there is no other reason to use a closed loop than to avoid scale, then it is advisable to use one of the widely available water softening devices.
Our solar collectors are ideal for large scale solar water heating applictions, able to be used in hotels, airports, apartment buildings or anywhere where hot water or heating is required. The economics of large scale applications are generally more favorable than domestic, as instead of having a pump and tank for every one or two solar collectors, a single tank and pump can be used for 50 solar collectors. Our solar collectors can accept mains pressure, are corrosion resistant and can be installed in series and/or parallel, thus are suited to a wide range of large and small scale applications.
The cost involved in repairing a household appliance is increasing all the time, not due so much to spare part costs, but rather the labour cost involved in having a technician visit. With this in mind our solar collector is designed to be maintenance free, but if for some reason a solar tube should ever be damaged, it can be replaced quickly and easily by any person possessing basic trade skills.
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