Evacuated Tubes
The engine of the Hills Solar water heaters distributed by Go Solar,are the evacuated tube collector panels. Evacuated tubes are extremely efficient at capturing and retaining the radiation from the sun. 
They are manufactured from very strong borosilicate glass (tested by SABS to withstand a 38mm hail strike) and have an inner and outer tube with a strong vacuum in between. The inner glass tube has a radiation trap consisting of 3 mineral coatings. Solar radiation enters the outer tube and is caught as heat by the radiation trap;the vacuum prevents the heat from escaping and so is effectively ‘locked’inside for transfer to the water. This heat is radiated down to a copper heat pipe in the centre of the tube by aluminium fins. A liquid sealed inside the heat pipe evaporates as it heats up and rises to the head of the heat pipe. The head is plugged into a pocket in the manifold on top of the collector. Water is circulated through here from your geyser and the heat is transferred from the heat pipe to the water. The liquid inside the heat pipe now cools,condenses and falls to the bottom again. This forms a continual cycle of heat transfer as shown in the diagram alongside.
It is an extremely efficient system that has been shown to be appreciably more effective than flat plate collectors. This is why evacuated tube collectors are even used to supply hot water at stations in the Antarctic. The Hills Solar collectors carry a 10 year warranty and are made of the highest quality materials. They also carry the SABS mark of approval.
Solar Controller
Depending on the application,we use various controllers to manange our Hills solar water heaters. We have one controller,the Microsol II Plus which enables monitoring and control of one or many systems from a local or remote PC. 
After extensive testing though we normally use the SR868C8 controller in most domestic systems. As well as controlling the solar circulation pump,it also enables total control over electrical backup heating depending on solar conditions. We set the controllers to the timer settings required by ESKOM on their rebate program and at a temperature to ensure optimum savings.
Users are able to easily adjust these timers and temperatures via a display panel installed in the house. The controller has great functions that also helps avoid freezing of the solar collector as well as overheating of the collector. It has extra outputs to control a ring main circulation pump,and another pump or solenoid valve to transfer excess heat to another part of the house if required. It has also proven to be an exceptionally reliable controller. Please see the following PDF file of a Quick Setup and Operation Guide. SR868C8 Quick Setup Guide
Other useful features include a Holiday Mode to prevent overheating when the hot water being generated by the system is not being used when people are away from home,and a quick heating button for those ocassions when you need extra hot water for guests.
Pumps
The circulation pump is the potential weak point in a pumped (active) solar system. 
If the system is running normally,the pump is protected by the solar controller,but if there is a failure such as an electrical outage,or the mains water supply to the system is interrupted,the pump can be subjected to very high temperatures as the solar collector heats up with lack of circulation. For this reason it is essential that a good quality pump is used that is made to withstand high temperatures. The Hills Solar Esteem solar water heaters make use of very high quality European pumps. On our 230 volt AC systems,we use a Grundfos pump for most applications. This pump is rated for temperatures up to 950C. 
You can view the specifications for this pump here. Grundfos Pump
For our 12 volt DC systems we use the Laing pump. Laing_DC_pumps_Ecocirc_vario_D5_english[1] Both the Grundfos and Laing pumps have a brass housing and use a spherical motor. Unlike the conventional canned-rotor motors,spherical pumps do not use a rotating bearing shaft. The stator transfers the magnetic field to the rotor in the water conducting part of the pump. This is hermetically separated from the stator with a stainless steel separator.
Solar Hot Water Cy
linder (Solar Geyser)
A storage geyser is still necessary for solar hot water systems as the water warmed during the day has to be stored for use either that night or the following morning. It also needs to operate as a normal electrically heated geyser in case of insufficient sunlight or higher usage. Solar water storage geysers require better insulation properties than normal geysers so that the energy (heat) from the sun is not lost through the shell of the tank.
The Hills Solar hot water systems make use of SABS approved Solartherm geysers,manufactered by WE Geysers in Krugersdorp. Manufactured since 1997,these geysers have proven to be extremely hardy and carry a 10 year,manufacturers guarantee,regardless of water quality. Unlike a conventional geyser which makes use of sacrificial anodes to delay the corrosion of the inner tank,the Solartherm geysers have a cross-linked polymer (PEX) lining inside,forming a barrier between the water and the steel tank and therefore preventing corrosion.
