Solar energy is the cleanest and most inexhaustible of all known energy sources. Solar radiation is the heat, light and other radiation that is emitted from the sun. Solar radiation contains huge amounts of energy and is responsible for almost all the natural processes on earth.

Solar Energy can be classified into two categories, Thermal and Light. Photo-voltaic cells (PV) use semiconductor-based technology to convert light energy directly into an electric current that can either be used immediately, or stored in a battery, for later use. PV panels are now becoming widely used as they are very versatile, and can be easily mounted on buildings and other structures. They can provide a clean, renewable energy source which can supplement and thus minimize the use of mains electricity supply.Thermal energy obtained from the sun can be used for a number of applications including producing hot water, space heating and even cooling via use of absorption chilling technology.

Flat plate thermal solar collectors have been in use for several decades, but only in relatively small numbers. Evacuated tubes have also been in use, but have been much more expensive than flat plate, and therefore only chosen for high temperature applications or by those with money. In recent years the production volume of evacuated tubes has exploded, resulting in greatly lower manufacturing and material costs. The result is that evacuated tubes are now similar in price to flat plate, but with the insulating benefits of the evacuated tube, they are set to become the default choice for thermal solar applications worldwide.

Evacuated tubes are the absorber of the solar water heater. They absorb solar energy converting it into heat for use in water heating. Evacuated tubes have already been used for years in Germany, Canada, China and the UK.

Each evacuated tube consists of two glass tubes made from extremely strong borosilicate glass. The outer tube is transparent allowing light rays to pass through with minimal reflection. The inner tube is coated with a special selective coating (Al-N/Al) which features excellent solar radiation absorption and minimal reflection properties.

The top of the two tubes are fused together and the air contained in the space between the two layers of glass is pumped out while exposing the tube to high temperatures. This "evacuation" of the gasses forms a vacuum, which is an important factor in the performance of the evacuated tubes.

As you would know if you have used a glass lined thermos flask, a vacuum is an excellent insulator. This is important because once the evacuated tube absorbs the radiation from the sun and converts it to heat; we don't want to lose it!! The vacuum helps to achieve this. The insulation properties are so good that while the inside of the tube may be 150oC, the outer tube is cold to touch.

This means that evacuated tube water heaters can perform well even in cold. The efficiency of a evacuated water heater is dependent upon a number of factors, one important one being the level of evacuated radiation (insolation) in your region.

Heat pipes might seem like a new concept, but you are probably using them every day and don't even know it. Laptop computers often using small heat pipes to conduct heat away from the CPU, and air-conditioning system commonly use heat pipes for heat conduction. The principle behind heat pipe's operation is actually very simple.

Structure and Principle:

The heat pipe is hollow with the space inside evacuated, much the same as the solar tube. In this case insulation is not the goal, but rather to alter the state of the liquid inside. Inside the heat pipe is a small quantity of purified water and some special additives. At sea level water boils at 100oC, but if you climb to the top of a mountain the boiling temperature will be less that 100oC. This is due to the difference in air pressure.

Based on this principle of water boiling at a lower temperature with decreased air pressure, by evacuating the heat pipe, we can achieve the same result. The heat pipes used in AP solar collectors have a boiling point of only 30oC. So when the heat pipe is heated above 30 oC the water vaporizes. This vapor rapidly rises to the top of the heat pipe transferring heat. As the heat is lost at the condenser (top), the vapor condenses to form a liquid (water) and returns to the bottom of the heat pipe to once again repeat the process.

This explanation makes heat pipes sound very simple. A hollow copper pipe with a little bit of water inside, and the air sucked out! Correct, but in order to achieve this result more than 20 manufacturing procedures are required and with strict quality control.

Quality Control:

Material quality and cleaning is extremely important to the creation of a good quality heat pipe. If there are any impurities inside the heat pipe it will affect the performance. The purity of the copper itself must also be very high, containing only trace amounts of oxygen and other elements. If the copper contains too much oxygen or other elements, they will leach out into the vacuum forming a pocket of air in the top of the heat pipe. This has the effect of moving the heat pipe's hottest point (of the heat condenser end) downward away from the condenser. This is obviously detrimental to performance, hence the need to use only very high purity copper.

The amount of electromagnetic energy (solar radiation) incident on the surface of the earth. Basically that means how much sunlight is shining down on us.

Why is knowing the Insolation level useful?
By knowing the insolation levels of a particular region we can determine the size of solar collector that is required. An area with poor insolation levels will need a larger collector than an area with high insolation levels. Once you know your region's insolation level you can more accurately calculate collector size and energy output.

Is my region's insolation level low, moderate or high?
The following scale is a basic guide for insolation levels. Although a value of 5 is not considered very high during the summer months, as an average annual value this is very high. You will see that in central Australia, which is a hot, sunny place, the annual average insolation is 5.89,

In Egypt the annual average insolation is 5.68

Solaris “Vacuum Tubes Solar Water Heaters” are much more affordable than many other solar hot water heaters. You will definitely make considerable savings. For a household of 4, the price of a full system may not be too much more than a new electric or gas system. Depending on your location (solar levels) and current hot water usage the annual electricity or gas saving will differ.

However in a normal household that spends 25% of its electricity bill on hot water heating, the full cost of the purchase may be recouped as quickly as 2 -3years in reduced bills. Of course this depends on the type and size of heater used.

Yes. “Vacuum Tubes Solar Water Heaters” can be used in temperatures as low as -30oC, although performance is reduced in such extreme conditions. Good heat output is still achieved in mild sub-zero conditions.

Yes. “Vacuum Tubes Solar Water Heaters” & “Collectors” can be connected in series or parallel to provide large scale hot water production for commercial settings such as a school, hotel or office building. There is really no limit to the size of the system, however collectors must be installed in banks of no more than 150 tubes (in series), otherwise the water may boil.

Firstly, tubes are very strong and not easily broken, but if the worst should happen, solar tubes can be replaced very easily. They are inexpensive and available though our maintenance service. Still the collectors can operate with several broken tubes, but of course the efficiency will be reduced.

Yes. “Vacuum Tubes Solar Water Heaters” will still be working efficiently. Still if it is a heavily clouded day or raining, then the preinstalled electric booster will maintain water at the required temperature. This system will be automated so you don't have to worry about running out of hot water on a rainy day.

Normally yes. Simple retrofit valves can often be used to allow solar to connect to your existing cold water inlet. If your tank cannot accept the solar input directly an additional storage tank can be installed to pre-heat the cold water prior to entering the existing tank.

If only the collector is mounted on the roof it should blend into the roof design quite well. Solar collectors are very thin and can be flush mounted on a roof. From a distance they look somewhat like a skylight.

Yes they may be mounted on a flat roof, or on the ground by using a stainless steel Flat Roof Frame. The collector should be installed at a minimum of 20o angle to ensure optimal heat pipe operation.

No. “Vacuum Tubes Solar Water Heaters” components are all high temperature rated and non-flammable so even during strong sunlight with the circulation pump turned off (stagnation), the system will not catch alight or give off any sparks.

The majority of the solar collector's components are stainless steel, aluminum, glass or glass wool. The manifold outlet should be fitted with a temperature relief valve, which will prevent the manifold temperature from exceeding 99oC

Yes, in good weather the Solar Heaters can bring water to boiling point. Generally, if hot water is not used for one day, the following day the system will be boiling and dumping hot water via the temperature relief valve.

Under normal circumstances no maintenance of the system is required. Due to the shape of the tubes regular rainfall and wind should keep the tubes clean. Should a tube even be broken it should be replaced. This, however, is an inexpensive and easy job.

“Vacuum Tubes Solar Water Heaters”  & “Solar Collectors” are high temperature collectors, and are therefore ideal for spas, as the volume of water is small and temperature requirements high. As for swimming pools, however, the volume of water is large and the temperature rise required is only several degrees. So, every case should be studied separately to reach the best cost effective solution.

1. Due to the cylindrical shape of the evacuated tube, the solar tubes are able to passively track the sun throughout the day. Flat plate collector only provide peak energy output at midday when the sun is perpendicular to the collector's surface.

2. Air is evacuated from the solar tube to form a vacuum. This greatly reduces conductive and convective heat loss from the interior of the tube. As a result wind and cold temperatures have less effect on the efficiency of the evacuated tube collector.

3. Solar collectors can often be used in subzero temperatures without the system sustaining damage. Flat plate systems often require expensive and complicated "antifreeze" systems to be installed.

4. Evacuated tubes are strong, long lasting, and should one be broken, inexpensive and easy to replace. If a flat plate collector panel is damaged the whole panel must be replaced.

5. Due to the high efficiency absorption of solar radiation even during overcast conditions, combined with excellent insulation properties of the solar tube, solar tube collectors can heat water all year round.

6. Due to the various advantages of evacuated tube collector over flat plate collectors, a smaller collector can be used to provide the same heating performance. For example, a standard household of 4-5 people would usually require a 250-300L water storage tank. Depending on your location, only 25 evacuated tubes would be required to provide all summer hot water needs.

7. Flat plate solar collectors can produce similar heat output to evacuated tube collectors, but generally only during hot, sunny conditions. When averaged over an entire year, evacuated tube collector heat output per net m2 of absorber area, is between 25% to 40% greater that a flat plate collector.

Rather than looking at just peak efficiency levels when comparing “Vacuum Tubes Solar Water Heaters” cost per unit of energy produced is much more logical. For example: Although collector A may be 20% more efficient than collector B, if collector A is 30% more expensive, then in fact collector B may be a better choice, as per kWh of energy produced per day it is cheaper. When payback time is of concern, not only price per kWh of the product is important, but also of the end system.

Our  “Vacuum Tubes Solar Water Heaters” are available through an official distribution network. Please contact us for details.