What is Solar Water Heating?

Solar water heating is the process of collecting radiation from the sun to capture heat and transferring it to water used for industrial and domestic purposes.
Considering the alarming situation of increasing global crises caused by climate change, there is an urgent need to shift to renewable and sustainable energy resources rather than being dependent on the already depleting fuels.

For this reason, the use of solar energy for energy production is one of the most popular choices to switch to, and can be easily incorporated in both industrial and domestic processes.
For the frigid winters in Pakistan, warm water becomes a luxury that only a small chunk of the population has easy access to, owing to the increased gas and electricity prices; and not only leaves a huge dent on the pocket, but also has a significant Carbon footprint adding to climate change.
In the fight of climate change, we here at ‘Bfreeze’ are actively focusing on cutting down energy consumption of heating and air-conditioning through our technology by 2030 to play our part in making the planet be inhabitable for future generations. 

For this year’s winter campaign, we are launching Evacuated Tube Solar Geysers. Evacuated tube collectors the backbone of our product, like Flat plate solar heat collectors gather both direct and diffused radiation. Their efficiency, however, compared to Flat Plate Collectors, is higher; which gives an advantage to the Evacuated Tube collectors in day-long performance.


Solar hot water systems that use Evacuated Tube Collectors as their heat source do not require a direct interaction with the sun’s rays most of the day because the individual rounded tubes that make up the radiation absorber system even though tilted are perpendicular to the sun’s rays for most of the day. This enables the evacuated tube collector solar geysers to operate at a much higher efficiency and temperature for longer periods of time than the conventional single flat plate collector systems.

Bfreeze’s evacuated tube collector consists of a number of rows of parallel transparent glass tubes connected to a header pipe, where the manifold containing water is warmed via heat transfer. The cylindrical glass tubes allow the sunlight to be in perpendicular contact with them, allowing for a good performance even when sunlight is low such as in early mornings, late afternoons or when it is cloudy. Our evacuated tube collectors are particularly useful in areas with cold, cloudy weathers.

So how do our geysers work? They are sunlight-operated geysers that can heat water without natural gas and electricity. It directly operates with sunlight radiations. Evacuated tube collectors absorb heat from sunlight and transmit it to the water without losing back to the atmosphere.

The absorber system, made of multiple rows of parallel, transparent glass tubes supported on a frame. Each tube consists of a thick glass outer tube and a thinner glass inner tube, covered with a special coating that absorbs solar energy but inhibits heat loss. The tubes are made of borosilicate or soda lime glass, which is strong, resistant to high temperatures and has a high transmittance for solar irradiation.

Evacuated Tube Collectors use the liquid–vapor phase change as a heat pipe to transfer heat effectively from the collector to the heat transfer medium, which in this case is water. They do not heat water directly within the tubes, instead a vacuum is formed between the outer and inner tubes, which acts as an insulator – reducing any heat loss significantly to the surrounding atmosphere either through convection or radiation, making the collector more efficient than the internal insulation that flat plate collectors offer. The insulation properties of the vacuum are so good that the inner tube may be as high as 100oC, but the outer tubes would be cool to the touch.
The inner tube uses sealed copper heat pipes that are connected to the common manifold of the absorber tubes, which has water passing through it into a storage tank and heats water during the day.

The hollow copper tubes contain a small quantity of a low-pressure liquid which vaporizes at lower temperatures than it would normally at atmospheric pressure

This vacuum enables the liquid to vaporise at very lower temperatures than it would normally at atmospheric pressure. When sunlight in the form of solar radiation hits the surface of the absorber plate inside the tube, the liquid in the heat pipe quickly turns into a hot vapour type gas due to presence of the vacuum. As this gas vapour is now lighter, it rises up to the top portion of the pipe heating it up to a very high temperature.

The top part of the heat pipe, and therefore the evacuated tube is connected to a copper heat exchanger called the “manifold”. When the hot vapours still inside the sealed heat tube enters the manifold, the heat energy of the vapour is transferred to the water flowing through the connecting manifold. As the hot vapour loses energy and cools, it condenses back from a gas to a liquid flowing back down the heat pipe to be reheated.

Bfreeze’s solar geyser has the ability to heat the maximum amount of water, dependent on the size of the geyser to the required temperature in about 5 hours in normal sunny winter days. The evacuated solar tubes are also hail resistive and do not break unless something heavy hits them directly. So yeah, you can break them with a bat if you want to, but that’d be a very stupid thing to do.

The main advantage of Heat Pipe Evacuated Tube Collectors is that there is a “dry” connection between the absorber tubes and the manifold making installation and maintenance easy. Also, in the event of an evacuated tube cracking or breaking and the vacuum becoming lost, individual tubes can be exchanged without emptying or dismantling the entire system. This flexibility makes heat pipe evacuated tube solar hot water collector ideal for easy installation and ability to easily expand by adding as many tubes as you want.

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Intelligent Temperature and Water Level Controller

Our Solar geysers also come with an intelligent control system and unique features. The Geyser is available with an insulated tank which can store the water heated and allows it to be used even the next day without significant loss of temperature.

We are also providing a free “Intelligent Temperature and Water Level Controller”, which enables users to adjust their desired temperature and water level in the tank. Even on rainy or snowy days, if sunlight is completely insufficient to get the desired temperature using the inherent system, enough sunlight will get through to keep the tubes well above freezing and still be able to preheat the water which can then be heated further using the controller which turns on the electric rod installed in the tank. This heating rod will provide the remaining heat to achieve the required temperature, and also reducing the costs of heating water in winter.
In the same way, when water level reaches a minimum value that you choose, the controller will either open the valve to allow water in from the main tank or the controller may turn on the electric motor to fill water in the tank. You can also specify a time when you need of water of a specific temperature, which allows for a stress-free experience of hot water usage.

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