A low pressure solar geyser (also referred to as a close coupled unit) is popular for many reasons, but there are two main attractions. The first is the solar power aspect. There’s is no need for any external electricity sources. Secondly, it’s a very basic setup. To heat water on a daily basis you literally only need the sun’s radiation. Another reason why a low pressure solar geyser system is popular can be the fact that there are no moving parts involved, bringing us back to the simplicity of the system. But how exactly will it work you wonder? With no pumps to circulate the heated water, how can it heat a large tank filled with cold water?
The Design of a Low Pressure Solar Geyser
The first thing you have to understand is that a low pressure system usually comes as a complete package. This will include the tank and the tube collector. The reason why an evacuated tube collector forms part of the system is because it’s more efficient than a typical panel. Apart from tracking the sun for longer (thanks to the round shape of the tubes), it also shows more efficiency during cloudy days.
Low pressure systems are Closed coupled systems, meaning that the tubes connect directly into the tank. Heated water is pushed up the pipes filling the tank with the hot water and subsequently pushing the cold water back down into the tubes for re-heating. This process happens continuously throughout the day.
When the low pressure solar geyser is installed, the tank is placed at the top and the collector at the bottom. A small section of the tubes lead into the tank, which establishes a direct connection between the two. Given the way it’s assembled, there’s no need for a pump to circulate the water. Instead, the natural process of gravity will make sure the hot water inside the tubes move up, while the cold water moves down. This is referred to as a thermosiphon process. Cold water is essentially heavier than hot water, and it will kick-start the convection cycle.
Mentioned earlier, the two main benefits can be divided between water heating without the need for electricity, and the basic setup. With a basic design such as this, the installation costs are usually cheaper. The overall package is also more affordable, because there aren’t any complicated components involved.
However, the benefits don’t stop there. Provided that there is less pressure and strain on the tank, it typically lasts longer. Add to this the lightweight components and the incredible efficiency, you’ve got a solar geyser that won’t stress you out.
There are two challenges to consider though. The first is that the installation needs to be very precise, because the temperature of the tubes can reach scolding temperatures. The second challenge is when one of the tubes fail. If this happens the entire system needs to be shut down before repairs can be made. But if controlled and installed correctly, there shouldn’t be any temperature problems. As for a single tube breaking, it doesn’t happen very often.
So, if you’re looking for a basic, efficient and affordable solar geyser system, you should definitely consider a low pressure one.