Evacuated tube solar collector is responsible for overall utilization of solar energy for hot water heating or air conditioning. Solar collector is easy to install since it can be positioned on a roof, wall or on the ground for optimum sunlight exposure. It is a system by itself, with four main components; evacuated tube, heat pipe, manifold, and mounting frame.
Evacuated tube converts the sun’s energy into usable heat. Heat pipe is a copper vacuum pipe within the evacuated tube, and transfers heat from the tube to the manifold. Manifold is a box hosting a pair of copper head pipes with sockets in which the heat pipes are plugged. Mounting frame holds the collector into position, and it is adjustable depending on the owner’s desire.
The heat pipe solar collector: This is a hollow copper pipe with a bulb at one end. The pipe contains a small amount of pure water, which has been heated to create a low pressure column with no air (vacuum). Unlike the vacuum space between the glass walls, it reduces the boiling point of liquid water inside to around 30oC (86 oF).
The Cycle Process
- Absorption of solar thermal energy begins within the inner tube of the evacuated tube, with the absorber coating taking in sunlight and converts it into heat. This energy is conducted to the vacuum copper heat pipe through the heat transfer fin.
- When the heat pipe gets heated, steam builds up in the pipe and then rises rapidly up to the manifold carrying huge amount of heat energy. The hot vapour condenses while in the bulb as it transfers the heat into the cooler liquid circulating through the header pipe. The condensed water returns to the bottom of the hot heat pipe, and the cycle repeats itself.
- A pump is used to circulate water from the storage tank through the header pipe and back to the tank, hence the tank gets heated up throughout the day.
Fundamental Benefits Of Evacuated Tube Solar Collector
The inner tube glass and heat pipe are positioned against each other, enhancing faster and high absorption of sunlight. The absorber coating is connected to a heat transfer fin, which conducts heat to the copper heat pipe. This design ensures optimal performance for a longer period of time. The evacuated tube reduces heat loss through conduction and radiation, thus increasing the energy output regardless of the surrounding temperatures.
Optimum surface area exposure
The round absorber surface of the evacuated tube enhances optimized sunlight absorption due to its curved surface area. Therefore, it is easy to maintain because no mechanical device required for tracking sunlight throughout the day. It is more efficient compared to a flat absorber.
The twin contoured header pipe is able to withstand the thermal expansion and contraction since there are more than two blazing points and the connection ports don’t penetrate the header pipe. Also, the silver brazed copper header is highly resistant to corrosion. The manifold is made up of lightweight aluminum alloy, making it easy to install.