The sun is humanity’s oldest energy source, and scientists and engineers have been trying to harness the power of sunlight for a wide range of heating, lighting, and industrial tasks for a long time. Every child knows that focused sunlight is hot enough to set things afire; engineers and scientists know that every square meter of the Earth receives about 1 kilowatt of thermal energy when the sun is overhead.

Solar thermal collectors are devices that take solar energy in the form of light and convert it into heat. Two types of solar thermal collectors are being used, evacuated tube collectors and flat-plate collectors.


Evacuated Tubes are the heart of the Sunpo SP collector, responsible for absorbing sunlight and converting it into usable heat.


Solar Vacuum Tube – Design

The evacuated tube used as the “twin-tube”, the tube is essentially two glass tubes that are fused at the top and bottom. The inner tube has a solar absorbing coating, and the space between the two tubes is evacuated to form a vacuum.


Solar Vacuum Tube – Strong Glass

The tubes are made from a type of glass called Borosilicate. Borosilicate glass has the characteristic of being very strong and also has excellent light transparency (>92% @ 1.6mm thick) .

The wall thickness of the glass greatly impacts the strength, longevity and naturally also the cost. Sunpo evacuated tubes are custom made to strict requirements that exceed the industry standards, including a 1.6mm thick wall ensuring excellent strength and resilience to hail impact.

To confirm the strength of the tubes, each batch of evacuated tubes assembled in the Sunpo factory have randomly selected samples tested by dropping a 25mm / 1.2″ diameter steel ball onto the tube from various heights.


Solar Vacuum Tube – Basic Specifications

Length 1800mm
Outer tube diameter 58mm
Inner tube diameter 47mm
Glass thickness 1.6mm
Material Borosilicate Glass 3.3
Thermal expansion 3.3×10-6 °C
Absorptive Coating Graded Al-N/Al
Absorptance >92% (AM1.5)
Emittance <8% (80°C)
Vacuum P<5×10-3 Pa
Stagnation Temperature >200°C
Heat Loss <0.8W/ ( m2°C )
Maximum Pressure 0.8MPa

Heat pipe

Compared with the general all glass vacuum tube, the heat pipe has more advantages like high heating speed, no scale formation, glass breakage prevention, water filled time unlimited, single broken tube having no influence on machine use.

The SP heat pipe series vacuum tube solar collector is designed for active or forced convection applications using a circulation pump, a hot water tank and an electronic controller. Heat pipes together with glycol allow for operations under deep freezing climates in closed loop configurations. In tropical climates a simpler lower cost open loop configuration can be used.

Resistant to water hardness and fouling, it is a high end, high efficiency solar collector certified under SRCC certificate strict testing procedures. Vacuum tubes and heat pipes allow the system to collect solar radiation quickly and efficiently even during early morning and late afternoon, making it a very efficient and cost effective solution. Its solid construction employs a low oxygen copper manifold insulated by a thick polyurethane layer and encapsulated in a weather proof aluminum casing. This collector is supported by a strong stainless steel or aluminum bracket that can be manufactured according to customer’s needs for different angles.

The Eco Series can be manufactured in many sizes and used for domestic or large scale commercial or industrial applications such as hotels, hospitals, schools, food processing and others.

Because each collector is composed of multiple vacuum tubes and heat pipes, if one tube breaks the system will not leak and continue to operate with minimum efficiency loss. It is a very robust design capable of sustaining hurricane winds. It’s very low maintenance requirements

and ease of individual tube replacement without tools guarantee decades of low operational costs.