Compare U-pipe with heat-pipe collector

By: Solar Commercial  05-Apr-2012
Keywords: Hot Water, Solar Energy, Evacuated Tube

Why we say our collector is the most suitable for NZ.

We designed our unique solar collector and solar water heater system specifically for New Zealand conditions.

Solar energy is a readily available free resource for everyone to use. Solar energy in New Zealand is plentiful and can be harnessed in all areas. On average, New Zealand has about 2000 hours of bright sunshine each year. Our isolation from large land masses, exposure to cold southerly winds and ocean currents can cause the weather conditions to change rapidly requiring a system which is specifically designed for NZ conditions.

A solar water heating system has as its main component, a collector. The function of the collector is to capture the sun’s energy which is then transferred as heat to the water in the collector.

There are two main types of collectors; a Flat-Plate Collector and an Evacuated-Tube Collector. They achieve both higher temperatures and have high efficiency ratings. They perform well in both direct and diffuse solar radiation. This characteristic, combined with the fact that the vacuum minimizes heat losses, makes these collectors particularly useful in areas with cold, cloudy winters(as in New Zealand). Because of the circular shape of the evacuated tube, sunlight is perpendicular to the absorber for most of the day. In comparison, for a flat-plate collector that is in a fixed position, the sun is only perpendicular to the collector at noon.

Most evacuated-tube collectors available are heat-pipe collectors. In this type of collector, a heat pipe collector incorporates a special fluid which begins to vaporize even at low temperatures. The steam rises in the individual heat pipes and warms up the carrier fluid in the main pipe by means of a heat exchanger. The condensed liquid then flows back into the base of the heat pipe. The pipes must be angled at a specific degree above horizontal so that the process of vaporizing and condensing occurs. This type of collector is designed for the northern hemisphere where it can get very cold, less than -25°C, and the water can be of poor quality. In time the poorer quality of water can cause blockages in smaller pipes. That is why a larger manifold pipe is used. It uses indirect heat distribution (through a heat exchanger), so it is less efficient than when heating the water directly. Some heat pipes contain chemicals such as antifreeze, which over a period of time can start to lose efficiency, resulting in the need to be replaced. Such a system should be tested approximately every 5 years.

At Solar Commercial, we do not use this type of system which contains chemicals. Instead we use specially designed “U-Pipe Evacuated Tube Solar Collectors”. U-Pipe Evacuated Tube Solar Collectors are smaller and more compact than heat pipe evacuated tube solar collectors. While the two collectors have nearly identical efficiency ratings, the U-Pipe Collectors actually require fewer tubes up on the roof to reach the same peak efficiency levels (5%-8% more efficiency).

The U-Pipe collectors have a 12mm copper pipe in the evacuated tube. It actually bends around on itself at the bottom of the glass tube and returns directly into the manifold. This enables the water to travel through the tube for direct gain from solar radiation and also eliminates the need for heat exchange which creates a far greater efficiency rating

The U-pipe collector is a maintenance free system and has a long life (over 25 years) . The tubes don't need to be tested as they don't lose efficiency and they don't need to be replaced unless damaged. As a bonus our system is easy to install.

Keywords: Evacuated Tube, Hot Water, Solar Energy

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Wallace Plumbing Mob: 027 244 0405. Stan Wallace Ph: 06 3749346.


U-Pipe Collector

Tianpu solar energy group first manufactured a "U" tube design twelve years ago to fit modular solar heating systems. The aim was to produce an all-glass vacuum tube that still works efficiently even if a tube is broken. Test pressure is at 12Kg/cm ², and system working pressure is up to 6Kg/cm. Tianpu has always been a leader in the field of solar energy technology.



To achieve these savings, Solar Commercial advise that large collectors and extra storage tanks are essential in order to have effective solar water heating and storage. The black coating on the inner cover of the evacuated tubes ensures high solar energy absorption and low heat radiance losses. For dairy farmers there is a huge potential for savings with an effective solar water heating solution from Solar Commercial.