Solar water heating is now a mature technology. Wide spread utilization of solar water heaters can reduce a significant portion of the conventional energy  being used for heating water in homes, factories and other commercial & institutional establishments. Internationally the market for solar water heaters  has expanded significantly during the last decade.  It is estimated that over 157 million sq.m. of collector area has so far been installed world wide for heating water.

XLHJ Group Limited offers range of solar energy products, such as solar water heaters, solar street lighting sytems, solar collectors and accessories. Please, request our managers for a quotation.

Working principle

This split solar water heating system has solar collectors on roof and water tanks inside the house, and transfers heat energy collected by the collectors into the tank by natural or forced circulation of the working fluid between collector and the tank. The solar hot water collectors are connected by a loop of piping to a heat exchanger unit located inside of a hot water storage tank located in the building. In other words, the building’s domestic water supply to be heated is not itself circulated through the solar collector but rather it is heated inside the water tank by a heat exchanger which itself contains a liquid (containing an anti-freeze in northern climates) which circulates in the solar collectors and inside the heat exchanger.

A hot water storage tank contains domestic hot water heated by the heat exchanger; the tank is supplied with incoming cold water and provides outgoing hot water to the building’s plumbing fixtures. In areas where there is plenty of sunlight and water usage is more modest, a simple collector, pump, controls, and small water tank are often adequate. Temperature sensors mounted at the water storage tank and also at the solar collectors monitor water temperatures and communicate with a solar controller module. The solar controller module determines when it is appropriate to circulate water from the hot water tank through the solar collectors, preventing water circulation when it would cool rather than warm the hot water.

A circulating pump is controlled by the solar controller module to move water between the solar collectors and the hot water storage tank. An expansion tank absorbs the pressure increase created in the system when water is heated. A pressure and temperature relief valve is provided on the hot water tank for safety. An air vent valve is provided at the solar collectors to avoid the piping becoming air bound, purging un-wanted air in the water circulation loop. A tempering valve or mixing valve is installed to mix cold water in with the outgoing hot water from the hot water tank, permitting storage of more heat in the water tank without risking scalding building occupants.A backup hot water heater is usually provided, using electricity, gas, oil, or other fuel to assure that there is adequate hot water when weather conditions do not provide enough solar energy.

1. Solar collector
2. Temp. sensor
3. High temp. air valve
4. Hot water outlet
5. Mixing tap
6. Heat agent forward flow pipeline
7. Check valve
8. Heat agent drain&fill transfer valve
9. Expansion tank
10. Offtake air valve
11. Circulation pump
12. Excessive pressure valve
13. Manometer
14. Heat agent reverse flow pipeline
15. Solar heat accumulating and saving reservoir
16. Heat-exchange coil (serpentine)
17. Standby electric heater
18. Electronic controller

 TC - solar collector temperature sensor, TR - reservoir temperature sensor

Components

The system comprises of solar collectors, a water tank, a heat exchanger, a controller and pump.

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Technical characteristics of solar collectors

Solar collector SLR4715-16

Solar collectors SLU series

• Sleek low profile design
• Extremely efficient heat transfer coefficient
• Can be retrofitted to existing hot water cylinder
• Ideal for new homes
• Low, medium and mains pressure capable
• Closed or open loop available
• Modular design means more units can be added in the future

 Positioning of collectors  

Evacuated tubes
The design of evacuated tubes means that the orientation is not as critical for maximum performance as a flat panel but following the criteria below will produce the best results.
 
Orientation
As close to north as possible +/- 45° acceptable
Facing more west than east or north is better
But options are available to mount on east/west roofs or even south facing roofs
 
Shading
For the best results avoid shading 3 hours either side of midday
Check for shading impact in winter when the sun is lowest
 
Inclination of collectors
Panels can be mounted from 0° to 90°
The optimum angle for all year round performance is the latitude of your location +/- 10°.
There is not a significant difference if panels are mounted within a further 20° of this
If panels are steeper performance in winter will be better, if lower then winter performance will not be quite so good
A frame can be used to adjust the angle to the most suitable for your roof
 
Roof loading
This is not an issue with pumped systems as each collector only weighs 45kgs
When installing close-coupled systems the weight of a full cylinder on the roof may mean additional roof strengthening is required. If there is any doubt an engineer should be consulted.
In any case the load should be spread over as many trusses as possible
The load should be positioned above an area where there are supporting walls below
Position the tank as close as possible to the main use areas of bathrooms, laundry and kitchen

Electronic solar controller

The electronic solar controller enables the operator to set the temperature and timing of the backup heater. The controller will check the temperature of the water in the cylinder at certain times of the day (set by owner) and if required will boost the temperature to the desired level. The controller will allow owner to heat water on night rate The controller will sense if there is a frost danger in the pipes and will circulate water Will heat water up to 70°C automatically if temperature in tank has not been up to 70°C within last 7 days

Circulating pump

The circulating pump is an industry standard German pump used by all leading Solar companies The Grunfos pump is used for larger applications and is recognised as the world leader in pump technology

How it works

TH Solar uses "Heat pipe" technology to harness the sun's energy and has NO WATER CIRCULATING in it's panels . The vacuum in the glass tube, being the best possible insulation for a solar collector, suppresses heat losses and also protects the absorber plate and the "heat-pipe" from the outside conditions. In a relatively cool climate especially the South Island this increases thermal output substantially. This results in exceptional performance far superior to any other type of solar collector. Each tube contains a sealed cooper pipe (heat pipe). The pipe is then attached to an aluminium fin that is in contact with the special absorber coating. . Protruding from the top of each tube is a metal tip this is in effect the condenser. These tubes are mounted, the metal tips up, into a heat exchanger. As the sun shines on the black surface, heating the inside of the fin, the refrigrerant is heated and hot vapor rises to the top of the pipe. This condensation within the tube is the basis of a heat pump and gives off large amounts of heat. Water, or glycol, when pumped through the copper pipe through the centre of the manifold picks up the heat from the manifold.
 

The system

The controller has three temperature sensors situated in:
 

1. The roof manifold
2. The bottom of the tank and
3. The top of the tank

When the roof manifold is 8°C more than the bottom of the cylinder it will start the pump and the water will be pumped through the manifold cooling the manifold and heating the passing water. When the manifold has dropped in temperature to 3°C more than the bottom of the cylinder it will stop. (This may take 2 minutes)
 

The controller will wait for the manifold temperature to rise again and the process starts again.

If during frost conditions the manifold sensor gets below 2°C the controller will tell the pump to start and circulate warm water through the pipes. This will stop when the manifold temperature reaches 6°C.

Functions

• Constant temperature circulation: adopt the auto circulation system to realize constant temperature of the water inside the solar system. Ex-factory default is to ensure the constant temperature of water inside the system and pipelines.
• Overheat protection: It includes protection of solar collector and electric booster. The former will be operated by the controller automatically to ensure the safety of the solar collector and the solar heat storage system; the later will be controlled by the temperature sensor automatically, to make sure the booster work in a safe condition. Take manual operation to resume to the working condition.
• Pressure limitation: It functions by automatically sensing the pressure and temperature of the parts, so as to ensure the normal operation of the system.
• Anti-freezing:  It is realized through the circulation of the working fluid to make sure the safety of the operation at the limited temperature.

 Features

• The solar collector is separated with the water tank, so the water tank can be located anywhere;
• Solar collector can be mounted on buildings in different styles;
• U-pipe solar collector with anti-freezing fluid inside the tubes will achieve high anti freezing effect;
• Intelligent control system is reliable and convenient;
• Pressurized operation will guarantee sufficient water flow;
• Solar water heating system can be connected with auxiliary heating system at the preset joint. 

Technical characteristics

Advantages of a  system:

SUZ series is a kind of remote storage solar water system that the collectors and the hot water tank are separated. This kind of system can integrate into the building very well. It is a heat exchange system that can transfer the solar radiation energy to the water and heat it. Every season in one year, the system can work safely and reliably even in very cold place, because the antifreeze liquid is used. It is the first chose for top grade house and villa, for it can meet the need of highly pressurized water and multi usage in the same time.

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