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Useful Info

2. Solar FAQ

1. What is Solar energy?
Solar energy is the cleanest and most inexhaustible of all known energy sources. Solar radiation is the heat, light and other radiation that is emitted from the sun. Solar radiation contains huge amounts of energy and is responsible for almost all the natural processes on earth. The suns energy, although plentiful, has been hard to directly harness until recently.

Solar Energy can be classified into two categories, Thermal and Light. Photo-voltaic cells (PV) use semiconductor-based technology to convert light energy directly into an electric current that can either be used immediately, or stored in a battery, for later use. PV panels are now becoming widely used as they are very versatile, and can be easily mounted on buildings and other structures. They can provide a clean, renewable energy source which can supplement and thus minimize the use of mains electricity supply. In regions without main electricity supply such as remote communities, emergency phones etc, PV energy can provide a reliable supply of electricity. The disadvantage of PV panels is their high cost and relatively low energy conversion rate (only 13-15%). Thermal solar on the other hand has average efficiency levels 4-5 times that of PV, and is therefore much cheaper per unit of energy produced.

Thermal energy can be used to passively heat buildings through the use of certain building materials and architectural design, or used directly to heat water for household use. In many regions, solar water heaters are now a viable supplement or alternative to electric or gas hot water production.

Thermal energy obtained from the sun can be used for a number of applications including producing hot water, space heating and even cooling via use of absorption chilling technology.

Using solar and other forms of renewable energy reduces reliance on fossil fuels for energy production, thus directly reducing CO2 emissions. CO2 emissions contribute to global warming, an environmental issue which is now of great concern. The average household can reduce CO2 emissions by as much as 20% by installing an INLIGHT solar water heater or solar collector.

Flat plate thermal solar collectors have been in use for several decades, but only in relatively small numbers, particularly in Western countries. Vacuum tubes have also been in use for more than 20 years, but have been much more expensive than flat plate, and therefore only chosen for high temperature applications or by those with money.

In recent years the production volume of vacuum tubes has exploded, resulting in greatly lower manufacturing and material costs. The result is that vacuum tubes are now similar in price to flat plate, but with the insulating benefits of the vacuum tube, they are set to become the default choice for thermal solar applications worldwide.

2. What is an All-glass Vacuum Tube?
Vacuum tubes are the absorber of the solar water heater. They absorb solar energy converting it into heat for use in water heating. Vacuum tubes have already been used for years in Germany, Canada, China and the UK. There are several types of vacuum tubes in use in the solar industry. INLIGHT solar water heater and collectors use the most common "twin-glass tube". This type of tube is chosen for its reliability, performance and low manufacturing cost.

1) Construction of glass vacuum tube
Each vacuum tube consists of two glass tubes made from extremely strong borosilicate glass. The outer tube is transparent allowing light rays to pass through with minimal reflection. The inner tube is coated with a special selective coating (AL/AL-ALN(H)/AL-ALN(L)/ALN) which features excellent solar radiation absorption and minimal reflection properties. The top of the two tubes are fused together and the air contained in the space between the two layers of glass is pumped out while exposing the tube to high temperatures. This "evacuation" of the gasses forms a vacuum, which is an important factor in the performance of the vacuum tubes.

2) Why a vacuum?
As you would know if you have used a glass lined thermos flask, a vacuum is an excellent insulator. This is important because once the vacuum tube absorbs the radiation from the sun and converts it to heat, we don't want to lose it!! The vacuum helps to achieve this. The insulation properties are so good that while the inside of the tube may be 150oC / 304oF , the outer tube is cold to touch. This means that vacuum tube water heaters can perform well even in cold weather when flat plate collectors perform poorly due to heat loss (during high Delta-T conditions).

In order to maintain the vacuum between the two glass layers, a barium getter is used (the same as in television tubes). During manufacture of the vacuum tube this getter is exposed to high temperatures which causes the bottom of the vacuum tube to be coated with a pure layer of barium. This barium layer actively absorbs any CO, CO2, N2, O2, H2O and H2 out-gassed from the vacuum tube during storage and operation, thus helping to maintaining the vacuum. The barium layer also provides a clear visual indicator of the vacuum status. The silver colored barium layer will turn white if the vacuum is ever lost. This makes it easy to determine whether or not a tube is in good condition. See picture below.

The Getter is located at the bottom  of the vacuum tube.

Left Tube = Vacuum Present
Right Tube = Faulty

Vacuum tubes are aligned in parallel, the angle of mounting depends upon the latitude of your location. In a North South orientation the tubes can passively track heat from the sun all day. In an East West orientation they can track the sun all year round.

The efficiency of a vacuum water heater is dependent upon a number of factors, an important one being the level of vacuum radiation (insolation) in your region.

3) Vacuum Tube Basic Specifications

Length (nominal)

1500mm /1800mm

Outer tube diameter

47mm / 58mm

Inner tube diameter

37mm / 47mm

Glass thickness


Thermal expansion

3.3x10-6 oC


Borosilicate Glass 3.3

Absorptive Coating

Graded Al-N/Al


>92% (AM1.5)


<8% (80oC)


P<5x10-3 Pa

Stagnation Temperature


Heat Loss

<0.8W/ ( m2oC )

Maximum Strength


4) How strong are the glass tubes?
The tubes are made from borosilicate glass (like Pyrex) and are very strong. They can withstand 25mm (1 inch) hailstones, (you would be quite likely to be injured if you were struck by a 25mm hailstone!)

3. What is a Heat Pipe?
Heat pipes might seem like a new concept, but you are probably using them everyday and don't even know it. Laptop computers often using small heat pipes to conduct heat away from the CPU, and air-conditioning system commonly use heat pipes for heat conduction.        
1) Structure and Principle
The heat pipe is hollow with the space inside evacuated, much the same as the glass vacuum tube. In this case insulation is not the goal, but rather to alter the state of the liquid inside. Inside the heat pipe is a small quantity of purified water and some special additives. At sea level water boils at 100oC (212oF), but if you climb to the top of a mountain the boiling temperature will be less that 100oC (212oF). This is due to the difference in air pressure.

Based on this principle of water boiling at a lower temperature with decreased air pressure, by evacuating the heat pipe, we can achieve the same result. The heat pipes used in INLIGHT solar collectors have a boiling point of only 30oC (86oF). So when the heat pipe is heated above 30oC (86oF) the water vaporizes. This vapor rapidly rises to the top of the heat pipe transferring heat. As the heat is lost at the condenser (top), the vapor condenses to form a liquid (water) and returns to the bottom of the heat pipe to once again repeat the process.

At room temperature the water forms a small ball, much like mercury does when poured out on a flat surface at room temperature. When the heat pipe is shaken, the ball of water can be heard rattling inside. Although it is just water, it sounds like a piece of metal rattling inside.

This explanation makes heat pipes sound very simple. A hollow copper pipe with a little bit of water inside, and the air sucked out! Correct, but in order to achieve this result more than 20 manufacturing procedures are required and with strict quality control.

2) Quality Control
Material quality and cleaning is extremely important to the creation of a good quality heat pipe. If there are any impurities inside the heat pipe it will affect the performance. The purity of the copper itself must also be very high, containing only trace amounts of oxygen and other elements. If the copper contains too much oxygen or other elements, they will leach out into the vacuum forming a pocket of air in the top of the heat pipe. This has the effect of moving the heat pipe's hottest point (of the heat condenser end) downward away from the condenser. This is obviously detrimental to performance, hence the need to use only very high purity copper.

Often heat pipes use a wick or capillary system to aid the flow of the liquid, but for the heat pipes used in INLIGHT solar collectors no such system is required as the interior surface of the copper is extremely smooth, allowing efficient flow of the liquid back to the bottom. Also INLIGHT heat pipes are not installed

The heat pipe used in INLIGHT solar collectors comprises two copper components, the shaft and the condenser. Prior to evacuation, the condenser is brazed to the shaft. Note that the condenser has a much larger diameter than the shaft, this is to provide a large surface area over which heat transfer to the header can occur. The copper used is oxygen free copper, thus ensuring excellent life span and performance.

Each heat pipe is tested for heat transfer performance and exposed to 250oC (482oF) temperatures prior to being approved for use. For this reason the copper heat pipes are relatively soft. Heat pipes that are very stiff have not been exposed to such stringent quality testing, and may form an air pocket in the top over time, thus greatly reducing heat transfer performance.


4. What is a solar water heater (SWH) / solar water heating system (SWHS)?

A solar water heater is such an efficient water heating system use the solar energy rather than electricity or gas to heat water, thus reducing your monthly utility bill. Generally speaking, it consists of storage water tank, solar collector, supporting bracket, optional controlling devices, pipelines and accessories accordingly. Installed properly, solar water heater is the most economical over the life among other heating systems. At the same time, solar water heater could work with other energies to assisting water or air heating, such as electricity, gas, oil, etc.

5. Types of Solar Water Heating Systems
Solar water heating systems (SWHS) can be either active or passive. An active system uses an electric pump to circulate the fluid through the collector; a passive system has no pump and relies on thermo-siphoning to circulate water. The amount of hot water a solar water heater produces depends on the type and size of the system, the amount of sun available at the site, installation angle and orientation. SWHS are also characterized as open loop (also called "direct") or closed loop (also called "indirect"). An open-loop system circulates household (potable) water through the collector. A closed-loop system uses a heat-transfer fluid (water or diluted antifreeze) to collect heat and a heat exchanger to transfer the heat to the household water. A disadvantage of closed looped system is that efficiency is lost during the heat exchange process.

1) Active Systems
Active systems use electric pumps, valves, and controllers to circulate water or other heat-transfer fluids through the collectors. They are usually more expensive than passive systems but generally more efficient. Active systems are often easier to retrofit than passive systems because their storage tanks do not need to be installed above or close to the collectors. If installed using a PV panel to operate the pump, an active system can operate even during a power outage.
a) Open-Loop Active Systems
Open-loop active systems use pumps to circulate household potable water through the collectors. This design is efficient and lowers operating costs but is not appropriate if water is hard or acidic because scale and corrosion will gradually disable the system. Open-loop active systems are popular in regions that do not experience subzero temperatures. Flat plate open-loop systems should never be installed in climates that experience sustained periods of subzero temperatures. The INLIGHT solar water heater can be installed in an open loop in areas that experience sub-zero temperatures as long as the solar controller has a low temperature function.
b) Closed-Loop Active Systems
These systems pump heat-transfer fluids (usually a glycol-water antifreeze mixture) through the solar water heater. Heat exchangers transfer the heat from the fluid to the water that is stored in tanks. Double-walled heat exchangers or twin coil solar tanks prevent contamination of household water. Some standards require double walls when the heat-transfer fluid is anything other than household water. Closed-loop glycol systems are popular in areas subject to extended subzero temperatures because they offer good freeze protection. However, glycol antifreeze systems are more expensive to purchase and install and the glycol must be checked each year and changed every few years, depending on glycol quality and system temperatures.
c) Drain-back systems
Use water as the heat-transfer fluid in the collector loop. A pump circulates the water through the solar water heater. When the pump is turned off, the solar water heater drains of water, which ensures freeze protection and also allows the system to turn off if the water in the storage tank becomes too hot. A problem with drain-back systems is that the solar water heater installation and plumbing must be carefully positioned to allow complete drainage. The pump must also have sufficient head pressure to pump the water up to the collector each time the pump starts. Electricity usage is therefore slightly higher than a sealed closed or open loop.
INLIGHT solar collectors are ideal for use in active (open or closed) systems.
2) Passive Systems
Passive systems move household water or a heat-transfer fluid through the system without pumps. Passive systems have the advantage that electricity outage and electric pump breakdown are not issues. This makes passive systems generally more reliable, easier to maintain, and possibly longer lasting than active systems. Passive systems are often less expensive than active systems, but are also generally less efficient due to slower water flow rates through the system.
a) Thermosiphon Systems
A thermosiphon system relies on warm water rising, a phenomenon known as natural convection, to circulate water through the solar absorber and to the tank. In this type of installation, the tank must be located above the absorber tubes/panel. As water in the absorber heats, it becomes lighter and naturally rises into the tank above. Meanwhile, cooler water in the tank flows downwards into the absorber, thus causing circulation throughout the system. This system is widely used with both flat plate and vacuum tube absorbers. The disadvantages of this design are the poor aesthetics of having a large tank on the roof and the ISS with structural integrity of the roof. Often the roof must be reinforced to cope with the weight of the tank.
b) Batch Heaters
Batch heaters are simple passive system consisting of one or more storage tanks placed in an insulated box that has a glazed side facing the sun. Batch heaters are inexpensive and have few components, but only perform well in summer when the weather is warm. Vacuum tube solar collectors are now an affordable and much more efficient alternative to either batch or flat plate collectors.

6. Types of Solar Collectors
There are basically three types of thermal solar collectors: flat-plate, vacuum-tube and concentrating.
1) Flat-Plate
Collectors comprise of an insulated, weatherproof box containing a dark absorber plate under one or more transparent or translucent covers. Water or heat conducting fluid passes through pipes located below the absorber plate. As the fluid flows through the pipes it is heated. This style of collector, although inferior in many ways to vacuum tube collectors, is still the most common type of collector in many countries.

2) Vacuum Tube
Solar water heaters are made up of rows of parallel glass tubes or heat pipe tubes. There are several types of vacuum tubes (sometimes also referred to as Solar Tubes).

a) Glass-Glass
Tubes consists of two glass tubes which are fused together at one end. The inner tube is coated with a selective surface that absorbs solar energy well but inhibits radiative heat loss. The air is withdrawn ("vacuum") from the space between the two glass tubes to form a vacuum, which eliminates conductive and convective heat loss. These tubes perform very well in overcast conditions as well as low temperatures. Because the tube is 100% glass, the problem with loss of vacuum due to a broken seal is greatly minimized. Glass-glass solar tubes may be used in a number of different ways, including direct flow, heat pipe, or U pipe configuration. INLIGHT uses a high efficiency heat pipe and heat transfer fin design to conduct the heat from within the vacuum tube up to the header.

b) Glass-Metal
Tubes consist of a single glass tube. Inside the tube is a flat or curved aluminum plate which is attached to a copper heat pipe or water flow pipe. The aluminum plate is generally coated with Tinox, or similar selective coating. These type of tubes are very efficient but can have problems relating to loss of vacuum. This is primarily due to the fact that their seal is glass to metal. The heat expansion rates of these two materials. Glass-glass tubes although not quite as efficient glass-metal tubes are generally more reliable and much cheaper.

c) Glass-glass - water flow path
Tubes incorporate a water flow path into the tube itself. The problem with these tubes is that if a tube is ever damaged water will pour from the collector onto the roof and the collector must be "shut-down" until the tube is replaced.

3) Concentrating
Collectors for are usually parabolic troughs that use mirrored surfaces to concentrate the sun's energy on an absorber tube (called a receiver) containing a heat-transfer fluid, or the water itself. This type of solar collector is generally only used for commercial power production applications, because very high temperatures can be achieved. It is however reliant on direct sunlight and therefore does not perform well in overcast conditions.

7. Is solar water heating a viable alternative to gas or electricity?
Solar should not be seen as an alternative to gas or electricity, but rather a supplement. Solar cannot totally replace the need for gas or electric heating as there are sometimes days when there is little sunlight. When averaged over a year, a correctly sized solar system can provide 60%-70% of a household's hot water needs. Providing more than this is unadvisable, as too much heat will be produced in the summer. The hot water system can easily be automated so hot water is guaranteed regardless of sunlight levels.

8. How long will it take to recoup my investment?
INLIGHT solar water heater and solar collectors are much more affordable than many other solar hot water heaters. For a household of 4, the price of a full system may not be too much more than a new electric or gas system. Depending on you location (solar levels) and current hot water usage the annual electricity or gas saving will differ. However in a normal household that spends 25% of its electricity bill on hot water heating, the full cost of the purchase may be recouped as quickly as 4-5 years in reduced bills. You will definitely make considerable savings during the life of the solar hot water heater.

9. Can INLIGHT solar products be used in cold conditions?
Yes. INLIGHT water heaters and collectors can be used in temperatures as low as -30oC, although performance is greatly reduced in such extreme conditions. Good heat output is still achieved in mild sub-zero conditions.

10. What happens if one of the solar tubes is broken?
Firstly, tubes are very strong and not easily broken, but if the worst should happen, solar tubes can be replaced very easily. They are inexpensive and available though your local solar distributor. The INLIGHT heat pipe solar collectors can operate with several broken tubes, but the efficiency will be reduced, so it is recommended that broken tubes be replaced immediately.

11. Will water be heated on a cloudy day?
Yes. Although the heat output of the solar heaters and collectors is reduced on overcast days it will still be able to provide heating. If it is a heavily clouded day or raining, then more gas or electric boosting may be required to maintain water at the required temperature. This system will be automated so you don't have to worry about running out of hot water on a rainy day.

12. Can I use a solar collector with my existing hot water system?
Normally yes. Simple retrofit valves can often be used to allow solar to connect to your existing cold water inlet. If your tank cannot accept the solar input directly an additional storage tank can be installed to pre-heat the cold water prior to entering the existing tank.

13. Are the solar collectors noticeable on the roof?
If only the collector is mounted on the roof it should blend into the roof design quite well. INLIGHT solar collectors are very thin and can be flush mounted on a roof. From a distance they look somewhat like a skylight. You may have to check with your local council regarding building restrictions when installing your solar collector.

14. Can INLIGHT solar products be mounted on a flat surface?
Yes they may be mounted on a flat roof, or on the ground by using a Flat Roof Frame. The collector should be installed at a minimum of 20o angle to ensure optimal heat pipe operation.

15. How do I protect my solar system during subzero temperatures?
If you have a system that is operating in areas with subzero temperatures then freeze protection must be implemented. The easiest means of preventing freezing is to use a controller with a low temperatures setting, so when the manifold temperature drops below a certain pre-set temperature (5oC/40oF), the pump will circulate, warming the collector with water from the bottom of the storage tank. The pump will not run continually, just periodically, the frequency of which will depend on the outside temperature. In extremely cold areas, a closed loop using a glycol/water mix may be appropriate.

16. Will the INLIGHT solar heater and collector be a fire hazard during hot, dry weather?
Definitely no. The INLIGHT solar heater and collector's components are all high temperature rated and non-flammable so even during strong sunlight with the circulation pump turned off (stagnation), the system will not catch alight or give off any sparks. The majority of the solar heater or collector's components are steel, aluminum, glass or glass wool. The manifold outlet should be fitted with a temperature relief valve, which will prevent the manifold temperature from exceeding 99oC / 212oF.

17. Can the INLIGHT solar heater and collector heat water to a high enough temperature?
Yes, in good weather the INLIGHT solar heater and collector can bring water to boiling point. Generally this is not necessary and so the system should be designed to provide a daily temperature rise of around 25-30oC (45-54oF) in the summer. Sizing a domestic system that can bring the cold water up to 60oC/141oF in a single day is not logical, because if hot water is not used for one day, the following day the system will be boiling and dumping hot water via the temperature relief valve. This is both a waste of energy and water! Please sensibly size solar water heating system to ensure optimal performance and minimal wastage of water.

18. What maintenance of the solar heater and collector is required?
Under normal circumstances no maintenance of the system is required. Due to the shape of the tubes regular rainfall and wind should keep the tank and tubes clean. Should a tube even be broken it should be replaced. This, however, is an inexpensive and easy job. Any "handy" person can install a new tube (while adhering to local health and safety regulations). INLIGHT heat pipe solar collectors can even operate with several broken tubes, however the efficiency will be reduced slightly.

19. Can INLIGHT solar heater and collectors be used for a large scale hot water production?
Yes. INLIGHT solar heaters or collectors can be connected in series or parallel to provide large scale hot water production for a commercial settings such as a school, hotel or office building. There is really no limit to the size of the system, however collectors must be installed no more than 150 tubes (in series), otherwise the water may boil.

20. Can I heat my swimming pool or spa using an INLIGHT solar collector?
INLIGHT collectors are high temperature collectors, and are therefore ideal for spas, as the volume of water is small and temperature requirements high. For swimming pools, however, the volume of water is large and the temperature rise required is only several degrees. The cost of heating a pool using solar tube collectors only (for domestic purposes) may be prohibitively high. For large scale swimming pools, however, INLIGHT collectors may be an extremely viable supplement to gas or electricity.

21. Are solar tube collectors more efficient than flat plate collectors?
When comparing peak efficiency levels it may seem that there is little difference between flat plate and vacuum tubes, in fact flat plate may actually be higher, but this is during minimal heat loss conditions. When averaged over a year vacuum tube collector have a clear advantage. The key points are:

1.) Due to the cylindrical shape of the vacuum tube, the solar tubes are able to passively track the sun throughout the day. Flat plate collector only provide peak energy output at midday when the sun is perpendicular to the collector's surface.

2.) Air is vacuum from the solar tube to form a vacuum. This greatly reduces conductive and convective heat loss from the interior of the tube. As a result wind and cold temperatures have less effect on the efficiency of the vacuum tube collector.

3.) INLIGHT solar collectors can often be used in subzero temperatures without the system sustaining damage. Flat plate systems often require expensive and complicated "antifreeze" systems to be installed.

4.) Vacuum tubes are strong, long lasting, and should one be broken, inexpensive and easy to replace. If a flat plate collector panel is damaged the whole panel must be replaced.

5.) Due to the high efficiency absorption of solar radiation even during overcast conditions, combined with excellent insulating properties of the solar tube, solar tube collectors can heat water all year round (backup from gas and electricity is still required).

6.) Due to the various advantages of vacuum tube collector over flat plate collectors, a smaller collector can be used to provide the same heating performance. For example, a standard household of 4-5 people would usually require a 250-300L water storage tank. Depending on your location, only 30 vacuum tubes would be required to provide all summer hot water needs and a large percentage in other seasons.

7.) Flat plate solar collectors can produce similar heat output to vacuum tube collectors, but generally only during hot, sunny conditions. When averaged over an entire year, vacuum tube collector heat output per net m2 of absorber area, is between 25% to 40% greater that a flat plate collector.

22. Which collector is the best value for money?
Rather than looking at just peak efficiency levels when comparing solar collectors, cost per unit of energy produced is much more logical. For example: Although collector A may be 20% more efficient than collector B, if collector A is 30% more expensive, then in fact collector B may be a better choice, as per kWh of energy produced per day it is cheaper. When payback time is of concern, not only price per kWh of the product is important, but also of the end system. In this regard INLIGHT solar collectors provides a further advantage as INLIGHT solar collectors are very easy to install, and that can make a huge difference in terms of total install costs.

23. How does swimming pool heating system work?
1) What is a Solar Swimming Pool Heaters
You can significantly reduce swimming pool heating costs by installing a solar pool heater. They're cost competitive with both gas and heat pump pool heaters, and they have very low annual operating costs. Actually, solar pool heating is the most cost-effective use of solar energy in many climates.

2) How They Work
Most solar pool heating systems include the following:

3) Example of a solar pool heating system.
Pool water is pumped through the filter and then through the solar collector(s), where it is heated before it is returned to the pool. In hot climates, the collector(s) can also be used to cool the pool during peak summer months by circulating the water through the collector(s) at night.
Some systems include sensors and an automatic or manual valve to divert water through the collector(s) when the collector temperature is sufficiently greater than the pool temperature. When the collector temperature is similar to the pool temperature, filtered water simply bypasses the collector(s) and is returned to the pool.
Solar pool collectors are made out of different materials. The type you'll need depends on your climate and how you intend to use the collector. If you'll only be using your pool when temperatures are above freezing, then you'll probably only need an unglazed collector system. Unglazed collectors don't include a glass covering (glazing). They are generally made of heavy-duty rubber or plastic treated with an ultraviolet (UV) light inhibitor to extend the life of the panels. Because of their inexpensive parts and simple design, unglazed collectors are usually less expensive than glazed collectors. These unglazed systems can even work for indoor pools in cold climates if the system is designed to drain back to the pool when not in use. Even if you have to shut the system down during cold weather, unglazed collectors may be more cost effective than installing a more expensive glazed collector system.
4) Example of how a solar collector works.
Glazed collector systems are generally made of copper tubing on an aluminum plate with an iron-tempered glass covering, which increases their cost. In colder weather, glazed collector systems—with heat exchangers and transfer fluids—capture solar heat more efficiently than unglazed systems. Therefore, they can be used year-round in many climates. Glazed collectors also can be used to heat domestic hot water year-round.
Both glazed and unglazed collector systems should include freeze protection if they'll be used in colder conditions.
5) Selecting a Solar Pool Heater
A solar pool heating system usually costs between $3,000 and $4,000 to buy and install. This provides a payback of between 1.5 and 7 years, depending on your local fuel costs. They also typically last longer than gas and heat pump pool heaters. Your actual cost and payback depend on many factors. Therefore, before you purchase and install a solar pool heating system, you should do the following:

6) Installation and Maintenance
The proper installation of a solar pool heating system depends on many factors. These factors include solar resource, climate, local building code requirements, and safety issues. Therefore, it's best to have a qualified solar thermal systems contractor install your system.
After installation, properly maintaining your system will keep it running smoothly for 10–20 years. Consult your contractor and read your owner's manual for maintenance requirements. Your collector should require little maintenance if the pool's chemical balance and filtering system are checked regularly. Glazed collectors may need to be cleaned in dry climates where rainwater doesn't provide a natural rinse.

24. What size collector do I need?
 When determining what size collector you need, A rule of thumb is to provide about 1m2 of absorber area per person in the household. you must consider two key factors: insolation level and energy requirements. Energy requirement will usually take into consideration the volume of water and rise in temperature required. Once you know these factors you can determine the size of collector you require. The bigger the collector you have, the more hot water, but you should make an economically sound decision. Generally it is wise to select a size which will provide you with 90% of your hot water needs in the summer.

Although it may seem strange to use a value of only 90% for summer solar contribution, it is for good reason. It is normal to size based on 100% of your summer hot water energy needs, with a percentage provided throughout other months, lowest obviously in winter. That is based on normal water usage, but often, and particularly in the summer, water usage patterns may not be that normal, with cooler than normal showers taken in hot weather, and greater possibility of the house being vacant for one or two days each week (weekends). As such, using a target value of 90% will probably actually result in a system that is able to supply more than 100% of your hot water needs in the summer, without excessive heat production, which can lead to water loss via pressure release and a waste of energy.
INLIGHT Solar collectors come in a set of standard sizing of 12, 15, 20, 25, or 30, depending on your region. Of course you can also combine collectors to increase the size.

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