FAQ'S

Is solar water heating a viable alternative to gas or electricity?

Solar heating, even though a most dependable technology, should not be considered as an alternative to gas or electricity, but rather a supplement, as there are some days when there is no sunlight or only a little sunshine. When averaged over a year, a correctly sized solar system can provide 85%-95% of a household's hot water needs. However, these systems, since provided with alternative heating power as backup, can be relied on all year round.

How long will it take to recoup my investment?

Depending on your location (solar radiation levels) and current hot water usage the annual electricity or gas saving will differ. However in a normal household that spends 25% to 40% of its electricity bill on hot water heating, the full cost of the purchase may be recouped as quickly as 1,5 -2,5 years in reduced bills. The SWG should provide reliable operation for many more years during which time you will definitely make considerable savings which can be more than the investment.

Can SWG solar collectors be used in cold conditions?

Yes SWG can be used in temperatures as low as - 30 Degrees C, although performance is greatly reduced in such extreme conditions. Good heat output is still achieved in mild sub-zero conditions.

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 through your local SWG distributor. Low pressure SWG will not work with a broken tube. All the high pressure units will operate with broken tubes but efficiency will be effected as the water will leak, so they must be replaced before continuing use. We will replace a broken tube within 24 hours.

Will water be heated on a cloudy day?

Yes. Although the heat output of the solar collector is reduced on overcast days it will still be able to provide heating due to the property of absorbing ultra infra red heat from the Sun. If it is a heavily clouded day or raining, then gas or electric back up may be required to be used to maintain water at the required temperature. This system will be automated with a thermostat so you don't have to worry about running out of hot water on a rainy day. However for a normal household this would only be necessary for about 10% in a year.

Can I use a solar collector with my existing hot water system?

Normally yes. Pipe connection with suitable valves can be used to allow you to use hot water from the solar heater or your existing unit. Our technical experts can provide you suitable guidelines.

Are the solar collectors noticeable on the roof?

SWG is a rooftop design. Our technical experts can provide you suitable guidelines.

Can SWG solar collectors be mounted on a sloped roof surface?

Yes they may be mounted on a sloped roof. Should your building necessitate such requirement, please revert back with complete details of your roof and our technical experts can provide you with suitable guidelines and a suitably modified support frame can be manufactured to suit your requirements.

Will the SWG solar collector be a fire hazard during hot, dry weather?

No. The SWG's components are all high temperature rated and non-flammable so even during strong sunlight, the system will not catch alight or give off any sparks. The majority of the solar collector's components are stainless steel, aluminium, glass or PUF. However, if there is a time when the system has become completely dry without any water, care should be taken to refill the system with cold water when the system is in cool conditions to avoid any damage to the tubes. Note that the aforesaid is not applicable to high pressure units.

Can the SWG solar collector heat water to a high enough temperature?

Yes, in good weather the SWG 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. Hence the sizing of a domestic system that can bring the cold water up to 60oC / 141oF in a single day in summer, is more than sufficient and if hot water is not used for one day, the following day the system will be boiling.

What maintenance of the solar 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 tubes clean. Should a tube be broken it should be replaced. This, however, is an inexpensive and easy job. Any "handy" person can install a new tube.

Can SWG be used for large scale hot water production?

Yes. SWG can be connected in series to provide large scale hot water production for 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 in banks of no more than 150 tubes, otherwise the water may boil. Mines all over are looking to reduce operational costs by utilising solar panels for change room boilers, drying rocks before it goes to the smelter etc.

Can I heat my swimming pool or Spa using an SWG solar collector?

SWG 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 (for domestic purposes) may be high. For large scale swimming pools, however, SWG may be an extremely viable supplement to gas or electricity.

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 evacuated tubes, in fact flat plate may actually be higher, but this is during minimal heat loss with hot ambient conditions. When averaged over a year evacuated tube collectors have a clear advantage. The key points are:

a. Due to the cylindrical shape of the evacuated tube, the sun is perpendicular to the surface of the glass for most of the day and IAM values actually increase away from perpendicular resulting in good heat output from morning through to late afternoon. Flat plate collector only provides peak energy output at midday when the sun is perpendicular to the collector's surface. High angles of sun incidence results in wasted energy 'reflected off' the flat glass cover.

b. Air is evacuated 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 evacuated tube collector. Cold outside air literally conducts valuable heat away from the warm collectors.

c. SWG 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.

d. Evacuated 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.

e. Due to the high efficiency absorption of solar radiation even during overcast conditions, combined with excellent isolative properties of the solar tube, solar tube collectors can heat water all year round (backup from gas and electricity is required for fewerf days in a year.)

f. Due to the various advantages of evacuated tube collectors 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 150 - 200L water storage tank. Depending on your location, only 22- 28 evacuated tubes would be required to provide all summer hot water needs and a large percentage in other seasons.

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

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. When payback time is of concern, price per unit of energy produced is the most important consideration, not peak efficiency levels. In this regard SWG provide great value for money.

How do I calculate what size collector I require?

Calculation of Size of Solar Water Heaters

The Size of any Solar water Heater is calculated by providing 25 litres per head (i.e., 1 bucket of water) plus 15-20 litres for pipeline wastage i.e. a family of 4 needs 25 x 4 =100+20= 120 litres.

We suggest the installation of a 210 litre SWG in a household of four.