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Solar Thermal Collectors

There are two types of collector: flat plate collectors and evacuated tubes.

Flat Plate Collectors

Flat plate collectors are composed of insulated flow tubes encased within an absorbing plate and surrounded by further insulation. This is all enclosed within a frame, usually aluminium or galvanised steel, and a transparent cover. The heat transfer fluid travels through the flow tubes, absorbing heat as it passes through. This then heats the domestic hot water.

Evacuated Tube Collectors

Evacuated or Vacuum Tubes are so-called because the absorber sits in a vacuum, significantly reducing the risk of heat loss, particularly in cold weather.

The tubes are made from glass - typically ultra-strong and heat resistant Pyrex with a double wall construction. One side of the tubes is covered in an absorbent coating and the other has a reflective surface; these work together to trap the energy from the sun. Inside each tube there is a copper heat pipe containing a glycol / anti-freeze mixture.

There are two types of evacuated tube collector: "direct flow" and "heat pipe".

In heat pipe technology, there is a second 'fluid circuit' running through the top of the tubes. The fluid in the copper heat pipe is sealed off from the fluid in the top. As the tube gets hot, the liquid in the copper heat pipe is vaporized; the hot vapours rise to the top of the heat pipe where the copper tip connects with a header pipe through which the top-layer fluid flows. The heat passes from the vapour to the fluid, which is then pumped through the heat exchanger in the cylinder.

The copper at the tip of the heat tube can reach well over 200�C easily heating water to 90�C on hot days and to 60�C even in the winter. This simple system is completely sealed and needs minimal maintenance over its 20+ year life-time.

In direct flow technology, the fluid running through the copper tube is pumped all the way around the system, passing through the heat exchanger in the cylinder, and thus transferring its heat directly to the water in the cylinder.

Flat Plate versus Evacuated Tube - Which one should I choose?

COST:	Flat plate collectors are generally cheaper per m� but produce less energy per area than evacuated tubes. A larger unit would be needed to produce an equivalent amount of energy. Furthermore, the size of a flat plate system is far less flexible than evacuated tubes which are constructed in a modular fashion. A much wider range of water demands can be accurately catered for by customised evacuated tubes. Therefore, we can only determine which system type would be the most cost effective for you when we know your hot water requirements and the potential energy you can expect to produce at your property.
EFFICIENCY:	Evacuated tubes are slightly more efficient than flat plate collectors as the vacuum ensures that heat loss is kept to a minimum. The efficiency difference is only really evident at low outdoor temperatures. The shape of the tubes also means that the collector is exposed to the sun for longer each day, giving more consistent heating even at lower temperatures. They can also be tilted by 15� to face South East, even when installed on East/West facing roofs.
INSTALLING:	Evacuated tubes are smaller and lighter than flat plates, making them easier to install in different locations and when the roof can only take a certain weight. Both types of collector can be installed on a flat roof with racking and evacuated tubes can also be fitted on a vertical wall with a specially adapted bracket. Evacuated tubes can be sized modularly, meaning they can be customised to specific hot water requirements by adding individual tubes Evacuated tubes can be effectively used on a split system when the only available roof space is East/West facing. Velux collectors can be fitted flush with the roof tiles to produce the most unobtrusive finish possible.
USAGE:	Flat plate collectors work well when the water only needs to be heated by a small amount. This makes them ideal for heating swimming pools. Evacuated tubes are very effective and are well suited to provide properties with high hot water demand.
PLANNING:	Flat plate collectors look similar to Velux windows (especially the units produced by Velux themselves), making them a popular choice for those worried about aesthetics. Their ability to blend in also means that they are more likely to get listed building consent, or planning consent in a conservation area.
MANUFACTURER ADVANTAGES:	FLAT PLATE COLLECTORS: Kingspan: Well-established company and offer unbeatable guarantees. Barilla: Most efficient of the flat plate collector options. Velux: Available with a number of accompanying products, producing an aesthetically pleasing installation. EVACUATED TUBES: Kingspan: Premium product available. Varisol system is highly customisable. Barilla: Good value-for-money (especially for larger installations).

In general, for most domestic hot water requirements (apart from pools) we recommend tube collectors. It is very important, however, to choose a high quality tube collector to ensure that the vacuum is not lost after a few years. See below for more information on our favoured tubes.

Our Flat Plate Collectors

Barilla F22AR:

Made in Germany by the largest manufacturer in Europe.
High efficiency.
Accompanying products are high quality.
Rated to temperatures far above the industry standard.
Guarantee of 15 years

Kingspan Marvel 2108 Flat Plate:

Manufactured in Turkey.
Produced and distributed by renowned renewable technology company based in the UK.
Collectors are efficient, reliable and good quality.
Unique patented technology to prevent stagnation issues.
Guarantee of 20 years

Velux:

A wide range of plate sizes on offer.
The Velux collectors come as part of a package, complete with cylinder, collector, control-unit and pump station.
Ideally suited to fitting in an in-roof scenario.
Most customisable of all the flat plate collectors.
Guarantee of 10 years

Our Evacuated Tube Collectors

Barilla TZ1800

Heat Pipe Technology
Manufactured in China by the 2nd largest manufacturer of solar thermal collectors.
High quality at competitive prices.
Easy to install and maintain as there is no need to drain the system.
Guarantee of 15 years

Kingspan HP200

Heat Pipe Technology
Manufactured in the UK to high quality standards.
The most efficient system available, capable of reaching high temperatures very quickly.
Vacuum assures that heat loss in minimised, even in cold weather and periods of lower solar radiation levels.
Easy to install and maintain as there is no need to drain the system to replace defective or broken tubes.
Unique patented technology to prevent the risk of stagnation.
Guarantee of 20 years

Kingspan DF100 and Varisol

Direct Flow Technology
Produced and distributed by renowned renewable technology company based in the UK.
Can be built modularly, making the units highly customisable.
Vacuum assures that heat loss in minimised, even in cold weather.
Unique patented technology to prevent the risk of stagnation.
Guarantee of 20 years

Our controllers

We use DeltaSol controllers from Resol. They are easy to use, are very reliable and have been on the market for 30 years.

Our cylinders

We recommend cylinders from two companies: Newark (copper) and Gledhill (stainless steel). We can also provide and install cylinders from Kingspan and Velux when required, or when the customer particularly requests them.

Copper cylinders are generally used with vented systems and steel cylinders are used with unvented systems.

Benefits of Copper:

Copper is anti-bacterial and can helps to prevent Legionella from forming.
Copper is a highly efficient heat conductor and can be up to 28 times more efficient than steel. Using copper for the heat exchanger coil in the hot water cylinder will ensure quick and efficient heat transfer.
Copper is a more flexible material to work with. It allows manufacturers to produce more versatile, and in some cases bespoke, cylinders.
Copper is 100% recyclable.

Benefits of Stainless Steel:

Steel is cheaper. This makes steel cylinders ideal for those installing solar thermal on a budget. The price of steel is also less volatile than copper on the open market. This means the chance of changing product costs is reduced.
Steel has a better tolerance to corrosion, even in hard water areas. Steel cylinders therefore come with significantly better product guarantees of up to 25 years, compared to just 2 to 5 years for copper alternatives.
Steel is more robust, making it ideal for high-pressure unvented systems. A very thick copper cylinder would be required to perform the same role.

Manufacturer		Material	Advantages
Newark		Copper	Company which specialises in producing custom and bespoke solutions for solar-ready cylinders. The units can be ordered with additional products, including immersion heaters and extra coils. 2 year guarantee (This may seem low but it is because the life span of a copper cylinder depends on the local water quality. Copper will deteriorate less in areas with soft water.)
Gledhill		Stainless Steel	Manufactured to meet strict British Standards, including: BS EN 12897 / BS6700 / Building Regs. G3 / Water Regs. Operates a quality management system. The accompanying EnviroFoam insulation is very effective and is less environmentally damaging to produce than other insulation options. Similar in quality to the more expensive Kingspan alternatives. 25 year guarantee
Kingspan	Tribune-Range	Stainless Steel	Premium quality ranges which meet British standards. Numerous models across the two ranges. All made of Duplex stainless steel. Fast reheat and high insulation levels, meaning they are very efficient. Ideal for multiple bathrooms or powerful showers. Complete package: just add pipework! 25 year guarantee
Kingspan	Albion	Stainless Steel
Velux		Stainless Steel	Only available as part of a Velux system package. Coated in environmentally friendly enamel to prevent corrosion, bacteria and lime-scale build up. CFC-free foam insulation. Easy installation and attractive design. 10 year guarantee (3 years for product accessories)

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