Flat Panel V Evacuated Tube

Thermal image showing heat loss from
a Flat Panel (left) and no heat loss
from an Evacuated Tube Panel (right)

Evacuated Tube Solar Hot Water Panel

These top-of-the-range solar panel heat collectors are suitable for heating domestic hot water, underfloor heating, swimming pools, etc - even in the winter! One unit is adequate for an average household (3-4people), and it is modular, so you can add more if required. A single panel is sufficient for a 200litre cylinder, but you can fit 2 or more for high water usage, or for heating swimming pools or underfloor heating. Some types of renewable energy are only available in certain locations, however free solar heating is potentially available to almost every house in the UK! Every house should have one -really! And with an overall efficiency of almost 80%, they are much more efficient than electric photovoltaic solar panels (efficiency of 7-15%). And if we compare them on a like-for-like basis, the price of a Solar Water Heater is around 30p/watt (compared to £6+/watt for solar photovoltaics!)

The vacuum tube solar panel has been around for over 10years, and has proved to be reliable and dependable. The vacuum tubes consist of a double wall glass tube (made from strong borosilicate glass ie pyrex) with a space in the centre which contains the heat pipe. The sun's radiation is absorbed by the selective coating on the inner glass surface, but prevented from re-radiating by the silvered innermost lining. This is in effect like a one-way mirror which has been optimised for infra-red radiation. In fact it is very efficient, of the sun light's energy hitting the tube's surface, 93% is absorbed, whereas only 7% is lost through reflection and re-emission. The presence of the vacuum wall prevents any losses by conduction or convection - just like a thermos flask. Because of this, the system will work even in very low temperatures, unlike traditional flat plate collectors. This is why this system can be used to heat up water at the South Pole Antarctic Science Base - where ambient air temperatures can drop below -40°C

Commercial applications for solar panels include, dairies, metal processing and anything else that uses a lot of hot water.

Large solar panel arrays can heat considerable quantities of water even through the winter months, reducing your energy bills significantly.

Swimming Pools

Swimming pools are an ideal application for solar water heating, as the temperature required is quite low - under 30°C. Most installers will recommend flat plates to keep the price down - because the amount of panels required is much larger than for heating domestic hot water - however, if you can buy a high efficiency evacuated tube solar panel for the same money - you might as well enjoy solar heated pool water all year round - instead of just in July and August! A rule of thumb each panel will heat 8m2 of pool area. A 40m2 pool would only need 5 solar panels. Compare this to the cost of heating a pool for a year!

How Much Heat Will I Gain?

Average Daily Irradiation (Insolation) Figures for Each Month of the Year:

(Solar energy reaching each 1m2 of the earth’s surface at UK latitudes)

Key Benefits of Vacuum Tube Solar Panels:

• High temperature output even in cold weather
• Warms water even during winter
• Produces heat even in overcast weather
• Higher efficiency and greater installation flexibility with heat to many of the more expensive brands on the market - as the tubes and headers are all manufactured in the same factory by an OEM supplier.

Solar Water Heating FAQ.