Are evacuated glass tube solar collectors easy to install?

Because the flat panel collector is larger it is considered to be more cumbersome to install whereas with the smaller size of the evacuated glass tube solar collector, installation is easier as the component parts are smaller and lighter. This also means a reduction in the installation costs.

Who will install the collector for me?

SEI maintains an extensive list of registered installers. To avail of the grant operated by Sustainable Energy Ireland you must use an SEI registered installer.

Where is your system manufactured?

The components in the Dennen Bos Sunsaver system are sourced from many countries. The glass tubes are manufactured, by our partner factory in China,( most evacuated tubes,even those which pretend to come from Europe, are manufactured in China). The Solar controller is manufactured in China. The cylinder is manufactured in England, the pump is German and the expansion vessel is Italian . The system has passed the European EN 12975 standard  for solar thermal collectors.

How long has this type of collector been in existance?

Pepole have been warming themselves with ths sun for many years. Following the energy crisis in the 1970s there was increased interest in using this energy to heat water. Evacuated tubes were created in the 1980s and, like many innovative products developed during that decade, they were very successful but came with a very high price tag.

The evacuated tube system was further improved in the early 1990s by Dr Yukun Pei. He took a number of advancements that were made in his work at the famous Massachusetts Institute of Technology (MIT) back to his native China. It was here that he shared the technology with a number of Chinese manufacturers, and the glass twin walled evacuated tube water heating system was born. Since 1998, Chinese manufacturers have been able to successfully train a  large workforce to conduct the skilled glass blowing techniques required to manufacture the evacuated tubes.

Are evacuated tube collectors more expensive than flat panel collectors?

Until recently evacuated glass tube solar collectors were considered to be more expensive than the flat panel collector, but now with modern production methods and economies of scale, the evacuated glass tube solar collectors have now become more affordable. The SEI grant now favours the evacuated glass tube solar collectors.

Which type is most efficient?

Evacuated glass tube solar collectors are more efficient during the marginal months. Both types work well during long, bright mid summer days but during the months either side of summer, the evacuated glass tube solar collector performs far better from, early morning till late evening, and so increases the length of time that you can obtain free hot water. A flat panel collector has a shorter maximum efficiency period, centred around midday when the sun is vertically overhead. Evacuated glass tube solar collectors are far more suitable for use in Northern Europe than the flat panel type.

What is the secret of the vacuum?

The secret of the evacuated glass tube solar collector lies with the vacuum which surrounds the absorber. This vacuum allows light to pass through and be absorbed by the absorber surface, here the absorbed light is converted to heat. Light will pass through a vacuum but heat cannot, so the heat that has been absorbed stays where we want it, and cannot escape by convection or conduction, back to the outside world. Flat plate collectors loose a significant amount of collected heat to convection and conduction. In other words, when the winds are cold, or it is raining, flat plates act like radiators and suffer from wind chill reducing the amount of heat harvested from the sun and are noticeably less efficient. The evacuated glass tube solar collector is insulated by its inbuilt vacuum and does not suffer heat loss in this way.

What does a roof mounted solar collector look like?

Visually, when mounted on a roof both types look like a roof window, but the evacuated glass tube solar collector is considerably smaller and more efficient. To obtain the same heat output, the flat panel variety would occupy a larger footprint on the roof than the evacuated glass tube solar panel.

What size and type of pipe should be used?

On a normal domestic single collector installation, DN 16 stainless steel flexible pipe is preferable as this makes the installation of the solar loop easier. However if the installation is to be expanded it is wise to consider upgrading the pipe to allow for the addition of extra panels in the future. With any installation it is sensible to locate the collector as close to the domestic hot water cylinder as possible.

What type of pipe insulation should be used?

 It is very important that the pipe insulation used can withstand the extremes of temperature that may occur in solar installations. High temperature pipe insulation such as K flex or Armaflex HT should be used. Standard central heating insulation could melt. On exposed external pipe work care should be to ensure the insulation is protected from the harmful effects of UV radiation. We have heard of insulation being robbed by resourceful birds, who obviously recognise the need for good home insulation! To guard against these we have found that if the insulation is covered with a good quality foil tape it is helpful with this problem.

What about anti-freeze?

For the U tube type of collector, a good quality anti-freeze like Sentinel R100 Solar Thermal Fluid should be used.

With the heat pipe model, the solar collector manifold is extremely well insulated; however some installations will require frost protection. There are two types of frost protection in common use.
If you live in a low frost area such as a costal area or other area which only receives occasional night-time frost the system controller has a frost protection circuit which can be enabled. With this system the sensor in the collector manifold registers when the temperature drops below 6 degrees. The controller then switches on the solar loop circulating pump until the temperature in the collector manifold reaches 10 degrees .This process continues until the threat of freezing is eliminated.
If the solar collector is being installed in an area which is prone to prolonged periods of freezing or has an unpredictable electricity supply, your installer might suggest that you consider filling the solar loop with a good quality anti-freeze like Sentinel R100 Solar Thermal Fluid. Anti-freeze may be added using a portable pumping unit which is disconnected when commissioning is completed,
When anti-freeze is used it is important that it is checked regularly to ensure the effectiveness of the freeze protection it offers, and that the anti-freeze is suitable for use in a copper solar collector and will not damage the copper pipe work or component parts. Once installed it is sensible to check the strength of glycol in the solar circuit to ensure the desired level of protection is available. Anti freeze can degrade and loose its effectiveness if you system overheats or stagnates
What about overheating?
The Dennen Bos Solar system is an extremely efficient and may overheat if the accumulated hot water is not used for a long time, during periods when you are on holiday for example. This can lead to premature breakdown of the anti-freeze is used in the solar circuit.
The most common way to deal this problem is to install a “heat dump circuit”. This is a usually a radiator in the bathroom which uses up the unused excess heat. When the system becomes too hot, a thermostat opens a three way valve, which diverts the hot water from the cylinder to the radiator, thus venting the excess heat to the bathroom.
Another method uses the fact that if the central heating pump is left on, (and the central heating turned off) the water circulating through the primary coil it will also dump heat.
(A greener method is to invite your neighbours in to use your excess free hot water while you are away!)
There is also the possibility that during normal use the water in the cylinder may overheat. This may present the problem of very hot water at the taps, this can be rectified by having a temperature regulating valve installed, and this can be set to ensure the hot water remains at a safe temperature.
Can I use a solar water heater for central heating?
Yes, but no!- In theory a solar collector collects the sun’s light and turns this into heat, so it would be possible to put together several collectors and heat a house.
But, in Ireland we are blessed with long hours of daylight during the summer months and during winter we have short days and long nights, and in winter we need central heating more than we need central heating in the summer! The way we try to size the collector is to give almost all of a households domestic hot water from the sun during the summer, thus saving on conventional methods of heating (boiler or electricity), and during the winter  the solar collector will assist your conventional method of heating water. If you were to size the collectors to heat a house during winter, you would have too far much hot water in the summer.
The most cost effective method is to install a 20, 30 or 40 tube collector and get nearly all of your hot water free from the sun during the summer and let the solar collector assist your conventional heating during the winter.
 What will the gross size of the collector be on my roof?
The 20 tube collector is 1.8m wide by 2,0m down
The 30 tube collector is 2,6m wide by 2.0m down.
You should allow approximately 0.1m for pipe fittings.
What size is the immersion backup heater in the Thermo Store cylinder?
The Thermo Store cylinder uses a 1.5 kW backup electric heater. By using a solar collector and using the Thermo Store factory insulated cylinder we are reducing  the amount of electricity we need to use.  Your electric heating requirements will be reduced by the addition of solar heat and increased levels of cylinder insulation, so a larger immersion is unnecessary. It is important to note that both the  DBSi or DBSn controllers are rated to switch 2 kW. Please consult your electrician if the DBSi or DBSn controllers are to be used with other immersion heaters.
What direction should my solar collector face?
Optimally solar collectors should face directly south (only in the northern hemisphere!), but they can face up to 45 degrees east or west of south without a significant decrease in performance. If this orientation is not available, we can supply an east / west controller which will regulate which collector is used depending on which collector is receiving sunshine. So in other words any direction except north (except if you live in the southern hemisphere!)
 
Why do I need a SWH when my heating heats my water?
 
SunSaver solar water heating can provide clean and free hot water for most of the summer months and will reduce the heating demand in winter. It is a great renewable resource which is freely available and requires little or no maintenance. Solar water heating is the easiest way to comply with the renewable energy requirements in the new 2007 building regulations where a minimum of 10 kW hr /m2 /annum supplied from renewable recourses.
 
Are most houses suitable for solar water heating?
 
Yes, most houses can avail of solar water heating provided the collector can get sunlight for a good period of the day. Most solar collectors are mounted on a south facing roof, out of the way, blending in with the roof line.
 
Is there enough sun in Ireland to make this worthwhile?
 
YES! Believe it or not a correctly sized solar collector will provide at least 60% of your domestic hot water requirements. The figure will be higher in summer and lower in winter,
 
Who will install it for me?
Your SunSaver supplier can recommend a trained, SEI approved, renewable energy installer who can undertake this task for you. The solar hot water system comes with a larger than normal water cylinder which replaces your existing copper cylinder in your hot press. The installation should take approximately a day and a half. Modern cylinders are factory insulated and loose very little heat , regardless of the heat source.
 
 
Will my solar collector  require maintenance?
 
Once installed the shape of the tubes and the occasional rain shower keeps the glass clean. In the unlikely event of a tube breaking, they are easily replaced. You should occasionally check the pressure to ensure there are no leaks in the solar loop.