Evacuated solar tubes were popular with homes with an emersion water tank
Evacuated solar tubes are a water heating technology, developed for northern European countries to heat water tanks using passive solar energy. Not suitable for homes with a combi-boiler.
Evacuated tubes, commonly known as solar tubes, are the most efficient traditional flat-plate panel. Installing this solar energy system will enhance your traditional heating system and bring it up to modern 'building regulation' standards too.
The evacuated tube system heat-up due to the sun's short-wave radiation output converting to long-wave radiation to a temperature of 40-80° Celcius.
A word to the wise.
In the past, we fully advocated for these great technologies, but today suggest adopting PV instead. I recommend installing photovoltaic solar panels working alongside a heat converter.
"A popular solar technology before the advent of PV with heat converters."
The benefits of solar heat.
Evacuated tubes are super-efficient vacuums that retain passive heat from the atmosphere. This system is ideal for northern European climates and so efficient that restrictions to temperatures of 85 degrees Celsius have to be applied.
A significant factor in a system's performance figures is how well-insulated the hot water tank is. Beware that not all installers upgrade the tank, and this omission will affect the year-round performance.
Homes with solar heating benefit from reduced boiler usage and boiler maintenance.
Questions about evacuated tubes
Most homes are suitable. If you have a S/SE/SW or east/west facing roof space, then great.Your internal plumbing needs to be checked for compatibility too.
A solar tube system heats up due to the sun's short-wave radiation output converting to long-wave radiation. This process creates heat.
The variable speed controller circulates based on temperatures within the panel.
The pump circulates a Glycol solution through the hot collector and backs down through a heat exchanger.
The system automatically shuts down when not in use, or when the collector temperature is lower than the cylinder.
Do evacuated tubes work consistently in the UK climate?
Evacuated tubes are the most efficient solar heating technology, but not as useful as PV-heating converters.
The UK receives 60% of the sun's radiation compared with the equator. Each square metre of the UK receives between 900 to 1,300 kWh annually. All can be captured and diverted into your hot water tank with evacuated tubes.
Evacuated tubes use a thermos flask principle that allows each vacuum tube to get hot regardless of external air temperature.
What about Combi boilers?
Combi boilers aren't possible in most cases. We would need to re-install a hot water tank. Most homes with Combi's won't have the space to install a hot water tank.
Can I install evacuated tubes myself?
In most cases no. However, if you're Part P electrical accredited, then it may be possible to install in a DIY capacity. All evacuated tube installations must be carried out and commissioned by an accredited MCS installer only.
Is there a danger that it could get too hot?
The system may never rise above 85° Celcius.
Why update my hot water tank?
Older 'copper' hot water tanks run exceptionally inefficiently, especially after many years of use. Limescale will reduce performance even further. When installing evacuated tubes, it's essential to establish a modern more efficient tank to get the most out of your system.
Will it contribute to my central heating?
We would need to check your management system is suitable. In most cases, evacuated tubes can contribute to your central heating via underfloor heating.
How long will it take to install?
Only a few hours in most cases.
Do I require planning permission?
Listed buildings, conservation area homes, national parks may require permission. Please consult with your local planning officer.
Do evacuated tubes work on cloudy days?
This question depends on the density of the cloud. In average cloud density, solar panels use passive energy. With dense cloud cover, probably not.
Can you upgrade my hot-water tank?
Does your tank has an unused twin coil? In most cases, we update the hot water tank to allow a secondary connection to the evacuated tube system.
How much CO2 will my system save?
Around half a tonne each year, but this is dependent on how much hot water gets used and how you heat the water at present.
How long do evacuated tubes last?
A system will easily last twenty-five years.
DIY evacuated solar tubes kits
Evacuated solar tubes are second-generation technologies manufactured to modern and MCS-accredited standards. A-frames are available for ground-mounted installation.
System requirements:
Tank size: 150-250 Litres
1 x Evacuated tubes collector. 1 x Roof fitting kit 1 x 25 Litre expansion vessel. 1 x Expansion installation kit. 1 x Controller & pump station. 1 x 20 Litres Glycol fluid. Connectors. Twin-coiled tank.
Specifications:
2 SQM Length: 1642mm x Width: 1392mm x Height: 102mm. Aperture Area: 2.0 m2. Efficiency: 95%. Max Power 1236 W.
3 SQM Length: 1642mm x Width: 2082mm x Height: 102mm. Aperture Area: 3.0 m2. Efficiency: 95%. Max Power: 1858 W.
"When working with heights, electrics, and plumbing, always use the correct safety equipment or work alongside an accredited professional."
The basics.
Solar tube technology includes a patented Low E glass. These use a unique 'low-iron' glass formula that has reduced reflective properties and increased absorption.
The glass surface has 360 degrees absorption ability to give better performance than flat-plate technologies. The reason is heat retention and production at lower outdoor temperatures.
Each tube is just like a thermos flask. Once the heat is in, it becomes trapped.
Installation guide.
For every 100-180 Litre tank size, you will need two m2 arrays or three m2 for 180-300 Litre.
The direct-flow systems.
Direct flow solar tubes come as a self-assemble for more comfortable and quicker installation times. The direct-flow system benefits from higher performance with fewer vacuum tubes.
The heat-pipe systems.
Heat pipes come with a self-built solar tube collector. This heat-pipe technology gives an excellent performance.
1. Scaffolding will be necessary up to the level of the guttering. This equipment will give you a safe working platform.
Making measurements from the inside of the roof space/loft may be helpful.
Choose the shortest route for your pipework to the hot water tank.
2. The roof anchors are fixed into the roof batons. You can remove a tile or slate to gain access. Measuring diagonally from corner to corner will help square up the anchors, ready for the aluminum mainframe.
The best part is attaching the header and tubes to the mainframe. Some styles of evacuated tube collectors allow you to piece together the array.
Pre-assembled collectors will need to be hoisted up using a roofers pulley system. Some self-installers may want to work alongside a roofing company.
An inlet and outlet hole for the pipes can be drilled through the tile/slate and resealed using roof-grade silicone.
Exposed pipework is insulated by an 'Armoflex' sheaf.
3. Routing pipework down towards the pump station can be done with 'ready insulated' pipe lengths containing the temperature sensor wire or more traditional copper pipe.
If the latter, then use 'compression' joints.
Connect the pump station to the correct hot and cold feeds.
An Expansion Vessel gets installed next to the pump station so, allow for this area.
4. Some installations may require an upgraded hot water tank. Unvented or pressurised cylinders are typical, but a traditional vented tank installed with a secondary solar coil is fine.
5. Now decide where to locate The Controller.
6. Pressurising the system with a Glycol fluid can be done with a plumber's pump unit. Flushing the system out of all air bubbles is essential, and the pressure of three bars is standard.
The final operation is to set up the Management Controller and test the temperature sensors are reporting accurate readings.
Check pipework and connections.
7. Enjoy a cup of tea. You've joined a growing army of people taking advantage of solar panel technology.
PV & water heating
