"Evacuated tubes are the most efficient solar heating."

Evacuated solar tubes are popular for homes with emersion heat tanks

Learn about evacuated solar tubes, a water-heating technology developed for northern European countries to heat water using passive solar energy.

Evacuated tubes work due to the sun's short-wave radiation converting to long-wave radiation. Installing this solar energy system will enhance your heating capabilities and bring it up to modern standards.

In a nutshell:

• Temperatures between 40-80° Celcius.

• Not suitable with a combi-boiler.

Evacuated tubes are super-efficient vacuums. The solar tubes retain heat gradually and pump it into a well-insulated hot water tank. Homes with solar heating benefit from reduced boiler usage.

My alternative to traditional solar heating is the PV-to-heat converter.

A popular solar technology before the advent of PV with heat converters

How do evacuated tubes work?

• 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 if the collector temperature falls below the cylinder temperature.

How do evacuated tubes work in the UK climate?

The UK receives 60% of the sun's radiation compared with the equator. Each square metre receive 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. Evacuated tubes are the most efficient solar heating technology, but PV-heating converters could be an option.

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?

Maybe. If you work with a Part P tradesperson, it may be possible in a DIY capacity. All evacuated tube installations must be carried out and commissioned by an accredited person.

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 an 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?

Most installations can be complete in one to two days.

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?

In most cases, we recommend updating the hot water tank to allow a secondary connection and improved insulation for an evacuated tube installation.

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.

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 offer 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.

Self-installing an evacuated solar tube system.

Health and safety should be a priority when self-installing evacuated solar tubes.

1. Scaffolding will be necessary up to the level of the guttering. This equipment will give you a safe working platform.

Make 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.

The collector array can 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.

Insulate with an Armoflex sheaf.

3. Route pipework to the pump station 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 to the pump station allows for expansion of the Glycol anti-freeze.

4. Some installations may require an upgraded hot water tank. Unvented or pressurised cylinders are typical, but a traditional vented tank with a secondary solar coil is usable too.

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 taking advantage of solar heating technology.