Installing a sophisticated control system can prove instrumental in unlocking the potential savings offered by a commercial solar thermal installation, as Stefan Gautsch explains.
Using renewable heating technology in conjunction with a condensing boiler system is proving a popular way of maximising economy for many organisations. However, in order to optimise operating efficiency, an intelligent controls module should be considered a key element of the complete system.

Because renewable technologies are a relatively recent addition to the market, there is a tendency for the boiler, solar and control packages to be specified and installed separately.

This, however, fails to take full advantage of the potential savings that a fully integrated system can offer where each element of the system is fully compatible with the others.

Used together, solar and condensing boilers can make an excellent partnership, combining the available energy from the sun, with a fuel efficient boiler to satisfy any additional heat requirements.

Manage energy usage

Adding a modern controls package that can precisely manage energy usage within a building, either through better zoned control, weather compensation or sequencing of multiple boilers will further increase the potential for fuel savings as well as increasing the lifespan of the entire heating system.

The overall efficiency of the system is very much down to the details of its design. This includes everything from the infrastructure of the building fabric to the provision of storage for hot water generated by the solar system. Incorporating a suitable control system should be considered a key part of this system design, as well as specified controls can help to increase the heating system's efficiency by up to 10 per cent.

A solar thermal system is primarily designed to meet hot water requirements, but in the right type of low temperature system, it can go some way to providing backup for the space heating within a building.

Up to 60 per cent of the domestic hot water requirement over the year can be met by the panels drawing thermal energy from the sun. A high efficiency or condensing boiler will be necessary to meet the majority of the heating load and to supplement the domestic hot water provision during the winter months.

A feature of the range of intelligent control systems many manufacturers are now able to offer is the intelligent solar optimisation function. By combining a boiler with a compatible solar thermal system and an intelligent control module, the system can be self-modulating. This ensures that, when enough solar energy is available, the boiler will not be called to action.

To ensure that the complete system is able to operate at optimum efficiency, a number of additional considerations should be taken into account when specifying the system requirements. These will also ensure that the end user is able to take advantage of the full functionality of their control system.

Each solar system must be designed and accurately sized to take into account hot water demand, heat requirement, insulation properties and fabrication of the building.

Three reasons for solar

After this there are three main reasons why solar should be considered for the hot water and heating specification; these are ethics, independence and economics.
While saving money and reducing the dependence on fossil fuels are key issues, we are increasingly finding that reducing carbon emissions is the key factor in the specification of solar systems.

This must be an aim for every responsible business as we all have to play a part in protecting the environment for future generations and the public sector in particular is tasked by Government to lead the way in lowering the carbon footprint of its buildings.

By referring to official records on weather patterns it is possible to provide realistic assessments of estimated fuel usage and fuel savings from the installation of solar collectors, either as a separate system for water heating or as part of a complete integrated heating and hot water solution.

To achieve this result, however, it is vital that the system is correctly sized, controlled and commissioned. Accurate sizing requires a realistic assessment of the hot water demand, which can be achieved by installing hot water metering prior to designing the solar arrangement.

To maximise carbon reduction, it is also important to avoid wasting the energy, which has been generated.

This means ensuring the secondary thermal storage and circulation system is properly insulated and effectively controlled. The fabric of the building is also an important factor here, and is often where the biggest heat losses can occur.

There is a tendency for solar installations to be oversized 'to be on the safe side', but this is not efficient as heating the domestic water beyond the requirement is a waste of energy.

It could be preferable in some cases to slightly reduce the output from the solar system and blend this with output from the boiler thereby boosting the temperature of the hot water to the required levels.

• Stefan Gautsch is design engineer at Buderus