Renewable energy and fossil fuels in harmony

The era of bivalent heating systems — Mark Northcott.

Mixing conventional and renewable heating technologies can lead to huge carbon savings and a significant boost in energy efficiency, especially in refurbishment projects says Mark Northcott.

Gas-fired condensing boilers are tried and trusted heat generators that have proved themselves over many years, offering outstanding performance in a range new-build and refurbishment applications.

They have made — and, indeed, continue to make — an enormous contribution to achieving greater efficiencies and fewer harmful carbon and NOx emissions in buildings. Their siting flexibility and high efficiency mean these boilers remain an exceptionally effective way to save carbon, NOx, fuel, time, money, hassle and effort.

Although the technical development of condensing equip­ment has gone just about as far as it can, improvements in controls, footprint and ancillary kit have enabled boiler manu­facturers to continue to make significant advances.

The controls packages on many of our own boilers, for example, allow the customer to read and adjust actual and set values on the built-in digital display (which also, incidentally, pro­vides normal operating and fault code in­dication to make the installer’s job easier).

The intelligent advanced boiler control (ABC) con­tinuously monitors boiler conditions, varying the heat output to suit the system load. It also varies the heat output to maintain operation in the event of negative influences on the system, thereby reducing nuisance lockouts that can require costly return visits to site.

Other innovations, too, mean that the condensing boiler continues to be an attractive proposition. For example, our new Quinta PRO wall-hung condensing boiler allows installers to replace an old, inefficient boiler easily with up-to-the-minute, efficient heating technology.

Modern modulating boilers are suitable for room-sealed or open flue applications and contain optional weather compensators that communicate directly with the boiler controls to make full use of its modulating capabilities, ensuring that the boiler closely matches the system demand at all times to reduce running costs and save energy.

Nonetheless, despite a vast array of enhancements that have been, and continue to be, made to condensing boilers, I believe that mixed technologies are set to change the future of heat generation in the UK. I am talking about renewables, particularly in the form of solar, biomass, and heat pumps.

The right choice of renewable energy offers remarkable environmental benefits. It can be consumed without depleting global resources and produces few polluting emissions. On top of this, the technology itself can offer impressive performance in terms of energy efficiency.

The trouble is that renewable technology has a long way to go before it can match the heating performance of a condensing gas-fired boiler installation.

Biomass boilers offer the potential to achieve carbon neutrality. This 550 kW Remeha-Gilles biomass boiler has replaced oil in a Norfolk School and reduced CO2 emissions by 177 t a year.

There is, however, a way to maximise the output of a heating system — combining the advantages of con­ventional and renewable technologies in a mixed heat-generation system.

This ‘bivalent’ arrangement involves combining two or more separate heat sources into a single heating scheme. So, for example, it might mean designing a heat pump, solar thermal or biomass boiler system as the primary heat generator, supported by conventional condensing boilers on the coldest days of the year. This arrangement enables the system to take advantage of the best attributes of both the conventional and renewable heat sources.

Indeed, my view is that the days of specifying a single heating technology may be numbered. I believe the future is mixed technology.

Bivalent heating systems are particularly effective on refurbishment projects because older buildings often enable the designer to take full advantage of the renewable source. For example, many Victorian buildings already have an old coal bunker that would be perfectly suited for storing the fuel for a modern biomass boiler.

Technology has developed to the point where retrofit systems can be made pretty much as efficient as a bespoke new heating system with the right controls such as weather compensation or sequencing controls in a multi-boiler configuration.

So, combining a condensing boiler with a renewable solution offers the potential to boost financial and energy savings while, at the same time, decreasing carbon and NOx emissions. Such a system can easily be retrofitted since there is no need to make costly and time-consuming alterations to the building. All these attributes make it an attractive and realistic option.

However, I have one caveat. I would argue that, if you are considering designing a bivalent heating system, it pays to use the same company to supply both the conventional and renewable technology in order to ensure a coherent approach that will enable the systems to work together at their optimum performance.

Manufacturers familiar with both conventional and renewable heat sources are best placed to offer the right advice when it comes to combining the systems, and they can guarantee that their equipment will work together at the optimum level.

Mark Northcott is director of commercial products with Remeha.

Remeha’s Quinta Pro range of boilers enables up to 107 kW of output to be delivered from a single wall-hung boiler, with more in multiple configurations, for renovation and refurbishment projects without having to replace existing pipework.
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