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n the light of recent global climate events, it is now clear that climate change is something we need to take seriously by reducing carbon emissions. Given that the boiler has traditionally been the primary source of heat for buildings and industrial processes, it follows that the future design and application of boilers needs to evolve. There are some who predict boilers will be phased out completely, but this is unlikely within the next few decades due to lack of viable alternatives.


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With the growing acceptance that climate change is a real threat there is growing pressure to change the ways in which we heat buildings. This has an inevitable impact on the design of boilers in the future, says Ian Dagley, general manager of Hoval


Through its Heat and Buildings Strategy, the UK government has put forward a boiler upgrade programme, promoting the use of low carbon technologies – with the main focus on heat pumps. However, as discussed in more detail below, there are limitations to the use of heat pumps with current building stock.


So while boilers are here to stay for quite a while, we can expect to see new generations of boilers incorporating greater flexibility. Where mixed heat sources are in use, for instance, the boilers will inevitably be firing less often and for shorter periods of time, often at part-load. To address this, boiler manufacturers are upgrading their designs to deliver optimum efficiency under all firing conditions.


A good example of this is a new range of condensing boilers that incorporates several new efficiency features. The already efficient heat exchanger, for instance, now employs special technology to generate turbulence on the heating gas side. This turbulence increases heat transfer and boosts efficiency by as much as 20% compared to conventional gas boilers. Furthermore, the ability to work with any flow/return temperature difference (Delta T) delivers optimum flexibility for easy integration with existing systems, supporting retrofit efficiency projects. With a maximum operating temperature of 95˚C they can also be used in district heating/heat network applications as part of a mixed-source heating system.


New generations of boilers also continue to drive down NOx emissions to minimise their effect on air quality.


BOILERS & HOT WATER The changing face of heating


Alternatives to gas and oil


Recognising that combustion will continue to play a role in heating systems, there is a lot of interest in alternative combustible fuels to the traditional gas and oil fuels. Biomethane and hydrogen are the main contenders for replacing natural gas, and hydrogen was included in the Prime Minister’s 10- point carbon plan – the second point being to ‘drive the growth of low carbon hydrogen’. To that end there are several projects underway to assess the use of hydrogen in a number of heating scenarios, ranging from boilers to gas cookers. Certainly, boiler and burner manufacturers are already working to ensure their products will be ‘hydrogen-ready’ when the time comes.


Whilst the main focus is on gas, there is also interest in finding alternatives for oil-fired combustion plant. A promising candidate appears to be hydrotreated vegetable oil (HVO). Recent research has shown HVO to be a direct ‘drop-in’ replacement for gas oil used in large combustion plant, and a partial ‘drop-in’ replacement for kerosene in residential heating systems, with some minor adjustments to the burner.


Heat pumps Hoval roof ventilator 14 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JANUARY 2022


As noted earlier, the Government is keen to make wider use of heat pumps, in the light of the growing generation capacity of the renewable energy sector. As a company that designs and manufactures both boilers and heat pumps we can certainly see considerable scope for the latter, but there are also issues that will limit the breadth and speed of their application. For instance, heat pumps operate at lower temperatures than boilers and will therefore emit less heat if used with radiators or other heat emitters that have been sized to use hot water from a boiler. This can be overcome either by using larger heat emitters or significantly increasing the thermal insulation of the building envelope (or both). These options have clear cost implications which are not fully addressed by the grants the government is introducing for replacing boilers with heat pumps.


Engineers within the industrial sector are also trying to include air source heat pumps (ASHP) within their systems and processes but are experiencing the same limitations on water temperature. However, ASHPs can be used for space heating with ventilation units in industrial buildings, providing both heating and cooling into the workspace. An added benefit is the whole system is then classed as carbon zero. ASHPs can also be used to pre-heat water in a wide range of scenarios to reduce boiler outputs.


Taking control


While there is considerable potential for the wider use of both air source and ground source heat pumps, we are a long way from these becoming the dominant heat source. In the meantime, heat pumps still have a valuable role as part of a mixed heating system.


However, this too brings its challenges, insofar as a traditional boiler installation could be operated efficiently using some fairly basic control strategies, whereas a mixture of heat sources requires a more sophisticated control strategy. To address this, heating controllers are now being introduced that deliver new levels of modularity and connectivity, whilst also presenting a simple interface to the people who will be commissioning the system, and to those who will be using the system on a day-to-day basis. An integral internet connection that monitors the system and informs the end client when servicing is required helps to ensure that efficiency is maintained through the life of the boiler.


Summary


There can be no doubt that the design of heating products and systems is changing rapidly – and needs to do so if the UK is to achieve its Net Zero transition aspirations. The increased flexibility of boilers and other heating plant, alongside more sophisticated control and monitoring, will play a major role in meeting these objectives.


www.hoval.co.uk Read the latest at: www.bsee.co.uk


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