Modern Building Services

FEATURE HEATING Moreover, many homes would require their electricity supply to be upgraded to make it suitable for heat pumps. So there are limitations, but we shouldn’t lose sight of the fact that heat pumps still have an important role to play in the UK’s transition to net zero carbon. Their inclusion in a mixed heating system, for instance, can make significant inroads into carbon emissions. For example, there are now air/water heat pumps entering the market that are designed specifically for high output applications in commercial and industrial applications, used on their own or – more likely - as part of a hybrid system alongside gas-fired condensing boilers. It’s also worth noting that in industrial, logistic and ‘shed’ style retail premises, heat pumps can be incorporated into ventilation systems to provide highly efficient space heating and cooling. Optimum efficiency, minimum carbon For all of the reasons above, there aremany commercial, industrial and residential applications where inclusion of combustion heat sources is the only way to generate the required temperatures. Therefore, it’s important tomake combustion plant as efficient as possible, and alsomake sure that today’s boilers are ready for tomorrow’s alternatives to fossil fuels. One key element in this respect is control. Whereas a traditional boiler installation could be operated efficiently using some fairly basic control strategies, a mixture of heat sources requires a more sophisticated control strategy. Fortunately, newer control systems are designed to address this issue whilst also offering higher levels of modularity and connectivity – making it easier for end users and/or their sub- contractors to better understand their energy consumption. Alongside improved control, boiler design needs to incorporate features that reflect their potential use in a mixed heating system, as well as improving their inherent efficiency. For example, boilers in a mixed heating systemwill inevitably be firing less often and for shorter periods of time, often at part-load. Some new boiler designs, therefore, incorporate special technology in the heat exchanger 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. Crucially, when part of a mixed heating system, the boilers need to work with any flow/ return temperature difference (Delta T) for easy integration with existing systems. This is particularly important for retrofit efficiency projects. Also, we shouldn’t lose sight of the growing use of heat networks, driven by mixed source energy centres, where a maximum operating temperature of 95Deg.C by the boiler is often necessary. Fuel alternatives Given that combustion for heating is with us for the foreseeable future, there is a strong imperative to find suitable alternatives to fossil fuels. Hydrogen and biomethane 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’. Whilst the switch to 100% hydrogen may still be some way off there is every chance that many heating systems will be burning some hydrogen in the very near future. This assertion follows the announcement by the Energy Networks Association (ENA) – a trade association for energy companies – that hydrogen could be blended into the gas mains supply – up to around 20% by volume - by 2023. A similar approach is likely to be taken with biomethane. In the case of oil-fired 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. These changes have clear implications for specifiers and building operators considering new heating plant, as they will need to ensure a level of ‘future- proofing’ that can accommodate fossil fuel alternatives as they are gradually introduced. Summary Currently, there are several unknowns but it is clear that we will see many more mixed heating systems in non-residential applications, exploiting the benefits of heat pumps whilst mitigating their limitations. Over a longer period we can expect to see alternative fuels gradually replacing fossil fuels. As yet, we haven’t got precise timescales to work with so Hoval is proactively addressing these challenges with new boilers and heat pumps that will give end clients the future readiness they require. MODERN BUILDING SERVICES NOVEMBER 2022 11 More information can be found at www.hoval.co.uk