Why the heart of the heating system is still the gas-fired boiler
Technologies such as combined heat and power and biomass boilers should not be regarded as distractions to ensuring that the gas-fired boiler plant that is still required operates as part of an efficient system — even before other technologies are added. Stuart Turner of Hamworthy Heating gives an insight.
In November last year Amber Rudd, Secretary of State for Energy & Climate Change, set out the new direction for the UK energy policy. Within this policy she hailed the UK gas supply as being amongst the cheapest and most secure in Europe. She also reminded us that heat accounts for around 45% of our energy consumption and a third of all carbon emissions. She also emphasised the importance of energy efficiency to reduce costs, improve productivity and competitiveness.
Echoing her words, something needs to be done to tackle energy use in heating in the long term, and I believe gas-fired boilers can help significantly with improving energy efficiency in commercial buildings. Making small changes in the heating system can make a considerable difference.
Helping to drive energy efficiency in the boiler industry was the introduction of the Energy Related Products Directive (ErP) last September for products that use energy. This legislation had a massive impact on the commercial heating and hot-water industry, as it set out minimum efficiency criteria for many products, including gas-fired boilers. The efficiency criteria effectively wiped out the use of atmospheric and non-condensing boilers for the sub-400 kW market.
2015 also saw the introduction of the Energy Savings Opportunity Scheme (ESOS) — a mandatory energy audit for large enterprises (non SMEs). The audit highlights how energy efficient an organisation is, in the hope they will act on the data to make improvements.
|By being inherently more efficient than large-output single-module old boiler, both at full and, more importantly, part load, smaller-output newer condensing boilers can achieve huge reductions in energy bills.|
But why is the Government doing this?
It recognises that lots can be done to improve the efficiencies of our existing buildings at a relatively low cost. Improvements in efficiency will lessen our impact on the environment and help meet the UK’s legally binding target of slashing current greenhouse-gas emissions to 160 Mt of CO2 equivalent by 2050.
There is not a one-size-fits-all approach when it comes to commercial-heating design, and each building needs to be reviewed in its own right. Renewable-energy products such as biomass boilers and combined heat and power (CHP) are very effective for the right building and location. When it comes to biomass boilers, careful consideration needs to be given to the location. Extra space will be required for the fuel store and easy access for delivery of wood for fuel. CHP is ideal for district-heating schemes because a large unit can supply several buildings with a proportion of their electrical demand as well as heating.
However, with most of these systems a gas boiler is also needed to support the renewable energy source at times of peak load, for security in case of failure or when service and maintenance is required.
One of our customers, Philip Kiss, building-services engineer at Canterbury City Council, is tasked with reducing energy use across council-run buildings in Canterbury and advocates the use of gas condensing boilers for doing this. He says. ‘I take a considered view at each site to review what option would be best suited. I may look at renewable-energy products, but I do believe we need to reduce the demand before changing the method of delivery. This is why we have installed high-efficiency condensing boilers across many of our sites.’
We know it is quite possible to achieve real, tangible savings right away by upgrading boilers to newer more efficient, condensing boilers.
A recent ‘Review of operational productivity in NHS providers’ saw some noticeable difference in the energy costs between two NHS providers. This was because of excessive oil use due to the age and condition of the boiler, which the hospital was unaware of. Indeed we have seen an example where a hospital could save over £1 million on its gas bills over the life of the boiler plant by changing from large output single-module old boilers to smaller-output newer condensing modular boilers. This is due to the ability of modular boilers to match the load as closely as possible without any wastage of energy.
|In this school heating installation a modular gas boiler (right) supports the biomass boiler (left) for peak loads and provides security in case of breakdown or failure.|
Selecting the right product is just the start, and I believe this is one of the problems of ErP. It is forcing customers to buy an efficient product based on static data such as efficiencies — but does not ensure that the product is set up and operating correctly.
Condensing boilers installed in a system set at traditional operating temperatures of 80/60°C flow/return will only achieve marginally higher efficiencies than a high-efficiency non-condensing boiler. If operating temperatures are reduced, typically to 50/30°C, or the temperature differentials can be widened to offer a lower return temperature (80/50°C) then there are significant efficiency gains to be had.
The boiler is very much still at the heart of the heating system, but just like the human body it needs to have efficient supporting equipment and regular maintenance to help it do its job effectively. The water in the system needs to be regularly cleaned as just a 1 mm layer of limescale build up in the boiler heat exchanger can reduce efficiency by 7.5%. Pipework needs to be free of debris to enable water to flow easily and efficiently. Intelligent controls are the ‘brains’ of the operation and needed to manage the flow and make sure the right amount of heat is delivered at the right time without overshooting and causing wastage.
Plus, we cannot fit and forget. Regular service and maintenance will help keep the heating system and boiler at optimum efficiency and ensure it has a long life.
Stuart Turner is national sales manager with Hamworthy Heating.