Mind the performance gap
Energy demand is continuing to rise. Despite the drive to design low-energy and -carbon commercial buildings, results show that commercial and industrial buildings can consume as much as three times the energy that they were anticipated to use at the design stage. This ‘performance gap’ is currently a much-debated issue in the building services industry.
There is arguably a similar performance gap to be found in the heating facility service. According to the Carbon Trust, heating and hot water production account for over half our total energy use and around 40 per cent of our greenhouse gas emissions, no small amount for commercial properties. New developments are designed not to require much boiler power, but the nation’s high percentage of old, inefficient building stock represents a real challenge for boiler manufacturers, one which is vital to address if we are to make carbon reduction in the UK a real prospect.
In commercial buildings that still depend upon wasteful ageing boilers for heating and hot water generation, retrofitting a tried and tested, clean-burning, modern condensing boiler can more than halve energy usage and costs and reduce harmful greenhouse gas emissions by as much as 90 per cent. But here’s the rub – the efficiencies manufacturers quote on their condensing boilers are produced under test conditions and do not always reflect real-life operation. A boiler operates most efficiently when operated at low temperatures (30-50°C) and half load. When operated at high load and higher flow and return temperatures, the efficiency figure can drop to the standard 80 per cent GCV. In a scenario like this, even with the addition of a smart control to optimise the boiler’s energy delivery, some 10 to 15 per cent of the energy input is typically wasted. To tackle this inefficiency in energy output, it’s time to reconsider how we present boiler efficiency figures.
In the car industry, for example, manufacturers provide drivers with both the maximum fuel efficiency achieved by a particular model and a combined fuel consumption figure, an average of the efficiencies achieved in its typical mix of town and motorway driving, or what is known as its ‘urban’ and ‘extra-urban’ cycles. This is in order to provide a more accurate reflection of the energy performance of a car on the road and a realistic estimation of its fuel consumption.
While this system is admittedly not without its flaws, isn’t it time boiler manufacturers adopted a more realistic representation of achievable fuel efficiencies? Depending on the weather, the season and how they are operated, boilers have to adjust and modulate – which they do with differing success. If heating manufacturers were to provide not only the maximum combustion efficiency figure of a boiler but also its seasonal efficiency, an average of how it performs across the different seasons and conditions, it would be easier to calculate more accurately the predicted energy performance. This would be an important first step towards increasing energy efficiency in heating, encouraging smarter system design to allow a boiler to achieve its full potential and ‘Blue Efficiency’ levels.
At Farley Junior School, for example, smarter system design from VSRW more than halved the school’s energy consumption from 660,995kWh to 273,148kWh with carbon savings in the region of 53 tonnes a year. The school’s ageing atmospheric boilers were replaced with three Remeha Quinta Pro 115 condensing boilers on a cascade system in the first phase of the project. Low temperature radiators and fan heaters were added the following year to allow the boilers to operate at the reduced maximum temperature of 50/40°C, achieving maximum efficiency and energy savings at lower installation costs than conventional systems.
Challenging accepted efficiency levels also prevents complacency and encourages innovation. At Remeha Commercial, we are looking beyond condensing technology with our ‘super condensing’ heat recovery systems which deliver full time maximum combustion efficiency regardless of the primary circuit temperatures.
The advantages of such a system have been proven at Knauf Insulation’s Cwmbran plant, where two Remeha Quinta Eco Plus 115 heat recovery systems were installed last year to replace old atmospheric boilers. Energy data shows that even in the extraordinarily cold winter and spring, annual gas consumption plummeted from 574,560kWh to 186,960kWh, with 74 tonnes of carbon saved in one year. In a complete reversal of the typical performance gap, the actual savings of 67 per cent exceed the predicted reduction of up to 40 per cent.
Given the question mark that hangs over our national energy security and the powerful environmental, legislative and financial reasons to reduce our high energy consumption, improving our energy efficiency – our ‘fifth fuel’ – is crucial. We in the heating industry should use our experience and knowledge of our products to provide more representative energy performance figures that will help accelerate the nation’s progress towards a sustainable future by reducing unnecessary waste.
Mark Northcott is managing director of Remeha Commercial
