Key steps to maximising heating efficiency

Published:  06 August, 2014

renewable energy, RHI, Renewable Heat Incentive,Remeha Commercial, absorption, heat pump, Fusion
The effective use of renewable energy — Mike Hefford.

Using renewable energy effectively requires thinking the ‘renewable way’ to achieve the predicted carbon savings in heating — says Mike Hefford of Remeha Commercial.

At last, some good news for the buildings services industry. In fact, the future is verging on rosy according to the latest Construction & Housing Forecast Bulletin issued by AMA Research, which reports a growth in the UK construction industry and a predicted rise of 30% in future total construction output in the next five years. Elsewhere, the April quarterly report from Glenigan reveals a rise in the number of construction projects from this time last year, with offices up 34%, retail up by 28%, and hotels and leisure up by 15%.

For the building-services industry, the challenge remains to achieve ever-higher efficiencies for our buildings combined with ever-lower carbon emissions. Within services, heating is the single largest user of energy in the UK and its main CO2 polluter, responsible for half the energy consumption of a building and over half of the UK’s total carbon emissions.

Recent tightening of energy-efficiency requirements in Part L of the Building Regulations means that new-build developments are designed to require less energy for heating, with the low-carbon requirement often fulfilled by tried-and-tested renewable technologies such as biomass or heat pumps.

Addressing the energy efficiency of our notoriously ‘inefficient’ existing stock is equally important if we are to achieve our environmental targets. Here again, renewable technologies may play a part in lowering the building’s carbon footprint, depending on the nature of the building and the system in place — either as the main provider of heating or as a bolt-on to the existing heating system to maximise the building’s carbon saving potential.

While the benefits of renewable technology are clear, it is important to remember that this is sophisticated equipment that requires thorough knowledge and understanding if the heating system is to deliver the anticipated savings.

Biomass boilers with outputs from 35 to 290 kW have replaced oil-fired boilers at RAF Brize Norton.

Building-performance evaluations have revealed a significant gap between the predicted energy usage and the actual energy consumption, with heat consumption being as much as 1.5 to 6 times higher than anticipated. A performance gap can also occur on refurbishment projects, where heating equipment frequently fails to achieve the headline efficiencies quoted by manufacturers. If the system does not deliver the predicted efficiencies, the temptation can be to blame the equipment when, in reality, the fault often lies with the design or specification.

From our years of experience working with renewable and condensing technologies, here are the five steps that we at Remeha have identified to help avoid an energy-performance gap.

1. Size right. Carrying out an accurate heat loss calculation of the building is the essential first step. Throughout the process, it is important to ‘think renewable’. Avoid basing the heat-loss calculation on the existing equipment as this will result in over-specification and failure to achieve the maximum efficiencies.

What output is required? With biomass, the solution might be to specify two lower-output biomass boilers rather than one larger one, using both in the winter months and just one in the summer.

2. Design right. Allow the system to operate the ‘renewable way’ at lower temperatures and design accordingly. Heat pumps, for example, work well with underfloor heating on new-build developments due to the low water temperature. On retrofit projects, consider designing in such a way as to maximise the energy from the renewable source. This might mean recalculating the number of radiators and resizing for lower flow temperatures in order to deliver the higher efficiencies. Including buffer vessels in the design for pre-heating hot water will also increase the efficiency of the system.

3. Install right. Poor installation can lead to the low-carbon technology failing to perform as expected, which will result in higher-than-expected operating costs. Or on bivalent systems, the two technologies may end up competing against each other, which, worst case scenario, could result in the renewable technology failing to operate at all. Where possible, try to use the same supplier for both technologies, as their knowledge of the two components will support smarter system design and installation.

Teaming up a gas-fired absorption heat pump with condensing boilers enables Remeha to produce tailored solutions for buildings.

4. Control right. Controls are an integral part of good system design and central to effective performance. Advanced controls also unite the two technologies in the system, optimising their combined operation and savings potential.

5. Commission right. Allocate sufficient time and budget for this important last step in the overall design concept. Hydraulic, combustion and controls commissioning is crucial to ensure high performance, reliability and efficiency of the heating system.

Responding to the need to address the energy performance gap in heating, Remeha has developed a one-stop, bivalent heating and hot-water system that combines gas-fired absorption heat pumps and high efficiency condensing boilers with a fully-integrated, scalable building-control system that can be specially tailored to meet the specific requirements of a building to maximise energy and carbon savings.

Called Fusion Hybrid, each solution is bespoke, meeting the particular needs of a building and addressing the five key steps above.

The specially-configured control system not only unites the technologies but can be easily integrated into an existing building-management system, making it perfectly suited for retrofit purposes as well as new build.

The control system also has an integrated touchscreen control panel for easy and accurate operation and monitoring, helping ensure a consistently reliable, high efficiency performance of between 120 and 130% NCV with carbon reductions of up to 40% compared to traditional gas equipment.

With the arrival of ever-more efficient products, the technology is arguably here now to eliminate the energy-performance gap from heating. As the economy begins to grow, we at Remeha look forward to using our knowledge and expertise, and our renewable solutions and condensing technology to support consultants and specifiers in producing well-designed systems to deliver the promised savings for our buildings.

Mike Hefford is head of renewable technologies at Remeha Commercial.

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