Renewable heating technologies provide clean energy, reducing carbon emissions and improving a building’s performance, claim manufacturers. So why are so many buildings using renewable equipment reporting a performance gap between predicted and actual heat consumption? It’s all down to system design, argues Mike Hefford
The Government’s recent investment in eight major new renewable projects throws the spotlight once more on the importance and potential of clean, green, low carbon energy for the UK’s energy security and growth. The renewable electricity generated from the projects will be enough to power millions of homes and support 8,500 jobs whilst ultimately lowering fuel bills, claims Energy and Climate Change Secretary Ed Davey.
Mind the gap
In new building development, renewable energy equipment is often selected as the prime source of energy for heating and hot water provision, fulfilling the low carbon requirements of building regulations. With heating and hot water generation accounting for as much as 60 per cent of the total energy use of a building and 40 per cent of carbon emissions, renewable solutions such as heat pumps and biomass are widely viewed as the environmentallyfriendly option for reduced energy use and a lower carbon footprint. Yet worryingly, research into building performance evaluations reveals that many commercial and public buildings show a significant performance gap between the energy use predicted at the design stage and the actual energy consumption. According to a report by the design practice Aedas on energy use in non-domestic buildings, actual energy use is between 1.5 and 2.5 times higher than anticipated, with heat consumption between 1.5 and six times higher.
Renewable technologies are often specified alongside gas-fired condensing boilers to ensure reliable delivery of heating and hot water at all times. However, technologies can compete against each other if the system is not properly designed. It is therefore essential to factor in at the design stage how the chosen renewable technology will work for a particular building and how it will operate with additional components in the heating system rather than focus on the efficiency potential of individual products. Failure to consider the operation of the system as a whole could result in unexpectedly high operating costs when the low-carbon technology fails to perform as expected. Controls are an integral part of good system design and central to effective performance. They not only enable individual components to operate at their maximum efficiency but unite the heating technologies, optimising their combined operation and thereby enabling a building to achieve its greatest saving potential.
Improved product data
In order to achieve good system design and control, a welldesigned bivalent heating system requires good specification. Manufacturers can assist consultants by providing more detailed and more accurate data on their products and how they perform in real life conditions. This might require a change in evaluation measures for renewable equipment if the information is to support the design and specification of the most energy-saving system for a particular building. Data such as the primary energy ratio (PER) of a product, which calculates the relationship between the amount of primary energy used and the amount of energy delivered to the end user, might be valuable in evaluating the energy efficiency of a renewable heating technology. Take heat pumps, for example; while electrically- and gas-powered pumps may score equally in terms of the coefficient of performance, the PER calculation would place a gas absorption heat pump, which is powered by natural gas and uses environmentally friendly ammonia as its refrigerant, far higher in terms of carbon reductions than an air pump powered by electricity generated by a fossil-fuelled power station.
Maximising saving potential
The importance of good system design and integration is also crucial for effective refurbishment projects as many have existing heating systems in place. The first stage towards optimum energy efficiency in older buildings is to work out how to achieve the maximum efficiency from the heating system; the second is to assess how to use the energy input as effectively as possible. In such projects, the most common approach is to replace ageing boilers with high efficiency condensing or super condensing boilers, an effective measure that undoubtedly brings significant energy and carbon savings. However, why stop there? Depending on the nature of the building, it is worth considering if more can be done to maximise the building’s carbon and energy saving potential through complementary LZC technologies such as biomass boilers or heat pumps. Size right, design right, install right and control right are the four steps to achieving the headline efficiencies and avoiding higher than anticipated energy consumption.
Bespoke hybrid system
Each building is unique with its individual requirements, making each a separate challenge for consultants. Remeha has responded with a unique bespoke bivalent heating and hot water system that can be specially tailored to meet the needs of each and every building for maximum energy and carbon savings. Remeha Fusion Hybrid combines our environmentally friendly gas absorption heat pumps and high efficiency condensing technology with a fully-integrated, scalable building control system to ensure a high-efficiency performance of between 120 and 130 per cent NCV. The specially-configured building management control system can be easily integrated into existing building management systems, making it suitable for retrofit purposes as well as new build. The control system also has an integrated touchscreen control panel, the Remeha Touch, for operation and monitoring.
The technology is arguably here now to eliminate the energy performance gap from heating. Many forward-thinking manufacturers already offer ErP-compliant heating equipment supported by BIM files, both ahead of the mandatory implementation date, to assist the buildings services in improving efficiencies. Once the industry offers greater transparency in product performance data, with greater collaboration and sharing of knowledge, this will further facilitate smart system design and help eliminate the performance gap. Meanwhile, we at Remeha Commercial continue to innovate and challenge heating efficiencies, adding our unique bespoke hybrid heating and hot water systems to our ‘one-stop-shop’ product range, to support consultants and specifiers in the move to a low carbon future.
// The author is Remeha Commercial’s head of renewables //