The energy-efficiency opportunities of refurbishment
Refurbishment projects provide a magnificent opportunity to make significant improvements in energy efficiency, but only if a series of pitfalls are avoided. Wayne Rose explains.
The energy savings that can be achieved by carrying out a successful HVAC refurbishment are frequently under-estimated, with cost savings amounting to many thousands of pounds. For example, the replacement by Lancashire Constabulary of an old oil-fired boiler house with four new offsite integrated plant rooms, has reduced the energy bills for the Hutton Hall site in Preston by over £245 500 a year. The equipment paid for itself in just 12 months, and carbon emissions at the site have been reduced by 744 t a year.
But why is it that so many refurbishment projects fall short of delivering this sort of return?
This article aims to highlight the most common reasons, and suggest practical ways of capitalising on the energy efficiency potential of the refurbishment project.
Projects often fail because they ‘tinker’ with the existing equipment, or reuse ageing pipework with unacceptable distribution losses. This builds in an element of inefficiency from the outset.
One of the factors in the success of the Lancashire Constabulary refurbishment project was that it tackled inefficiencies inherent in the existing infrastructure. The centralised oil-fired boiler, with two calorifiers for supplying hot-water to the Hutton Hall Police Training Centre, proved insufficient to manage the site’s demand some years ago, and new heating systems were installed for the accommodation blocks. In 2006, it became necessary to install replacement systems for the remaining buildings at the site — including a sports hall, administrative centre, firing range, dining room and teaching block.
The energy manager at the time, Ed Palmer, carried out a feasibility study comparing three alternative approaches, with detailed estimates of payback period and ongoing energy costs. The best solution proved to be the installation of four new integrated plant rooms, made offsite by Armstrong.
The project also avoided the very common pitfall of ‘like-for-like’ replacement of equipment. Improvements in efficiency were therefore achieved through a combination of:
• Specification of best-in-class system components, including Armstrong IVS variable-speed pumps and condensing boilers;
• Integration of components by the equipment manufacturer using advanced control methodologies to automatically ensure the maximum wire to water efficiency at part loads.
The project also used this opportunity to prepare the site for increasingly stringent environmental requirements in the future by moving away from oil towards a gas-fired system with reduced carbon impact per kWh.
Returning to the site some years after the installation of the plant rooms it has been possible to compare actual energy data with the feasibility study. The projected energy consumption proved to be remarkably accurate. The actual cost-savings, however, have been higher than estimated due to increases in the costs of oil that were not anticipated back in 2006. The results are listed in the table.
The project also managed to avoid a number of other common pitfalls.
Many projects start out with good intentions and an energy-efficient equipment specification, but things go wrong before installation.
Budgets often get squeezed, and the HVAC spend is cut late in the project. A few pounds saved in upfront capital cost usually equates to higher energy bills throughout the lifetime of the equipment. Because this may not be immediately apparent to the site owner, the practice is all too common.
As awareness of the impact of technology choices on energy consumption grows, with the introduction of the CRC Energy Efficiency Scheme, it will undoubtedly be possible for HVAC system designers to put forward stronger arguments to retain their original intentions for sites.
The final factor is one that outdated approaches to system design refuse to lay down and die. Some replacement systems are still being overspecified, with the installation of unnecessary standby capacity, instead of exploring parallel pumping or avoiding wastage in the form of over-sized pumps or unnecessary pipework.
As a result, the commissioning throttles an oversized pump to achieve the desired design flow. This, of course, hikes up the head. The wasted head continues throughout the pump’s lifetime. The pump motor has to work harder, absorbing more energy than planned, to create a head (and maintain an operating point) that nobody actually wanted in the first place!
In summary, there are a number of key factors to consider, but the refurbishment project remains a magnificent opportunity to make significant improvements in energy efficiency when a client is willing to consider the sums. And the figures often speak for themselves.
Wayne Rose is marketing director of Armstrong.