With attention focused on cutting carbon emissions with renewable and sustainable technologies, Paul Hardy, managing director of Andrews Water Heaters and Potterton Commercial, gives a reminder that traditional basic system design principles still apply
One of the main drivers of the EU energy policy is the Eco-design of Energy-using Products (EuP) Directive expected to be fully effective in 2011.
This will take into account the efficiency and sustainability of the whole heating and hot water system rather than individual products, with the stated aim that the best energy efficiency is obtained from the best available technology.
Efficient domestic hot-water production in buildings is extremely important, as their heating and cooling accounts for 24% of all Europe-wide carbon emissions. Demand for space heating has diminished in recent years because of global warming and improved building insulation, materials and design.
Hot water consumption, both in homes and commercial buildings, has risen, reflecting improved hygiene alongside users' expectations of instant and constantly available hot water a high flow rates.
Direct-fired water heaters were introduced to the UK more than 30 years ago. And the principles of separating the hot water from the space-heating load, and decentralising production closer to the point of use, are generally accepted as providing the most efficient solution for commercial buildings.
This efficiency has been enhanced by applying condensing technology, which now achieves operating efficiencies in commercial water heaters of up to 109% (net).
The lower running cost of dedicated hot-water equipment, when compared with central plant boiler/calorifier configurations, was first proven by the catering industry, with volume hot water needed at peak times.
The message quickly spread to larger-volume peak users with multiple hot-water outlets, such as hotels, sports facilities, hospitals, educational and military establishments.
Separating the heat load also has seasonal advantages, enabling shut down of the main heating boiler during summer months, eliminating part-load inefficiencies. It also reduces standing losses from the calorifier and long pipe runs that are no longer necessary with independent direct-fired high-volume units, installed in zones or even closer to the point of use.
A system of this type offers improved operating efficiencies, as boilers are sized and dedicated to the space heating load, while water heaters are sized correctly for their specific demand, delivering substantial fuel savings over the traditional boiler/calorifier installation.
In fact, in a trial conducted in 1997 by North Yorkshire County Council at one of its schools, two Andrews standard-efficiency gas-fired Hi-Flo storage water heaters were shown to use about 65% less gas compared with the traditional boiler/calorifier solution replaced.
Notably, ahead of the Kyoto agreement, this was a groundbreaking improvement in terms of running economy, fossil fuel consumption and carbon emissions.
Since then, the challenge has been to improve on energy savings further still, while providing greater flexibility in system design. This has been achieved through applying condensing technology to both non-storage and more recently storage water heaters.
A leading hospitality company managing major brands in hotels, restaurants and health clubs, working towards reducing carbon emissions in compliance with Part L2 of the Building Regulations, recently carried out a performance comparison trial involving replacing standard gas-fired storage water heaters with the best of the new condensing technology available.
Existing Andrews standard-efficiency gas-fired Hi-Flo storage water heaters were replaced with two MAXXflo stainless-steel condensing storage water heaters. Results during an initial four-week period showed the new units used about 16% less gas. And monitoring for a further four weeks showed possible energy savings of as high as 20% a year. This, together with lower NOx emissions, significantly reduced the carbon footprint of the test installation.
Because the laws of physics
limit the extent to which conventional technology can achieve greater efficiencies, Baxi Commercial Heating is facilitating specialist technical support, bringing together its compatible brands such as Andrews and Potterton Commercial, combining advanced condensing capability with low- and zero-carbon renewable and sustainable solutions.
Most renewable technologies require some form of back-up from conventional boilers or water heaters to bring system temperatures up to the required levels.
For example, SOLARflo, the commercial solar-thermal water-heating package, transfers the heat from solar energy absorbed by the collectors into a thermal store, where the temperature is topped up, as required, by conventional direct-fired condensing water-heating equipment.
The solar energy reduces the amount of fuel required to reach the water outlet temperature by pre-heating the cold-water feed to the water heater via the indirect solar cylinder.
In order to exploit the optimum performance potential of this and other low- or zero-carbon technologies to the full, it is essential that the proven system design principles of separation and decentralisation and use of the most advanced conventional system components, such as direct-fired condensing water heaters, be employed.
www.andrewswaterheaters.co.uk