heating, ventilation & services
Realising the full potential of biomass
By Ross Donovan, managing director of Asgard Biomass.
T
he potential benefits of biomass heating can be considerable, whether installing into a new building or retrofitting into an existing
premises. As biomass can be derived from a whole variety of animal and plant waste – usually wood logs, chips or pellets – it is generally considered to
be ‘carbon neutral’, as the amount of CO2 released in the combustion process is the same as that absorbed during its life cycle. Not surprisingly, with its Excellent rating under the BREEAM points system and the Code for Sustainable Homes, biomass technology is becoming particularly att- ractive to architects, builders and contractors, as one of the most effective ways of meeting their renewable energy targets. However, this is still a relatively new market
and in the general enthusiasm to be ‘green’ and ‘carbon neutral’, it is important that specifiers carefully consider the practicalities of specifying biomass so that its full potential can be realised.
Location, location, location The first major consideration should be the loca- tion of the project, which will usually determine the type of biomass fuel used and whether it can be delivered and stored safely. Wood chip fuel can be superbly cost effective and efficient for farms, factories or country houses situated in rural loca- tions, near to renewable woodlands with the facil- ity to chip on site, provided there is sufficient space for large storage bunkers and safe access for delivery tipper trucks to unload. Wood pellet fuel is usually more appropriate for schools, nursing homes or commercial buildings situated
in urban locations, as it requires less storage space (typically 1m³ of wood pellet has the same energy content as 4m³ of wood chip) and can be easily and conveniently blown into the store through pipes. Wherever the location, it is important to estab-
lish the availability of a reputable local pellet sup- plier and allow sufficient access for delivery vehicles, particularly if the project is located on a busy road or on narrow residential streets.
Size and specification matters The most successful new build proj- ects always take into account the specific requirements of a biomass system early in the building design or planning stage before construc- tion works have begun. By doing so, specifiers can avoid most potential installation problems, usually caused by allocating an area for the boiler and store, which is too small, awk- wardly shaped and poorly accessible. It is easy to under specify the amount of space
a biomass system actually requires. Pellet stores need, at the very least, to be large enough to accommodate the pellet supplier’s minimum blown delivery quantities (usually six tonnes) –
and the larger the store, the greater the efficiency and cost savings of bulk delivery. On the other hand, it is easy to over specify the
‘Wood chip fuel can be superbly cost effective and efficient’
size and output of the boiler itself, by treating it as if it were an oil or gas fired system. Specifiers wishing to take advantage of the exceptional effi- ciencies of a biomass system should always look to satisfy the base load demand of a building so that the boiler can operate continuously at full strength without having to fire on and off. It is also important to remember that most towns and cities are ‘Smoke Control Areas’, under the ‘Clean Air Act 1993’, and so wood chip/pellet burning appli- ances installed in these areas must be certified to EN 303-5 and hold an exemption certificate.
As with any heating system, a certain amount
of maintenance is required. Although biomass boilers do produce some ash (approximately 0.7 kg of ash to every 100 kg of pellets), this does not pose a problem if the ashbins are emptied regu- larly as, once properly installed, biomass systems are generally very easy to maintain and operate.
Delivering a turnkey solution As the renewable energy market continues to grow, and more manufacturers, contractors, installers and end users recognise the benefits of biomass technology, it is important that there is not an equal rise in the instances of poorly speci- fied and malfunctioning installations. Most opera- tional problems arise from insufficient knowledge of the complexities of biomass, as compared to traditional oil, gas and coal fired heating, and the need to consider all the potential problems at the planning or early build stage. Furthermore, as the boiler, pellet store and necessary components are often sourced and installed by different suppliers, there can be the question of accountability if there are any prob- lems. Many of these issues can easily be avoided by appointing a single specialist company, with sufficient expertise and experience in biomass technology to take complete responsibility for the design and installation of both the boiler and woodchip/pellet store, through to the ongoing maintenance of the entire system.
enq. 208
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