With the advent of Part L 2006 of The Building Regulations, renewable energy technologies, such as biomass boilers have become an integral part of almost every new building. Stephen Laws, technical director at Clyde Energy Solutions, considers the issues surrounding the specification of biomass boilers for heating and hot water in commercial applications.
GOVERNMENT initiatives for sustainable energy systems are providing a real incentive for all sectors of the market to take a greener approach, from private developers to public sector specifiers.

Biomass is considered to be carbon neutral - its combustion does not add to the existing carbon cycle, unlike burning fossil fuels which re-introduces carbon that has been stored for millions of years.

Biomass is one of the oldest sources of fuel for mankind, and still one of the most abundantly used worldwide.

Biomass is usually applied to a huge range of solid organic fuels, ranging from specifically-grown energy crops (such as straw, willow-rotation coppice and wood) to organic by-products of manufacturing or land management (including wood pellets and wood chips). Wood pellets are the most refined biomass fuel, being made exclusively from compressed sawdust and wood shavings.

An important factor in the selection of an appropriate fuel is the calorific value. This can range from as much as 17MJ/kg for wood pellets to as little as 8MJ/kg for green softwood.

A key factor in the difference is the moisture content of the fuel. Wood products are composed of long chain hydrocarbons that have to undergo pyrolytic decomposition into short chain compounds to produce heat. Before this can happen, all moisture has to be driven off, which takes a percentage of the internal energy of the fuel.

Logically, the greater the moisture content of the fuel, the more energy will be used for this instead of creating usable heat. Wood pellets have a carefully-controlled moisture content, typically around 10% by volume, whereas wood that has been air-dried for at least a year will contain a minimum of 20% moisture.

Key advantages for wood pellets over other wood-based fuels are significantly lower storage, transportation and handling costs, and also a consistent and reliable heat output. Currently, wood pellet fuel suppliers in the UK are tending to pitch the price a little below that of 35 second heating oil (for a comparable calorific value). This is not the case in some European countries where wood pellet burning is an established technology and higher volumes mean prices are much lower than oil and gas.

Complete package
Biomass is still a developing market in the UK and, as with any new technology, potential users tend to look to suppliers for a complete solution. This is reflected in Clyde's approach to developing its biomass boiler package, which includes advice on specification, commissioning, installation and maintenance. Clyde will tailor a complete package to your specific requirements that includes boiler, storage silo and automated pellet delivery system.

The company also recognises that although there is growing interest in renewable energy, some users may not want to feel locked in to this type of system.

So unlike many dedicated bio-fuel boilers on the market, Clyde's Trio biomass solution is a regular high-efficiency boiler with interchangeable burners which can be switched from wood pellet to natural gas or oil burning if required at any point in the future.

Therefore, a secure heat supply can be ensured without the need for an additional, fossil fuel boiler. As an added benefit, this standard configuration also ensures a highly competitive price.

Safety first
Advanced control of heat output and safety considerations are of paramount importance today. Although biomass may be an age-old fuel, our expectations of combustion technology should be no less than for gas or oil.

The biggest danger for a biomass boiler is back-burning, particularly when it has an automated fuel feed system providing an uninterrupted conduit all the way back to the storage silo.
Incoming European legislation will stipulate at least two levels of protection against back-burning for pellet burners.

Pre-empting this, Clyde already has three levels of protection for the burner - safety shut-off valves on the fuel feed, an internal water sprinkler system and physical disconnection of the pellet supply.

Growing market
There's little doubt that demand for environmentally sensitive approaches to commercial heating and hot water is set to grow in our bid to reverse, or at least delay, the damaging effects of climate change.

As developer of a range of sustainable energy products, Clyde is finding that biomass boilers are proving one of the most popular options.

However, Clyde believes it is important the industry doesn't see this market simply as a huge sales opportunity.

If renewable energy is going to be truly successful in the UK then it is essential that companies offering these products take the time to look at the overall requirements of each application and consider the practicalities of the system before securing a sale.