Heating Solar and biomass
> George Fletcher, technical sales manager for different renewable technologies to work effectively with
woodboilers at Viessmann, believes the advantages of each other and with conventional plant.’
biomass in commercial applications are particularly He adds: ‘Some boiler and heat pump
meaningful in off-gas areas where, he says, an controllers already allow for easy integration of a solar
installation can offer a lower total cost of ownership as thermal contribution.’
well as a reduction in carbon footprint. Combined heat and power will be important to
He adds: ‘In industrial situations, where wood biomass, while solar thermal systems could become
is processed – for example, kitchen and joinery combined with photovotaic ones, according to Lelyveld:
manufacturing – the benefits of biomass are huge as ‘These combined panels could make more efficient
the waste can be used to heat the factory. This reduces use of limited unshaded roof area, but have generally
or eliminates the heating bill, reduces landfill costs, and lower efficiencies than their standalone, uncombined
reduces transport. However, for the domestic market, counterparts – PV and solar thermal.’
I believe that the only viable route for biomass is to Alan Hogan of Kingspan Renewables believes that,
install district heating schemes. over the next five years, solar-driven air conditioning
‘As fossil fuel costs rise, which they will do, then will become more the norm, using absorption chillers:
biomass boilers will become more appealing. During ‘In domestic applications, we will see more solar-
the next 10 years we would expect to see many more assisted heating systems. With current research and
pellet boilers installed in larger and also in older improvement of compact storage materials, such
domestic properties.’ as zeolites, silica gels and other thermo-chemical
As to what the future holds for solar and biomass, materials, the performance of solar-assisted heating
Brown says: ‘Technical developments will be systems will greatly increase without having to use
Our sector
in intelligent controls and integration solutions to allow large-volume thermal stores.’ l
must be ready to
deal with a surge
Case study Carbon-neutral biomass heating for National Trust
in demand for
As part of its drive to reduce carbon emissions
solar thermal across its estate, the National Trust has replaced two
systems in
oil-fired boilers at Sudbury Hall in Derbyshire with
a pair of 150kW STU wood pellet biomass boilers,
2010 – James
manufactured by Hoval.
Parkinson First, the existing oil boilers and oil tank were
removed from the designated cellar space. Working
with installer Instatherm, which also supplied the
pellet feed system and underfeed stokers, Hoval took
a turnkey role in managing these works through to
the commissioning of the new boilers.
The pellet hopper, located adjacent to the boilers, Biomass boilers are installed at Sudbury Hall, Derbyshire.
is manufactured from a special fabric and mounted
on a steel frame. The fabric is designed to allow air The level of the pellet feed within the transfer box
to pass through while retaining dust, so the hopper is regulated to maintain a break or gap between
does not need to be vented during filling. the delivery auger at the bottom and the fill system,
At Sudbury Hall, the wood pellets are delivered which transfers pellets from the fuel store to the top
pneumatically into the fabric storage silo, which of the transfer box via a separate auger or pick-up.
holds around seven tonnes of wood pellets. Pellets The delivery auger is also fitted with two separate
are transferred to each of the boilers via a dedicated safety thermostats to protect against fuel burn-back.
auger in another cellar room adjacent to the fuel Combustion air is supplied from one of two
store area, where they are fed into the respective fans fitted to the boiler. The forced draught fan is
transfer boxes of each stoker. mounted on the floor adjacent to the delivery auger
The stoker automatically adjusts the fuel feed and has a motorised damper arrangement fitted to
to match the boiler load. Continuous oxygen gas its inlet. An induced draft fan is fitted in the ductwork
monitoring of the flue gases is designed to ensure at the outlet of the boiler, which draws secondary
close control of combustion, as the air supply is combustion air into the furnace of the boiler as
adjusted to match the fuel feed. well as assisting with the flow of the products of
The Hoval boiler comprises a welded steel shell combustion through the boiler.
with a water jacket surrounding an oval combustion Air supply is regulated (via a lambda probe
chamber. A dedicated delivery auger meters wood mounted in the flue ductwork) to match the fuel feed
pellet fuel into the boiler at the desired rate. It into the boiler. Any incombustible material or ash
collects wood pellets from a hopper mounted at the collects on a hearth and requires removal – typically,
rear of the boiler. every other week.
46 CIBSE Journal November 2009 www.cibsejournal.com
CIBSEnov09 pp42-44,46 SolarBio.indd 46 23/10/09 13:15:37
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