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With schools under pressure to make dramatic reductions in their carbon
emissions, they need to consider cost-effective, ‘quick win’ options for
their heating and hot water. Ian Dagley of Hoval explains.
Now that the government has stated an intention that all schools should be
carbon-neutral by 2012, there is a very strong imperative to make wider use of
low and zero carbon (LZC) heating technologies. At the same time, the chosen
systems need to be relatively straightforward and easy to operate for the
maintenance staff responsible.
In addition, the variable nature of renewable energy sources such as solar
energy presents something of an engineering challenge. For example, there will
be times when solar heating is able to meet all hot water requirements and there
will be times when it needs ‘topping up’. Similarly, the heat available from air
source or ground source heat pumps can vary with the outdoor air temperature
or the temperature of the ground.
All of which means that easily controllable back-up sources of heat are required
to maintain comfortable temperatures in the rooms and ensure a plentiful supply
of hot water. Here, boilers are the obvious answer and these could either be
biomass boilers or ultra-efficient gas-fired condensing boilers – or a combination
of the two.
Here, wood burning biomass boilers can make a significant contribution to a
school’s carbon footprint, as wood can be considered as a carbon neutral fuel.
Although carbon dioxide is released during combustion, this is equivalent to the
carbon dioxide that was ‘fixed’ by the plants while they were growing just a few
years earlier. In contrast, with fossil fuels we are releasing the CO2 that was fixed
over a period of millions of years in the space of just a few hundred years.
It’s also worth noting that wood-burning boilers are now very sophisticated and
able to offer very high efficiencies as well as ease of use. These were both
important considerations for Caerphilly Council, when it replaced four old coalfired
boilers at Pontllanfraith secondary school with three 350kW STU woodburning
boilers from Hoval. New stokers and feeders were also installed,
enabling the pellets to be fed automatically to the boilers to provide precise
control of heat output. The boilers are linked to a control system which brings
them on in sequence as and when required.
“Although wood has a slightly lower calorific value than coal, the new Hoval
boilers are more than 90% efficient, compared to the 68% efficiency of the coalfired
boilers, so we are achieving significant improvements in efficiency,”
commented John Davies of the council’s Property Service’s department.
Similarly, at Bowbridge Road Primary School in Newark, BioLyt biomass boilers
are designed to minimise input from the school’s maintenance staff, an important
consideration for any school where such resources are limited – and especially
so in primary schools where support staff are often shared between schools.
Consequently, incorporation of features such as self-cleaning, automatic fuel
feed and automatic ash removal in the boiler all help to keep maintenance costs
down.
At the same time, it’s important to address the individual needs of each school
and use the most appropriate technologies to achieve optimum efficiency. So, for
instance, in some circumstances it will make sense to combine biomass boilers,
or other LZC technologies, with high efficiency condensing boilers, such as
Hoval’s UltraGas.
Condensing boilers require a relatively low water temperature returning to the
boiler to achieve maximum condensing of the water vapour in the combustion
gases, to extract additional heat. Thus, any systems using low water
temperatures, such as underfloor heating or low temperature fan convectors can
provide very high efficiencies when used with condensing boilers.
Clearly, though, this multiple heat source scenario is a more complex situation
than simply using boilers as the only heating plant. The system needs to be
configured so that optimum use is made of each heating technology – and this
needs to happen automatically using sophisticated controls.
As a company that manufactures biomass boilers, solar heating systems and
heat pumps – as well as ultra-efficient gas and oil fired boilers - Hoval has vast
experience of providing integrated, optimised systems that give maximum
performance throughout the year. This results from a combination of engineering
expertise and a profound understanding of each technology, backed by
advanced controls systems that we have developed to address these challenges.
In addition, we are able to offer comprehensive packages that go far beyond the
supply of equipment to encompass every stage of the project from initial design
right through to final commissioning and ongoing maintenance. We also have
considerable experience of working with local authorities and individual schools
to ensure that individual requirements are fully addressed. |
