01 Dec 2010 12:12:05
Carbon reduction and energy efficiency..
With all the eyes focused on carbon emissions prior to Cancun, it’s vital not to lose sight of the need to combine carbon reduction with energy efficiency.
Reducing carbon emissions is generally associated with an increase in energy efficiency. But, it is possible to reduce such carbon emissions while still operating inefficient systems.
A biomass boiler, for example, reduces carbon emissions because wood fuels are close to carbon neutral, but the biomass boiler should be energy efficient. Fortunately, modern biomass boilers are very efficient (up to 92% for the better designs), but as with all the building services plant their energy efficiency will vary with the nature of the system they serve. For instance, they are able to cope effectively with variable heat loads but not, perhaps, as a gas-fired condensing boiler.
Biomass boilers will operate at maximum energy efficiency when combined with a steady base load. Consequently, there will be occasions when a mix of biomass and conventional boilers gives the highest overall energy efficiency in relation to the way the building is used and demands it makes on its heating systems.
Other considerations also need to be taken into account in the design of such systems, including local planning consents that require a percentage of renewable energy sources, and the desire o f the end client to be ‘seen to be green’. And, as a result there may be an imperative to consider the use of other renewable heat sources, such as solar thermal and heat pumps, as part of the overall mix.
The best solution in terms of energy efficiency is to decide which renewable and conventional heat sources will work together in a controllable fashion
With new build projects, there may be more scope to make wider use of renewable heat sources, as early collaboration at the design stage can help to ensure the fabric design reduces heating loads.
In refurbishment projects, where the requirement for consequential improvements under Part L of the Building Regulations is likely to encourage the use of low-carbon technologies, this can be more challenging. For instance, if the central plant is being replaced but the distribution system and the heat emitters remain unchanged, the original design water temperatures may need to be retained.
Finally, the key to arriving at the best solution in terms of energy efficiency and carbon reduction is to decide which renewable and conventional heat sources will work together in a controllable fashion. Moreover, these choices need to be made in the context of the nature of the building and how it is used on a daily basis, lo