Responding to the urge to reduce energy use
The key elements in responding to the carbon 60 challenge — Mike Lawrence.
The UK Government’s intention to reduce carbon emissions by 60% by 2060 is helping everyone agree that energy must be used more efficiently. MIKE LAWRENCE examines ways of deliveringThe need for energy efficiency is now high on everyone’s agenda There are three driving forces. • The environment — climate change etc. • The cost of energy. • Worries about the political stability of energy-producing areas. The priority in which organisations hold these forces varies. However, one of the conclusions that everyone comes to is the same — energy must be used more efficiently. This requirement is encapsulated in the UK Government’s intention to reduce carbon emissions by 60% by 2050. Improvements
In building services, there are two axes on which improvements will result in increased energy efficiency — equipment and control. Equipment encompasses individual components and total systems. Achieving an efficient system requires the right mentality at the design stage and for the design team to have a good interface with those responsible for the hard building shell. In practice, this requires co-ordination by an expert project manager. Ideally, the outcome will be sensible duct runs, sensible positioning of plant rooms etc. It should also result in the selection of equipment that is energy efficient. This can mean a higher first cost, which is more than paid back by lower running costs. There is a motivational problem in this area because capital budgets are rarely organised so that money can easily be transferred from the recurrent budget to the capital budget. Indeed the payer of capital expenditure may well be a separate legal entity to the payer of recurring bills such as energy. To find ways of addressing this conundrum, FETA has established ERG — the Energy Reduction Group. At the component level, products become more energy efficient as designs improve. An area that is significant in building services, because of the large amount of air movement involved, is fans. Modern electronically commutated fan motors use about a quarter of the amount of electricity of traditional shaded-pole motor. There are many other examples, including compressors, duct design to enable easier air movement etc. Control
Better control algorithms can often have a beneficial effect on energy efficiency. Set points can frequently be altered adaptively according to longer term trends, whilst local control works through local set points. For example, if a heating system is required to supply relatively small amounts of heat (because of time of year), the temperature of the water supplied to the fan-coil units can be reduced. The local control unit continues to supply the required amount of heat in the usual on/off way but stays on for a greater proportion of the time. The lower flow temperature will lead to higher thermodynamic efficiency. Another example is replacing boilers with heat pumps. These will generally more than halve the amount of energy input for a given amount of heat supplied to the occupied area — and they could even use green electricity. There are human-based problems with sophisticated control and components. Experience shows that users often have difficulty understanding and using the controller human interface. It is often insufficiently intuitive and/or the user training has been insufficient. This is a matter on which the Building Controls Industry Association — part of FETA — has a project underway. There is a temptation for maintenance people to by-pass control mechanisms. For example, the optimiser in the heating system outlined above could be by-passed so that the system operates continuously with water at the maximum temperature. This is especially likely if the person involved has received inadequate training and does not understand the basis on which the optimisation works. However, it can also happen as a ‘get-you-home’ fix. With good training the first reason should cease to exist. When the change has been made as a ‘get-you-home’ strategy, it is important that the system is revisited as soon as possible and the proper mend performed. The system should not be left operating in the sub-optimal state. Whenever equipment has to do work to overcome ‘friction’, there is an energy penalty. ‘Friction’ covers partially blocked air filters, partially blocked liquid filters etc. To maintain good energy efficiency, good housekeeping is essential. Key elements
There are six key elements in responding to the carbon 60 challenge. • Design systems as a whole. • Be willing to spend a bit more as first cost for energy efficient components. • Be willing to use nested control algorithms (like the optimiser discussed.) • The controls industry needs to focus on the usability of control interfaces; they need to be intuitive. • Systems need to be maintained. ‘Get-home’ fixes need to be correctly replaced by proper fixes quickly after the initial fix. • House keeping needs to be good and regular. Mike Lawrence is chairman of the Energy Reduction Group of the Federation of Environmental Trade Associations.