Beyond weather compensation

Swansea
The gas used by boilers serving the heating system in County Hall, Swansea, was reduced by 21% during monitored trials of a controller that predicts the demand likely to be placed on boilers.
Do you fancy reducing your heating bills by 20 per cent? PETER JENNINGS believes he has the answer.Modern boilers are very efficient pieces of kit, with condensing technology enabling their efficiency to approach 100% (gross). The heating systems that they serve are seldom as efficient and often demand more heat than necessary, which is clearly wasteful, even if that heat is generated very efficiently by the boiler. Weather compensation Control is the key, and one of the key approaches is to take account of the weather outside. Building-management systems have traditionally played an important role in this approach to control — known as weather compensation. However, according to Peter Jennings, managing director of Fuelstretcher, BMSs have their limitations. His approach is to reduce boiler output more than the recognised BMS compensation strategy — without sacrificing comfort. This patented unit has been proven in field trials to reduce fuel consumption by predicting the demands that are likely to be placed upon the boilers rather than controlling them by reactive methods. He explains that it was developed because of the limitations of building-management systems that relate sensed outside air temperature to inside space temperatures and compensate for demand by adjusting boiler temperature, sequencing or shedding as its programme dictates. Research by the Building Research Establishment, backed up by three years’ practical experience, accepts that such actions do usually lead to a comfortable working environment for the occupants — but still leave boilers working unnecessarily. ‘BMS compensation is a reactive process,’ says Peter Jennings. ‘Such spontaneous actions do not fully reconcile the dynamics of heat loss or heat gain. They have to cope with boilers generally being pre-set at an unnecessarily high flow temperature of 80°C. Compensation strategies will be applied through temperature sensing relationships and mixing valves, but zone comfort can often be achieved with much lower primary temperatures. ‘As a result, all buildings waste heat at some time during the heating season; many buildings waste heat throughout the season.’ Predictive approach He suggests that a predictive approach significantly reduces boiler activity and, therefore, fuel consumption. The Fuelstretcher principle involves creating a predictive process which is undertaken daily for a stipulated programmable period when the likely demand of the building during occupancy is ascertained by analysis of primary temperatures in flow and return circuits. Predictions are based on the dynamic heat gain or loss of the premises over the stated period of time. Boiler temperatures are then set to accommodate them. Significantly, outside air temperatures are not taken into account. The effectiveness of this approach has been demonstrated not only by BRE research and computer modelling but on many installations across the UK over the last three years. One of those locations was County Hall at Swansea, where an independent analysis of gas consumption and building-plant performance confirmed that the heating-energy controller dramatically reduced fuel consumption. The analysis was carried out by TAC Satchwell Energy Services on behalf of the Consortium of Local Authorities of Wales Energy Managers Group and identified a 21% reduction in gas consumption when the building was under the control of the patented controller. Data was collected for six weeks — three with the Fuelstretcher in operation and three when it was over-ridden. Weather correction was built in through degree-day values calculated half-hourly from an outside air temperature sensor. Average savings in gas consumption in excess of 20% were recorded at The London Borough of Sutton’s Grove education administration building at Carshalton. The first leisure centre to be equipped with the controller, at Rushcliffe, saw its gas bills for heating a swimming pool, pool air and hot water services slashed by £10 000 over an 18-month period. Many schools, leisure centres, sheltered homes and offices in GB and Northern Ireland have benefited from the technology. Payback Paybacks generally are best calculated in usage. A controller fitted in a building with an annual consumption of 400 000 kWh can expect a payback in two to three years, according to Peter Jennings. Developed as a result of a €1emillion EC-supported project undertaken by the Building Research Establishment at Watford, the controller can be retrofitted or incorporated in the M&E designs for new buildings. However, despite Government legislation aimed at cutting energy costs, Peter Jennings says there is reluctance to adopt the controller as a matter of course. ‘From the point of new build, we need consulting engineers to take on board the opportunities offered by energy-saving units such ours and then include them in the initial design,’ says Mr Jennings. ‘This would encourage the building-management-systems integrators to incorporate them when undertaking the specification and installation of the systems. ‘And as far as retrofit is concerned, even though the units are easily installed on an existing system and thereafter operate in standalone mode, we are coming up against a reluctance from in-house and outsourced plant maintenance teams — and even in-house facilities managers — to accept the technology, claiming sceptically that they have “seen it all before” or that “the BMS can do that”. ‘We are always prepared to install a unit on a trial basis, and our latest enhancement is to provide a remote metering service with monthly reports on consumption (and comparisons using historical data), but it does appear that it takes time in our industry for new technology to be accepted.’ He suggests the time has come for partnerships to be forged between all interested parties in the interests of fuel conservation — and compliance with Government requirements.
For more information on this story, click here:Jan 07, 70
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