Bennett George, Elwell Cliff
University College London, London, UK.
Build Serv Eng Res Technol. 2020 Nov;41(6):709-726. doi: 10.1177/0143624420927352. Epub 2020 May 22.
Gas boilers dominate domestic heating in the UK, and significant efficiency improvements have been associated with condensing boilers. However, the potential remains for further efficiency improvement by refining the control, system specification and installation in real dwellings. Dynamic building simulation modelling, including detailed heating system componentry, enables a deeper analysis of boiler underperformance. This paper explores the link between the space heat oversizing of boilers and on/off cycling using dynamic simulation, and their subsequent effect on boiler efficiency and internal temperatures. At plant size ratio (PSR) 8.5 daily cycles numbered over 50, similar to median levels seen in real homes. Simulations show that typical oversizing (PSR >3) significantly increases cycling behaviour and brings an efficiency penalty of 6-9%. There is a clear link between raising PSR, increased cycling and an associated decreased efficiency; however, in the UK, boilers are regularly oversized with respect to space heating, especially combination boilers to cover peak hot water demand. Current legislation and labelling (ErP and SAP) overlook PSR as a determinant of system efficiency, failing to incentivise appropriate sizing. Reducing boiler oversizing through addressing installation practices and certification has the potential to significantly improve efficiency at low cost, decreasing associated carbon emissions. This research provides the basis for a practical and cost effective means of assessing the potential for underperformance of boiler heating systems at the point of installation or refurbishment. By assessing the oversizing of the boiler with respect to space heating, unnecessary cycling and the associated efficiency penalty can be avoided. Plant size ratio, as an indicator of cycling potential, can be implemented in energy performance certificates (EPCs), through the standard assessment procedure (SAP), using existing data. The potential for real carbon savings in the existing boiler stock is considerable, and the findings have wider implications for next generation heating systems.
燃气锅炉在英国的家庭供暖中占据主导地位，冷凝锅炉带来了显著的效率提升。然而，通过优化实际住宅中的控制、系统规格和安装，仍有进一步提高效率的潜力。动态建筑模拟建模，包括详细的供热系统组件，能够更深入地分析锅炉性能不佳的情况。本文利用动态模拟探讨了锅炉空间供热容量过大与启停循环之间的联系，以及它们随后对锅炉效率和室内温度的影响。在设备容量比（PSR）为8.5时，每日循环次数超过50次，与实际家庭中的中位数水平相似。模拟表明，典型的容量过大（PSR>3）会显著增加循环行为，并带来6-9%的效率损失。提高PSR、增加循环和效率下降之间存在明显的联系；然而，在英国，锅炉在空间供热方面经常容量过大，尤其是组合锅炉，以满足高峰热水需求。当前的法规和标签（能源相关产品指令和标准评估程序）忽视了PSR作为系统效率的决定因素，未能激励合理的容量配置。通过解决安装实践和认证问题来减少锅炉容量过大，有可能以低成本显著提高效率，减少相关的碳排放。 本研究为在安装或翻新时评估锅炉供热系统性能不佳潜力提供了一种实用且经济高效的方法基础。通过评估锅炉在空间供热方面的容量过大情况，可以避免不必要的循环和相关的效率损失。作为循环潜力指标的设备容量比，可以通过标准评估程序（SAP），利用现有数据在能源性能证书（EPC）中实施。现有锅炉存量实现实际碳减排的潜力相当大，研究结果对下一代供热系统具有更广泛的意义。
