HEAT NETWORKS | OPTIMISATION GUIDE stability, maintenance frequency, and time below minimum flow temperature, which reflect the reliability of the system for end users. There is also a KPI for carbon intensity of heat. This is very useful for operators, as they can look at the KPI numbers across portfolios and see the worst-performing systems and where to prioritise spending, says Burton. Site audits and making a business case There is a section in the guide on conducting site audits, which are designed to determine the condition and method of operation of heat network elements. It lays out the audit process, as well as data analysis and modelling techniques that can be used to assess performance. The section on making a business case looks at two methodologies to analyse financial impacts of potential interventions: simple payback and net present value. There is also a section on interventions that do not have a direct impact on performance, but that reduce operational 16 COMMON REASONS FOR FAILURE Key failures in heat networks were identified following the review of existing systems by FairHeat. Burton says that many systems will be failing for at least one of these reasons: 1 Insufficient consideration of heat network requirements at concept design stage 2 Incorrect sizing 3 Unnecessary complexity 4 Unsuitable hydraulic arrangement 5 Poor insulation specification and installation 6 Poor planning and civil works for underground pipework 7 Poor underground pipework installation 8 Insufficient monitoring and data collection 9 Inappropriate design and commissioning of consumer connection and/or heat system 10 Lack of consideration given to system pressures 11 Lack of consideration given to maintainability 12 Poor installation and commissioning practices 13 Inefficient control 14 Uncontrolled network flows 15 High return temperatures 16 Poor water quality 40 August 2023 www.cibsejournal.com risk, such as improvement in water quality. It includes a process for identifying and mitigating risks. Knowledge requirements For studies, the guidance defines two roles: study lead and study engineer. The study lead is accountable for the technical quality of the report, conclusions and recommendations, and should have more than five years experience in the heat network sector. Study engineers, with a minimum of two years experience, lead the onsite audit and are responsible for managing the technical and financial analysis of the optimisation study. Template scope of works A separate version of the optimisation guide, the Template Scope of Works, is aimed at operators. It can be used to procure an optimisation study and be appended to a tender pack, and has an outline of the process and knowledge requirements. Operators can ask for a quote based on this document and anyone undertaking the work has to follow the guidance, says Burton. There are also videos for operators, to help them understand the technical language and identify when heat networks are not performing.. The optimisation guide is essential for anyone operating a heat network and not just because it will cut carbon and reduce heating bills. Burton says a form of the KPIs will be included in the mandatory HNTAS, and adds: Its likely that there will be a requirement for existing heat networks to put in a plan to get from current to compliant. CJ Study engineers will need a minimum of two years experience to carry out studies