Heat networks require more efficient design

Blackwell, a design management consultant at Hoare Lea, makes the case for more careful and efficient design of district heating systems and highlights the common issues that can contribute to operating inefficiencies.

“Without careful design,” writes Blackwell, “district heating systems can lose unacceptable levels of heat through their vast network of pipes. We need to educate clients to look beyond low capital costs and demand better long term performance.”

Part of the problem, says Blackwell, rests with private-sector developers of new heat networks who are focused on reducing costs. “It is common to procure district heating built to minimal compliance levels under a design-and-build arrangement where the focus is to deliver a system for a low capital cost,” he says.

Blackwell also outlines a range of design issues that contribute to operational inefficiencies, including:

• poor pipework layout which could increase the length of pipework ultimately leading to increased distribution losses

• lack of accurate metering which makes it difficult to determine the operational efficiency of heating plant and how the heat is being distributed

• poor initial commissioning and the subsequent lack of seasonal commissioning, which makes it difficult to detect high operational costs at the earliest stages

• poor pumping and flow control

• high, fixed operating temperatures, but low temperature differences resulting in reduced primary plant efficiency and a potential increase in pipework losses

Welcoming the views expressed in Blackwell's article is Simon Woodward, Chairman of the UK District Energy Association (UKDEA). He comments:

"The UKDEA has long advocated the efficient and careful design of heat networks as a means of attaining long-term operational efficiency and reducing high operational costs, ultimately benefiting the customers of the low carbon district energy schemes."

The UKDEA is currently looking into the development of technical standards with the hope that wide industry acceptance will make good standards the norm.

Partnership for standards

CIBSE and the Combined Heat & Power Association (CHPA) have formed a partnership to assure the quality of heat networks. It is thought that the development of a Standard could help take this sector to the next level, which would see training, accreditation and registration of engineers in this area to enhance the quality of heat networks from design through to operation.

Phil Jones, Chairman of the CIBSE CHP-District Heating Group, says: “The district heating industry has recognised the real threat to the reputation of its technology because of the lack of agreed minimum standards and the absence of accreditation of designers, installers and operators.”

Get involved

CIBSE is seeking to obtain case study examples of measured performance of recently completed residential and mixed-use development district heating projects in order to gather evidence of scenarios where there are potential performance gaps. The case studies, which can be kept anonymous, may help CIBSE identify critical issues about the design, application, procurement and operation of community energy systems. Examples of good performing systems would also be welcome. Those who are able to provide examples of measured performance are asked to email DHN@cibse.org.

There is also a LinkedIn discussion thread about heat network quality and standards. Simply log into LinkedIn and search ‘CIBSE CHP & District Heating Group’ in groups, or click here: LinkedIn

Hue Blackwell’s article in CIBSE Journal can be viewed here: http://www.cibsejournal.com/archive/PDFs/CIBSE-Journal-2013-08.pdf