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Keeping up with district heating schemes

Is the UK missing a trick when it comes to specifying the pipework associated with district heating schemes?

There is growing evidence that the use of pre-insulated “plastic” piping offers significant advantages over steel piping when taking heat loss and overall system life cycle cost into account.

Numerous research projects have highlighted the advantages of plastic systems that can reduce heat loss potential over steel piping, for example. The effect is the ability to reduce boiler source temperature (and enhance efficiency) and allow for more extended replacement schedules because plastic networks do not suffer from the same corrosive limitations as steel.

This creates a number of benefits for scheme owners and operators – improved overall energy efficiency, lower long-term system lifecycle costs and extended operational periods between pipe replacements.

Steel and hot water do not make comfortable bedfellows but with the superior flow characteristic of plastics resulting in the use of smaller pipes and improved heat loss performance, source temperatures can be reduced to the point where plastic networks are now a viable alternative to the conventional rigid steel pipework. In addition, they also have greater flexibility in site storage, laying and connecting.

As we are aware, most district heating schemes in the UK use steel pipework, but this inevitably means that city centre schemes need to be maintained, repaired, and replaced due to corrosion and the corresponding risk of leakage.

Historically, in the UK there has been resistance to the use of “plastic” in district heating schemes, but the wide diversity of such schemes means that a re-evaluation of new-generation flexible pre-insulated piping is required, if not for primary ring mains around a city, then certainly for secondary and tertiary lower temperature connections.

Numerous studies about the value of this maturing pipe technology, focusing mainly on its flexibility and its advantageous heat loss properties, have resulted from the ability to lay dual pipes (flow and return) next to each other in one fully insulated system.

So where can such flexible pipe systems add value? Certainly, in many city-wide schemes with district heating mains, such as Sheffield, Leicester and Nottingham, a sound business case can be made for the inclusion of “plastic” for secondary systems, based on network design, ease of installation and whole lifecycle costs.

Any reluctance is as much to do with historic attitudes to materials usage – but the opening up of the DHS ownership and management market looks set to bring with it a more open attitude to plastic based on proven cost advantages, ease of installation, low maintenance, eco benefits and enhanced ROI when replacement schedules are taken into account.

Indeed, the emergence of energy service companies provides an apt moment to take stock of how we intend optimising the value of district heating schemes in the future.

Moreover, scheme owners owe it to the public to provide the most cost effective service available, for example in social housing properties where utility cost is key for users, or in high profile publicly funded developments where ROI, energy efficiency and environmental benefits are key considerations.

Sandy Fairley is sales director for Flexenergy

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