Is the UK missing a trick?

Feb 25, 2014 by

Is the UK missing a trick when it comes to specifying the pipe work associated with the country’s growing enthusiasm for District Heating Schemes?

Conventionally, district heating applications use steel piping but there is growing evidence that the use of pre-insulated ‘plastic’ piping can offer significant advantages when taking heat loss and overall system life cycle cost into account.

Numerous research projects have pointed to the advantages of products such as Flexalen the plastic system that can reduce heat loss potential over steel piping. The effect is the ability to reduce boiler source temperature (and enhance efficiency) and to commit to 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 life cycle costs and extended operational periods between pipe replacements.

The enduring truth is that steel and hot water do not make comfortable bed fellows 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 viability alternative to the conventional rigid Steel  pipework. Add in the greater flexibility in site storage, laying and connecting and it’s no wonder that plastic is now on the radar for scheme specifier’s and operators.

As we are aware, most district heating schemes in the UK use steel pipework to meet the high operational temperatures that are needed to compensate for heat loss over often quite large distances. However, this inevitably means that city centre schemes need replacing every 10 years or so because the system pipework will have corroded, with 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.

There have been numerous studies about the value of this maturing pipe technology, focused mainly on its flexibility and it advantageous heat loss properties, resulting 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 life cycle 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 schedule are taken into account.

Indeed, the emergence of Energy Service Companies (ESCo) provides an apt moment to take stock of how we intend optimising the value of district heating schemes in the future, particularly since source heat is now being delivered in many more ways, including smaller scale biomass energy systems.

Moreover, scheme owners owe it to the populations they serve 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.

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