District heating system with intelligent leak protection

Paul Boughton

An innovative combination of heat meters with leak surveillance and an automatic leak protection system results in higher energy efficiency and optimised customer service. Gert Skriver reports.

The fact that District Heating Thisted, which supplies a community of 15.000 people with heat energy, is located on the outskirts of Europe in northern Denmark does not hinder the utility from applying newest technology and still supply its customers with cheap and stable energy. The utility follows an ambitious strategy for intelligent energy management with the aim of being energy efficient and keeping costs down.

One important parameter with respect to district heating efficiency is to maximize the difference between incoming and return temperature - known as Delta-T - which means that as much energy as possible is being extracted from the water. For the sake of maximising Delta-T, Thisted District Heating recently chose to phase out all heat exchangers and replace them by a direct heating system with leak protection.

Heat exchangers in each household offer a way of regulating the energy consumption and of securing the district heating system by separating the heating system in a primary system on supply side and a secondary system on consumer side. In this way a leakage can be limited to the secondary system.[Page Break]

Heat loss

But heat exchangers are not very energy efficient. The heat exchanger itself causes a heat loss of 5-7°C, and because it is being manually controlled by the consumer it is very common that the thermostat is not set according to guidelines which often causes the heating installation to return too hot water (low Delta-T).

And as just 1°C improvement in Delta-T for the whole town means a total saving of more than 100,000 Euro, there lies a huge saving potential here.

Thisted District Heating therefore decided to dismount all heat exchangers and instead use a direct system which distributes district heating water all the way into the hot-water elements in the homes. An ordinary direct heating system, though, raises a security question because a leakage could affect the whole system.

So in order to maintain the same level of leakage protection, Thisted District Heating introduced the combined Kamstrup-Dantaet solution.

Kamstrup flow sensors installed in the inlet pipe and in the outlet pipe register volume and temperature of the water. The heat meter integrator then translates volume into mass in order to make a comparison of incoming and returned water independent of temperature. Constantly monitoring the water flow, the meter will register any imbalance between incoming and returned water indicating a possible leak. The heat meter will then send a signal to the Dantaet leak protection system which will immediately shut off the installation.[Page Break]

The Dantaet leak protection consists of a control unit and two check valves which will automatically seal off the installation. This not only limits the damage, but also provides an even safer system than before. Once every night the valve in return flow will shut down and cause an increased pressure in the installation. The higher pressure will reveal any small leakages which could over time aggravate and become detrimental.

This intelligent energy management system heightens energy efficiency, reduces the need for manual work, keeps costs down and even improves home security. Most insurance companies give 25-50 per cent off on premium when the Kamstrup-Dantaet solution is applied.

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Gert Skriver is Corporate Editor, Kamstrup, Denmark. www.kamstrup.com

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