System solutions for multifamily houses and tertiary buildings

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The pipe heat losses in the circulation of domestic hot water (DHW) can be high in comparison to the demand and use of DHW. Flat stations can be used in order to potentially lower these heat losses. Kraftringen, COWI A/S and Cetetherm have looked closer on solutions with flat stations in buildings with low district heating (LTDH). Arnela Kursumovic from Kraftringen presents some of their findings in the summary of this deliverable.

What is the main purpose of the working paper?

Flat stations can potentially lower pipe heat losses in the circulation of domestic hot water DHW. This deliverable aims to provide future property owners, architects, constructors and developers information on how flat stations (micro heat exchangers for each apartment) would work when implemented in buildings with low temperature district heating (LTDH). The aim is to evaluate and describe pros and cons of implementing flat stations and compare this solution to the traditional solution with one main substation in each building.

What are the main findings in your study?

In short, the results of our evaluation show that there is no evidence for the hypothesis that implementation of flat stations would increase energy efficiency in multifamily buildings. A solution with flat stations will lead to higher investment and operational cost compared to an adapted traditional solution with only one substation.

The pros of using flat stations are that they make it easier to implement individual metering and charging. The district heating grid could use a lower primary supply temperature when using flat stations without increasing the risk of legionella due to the German standard (also applicable in Denmark). Another advantage is that the residents can regulate their indoor temperature individually. A flat station solution without substation is considered too risky, both for the district heating company and the customers due to consequences if leaks occur, and was thereby not included as a feasible solution in the Swedish context. However, this solution could be suitable for buildings with only a few flats and is often used in Denmark.

Flat stations are not suitable for tertiary buildings like hotels, offices and hospitals since they are normally not in need of individual metering and charging. Neither would a district heating with a 45⁰C temperature on the tapping water be suitable for these type of buildings. Offices that does not consume much DHW could keep using local boilers and make efforts to cluster and locate all water usage so that one boiler can cover as many taps, showers etc. as possible.

From an environmental perspective, an implementation of flat stations in multifamily buildings, compared to the traditional solution, would generate a larger need for both material and energy during the production phase of the products life cycle.

The picture shows the distribution for the three evaluated cases. From the left: the adapted traditional solution, the flat station solution with a substation, the flat station solution but without the substation.

What happens now?

The flat station solution will be tested in real life in a building called Xplorion that LKF (the municipal housing company) is building in Brunnshög, Lund. Individual metering is going to be integrated in the flat stations and we will supply the flat stations with a lower primary temperature. By trying the solution in real life, we can compare the actual costs and heat losses to the results of this task.

Since there are advantages with flat station solution, and the price being their biggest issue, there are incentives to lower the service cost and the costs for flat station in the future.

The issue remains whether it is environmentally beneficial to produce a flat station for each apartment to save energy, or if the production of these do more harm than good to the environment. Especially in future buildings that are not using a lot of energy to begin with.

More information

Since this is a confidential report, you will not find it for download. However, if you are interested in learning more, please contact Arnela Kursumovic at Kraftringen: