Solutions for local integration of renewable energy sources (RES)

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This deliverable summarizes and gives an overview of existing and newly developed technical solutions used for the domestic hot water production that can be implemented in low temperature or ultra-low temperature district heating networks, and that can increase the share of renewable energy in the building sector. The deliverable was prepared by COWI Denmark A/S, Kraftringen Energi AB and Cetetherm AB

A technology catalogue

Due to reduced heat demand in new and renovated buildings, the supply temperature of the district heating network can be lowered. However, with the risk of Legionella contamination, the temperature of the domestic hot water has to keep a certain safety level. Decentralized solutions can help to fulfill the temperature requirements so that the district heating network can supply a lower temperature.

In this deliverable, we have completed a technology catalogue composed by datasheets of the solutions chosen that are available on the market or that will be available in the near future. Each datasheet contains the main information of each technology, with a short technical description, the main characteristics, advantages and disadvantages and a brief overview of the main costs.

Solutions for single-family and multi-family buildings

The solutions are divided into two categories, in terms of their applications for single-family or multi-family buildings. Based on the two categories, we conducted a deeper analysis considering the economic evaluation of the technologies. In particular, we compared the extra investment cost of each technology to a reference technology. In single-family houses, the installation of a district heating unit for direct connection in each dwelling functioned as a reference case. The evaluation of the extra investment cost together with the operation cost of each technology made it possible to calculate a payback time that can give an estimation of the feasibility of an alternative technology.

Resluts single family-houses

The main results of the single-family buildings highlighted a good performance of an air-to-water heat pumps that use the indoor air as heat source, thanks to the low installation cost and the possibility of using a heat source that is free of charge. An alternative technology is the use of a solar collector system installed on the building, which can guarantee a reasonable payback time. On the other hand, the installation of a booster heat pump for single-family houses connected to the district heating network highlighted a problem related to the cost of the heat source. In fact, this interesting technology is limited by the operation costs due to the cost of the heat source. An incentive scheme should be adopted to make the technology competitive in connection to the district heating network. Nevertheless, interesting applications with Photovoltaic Thermal (PVT) panels and ground heat source are under development, which can make the technologies competitive.

Results multi-family houses

In case of multi-family buildings, the installation of a main substation (traditional Nordic) that centralize the production of domestic hot water as well as space heating was set as reference for the economic evaluation. The evaluation found that the split flow technology can be a valid technology to introduce renewable energy in the domestic hot water production. Another alternative to consider is the introduction of a solar collector system with a buffer tank. On the other hand, it was found in the single-family buildings evaluation that an implementation of a booster heat pump will result in an expensive solution due to the high operation cost. This makes the booster heat pump non-competitive with other solutions that use other heat sources. To be competitive, some considerations about the price of the heat source have to be made.

Lastly, the deliverable presents solutions for the space heating system in low temperature district heating networks to give a complete overview of the possible installations that can be used in a building to fulfill the heating requirements in the next generation of district heating.

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 Emanuele Zilio at COWI: