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Planning a district heating system

Planning a DH project

Good planning of a DH system is adapted to the local situation, and that also explains why DH systems can look very different but still be the best choice for each city. The demand for heat and cooling will depend on the buildings in the area, how closely they are spaced, and whether the buildings are used for housing, services, or local industry. It will depend on the weather, or more precisely, the statistical weather data for temperatures and wind.

The heat demand is only one part of a DH system. The technical-economic planning of a DH system also takes the potential heat sources, the supply and return temperatures in the pipes, and the overall operability and robustness of the whole system into account.

A DH system is established one project at the time but is developed in harmony with an overall plan and strategy for the entire DH system.

It starts with a good idea for a DH project that is then discussed, sketched, and tested by considering benefits, challenges, and alternatives. Like any other project.
The fundamental things to get right in this phase are estimations of current and future heat demand, sources for heat supply, cost estimations, main risks and challenges, the need for stakeholder involvement, and last but not least, a good sense of how the project fits into the overall plans for the area and the DH company.
The feasibility study aims to decide whether to commit resources to develop a detailed project proposal. Often, it is a good idea to start communicating now.

The pitfall in this phase is to consider only the time until the project is commissioned. Not only will a specific DH project influence the future planning of the whole system, but the design choices will also affect how easy and costly the system will be to operate and maintain. That being said, good DH projects are being planned all the time, and it is not as complicated as it may sound.

The project proposal or business case is basically the feasibility study in a more detailed version. The data foundation is more elaborate, the analyses include more parameters, the risks are examined more carefully, the compatibility with the overall plan is challenged, the technical designs are specified, communication is planned, and the methods for financing are investigated.

Time horizons are critical when planning DH projects. The technical lifetime is one of these time horizons, and this is often very long in DH projects. The lifetime varies for different types of equipment, with pipes usually having the longest lifetime – with over 50 years not being uncommon. Depreciation period is another time horizon. It is related to the technical lifetime, but other things also factor in.
There will be investment costs for all DH projects, and a third time horizon crucial for the feasibility of a DH project is the purpose and patience of the investors. In Denmark, DH projects, such as converting an area from heating based on natural gas to DH or changing the heat supply to include a large-scale heat pump, are often expected to pay themselves back within 20 years. Other investments, like switching to more efficient pumps or better digital solutions, often have much shorter payback times.

Based on the detailed project proposal, the DH company will decide whether to carry out the project.

The specific conditions and requirements depend on the type of project, and they will vary from country to country. The best advice here is to start early and not to underestimate the calendar time that might be needed.

This is also the phase where communication with stakeholders becomes very important, so if it hasn’t begun already, now is the time to start communicating.

Now that the DH company knows what it wants and has decided to move forward with the project, it is time for the tendering process to determine who will be involved in the construction work. Adjustments to the project and the business case may occur during the tendering process, but at the end of the process, the plans for construction and commissioning are in place.

A piece of good advice is to find the type of tender that matches the project and skills of the DH company. The tendering process requires negotiating and technical skills, and the pros and cons are different for a turn-key solution and a tender based on functional specifications.

It is now time to benefit from a good planning process. The better the planning, the more likely it is to have a good construction and commission of the project. It is also more likely that customers will be happy and well-informed and that the project will meet the expectations of the DH company.

Notice the word choice here – “infrastructure,” not “grid.” The overall efficiency and robustness of a DH system depend not only on the pipes in the ground but also on the units at the consumers, the quality and placement of the pumps, monitoring, operational control, and the ability to integrate different heat sources efficiently. All this determines the temperatures and the flows through the entire DH infrastructure, and a well-dimensioned system means a high level of energy efficiency. Expert knowledge is needed to optimize the infrastructure design and operation, but it is well worth the investment as it will keep losses low and flexibility high.
With the integration of more and more large-scale heat pumps, it is becoming increasingly important to reduce the temperatures in the DH system as much as possible – while still maintaining high enough temperatures for efficient energy transport through the system. The lower the temperature, the bigger the pipes are needed to transport the necessary heat. With new types of low-temperature heat sources such as surplus heat, geothermal, ambient air and water, and cleaned wastewater, good infrastructure planning has even more significant benefits.
Optimising and operating DH systems rely increasingly on extensive data collection and new digital tools. [read more — > DH technology]

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