District heating is facing new challenges. Conversion towards an energy system based on renewable sources demands that the energy industry adapts to new means of production as well as more fluctuating energy prices. In addition, higher emission standards and other legislations must be met. Adjusting to these changes presents a challenge for energy producers to meet the demand for energy. At the same time, more efficient use of district heating is expected to lead to changed consumption patterns in the future.
Sweden has been ranked as the world’s second most innovative country. Changing conditions in the future does not only present challenges, but also the opportunity to develop new solutions. Modern building techniques and new energy system solutions are paving the way for lower temperature in future district heating networks. This technology has promising benefits for network operators as well as the heat producing companies. There are already several trends that indicate the future of district heating systems. The following trends are prominent today:
- Digitalization – Achieving an overview of the entire energy system presents new possibilities to streamline production. Computer tools are used to support production planning by collecting and presenting data in real time.
- Regionalization – Connecting several heating networks allow for more efficient use of each system’s productions units.
- Total optimization of the energy system.
Unused potential
Several district heating companies are working actively with energy system optimization, with better use of resources as a result. One aspect that is often overlooked is whether the forward temperature is optimal. Historically, the district heating network has been seen as a separated part of the system, partly due to a lack of real time feedback of network temperatures. As today’s energy systems move towards optimization and digitalization there are several benefits that can be achieved;
- Higher total efficiency and increased profit. Even slightly decreased forward temperatures gives cost savings.
- Less heat losses in the district heating network.
- Higher efficiency of production units.
- Fewer unnecessary starts of peak load units.
Economic total optimization of the district heating network
The innovative software Energy Optima 3 Smart Optima Heat Network (SOHN) is developed by Energy Opticon in Lund, Sweden. It aims for a total economical optimization of the district heating network, which also includes optimizing the forward temperature. The model accounts for heat accumulation and temperature dependency in the district heating network and thereby increases the overall flexibility of the network. The optimization is made for the whole energy system, from heat and power production and electricity trading to final consumption. Restrictions on emissions and other legislations are considered in order to present the economically optimized production plan.
A benefit from using SOHN is higher utilization of main production units when bottlenecks are present in the heat distribution grid. Certain district heating networks, particularly those with long distribution pipes, experience limited pump capacity which limits the supply capability from centralised production plants. Therefore, peak load units might be forced into operation to support the heat load in the whole network. In an optimized scenario the forward temperature can be increased before a load peak and thereby supply the higher load without starting expensive peak units. The heat is instead supplied from the temporary heat accumulation that results from increasing the forward temperature.
Example:
Kraftringen AB is an energy company based in Lund, Sweden, that is continuing its role in developing a sustainable energy system. Kraftringen supplies about 50 000 households with district heating, with an annual heat supply of 1 100 GWh. In 2018, the company achieved a completely fossil free production. In addition, Kraftringen is currently building the world’s largest low temperature district heating network which will be supplied from waste heat from research facilities ESS and MaxIV. The company is at the same time working with new means of optimizing the existing network. As a part of this project, SOHN was installed in the beginning of 2019 with the purpose of optimizing the forward temperature. During the first two months in operation the forward temperature was decreased with 2 degrees on average and total costs were decreased by 200 000 SEK.
Quote on Smart Optima Heat Network from Kraftringen:
“To achieve efficiency, it is important to not only look at the latest technology in new constructions but also to optimize the existing systems. The majority of Lund already has district heating installed and replacing this would not be economically feasible. SOHN is a good example of how to efficiently optimize the existing district heating network by utilizing the latest controller strategies.”
Authors:
Moa Dahlman Truesdale
CFO, Energy Opticon
