At first glance, it sounds strange when cold local heating is to take over the heat supply. Is that a contradiction? No, cold heat really does exist. It is a heat supply with relatively low temperatures. Compared to conventional heat networks, these are almost cold - hence the name. This article shows exactly what cold local heating means, where its advantages lie and what subsidies are available. It also includes some practical examples.
What is cold local heating?
A heat supply via heat networks, district heating or local heating, usually has a flow temperature of 70 to over 100 degrees Celsius. Heat networks in densely built-up settlements or neighborhoods can also manage with very low temperatures, between 8 and 30 degrees Celsius. To achieve the necessary temperature, decentralized heat pumps are used in the houses. Due to the low temperatures in the heating network, there is only a small difference to the temperature in the ground. Insulation of the pipes is thus not necessary; ideally, the network can also absorb heat from the surroundings. For reasons of frost protection, a water-glycol mixture (brine) flows through the pipelines.
This type of heat networks is called cold local heat, physically correct as anergy networks or also heat networks 4.0. One reads about heat networks more and more often, they gain in importance.
Even at these low temperatures, a heat source is available Depending on the structure of the network, reverse operation for cooling the buildings is also possible.
Different heat sources can be considered for the cold local heat. This principle of heat supply is particularly interesting with regard to climate protection, because it allows waste heat from industry or renewable energies to be used.
Advantages of cold local heating
A heat supply with the principle of cold local heat has some advantages that make it very interesting.
- Due to the temperatures close to the ambient temperature, the pipelines do not require thermal insulation. There are no or only minor losses in the pipeline network. Ideally, this even allows heat to be absorbed from the ground. This reduces costs.
- Different heat sources can be used, depending on local supply and availability. Waste heat and renewable energies, such as geothermal energy and solar thermal energy, can be used. This makes this type of heat supply interesting for the heat turnaround on the way to CO2-free heating systems.
- Due to the low temperatures, the storage of heat does not require any complex insulation and thus becomes significantly cheaper.
- Due to the constant temperature of the heat source, heat pumps achieve an annual performance factor of 4.0 or higher.
- With cold local heating, the economic risk for the operator is smaller than with classic heating networks due to lower heat loss. Therefore, the unpopular connection requirement is usually waived and owners or builders continue to have a free choice for their heating system.
- Local heating networks are generally a good opportunity for citizen energy cooperativesto convert the local energy supply to renewable energies and to operate them themselves.
Disadvantages of the heat supply with cold local heating networks
I do not want to hide the disadvantages of cold local heating, so I add the text (subsequently):
- High investment costs for homeowners for heat pump and for connection to the local heating network.
- Due to the low temperature difference between flow and return and the low temperature level, large volume flows are required. This means larger diameters for the pipelines and a higher power requirement for the pumps.
Funding for cold local heating
The German Federal Ministry for Economic Affairs and Energy (BMWi) has been funding feasibility studies and the implementation of heat network systems 4.0 since 01.07.2017. Even though the temperature level in the funding conditions assumes a minimum of 20 degrees Celsius, this funding can also be granted for cold local heating. A feasibility study must prove that lower temperatures will save costs, energy or CO2 emissions.
The funding for Heat Networks 4.0 is the first funding program to support not only individual technologies and components, but also complete systems. For the BMWi, fourth-generation heating networks are characterized are characterized by a high proportion of renewable energies, the efficient use of waste heat and a significantly lower temperature level compared to conventional heating networks. This minimizes losses, increases efficiency and facilitates the switch to renewables in local and district heating supply. Such systems can provide additional flexibility for the electricity market by combining heat pumps and seasonal large-scale heat storage systems and offer the opportunity to supply building stock that is difficult to insulate with high proportions of climate-friendly heat.
The BMWi is initially funding feasibility studies with up to 60 percent, and in a second step the realization of a heat grid system 4.0 with up to 50 percent of the total eligible costs of the project. Information on the technical requirements and the application is made via the BAFA.
Practical examples of cold local heating
Cold local heating is illustrated by a number of practical examples:
Near-surface geothermal energy in Schifferstadt
On the initiative and with the support of the Energy Agency Rhineland-Palatinate the city of Schifferstadt has decided to install a cold local heating network. The network is operated by Stadtwerke Schifferstadt and has been in operation since January 2017. The ground serves as the heat source here. For this purpose, probes were inserted in a central borehole field and connected to a ring mains network. A water-glycol mixture circulates in this network, absorbing the heat from the ground with its constant year-round temperatures of ten to twelve degrees Celsius. The absorbed energy is transported to the buildings via the ring mains. There, heat pumps ensure that energy from the network reaches the desired temperature level.
In summer, the principle can be reversed and the living spaces can be cooled economically and ecologically. The absorbed heat is returned to the ground through the pipes, thus enabling the borehole heat exchanger field to be regenerated at the same time.
Utilization of industrial waste heat in the market town of Meitingen
For the low-temperature network in a new development area in the Bavarian market town of Meitingen, all the waste heat from a neighboring industrial company is used. SGL Carbon GmbH provides the industrial waste heat free of charge to the approximately 125 residential units in the form of hot water at a temperature of around 31 °C. The heat is then used to generate electricity. The high temperature level of the waste heat throughout the year allows the heat pumps to operate very effectively.
The water comes from the cooling of the products, whose manufacturing processes require high temperatures of up to 3,000° C. The water is used to cool the products. To cool down the products manufactured in the process, cooling water is used, which heats up to about 30° C in the process. This cooling water now serves as a heat source for the heating systems in the new development area. Electricity from renewable sources can be used to operate the heat pumps at times when sufficient power is available. The heat is temporarily stored in a buffer tank.
The companies have voluntarily agreed to provide the warm cooling water free of charge for 20 years. Approximately 40 cubic meters per hour are fed into the local heat pipeline. This can produce up to 1.5 million kilowatt hours of energy per year, which is equivalent to the heating capacity of about 150,000 liters of heating oil.
The cooled water, which has less energy, is then returned to the plant and used again for cooling - the cycle starts all over again. (Source: KUMAS environmental network)
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About Andreas Kuehl
Content Manager, Online Marketing, Social Media, Building Energy, Energy Efficiency and Renewable Energy Expert specialising in climate-neutral buildings and neighbourhoods, tenant electricity, energy efficiency, renewable energies, energy storage and innovations for the comprehensive energy transition. Content specialist for companies in the field of energy transition, climate-neutral buildings and sustainability.