Experience with 5GDHC (anergy) networks in practice
A large number of 5GDHC networks have already been successfully built and are in operation. Numerous experiences have been made, which are described in brief on this page, e.g. what problems and difficulties arose during implementation?
Are 5GDHC networks a proven technology?
It is estimated that around 100 5GDHC networks are in operation or being implemented in Germany. On nPro you will find a list of 5GDHC networks in Germany and worldwide. In addition, about 25 5GDHC networks are in operation in Switzerland. This means that experience already exists in the implementation and for the operation of 5GDHC networks, even if it is not yet very widespread. The key figures and feedback from the 5GDHC networks already in operation is predominantly positive. This is especially true for proven applications such as small to medium-sized new-build neighborhoods. Newly built neighborhoods are by far the most common application. There is also a great deal of experience in the development of geothermal probe fields as a heat source for 5GDHC networks. Recently, near-surface, horizontally installed geothermal collectors have also been used more and more. 5GDHC networks for existing neighborhoods are not yet widespread, but this is likely to change in the future as geothermal is one of the most important renewable heat sources. Overall, 5GDHC for new districts can be described as proven and tested. Nevertheless, by far not every planning office has experience in the construction of 5GDHC grids. For the conceptual design and planning of 5GDHC grids, planning offices should therefore be commissioned that have experience with this type of heating network.
What is the political experience and what is the acceptance of the technology?
Comprehensive studies on the acceptance of 5GDHC networks are still lacking, but initial statements can be made: In principle, a renewable heat supply is important to building owners (especially in newly built neighborhoods). A move away from fossil fuels is generally welcomed, especially because fossil fuels are subject to unpredictable price fluctuations. This applies to natural gas, heating oil as well as wood pellets or wood chips. With environmental heat and local renewable energy sources, this dependence is reduced to the price of electricity. Operating costs are eliminated to a large extent and increased investments are incurred only at the beginning. In the construction of 5GDHC networks, the combination of geothermal energy and photovoltaic systems is therefore often sensible and also economical. Geothermal probes reliably supply heat for 25 years and more, and the decentralized building heat pumps can be operated in part with low-cost in-house electricity from the building's own PV system. Overall, this increases the degree of self-sufficiency of the individual building and the entire neighborhood. Skepticism among building owners is sometimes evident due to dependence on only one heat supplier (heat grid operator). In a certain way, this operator has a monopoly on the heat supply in the neighborhood. This skepticism should be countered with transparent and long-term supply contracts: Price escalator clauses can often facilitate the estimation of future heat prices, e.g., if the heat price is presented as a function of the electricity price. For 5GDHC, the major advantage is that the initial investment is a large part of the total cost: The investments can usually be well estimated and therefore largely stable heat prices can also be guaranteed over long time horizons. This is not the case for conventional heating networks with a central natural gas firing system, since natural gas costs represent a significant share of subsequent operating costs and the price of natural gas is difficult to predict. In some neighborhoods, property owners are also required to connect to the 5GDHC network. This can make sense, as it reduces costs for all property owners if everyone participates. Nevertheless, in many cases, mandatory connection is considered politically sensitive and is avoided.
Are 5GDHC networks better than normal heating networks?
Whether a 5GDHC network or a conventional (hot) heating network is more suitable depends entirely on the district. In many cases, there are no major differences in economic efficiency, at least these cannot be generalized. An important influencing factor is the heat source to be used. If no hot heat source can be considered (solar thermal, waste heat from industry, etc.) and environmental heat (geothermal, ambient air) is used, 5GDHC networks are often advantageous. For the use of environmental heat, 5GDHC networks have some important advantages compared to normal heating networks. Especially in areas with low heat density (i.e., low heat demand per area), such as construction areas with single-family homes, 5GDHC networks can therefore be particularly advantageous. In urban areas with high heat demand density (apartment blocks with older construction year, etc.) and a suitable central heat source, hot heat networks may be more suitable. The central advantage of 5GDHC is that both heat in winter and cold in summer can be provided without the additional cold supply causing significant additional costs. For this reason, 5GDHC networks are increasingly interesting for urban areas as well, since here the heat periods are particularly increasing and are even more noticeable than in rural areas. In addition, there is a lack of alternatives for air conditioning, unless noise-emitting, decentralized air conditioning units in windows are an accepted option. To examine the economic viability of 5GDHC or conventional heating networks, concept studies or feasibility studies are usually carried out, which can also be publicly funded. These studies examine which supply concept is best suited for the respective neighborhood from a technical and economic point of view and also which subsidies can be used.
What should be considered for heat pumps in buildings?
An important aspect is the ownership of the decentralized heat pumps in the buildings. There are two possibilities here: Either the grid operator takes over the investment in the heat pumps and settles with the building owner for the delivered heat (at the condenser of the heat pump, building side), or the building owner procures the heat pump and pays for the delivered low-temperature heat at the evaporator of the heat pump. Both options have advantages and disadvantages. From a funding perspective, it often makes sense for the grid operator to cover the cost of the heat pumps, as they can then be funded through appropriate incentive programs (Federal Funding for Efficient Heat Networks (BEW)). If the heat pumps are owned by the heat network operator, it is important from the network operator's point of view to implement good monitoring of the decentralized heat pumps, i.e. to centrally monitor power consumption and operating states. The building owner - if he only has to pay for the supplied heat - has no vested interest in ensuring proper and efficient operation of the heat pump. In the worst case, significant malfunctions can occur in the heat pump, which remain undetected and unrepaired for a long time. The heat network operator must then expect higher operating costs (electricity costs). If the heat pumps are the responsibility of the building owner and he only pays for low-temperature heat (cold water), he also has an economic interest in ensuring optimal operation of the heat pump. In many cases, the decentralized heat pumps are initially purchased by the heat network operator and then become the property of the building owner after a certain period of time (e.g. 10 years).
Hydraulics and design of the heating network
For 5GDHC networks, the hydraulic design can be a particular challenge. In many cases, no central circulation pumps are used, but decentralized pumps in the individual buildings. These decentralized pumps supply the volume flow required by the heat pump in the building from the network to the building. Care must be taken here to ensure that the decentralized building pumps have sufficient power to be able to draw sufficiently large volumes of cold water from the energy center, which is sometimes further away. If this is not the case, the electric auxiliary heating in the heat pumps may operate, which has a strong negative impact on the efficiency of the heat pump. Alternatively, central pumps can be used. These should have frequency-controlled drives so that their delivery rate can be controlled. In this case, control (similar to conventional heating networks) takes place via measurement at the point in the network that is hydraulically furthest away from the energy center.
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