Operations Optimization of Heat Substations

Heat substations can be operated significantly more efficiently through demand-driven sizing, variable-speed high-efficiency pumps, comprehensive thermal insulation and consistent flue gas condensation — achieving efficiency improvements of 5 to 15 percentage points and disproportionate reductions in pump electricity costs. On the consumer side, short-term heating interruptions of 15 to 20 minutes enable a reduction of connection capacity by 15 to 20% without noticeably affecting comfort.

Efficiency-Oriented Plant Design

Demand-Driven Sizing

The heat generation capacity must match the actual demand. Oversizing leads to high standby losses, frequent cycling and inefficient part-load operation. The consequences are lower annual utilization rates and increased wear on burners and control components. The basis for any sizing is a precise load profile analysis that captures both the peak load case and typical part-load behavior.

Modular Design and Phased Expansion

A modular design with cascade arrangement of multiple smaller generators offers decisive advantages over a single large boiler:

• Each generator operates closer to its optimal operating point
• At low demand, only a few modules are in operation — standby losses decrease
• Individual modules can be shut down for maintenance without interrupting the supply

Where network expansion is planned, generation should be expanded in phases. This means: Install only the capacity currently needed and add further modules as demand increases. Oversizing for future expansion stages ties up capital and causes unnecessary losses in the interim.

Pumps and Hydraulics

Circulation pumps have a significant influence on the operating costs of a heating network. Modern high-efficiency pumps with variable-speed EC motors and differential pressure control automatically adjust their output to the momentary demand. The relationship between speed and power consumption follows the cubic affinity law — a speed reduction to 80 % lowers power consumption to approximately 51 %. In part-load operation, which dominates for the majority of the year, electricity consumption drops considerably.

Hydraulic Optimization

In addition to pump selection, the hydraulic design of the plant is critical:

• Careful pipe routing with as few directional changes as possible
• Generously sized fittings with low pressure loss coefficients
• Avoidance of unnecessary bends, tee junctions and cross-section reductions
• Short pipe runs between generator, storage tank and network feed-in point

Every avoided pressure loss in the plant reduces the required pump head and thus the annual pump electricity consumption.

Thermal Insulation and Loss Minimization

Comprehensive thermal insulation of all pipelines, fittings, pump housings and storage surfaces within the plant is essential. Even small uninsulated areas — flange connections, shut-off valves, vent valves — cause significant losses over an operating year. A single uninsulated DN 100 flange can release over 500 kWh per year to the surroundings.

Regulations and Standards

The insulation must meet at least the requirements of the MuKEn (Model Regulations of the Cantons in the Energy Sector) or the cantonal energy ordinances. In practice, execution above the minimum requirements is recommended, as the additional cost for thicker insulation is low compared to the saved heat losses.

Standby and Idle Losses

Boilers and storage tanks lose heat even when idle. An optimized control strategy — for example, deliberately shutting down unneeded generators and reducing storage temperature during low-load periods — effectively minimizes these losses.

Waste Heat Recovery

Flue Gas Condensation

Utilizing the latent heat in the flue gas is state of the art for wood-fired and gas boilers. The prerequisite is low return temperatures — for natural gas, the return temperature must be below approximately 55 °C for flue gas condensation to occur. For wood-fired boilers, additional measures against condensate corrosion and dust separation are required. The achievable efficiency improvement is 5 to 15 percentage points depending on the installation.

Internal Waste Heat Sources

In many heat substations, internal waste heat sources arise that frequently remain unused:

• Cooling systems for electrical cabinets and power electronics
• Compressor waste heat from compressed air systems
• Transformer losses

These sources can be integrated into the return line or into preheating via heat exchangers.

Return Line Utilization and Storage Stratification

Optimal temperature stratification in buffer storage tanks is critical: hot water at the top, cold water at the bottom. Well-stratified storage tanks make it possible to feed the return into the storage at the lowest temperature level, thereby maximizing the efficiency of heat pumps, solar thermal systems and condensing technology.

Control and Operations Management

Optimized Control Strategies

The control of the heat substation largely determines the annual utilization rate. Central objectives are:

• Reducing cycling losses: Frequent switching of boilers on and off reduces efficiency and increases wear. Modulating burners and an intelligent generator cascade avoid unnecessary cycling.
• Demand-driven supply temperature management: Weather-compensated control with night setback and seasonal adjustment.
• Optimizing storage management: Aligning charge and discharge cycles with the load profile.

Monitoring and Data Analysis

Continuous monitoring of key operational parameters — temperatures, volume flows, energy quantities, burner starts, operating hours — is a prerequisite for systematic operations optimization. Modern control systems capture this data automatically and enable:

• Early detection of malfunctions or unfavorable operating states
• Comparison of setpoint and actual values over extended periods
• Identification of efficiency losses due to aging or fouling

Load Management

Through the temporal shifting of generation and consumption, peak loads can be smoothed and generation shifted to more efficient operating points. Thermal storage tanks serve as buffers — they decouple the time of heat generation from the time of consumption.

Customer-Side Optimization

Peak Load Management in Buildings

A short-term heating interruption of 15 to 20 minutes during peak load periods significantly reduces the simultaneous load demand on the network. The thermal inertia of the buildings bridges this interruption without noticeable comfort loss. In commercial and residential buildings, a reduction of connection capacity by 15 to 20 % is achievable — with correspondingly smaller sizing of the network infrastructure.

Process Optimization in Industry

Industrial consumers offer particular optimization potential. A pinch analysis systematically determines the optimal waste heat recovery and identifies heat exchange opportunities between process streams. The principle of the process heat cascade utilizes heat at decreasing temperature levels: first high-temperature processes, then low-temperature applications, and finally space heating or preheating.

Optimal Domestic Hot Water Preparation

Instantaneous hot water stations (flow-through principle) are preferable to conventional storage tanks. They avoid storage losses, minimize the Legionella risk and enable significantly lower return temperatures — a key factor for the efficiency of the overall network.

Review Control Parameters

On the customer side, heating curves, setpoints and time programs should be regularly re-optimized. Experience shows that settings deteriorate over time — due to changes in use, refurbishments or simply manual interventions by users. An annual review by the network operator or a service partner ensures efficient operation on a permanent basis.

Sustainable Development

The gradual integration of renewable energy sources — solar thermal, heat pumps, biomass — is possible at any time with a modular plant design. Already during initial planning, the following aspects should be considered:

• Adequately sized connection points for future feed-in sources
• Flexible control systems capable of integrating additional generators and storage
• Space reserves in the plant for subsequent extensions

This preparation avoids costly retrofits and enables the economical decarbonization of the heating network in line with energy policy objectives.

Conclusion

Operations optimization is not a one-off project but a continuous process. The combination of demand-driven sizing, efficient pumps, comprehensive thermal insulation, consistent waste heat recovery and intelligent control unlocks significant efficiency potential — both on the generation and the consumption side. Software such as VICUS Districts enables the simulation of various operating scenarios and supports the identification of the optimal combination of measures before investment decisions are made.

Further reading: Heat Generation in Thermal Networks provides an overview of generation technologies and their application areas, Network Control covers the control engineering fundamentals of thermal networks, and Digital Twin and Monitoring describes the use of digital tools for data-driven operations optimization.

References and Standards

• VDI 2067 Part 1 — Economic Efficiency of Building Installations — Fundamentals and Cost Calculation
• Nussbaumer, T.; Thalmann, S.; Zaugg, D.; Cueni, M. (2025): Planungshandbuch Thermische Netze. Version 2.0, EnergieSchweiz / Bundesamt fuer Energie BFE.