The scenario aims to maximise the utilization of low‑emission electricity, enhance seasonal flexibility, and enable the system to respond optimally to volatile electricity‑market conditions. The PTES installation serves multiple strategic functions: it allows the system to absorb surplus thermal capacity during summer periods,
The PTES installation is combined with a 1.1 MWp PV plant mounted on top of it. This configuration allows direct power supply to the heat‑pump installation at the nearby sewage water treatment plant via a direct line connection, thereby avoiding network charges and increasing the economic efficiency of both the PV and heat‑pump systems. Scenario S2 - Fuel Mix Diversification The scenario extends the Reference scenario by adding a set of natural gas-fired boilers, whose primary function is to diversify the heat‑generation portfolio while maintaining low capital expenditure requirements. The strategic rationale behind this investment is to reduce the system’s exposure to volatility in pellet prices, which becomes increasingly relevant as biomass- fired capacity expands in earlier scenarios. Gas boilers, due to their compactness and modular design, offer considerable locational flexibility. Like natural gas engines in scenario W1, these units may be installed outside the main heat‑plant site, reducing distribution losses by producing heat closer to consumption nodes. There is no natural gas grid connection close to Radzionków heating plant (as of 2026) – so the same challenge here as in scenario S1. Overall, the scenario offers a moderate economic benefit with relatively low investment risk. This is a cost‑effective, operationally robust diversification strategy that enhances system reliability, limits exposure to biomass market volatility, and provides a flexible, dispatchable heat source that complements the low-emission technologies deployed under the Reference scenario. Scenario S2 - Fuel Mix Diversification Year Action 2026 no changes, 3 coal-fired boilers. 2030 heat pump 4 MWt, 3 coal-fired boilers converted to wood pellets. 2035 additional heat pump 2 MWt. 2040 increase the amount of burnt pellets to reach a 75% share of renewable heat; add 2x2,7 MWt of new gas boilers, diversifying the fuel mix.
reduces the consumption of other fuels during low‑demand months,
enables operational optimisation in response to variable electricity prices.
The co‑located PV array, directly connected to the heat pumps at the nearby sewage water treatment plant via a direct line connection, ensures that electricity can be supplied without incurring network charges, thereby improving the economic performance of both assets. In addition to PTES and PV, the scenario incorporates electric boilers as a low‑CAPEX, high‑flexibility technology capable of taking advantage of market opportunities such as zero or negative electricity prices. While electrode boilers are available commercially at capacities above 5 MWt, the scale of the Radzionków heating plant implies the application of resistance boilers, which are more suitable for smaller installations. When integrated with PTES, these boilers provide a highly flexible and cost‑effective means of converting surplus electricity into stored thermal energy, significantly enhancing system responsiveness and enabling partial decarbonisation of peak‑load operation. Scenario S3 - Electrification and Flexibility Year Action 2026 No changes, 3 coal-fired boilers. 2030 Heat pump: 4 MWt; 3 coal-fired boilers converted to wood pellets. 2035 additional heat pump 2 MWt + e-boilers 2x2 MWt. 2036 PTES fully operational (charged for the first time in 2035) 2040 Increase the amount of burnt pellets to reach a 75% share of renewable heat; new gas boilers 2x2,7 MWt, diversifying the fuel mix.
2050
increase the amount of burnt pellets to reach 100% share of renewable heat (meeting EED requirements); decarbonize natural gas used in gas boilers.
2050
increased amount of burnt pellets to reach 100% share of renewable heat (meeting EED requirements).
Scenario S3 - Electrification and Flexibility The scenario S3 represents an advanced electrification pathway that expands upon the baseline investments of the Reference scenario by integrating additional electric boilers, a large‑scale PTES (Pit Thermal Energy Storage) system of approx. 175 × 100 m, and a 1.1 MWp photovoltaic installation positioned directly on top of PTES.
Recommendation for Roadmap The four scenarios presented show that it is possible to maintain heat prices broadly lower than individual air source heat pumps, preserving the competitiveness of district
26 HOTCOOL no.5 2026
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