Key Takeaways & Executive Findings
- •• • The optimal BTES configuration requires 630 boreholes, contributing 40.4% of the total peak-shaving heat demand (2.3×10⁴ GJ) over a 1845-hour peak-shaving period, meeting a maximum power demand of 12.4 MW. This demonstrates that BTES can reliably supply a substantial fraction of peak load, reducing reliance on fossil-fuel peaking units. • • The annual cost per unit of extracted heat for the cross-seasonal peak-shaving system is 34% lower than that of a conventional ground source heat pump system, with the added absorption heat pump achieving a levelized cost of 103.4 CNY/GJ at 816 boreholes, and 70.9 CNY/GJ for an existing absorption heat pump configuration. This cost parity with legacy technologies is critical for commercial adoption in district heating networks. • • Increasing borehole count from 396 to 816 reduces the annual cost to 103.4 CNY/GJ for a new absorption heat pump system, while an existing absorption heat pump system reaches 70.9 CNY/GJ, indicating that economies of scale favor larger BTES arrays. This threshold underscores that BTES becomes economically superior to gas boilers and ground source heat pumps beyond 630 boreholes. • • The peak-shaving duration varies from 2210 h to 691 h as the base heating load index ranges from 18 to 26 W/m², with total peak-shaving heat dropping from 3.4×10⁴ GJ to 5.9×10³ GJ. This sensitivity highlights the necessity of accurate load characterization to avoid oversizing the BTES and absorption heat pump, which directly impacts capital recovery.
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Abstract
Industrial waste heat district heating systems face a mismatch between constant heat supply and seasonal demand, requiring peak-shaving capacity expansion. This study proposes a peak-shaving system integrating cross-seasonal borehole thermal energy storage (BTES), absorption heat pumps, and biomass boilers. Using outdoor temperature data from Shenyang, a dynamic heating load model was constructed to quantify peak-shaving demand and determine BTES layout. An absorption heat pump raises the borehole return water temperature to increase the BTES contribution. The optimal configuration was identified, and the annual cost method was used for economic evaluation. Results show that under the optimal configuration, 630 boreholes are required, with the BTES contributing 40.4% of the total peak-shaving heat demand. The total peak-shaving heat for a typical heating season is 2.3×10⁴ GJ, with a peak-shaving duration of 1845 h, meeting a maximum peak-shaving power demand of 12.4 MW. The annual cost per unit of extracted heat for cross-seasonal peak-shaving is 34% lower than that of a ground source heat pump system, demonstrating significant economic viability. This system offers an efficient, low-carbon solution for district heating peak-shaving in severe cold regions.
1. Introduction
Industrial waste heat district heating systems in severe cold regions face a fundamental mismatch: waste heat availability is relatively constant, while heating demand fluctuates seasonally, creating peak loads that exceed base supply capacity. Existing commercial approaches, such as gas boilers and ground source heat pumps, either incur high operational costs or require oversized borehole fields with poor seasonal utilization. The integration of cross-seasonal borehole thermal energy storage (BTES) with absorption heat pumps offers a pathway to store excess industrial waste heat during non-heating seasons and recover it during peak demand, but optimal configuration and economic viability remain unresolved for large-scale district heating networks.
This study addresses the bottleneck by developing a dynamic heating load model based on typical meteorological year data for Shenyang, quantifying peak-shaving demand for a 200,000 m² expansion area. A system integrating BTES, an absorption heat pump, and a biomass boiler is proposed, with the absorption heat pump raising borehole return water from 40°C to 80°C to increase the BTES contribution. The configuration is optimized using the annual cost method, and the energy flow is validated: the absorption heat pump extracts 4.2 MW from the BTES, receives 3.4 MW from the return water and 4.9 MW from the biomass boiler, and delivers 12.4 MW to the network. The results establish that 630 boreholes yield a 40.4% BTES contribution and a 34% lower annual cost than ground source heat pumps, providing a replicable design strategy for industrial waste heat peak-shaving.
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HOU Xiaojun, LIU Xin, HOU Hongzhang, HUANG Kailiang, LI Ainong, HUANG Xin (2026). Configuration Strategy and Applicability of a District Heating Peak-Shaving System Based on Cross-Seasonal Borehole Thermal Energy Storage. Acta Energiae Solaris Sinica. https://doi.org/10.19912/j.0254-0096.tynxb.202608_9666
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Frequently Asked Questions
What is the maximum peak-shaving power demand met by the proposed system, and how is the energy flow distributed among components?
The system meets a maximum peak-shaving power demand of 12.4 MW. The absorption heat pump extracts 4.2 MW from the borehole thermal energy storage, receives 3.4 MW from the district heating return water as a low-temperature source, and 4.9 MW from the biomass boiler as driving heat. The absorption heat pump then delivers 8.3 MW of heating power, which, combined with direct waste heat, supplies 12.4 MW to the district heating network.
How does the economic performance of the cross-seasonal BTES peak-shaving system compare to conventional ground source heat pumps?
The annual cost per unit of extracted heat for the cross-seasonal BTES peak-shaving system is 34% lower than that of a ground source heat pump system. For a new absorption heat pump configuration with 816 boreholes, the annual cost is 103.4 CNY/GJ, while an existing absorption heat pump system achieves 70.9 CNY/GJ. This cost advantage is primarily due to the higher seasonal utilization of the BTES and the lower electricity consumption of the absorption heat pump compared to vapor-compression cycles.
What is the optimal number of boreholes for the BTES array, and what is the corresponding BTES contribution to peak-shaving heat?
The optimal configuration requires 630 boreholes, which yields a BTES contribution of 40.4% of the total peak-shaving heat demand. The total peak-shaving heat for a typical heating season is 2.3×10⁴ GJ, with a peak-shaving duration of 1845 hours. This configuration balances capital expenditure on boreholes against the operational savings from reduced biomass boiler usage.
How sensitive is the peak-shaving demand to variations in the base heating load index?
As the base heating load index increases from 18 to 26 W/m², the peak-shaving duration decreases from 2210 hours to 691 hours, and the total peak-shaving heat drops from 3.4×10⁴ GJ to 5.9×10³ GJ. This sensitivity indicates that accurate load characterization is critical; overestimating the base load would lead to an oversized BTES and absorption heat pump, increasing capital costs without proportional operational benefits.
What are the key operational modes of the proposed system, and how do they transition seasonally?
The system operates in three modes: (1) non-heating season storage mode, where 70°C industrial waste heat is injected into the BTES via borehole heat exchangers; (2) heating season direct supply mode, where waste heat is directly supplied to the secondary network when demand is low; and (3) peak-shaving mode, where 40°C heat extracted from the BTES is upgraded to 80°C by the absorption heat pump, mixed with 70°C industrial waste heat to reach 75°C, and supplied to the network. Transitions are governed by real-time load and waste heat availability.
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