Peak shaving potential using a novel flexible two-stage heat pump for heating and cooling

Mokarram, Narges Hassani (2025) Peak shaving potential using a novel flexible two-stage heat pump for heating and cooling. PhD thesis, University of Glasgow.

Abstract

Developing net-zero emission buildings is crucial, as the building sector is responsible for significant global energy consumption and greenhouse gas emissions. Governors have set a carbon-neutral target for 2050, mandating that all new constructions achieve net-zero emissions. This study introduces a thermal energy storage system integrated with a two-stage heat pump in a novel configuration, as heat pumps are considered a viable alternative to gas boilers.

The innovative, flexible two-stage heat pump has been analysed and compared with a baseline two-stage heat pump, as well as with both flexible and baseline single-stage heat pumps, under the same operating conditions. A control strategy was formulated based on heating duty, time of day, and storage tank status to enable the system to function in four different modes: 1) Normal operation, 2) Charging, 3) Discharging, and 4) Standby (Off). The weather data for heating systems in Glasgow and Birmingham, UK, were utilised to obtain variable hourly heating loads for a typical four-story residential building through IESVE software. A sinusoidal daily heating load profile was created to investigate the effect of heating load shape, maintaining the same maximum duty as the variable load derived from IESVE software. All proposed flexible cycles are named 1st configuration - config. 1, and the second flexible cycle in each model is named second configuration - config. 2.

Results indicate that the flexible two-stage system exhibits a 1.67% higher seasonal coefficient of performance (SCOP) with real variable loads and a 5.31% increase with sinusoidal loads. Furthermore, while the maximum price cut achieved was 2.1% with sinusoidal loads, the price reduction for real variable loads was less significant.

Additionally, this thesis introduces and thoroughly examines the novel configuration of the flexible two-stage heat pump system for cooling applications. Under identical operating conditions as far as possible, a baseline two-stage heat pump, a comparable flexible single-stage heat pump, and a second configuration of a flexible two-stage heat pump were compared and analysed alongside the newly proposed flexible two-stage heat pump. A control strategy was established to operate the system in four modes, normal operation, charging, discharging, and standby, based on cooling duty, time of day, and the status of storage tanks. Weather data for London/UK, and Rome/Italy, were used to acquire variable hourly cooling loads for a typical four-story residential building via IESVE software. The findings show that the flexible two-stage and single-stage systems achieved SCOP equal to 2.33% and 2.55% higher, respectively. Additionally, the heat pump demonstrated a higher SCOP and better flexibility in milder weather conditions, such as those in London, compared to Rome. Overall, the newly proposed system in this study shows superior performance compared to other similar heat pump systems.

In the third phase of this thesis, a techno-economic analysis was conducted on the two-stage flexible heat pump. An Al-extruded tube micro-channel evaporator and a corresponding condenser were designed for this system. The techno-economic analysis included calculating various economic parameters to assess the system's feasibility. Results indicate the system's economic viability, supported by calculated metrics such as Annual Profit (AP), Net Present Value (NPV), Period Payback (PP), Internal Rate of Return (IRR), and Multiple on Invested Capital (MOIC). The Al-extruded tube micro-channel heat exchangers achieved heat transfer rates of 106.28 kW for condenser and 76.34 kW for evaporator, with overall heat transfer coefficients of 1,790.8 W/m²K and 1,011.8 W.m-2.K-1, respectively. The system demonstrates economic feasibility, with an NPV of £177,903, an IRR of 16.4%, and a payback period of 7.8 years. The total capital investment for 40 flats amounts to £163,880, yielding a MOIC of 2.08.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > T Technology (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Supervisor's Name: Yu, Professor Zhibin and Lu, Dr. Yiji
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85448
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 16 Sep 2025 12:46
• Last Modified: 16 Sep 2025 13:40
• Thesis DOI: 10.5525/gla.thesis.85448
• URI: https://theses.gla.ac.uk/id/eprint/85448

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