Investigation of a ground-cooled organic Rankine cycle for waste heat recovery

Abstract

This paper investigates a ground-cooled organic Rankine cycle (ORC) for waste heat recovery from a diesel generator. The ambient and ground temperatures used in the current study are based on real-time data collected from experimental measurements. ANSYS Mechanical APDL was used to simulate the effect of the proposed system on the ground in order to calculate the soil thermal interference radius. In addition, the simulation study compared two scenarios: with and without phase change material. Based on the simulation results, the required ground loop size was calculated using the Engineering Equation Solver (EES). The economic feasibility of the proposed system was investigated, considering both basic and regenerative ORCs. The original rated output power of the diesel generator considered in this study was 30 kW. The results showed that the soil thermal interference radius and the ground loop length were 0.32 m and 1480 m, respectively. The ORC system, with a design operating temperature of 300 °C, enhanced the overall output power by 7.98%, compared to that of diesel generator alone. Replacement of the basic ORC with a regenerative ORC increased the enhancement up to 15.31%. The capital cost and payback period ranges for the basic ORC were £11,945–18,770 and 4.9–7.8 years, respectively, while those for the regenerative ORC are £17,062–25,592 and 3.7–5.5 years.

Keywords

• Shallow geothermal energy
• Ground-cooled
• Organic Rankine cycle
• Power generation
• Waste heat recovery
• Economic analysis