Figure 7.
The image shows a vertical dot and line chart with year on the vertical axis from 0 to 50 and eight parameters on the horizontal axis: electricity price, heat pump S P F, unitary price of heat real 2024, annual heat availability from G H E in gigawatt hours per year, tunnel lining capital expenditure, duration of construction, heat pump capital expenditure, and maintenance cost. For each parameter, a green point marks the optimistic value and a red point marks the pessimistic value, connected by a vertical black line. A horizontal dotted line at about 23 years indicates the base value, which aligns closely with several parameters, including duration of construction and maintenance cost. The widest uncertainty range appears for the electricity price, spanning roughly 18 to 46 years, while uncertainty narrows progressively across the remaining parameters.Sensitivity analysis of the impact of various inputs on payback time. GHE, ground heat exchanger