What is a geothermal gradient and how does it influence geothermal power feasibility?

• A. Geothermal gradient is the rate of temperature decrease with depth; lower gradients help viability.
• B. Geothermal gradient is the rate of temperature increase with depth; higher gradients make geothermal power more economically viable at shallower depths.
• C. Geothermal gradient is the pressure gradient in rock; gradient has no effect on feasibility.
• D. Geothermal gradient is the humidity gradient; it determines water availability.

Answer: (B)

Geothermal gradient is the rate at which rock temperature increases with depth. When this gradient is higher, you reach useful temperatures at shallower depths, which lowers drilling and completion costs and makes geothermal power more economically viable with available technologies (such as flash steam or binary-cycle plants). If the gradient is low, you must drill deeper to reach the same temperatures, raising capital costs and reducing feasibility. The temperature at depth dictates which power conversion method you can use and the overall project economics. The other options describe temperature decreasing with depth or refer to pressure or humidity gradients, which don’t determine geothermal feasibility in this context.