Which of the following is a method that does NOT generate electricity directly?

Geothermal heating does not directly generate electricity; instead, it utilizes the heat from the Earth's interior for heating applications. This method can include heating buildings or supplying hot water for various uses. While geothermal energy can also be harnessed to produce electricity through geothermal power plants, in the context of the question, “geothermal heating” specifically refers to the use of geothermal energy primarily for heating purposes rather than for generating electrical power.

In contrast, hydroelectric generation involves the conversion of the energy of flowing or falling water into electricity, solar thermal generation captures sunlight to heat a fluid, which can then be used to produce steam that drives turbines for electricity generation, and wind generation harnesses the kinetic energy of wind to turn turbines directly into electrical energy. Each of these methods directly produces electricity through their respective conversion processes.