Geothermal Hydrogen Well Modelling

Abstract

A geothermal hydrogen well is a potential renewable energy solution to utilise otherwise unused geothermal or hydrocarbon wells as a passive source of hydrogen. This solution uses thermoelectric generators (TEG) to produce high current, low voltage electricity in situ. The electrical current is also used in situ to produce hydrogen through electrolysis of water. The solution is circulated in a coaxial borehole heat exchanger (CBHE) with the electrolyser situated in the annulus. This circulating fluid is necessary for electrolysis but also removes unwanted heat from the TEG and electrolyser. This work describes the developed solution and accompanying model in detail. A one-dimensional ordinary differential equation is used to simulate the heat transfer from the reservoir through the TEG, electrolysis and CBHE sections, predicting power and hydrogen production along the length of the well. An optimisation is performed to maximise hydrogen production rate while minimising parasitic pump and cooling tower power.