Geothermal wellhead technology power plants in grid electricity generation : a review

Geothermal energy has a significant role to play in the global transition to renewable and low-carbon energy systems because of its ability to supply steady and flexible electricity particularly for baseload demand because of its cost competitiveness compared to fossil fuel energy options. However, geothermal faces a challenge of long project development times with conventional power plant taking an average of 5-10 years and with high risks associated with drilling of unproductive wells which discourage private investment and quick deployment. Although geothermal energy has a huge potential for power generation, it currently contributes less than 1% of global electricity generation capacity. The generation capacity grew from 8.7 GWe in 2005 to 15.61 GWe at the end of the year 2020, representing average annual growth of 4.01%. The overall objective of this study was to determine the potential, features and application of wellhead power plants in electricity generation both to complement and substitute central powerplants. It was established that wellhead power plants can be used on temporary basis during the project development or permanently as grid connected or off grid generation facilities. With current technology, wellhead generators of up to 15 MW capacity can be installed on well pads of production wells for temporary or permanent electricity supply. Wellhead generators can facilitate optimum resource utilization especially for wells with unique conditions like too high or too low pressure and temperature compared to others in the same steam. They are generally inferior to central power plants due to lack of economies of scale hence higher unit cost of power. Successful adoption of wellhead powerplants for faster electrifications calls for state support and incentives in terms of subsidies, development of electricity gid, attractive feed in tariffs and tax incentives without which they won't compete favorably against the conventional central powerplants. Generally, wellhead powerplants can make geothermal electricity projects more feasible with reduced barriers in investment and early electricity and revenue generation for investors. However, investment on temporary basis makes reasonable economic sense if the time between drilling the first productive well and completion of a central plant is more than one year. Incentives like high feed in tariffs and tax incentives may be necessary to make them competitive against the superior conventional powerplants.