A Pre-Feasibility Study for Energy Recovery from Geothermal Prospects in Scotland

Abstract

An appraisal of geothermal prospects across Scotland has been undertaken by Sinclair Knight Merz (SKM). This appraisal has led to a concept study for the potential design, build and operation of a geothermal technology demonstration project in North East Scotland. The assessment of prospects has indicated that the Cairngorm Granite Suite (Petrothermal/Engineered Geothermal System) and Midland Valley (Hydrothermal/Hot Sedimentary Aquifer) have the best potential for energy recovery. A stored heat assessment indicates recoverable reserves of 7,000 PJth and 4,800 PJth respectively. In the Cairngorm Granites, resource temperatures are estimated to be 135 °C at 5 km depth. In the Midland valley, temperatures are estimated to be 100 °C at 4 km depth. These prospects are considered as Inferred Resources due to the absence of offset well data to target depth. The temperatures are low compared to other geothermal project developments. A project concept of two production wells, two injection wells and electricity generation from an Organic Rankine Cycle Plant was analysed, with well productivity based on analogous systems. This concept is estimated to produce 1.6 MWe (gross), 740 kWe (net) of electrical power. Financial analysis indicates a levelised cost of £875/MWh which is not economically feasible compared to alternative forms of renewable generation. A sensitivity analysis offered a comparison of how levelised costs may be impacted by a change in well configuration, temperature increase, or reduced capital costs. SKM’s technical and financial analysis of a conceptual geothermal project in Scotland suggests that at this stage such a project would rely heavily on government subsidies in order to become a commercial power generation plant. Given this, SKM recommends that the conceptual project is more suited to technology demonstration rather than ‘fully commercial’ project development. This would serve to demonstrate the transfer of knowledge and engineering skills that exist in Scotland.