The application of Vacuum Insulated Tubing in Deep Borehole Heat Exchangers

Abstract

The world’s demand for energy is constantly increasing mainly due to population growth and improved living standards. Currently, the share of electricity generation is 37% of the global primary energy consumption. Fossil-based electricity production is accounted for 68% of the total generation with coal, the most carbon-intensive fossil fuel, being the largest contributor (41%) to the world’s electricity supply in 2012. Electricity demand is projected to grow rapidly and is also expected to be 70% higher in 2035, than the current demand. The Polish energy sector is heavily dependent on coal, resulting in large $CO_2$ emission per capita. Poland has considerable potential for geothermal energy production, as there is a large number of deep, abandoned wells that might be utilized for geothermal energy production. Utilizing these resources would contribute to the $CO_2$ emission reduction without negative impact on security of energy supply. Following paper describes method of reconstructing negative or abandoned oil and gas wells for Deep Borehole Heat Exchangers (DBHE). In many old boreholes, exploiting underground geothermal waters is impossible, thus adaptation for DBHE is sometimes the only option to utilize geothermal heat reservoirs. The insulated coaxial inner column which enables the circulation of heat carrier plays the crucial role in effective functioning of DBHE systems. Vacuum Insulated Tubing (VIT) can improve heat production as well as increase efficient energy use. This technique found plethora of applications in offshore and onshore deep drilling and production. Throughout recent years, VIT technology is being more commonly applied in geothermal industry. Negative or abandoned wells could be reconstructed for DBHE. To maximize the heat uptake from such boreholes, it is advised to use inner column made from material with lowest possible thermal conductivity coefficient. Article deals with possible application of vacuum pipes as inner column in deep coaxial borehole heat exchangers.