A reliable transient heat transfer model is used to ascertain the effect of solar thermal energy storage on a geothermal system. The proposed closed loop system is comprised of a double pipe heat exchanger, and is supplied with solar thermal energy during the summer months. The numerical simulations are based on cases that are common in northern climates (e.g. Canada). A conduction-advection based model is used to simulate heat transfer in the ground and in the heat exchange pipes for both heat extraction and heat injection scenarios. The constant power configuration is employed to accurately assess the effects of injecting thermal energy into a geothermal resource. The mass flow rate through the heat exchanger and the solar energy input are varied during summer cycles to investigate the influence on the uptake of thermal energy into the geothermal resource. The effects of rate of heat extraction and injection on the techno-economic performance of geothermal energy production have been investigated. (C) 2015 Elsevier Ltd. All rights reserved.