"Standing column wells can be used as highly eficient ground heat exchangers in geothermal heat pump systems@ where hydrological and geological conditions are suitable. A numerical model ofgroundwaterflow and heat transfer in and around standing column wells has been developed. This model has been used in aparametric study to identih the most significant design parameters and their effect on well performance. For each case in the study@ performance has been evaluated in terms of minimum and maximum annual temperatures and design well depth. Energy consumption and annual costs have also been calculated. Groundwater ""bled"" from the system is one of the most sign$cantparameters a system designer can use to improve wellperformance for a given load. The efects of bleed rate@ well depth@ and rock properties on heat transfer and energy consumption are discussed."