“…In relation to the internal surface area of EAHE, the annual unit heat was −35.9 kWh/m 2 , −36.3 kWh/m 2 , −35.5 kWh/m 2 , −35.1 kWh/m 2 and −34.9 kWh/m 2 .Simulation study for Swedish conditions[24] with a 10 m long polyethylene pipe of 20 cm diameter, buried at 2 m resulted in the estimated annual energy saving at 525 kWh and 300 kWh for heating and cooling season, respectively. It means the average gain per unit surface area of EAHE at 83.6 kWh/m 2 and 47.8 kWh/m 2 .Łuczak et al[92] analysed various configurations of EAHE of EAHE connected with an air conditioning system in Polish conditions using the Rehau company program for the selection of ground heat exchangers. Unit heat gain per internal surface area of EAHE during the heating period (from 1 September to 31 March) was 40.7 kWh/m 2 , 35.2, kWh/m 2 , 34.2 kWh/m 2 , 34.1 kWh/m 2 for the Tichelmanns' system (200 mm diameter, 1330 m and 182 m long), for the meandering system (315 mm diameter and 120 m long) and for the ring system ((315 mm diameter and 120 m long), respectively.…”