Power Supply Systems for Remote, Unmanned Microwave Repeater Stations in Greenland

Since 1972 the Greenland Telecom Service has been operating a 1500 km microwave radiolink from Cape Farewell to the Diskobay area on the westcoast of Greenland. This link system incorporates 25 unmanned, rather inaccessible repeater stations on mountain sites at heights from 100 to 1500 meters above sea level. The supply of such stations with the necessary electric power has created many problems both with respect to choosing the most reliable and economic equipment and with respect to keeping the running- and maintenance costs as low as possible. Our paper presents a number of the solutions tried out in Greenland and our conclusions concerning the usefullness of different solutions under different conditions of climate and accessability. Our paper touches upon the use of thermoelectric generators heated by propane-gas, windgenerators, photoelectric solar panels, and dieselgenerators in different working configurations together with primary and storage batteries for buffer- and emergency supply purposes. The batteries are air-depolarized alcaline and lithium batteries as well as lead-acid and nickel-cadmium accumulators. The main conclusion is that it has proved possible - also under severe weather conditions and very low outdoor temperatures to work specially reinforced windgenerators with lead-acid accumulators as buffer batteries and with alcaline primary batteries as an emergency supply and to do it with high reliability. The paper stresses the need to add a state of the art supervisory- and control system to the combined power supply system to keep down the failure rate and the maintenance costs of the whole system.