The Green Base Station

In times of steadily increasing energy costs and with the vanishing resources of the classic, non-regenerative energy sources, we see the challenge of finding new solutions for the uninterruptable power supply of mobile radio base stations (BTS). A growing environmental consciousness and the demand for reduction of the emission of greenhouse gases like CO2 increase the motivation to develop alternative power supply concepts. The paper introduces a concept: how to feed a BTS with all known suitable power supply technologies, including PEM fuel cell, wind power, photovoltaic power and high-efficiency-power conversion technology. The application of these building blocks can be adapted individually to the local environmental conditions and requirements. These technologies also offer the possibility to build up mobile radio base stations in locations that are miles away from the public mains grid (off-grid). The Green Base Station which is introduced is equipped with the regenerative energy sources wind power and photo-voltaic energy to reduce the power consumption taken out of the public grid to a minimum, whenever sunlight or wind is present. During operation times when wind power and solar energy are not sufficient to feed the BTS, additional energy is taken out of the public mains grid. High-efficiency rectifier modules convert the mains AC to a 48V DC voltage for the radio equipment. High-efficiency technology reduces losses of the AC/DC and DC/DC power conversion to a minimum and also contributes to the reduction of the requested air conditioning power. A Free-Cooling air conditioning system reduces the energy consumption of the base station additionally, in comparison to traditional solutions. If all of the mentioned power sources fail or cannot provide the total requested power of the BTS equipment, an additionally installed PEM fuel cell starts up automatically. The PEM fuel cell is able to provide long backup times with minimal space demand and low weight. The fuel cell does not produce hazardous emissions and acoustic noise like traditional diesel generators. Only a small backup battery is used during the start-up time of the fuel cell. Thus, the amount of lead is reduced to a minimum in the Green Base Station. Depending on the system configuration, it is even possible to completely avoid the usage of lead acid batteries. The pros and cons of the Green Base Station concept will be presented and evaluated, as well as chances and challenges stated. The technology for a Green Base Station is already available, but costs and reliability are two of the most important challenges to solve before the Green Base Station can become a widespread reality.