Mobile Phone towers or microwave towers require continues power supply from 500 watts to 2000 watts depending on the system capacity. This would mean consumption of energy between 14 to 48 KWH energy consumption per day in different cases.
More than 30% of these towers are in the locations with no electricity or bad quality electricity with frequent power cuts.
The present solution has been to use diesel generators for these off-grid areas. However the running cost is extremely high i.e. between Rs. 400,000 (USD 8500) to Rs. 700,000 (USD 15000) per year on fuel cost alone.
In remote areas like mountains & islands where diesel has to be carried by trucks, boats & even helicopters, the cost of carriage is more than the cost of fuel as mentioned above.
The telecom companies, the railways microwave system are all trying to convert to Solar & Wind power for these remote locations. However neither wind power nor solar power are constantly available whereas telecom power requirement is constant. This leads to a special hybrid system known as Wind – Solar – Mains – Battery - Diesel intelligent hybrid. For details continue reading.
Generally the wind speed profile through the year is bell shaped where during January and February it is lowest, it keeps on rising from February onwards, goes to maximum during June, July, August & September and again starts going down after October. An optimum wind solar hybrid design uses the average output of wind solar hybrid system during May to October by which the system sizing can be kept at a lower capacity as compared to a design which uses the lowest output during the year. If the lowest output is used for designing, during the peak season the energy output will be much more than that is required and excess energy will be wasted.
For providing the balance energy during the lean months that is when the generation is low, a mains supply or diesel generator is operated for very short duration to recharge the battery bank very quickly by a micro processor based master controller which automatically starts and stops the generator for feeding exact amount of energy needed.
The master controller consists of wind charge controllers and solar charge controllers and computes the energy fed to the battery after factoring in the charging efficiency of the battery.
It also monitors energy output from the battery and thereby keeps a track of balance energy remaining inside battery. In case of low generation during off seasons and also in case of low wind and solar generation during some days, the battery delivers the balance power and its energy level falls. The master controller tracks this and connects with the mains electricity grid at a pre-determined low battery state of charge level. If the mains grid power is not available at that time, it will change over to the diesel generator starter and start the diesel generator. The master controller has a intelligent control battery charger which will convert the AC input from the mains or diesel generator and charge the battery with DC in about 3 to 4 hours. Once the required energy is fed into the battery it will command the AC mains to be disconnected or diesel generator to stop.
During quick charging, there may be a sharp increase in battery voltage. If this high voltage is not acceptable to the load, for example a telecom load etc, the output to the load is taken through a voltage regulator which keeps the DC power supply within the acceptable voltage band for the load.
With the help of this master controller, wind solar diesel intelligent hybrid power plants can be sized optimally keeping the investment low and they also help in delivering guaranteed energy output everyday which is not possible with normal solar or wind power plants. The diesel generator or mains supply operation is well controlled for using maximum power at maximum efficiency for a short duration, thereby keeping the diesel generator running time less and fuel costs low.
The bio fuel can also be used in place of diesel. For more details on Biomass, benefits and types of Biomass visit biomass.net