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Smart Solutions: Green energy storage systems for telecom sites

October 31, 2012
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Nilakantha Rath, Director, Business Development, Telecom Site Solution, Delta Power Solutions (India)

The telecom tower segment has witnessed significant growth in the past few years. The tower base has more than doubled from 160,000 in 2008 to about 392,000 currently. The number of base transceiver stations (BTSs) has increased from 236,000 to 735,000 during the same period. As a result, the energy needs and requirements of the tower industry have increased significantly. However, the scenario of grid access and availability for these sites continues to be dismal. Of the 22 telecom circles in the country, only 13 have grid power availability for more than 15 hours. Faced with erratic and unreliable grid power supply, the telecom tower industry has adopted several energy storage solutions for powering sites.

While diesel generator (DG) sets have been the preferred option for reducing  dependence on the grid, the resultant carbon dioxide emissions and increasing costs of diesel have become a major area of concern. The Indian telecom industry consumes around 2 billion litres of diesel every year for tower operations and every litre of diesel emits about 2.7 kg of carbon dioxide. Therefore, the total annual carbon dioxide emissions from the telecom industry stand at about 6 million tonnes.

The need of the hour is to follow a strategy to reduce and ultimately eliminate DG use at telecom sites. This includes exploring an energy efficient storage mechanism, designing intelligent site-specific solutions and optimisation of resources.

Energy storage solutions

Currently available energy storage solutions include advanced valve-regulated lead-acid (VRLA) batteries, fuel cells and lithium ion batteries.

Significant cost savings can be achieved by using advanced VRLA batteries. This solution can reduce DG operation hours by around 12 hours at an off-grid site and by 8 hours at a site with poor grid availability, thereby resulting in 60 per cent and 52 per cent cost savings respectively. The solution brings maximum cost savings (about 80 per cent) at a solar hybrid site where DG set use can be fully eliminated and towers can be operated through a battery, solar energy and grid electricity.

Such a solution can result in annual opex savings of Rs 290,000 to Rs 460,000, and a carbon dioxide emission reduction of 13-21 tonnes per outdoor BTS site. Other assumptions include an average load of 1,200 W, a DG set capacity of 15 kVA, solar power generation at 2 kW and a diesel cost of Rs 45 per litre. Using an advanced VRLA battery along with other conventional energy solutions at an off-grid site could result in annual opex savings of Rs 440,000 and a carbon dioxide emission reduction of over 60 per cent (20 tonnes). For a poor grid site, a company would be able to achieve yearly opex savings of Rs 290,000 by employing this solution. Carbon dioxide emission at such a site would be reduced by over 70 per cent (13 tonnes). Finally, for a solar hybrid site, an advanced VRLA battery can result in opex savings of Rs 460,000 per year. Since it is assumed that such a site would ultimately remove the need for a DG set, carbon dioxide emission reduction of almost 100 per cent can be achieved.

Fuel cell, another energy storage solution, results in the complete elimination of DG sets from a site. At such a site, an advanced VRLA battery is used for primary backup while a fuel cell is used for providing extended backup. Such a solution is appropriate for sites located in the vicinity of a hydrogen source. Further, sites with erratic and discontinuous grid availability and those having ground-based towers can also deploy fuel cell solutions for energy storage. However, it is an expensive solution as the per unit cost is around Rs 24. This includes both fuel and logistics costs.

The use of lithium ion battery can also result in the complete elimination of a DG set from a site. These battery solutions are generally used for cyclic applications, while a VRLA battery provides extended backup for exigencies. Such a solution is suited for sites with poor and erratic grid supply. It is also suitable for both ground-based tower and rooftop sites.

Further, a lithium ion battery has several advantages over one using VRLA technology. The former provides higher energy densities (almost three times) and a longer cyclic life (almost three times) as compared to the latter.  It is a highly cost-effective solution; involves lower space and maintenance requirements; provides improved performance; and offers higher reliability. Further, there is no memory effect and the discharge capacity does not reduce on each charge/discharge cycle.  Also, a lithium ion battery is usually lighter than other rechargeable batteries of a similar size. A battery management system is used to monitor the battery charge/discharge arrangement.

Going forward, the Indian telecom industry is expected to witness higher tenancies with limited greenfield roll-outs. The telecom tower base will increase to 490,000 by 2016, while the BTS base would grow to 1.16 million. However, going by the current grid availability scenario, tower companies will increasingly deploy energy storage solutions to operate towers. The use of site monitoring and control systems to monitor tower sites in real time will gain importance with the deployment of these solutions.

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