Evaluation of the Viability of Solar and Wind Power System Hybridization for Safaricom Off-grid Gsm Base Station Sites

Abstract

To enable people in remote marginalized areas, communicate with the rest of the world, it has been increasingly important for the telecommunication network providers to install transmitting base stations in these regions. The study focused on the use of a hybrid system consisting of diesel generator, the solar panels and wind turbine generator. Diesel generators provides energy all the time, whereas PV and wind are dependent on of solar radiation and wind speed, respectively. Load demand and renewable resources (wind speeds and solar radiation) are the major problems that face power generation using hybrid systems. The major concern therefore is the accurate choice of system components that economically satisfy the load demand. The study looked at Safaricom Limited. Safaricom Limited formed in May 2000 as a joint venture between Telkom Kenya and Vodafone UK. It enjoys countrywide network coverage of over 80% of the Kenyan population estimated at 46 million people in the 2016 UNESCO population estimate; it provides voice and data services that include GPRS, EDGE, HSPDA and WiMAX. Safaricom has about 2,500 base stations with a mix of 2G, 3G, 4G and WiMAX technologies, most of which are powered the grid with diesel generator as back up. However, 10% of the sites are solely on diesel-powered generators on a 24-hour basis. Additionally, 3% of the BTS are on renewable energy hybrid system. This research sought to evaluate the viability of solar, wind and diesel generator energy sources that are used to power typical remote off grid GSM base stations. The objectives of the study were to establish the Return on Investment (ROI) and Total Cost of Ownership (TCO) for the various hybrid configurations, find out the main hindrance to the deployment of alternative energy solutions by operators, assess the environmental impact in deploying the different alternative sources of energy, establish the regulations and standards in place for benchmarking various alternative energy technologies and establish the key players in the provision of renewable energy technologies in the telecommunications sector in Kenya. Hybrid systems seek to reduce operation, maintenance and logistics cost by minimizing diesel runtime and consumption of fuel. To achieve this, the generator only runs when the batteries reach a preset discharge level to recharge the battery and supply excess load. The study employed both quantitative and qualitative methods for data acquisition. The evaluation of the viability of solar and wind hybridization of Safaricom off-grid GSM base station site was carried out in Sekanani, Masai Mara, Narok County in Kenya. ix HOMER was used to optimize the various energy options in the study. For optimal hybrid system and determination of the proper electrical power supply that meets the required load demand at the lowest possible cost several simulations were done. The diesel engine at the site would consume between 2.02 litres per hour and 5.5 litres per hour. The Perkins Engine 400 series at the site has the capacity to consume up to 10.4 litres per hour, on maximum load. It is apparent that the engine is not put to maximum capacity, possibly due to the existence of the other sources of renewable energy. Total annual energy demand is therefore the energy to run the BTS and its auxiliaries and the energy to have the batteries fully charged. The main power requirement annually is 17.5 MWh. The total energy produced annually from the photovoltaic panels is 20.83 MWh, this is the value given by HOMER for the region of study. The total energy produced from the diesel generator set for the year was 5.38MWh. The month of December contributed the highest from the diesel generator set at 519KWh. However, in this month the speed of wind recorded was high and it was expected that there would be low use of diesel generator. The total hybrid energy produced at Sekanani therefore was the energy from wind, solar and diesel engine. This translates to (Solar panels 20.83 MWh + Wind turbine 11.55 MWh + Diesel Engine 5.38 MWh) = Total 37.76 MWh against the net requirement of the BTS and the storage batteries annual demand of 17.50MWh. The amount of energy generated from green sources in the hybrid per annum is 32.38 MWh which is adequate to satisfy the BTS and its accessories demand which is 17.50 MWh. The diesel generator is just supplementing the energy demand by only 5.38 MWh annually. Amount of excess energy 37.75-17.50MWh = 20.26MWh annually. An indication of overcapacity. It is worth noting that even though the initial installation cost of the hybrid system is higher than the installation of a diesel engine, in the long run the cost of operating a hybrid system is lower than the cost of running a diesel system. The operating cost of a hybrid system of PV, wind and diesel is three times lower than a diesel engine system. On economic terms the Net Present Costs (NPC) of various combinations from HOMER simulations were found to be as follows: -Genset and ancillaries NPC/kWh is $21.8/MWh -Solar PV and Wind Turbine Hybrid and ancillaries NPC/kWh is $8.24/MWh - Solar PV and Wind Turbine and Genset Hybrid and ancillaries NPC/kWh is $6.89/MWh Therefore, the hybrid architect with the least net present cost is the triplet one that combines all the three sources of energy.