HOW TO USE SOLAR ENERGY TO POWER BASE STATIONS

This article explicitly explains how to harness solar energy to power base stations which is a better solution and a comparison of of solar energy technology and other forms of energies.
using solar energy to power base stations

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Article Content

•    Introduction
•    Background
•    GSM BTS and UTMS Node B
•    BTS Site Daily Load Usage Calculation
•    Solar Power System Component Specification
•    Solar Power Sizing calculations for BTS site
•    Diesel Electricity Generator System Setup and Running Cost Estimate
•    Public Mains Power System Setup and Running Cost Estimate
•    Comparative Analysis of Results
•    Conclusion and Recommendations

See Also: How to Integrate Photo Voltaic Solar Systems As an Alternative Energy Source

See Also: How to Implement Control Systems

Introduction

•    Nigeria’s quest for sustainable and efficient power supply is the main issue debilitating the economy of the country apart from its overdependence on crude oil and it has risen to a critical point.

•    Very high cost of running diesel electricity generators.


•    Hence the analysis of solar power, challenges and cost of its operation was carried for telecommunication BTS site in Port Harcourt Nigeria as case study.


•    Field data collection was carried out to ascertain the average load size of a telecommunication BTS in Port Harcourt Nigeria and proper computation of the solar sizing.


•    This could reduce telecom operator’s OPEX, and is a green, efficient source of electrical power.

Background

•    Nigeria has average sunshine hours of about 6.5 hours across the federation.

•    During the day it is estimated that Nigeria receives about 4.851x10¹² kWh of energy from the sun.


•    All this energy is equivalent to about 1.082 million tons of oil per day.


•    Electricity outage is one of the main challenges confronting the industrial sectors of the Nigeria’s economy.


•    The ubiquitous Base Station Sites (BSS) all over have poised so many researchers to proffer alternative solutions in terms of cost to its power supply.


•    Results from such BSS with standalone systems based on a fuel generator were high compared to those powered with the Renewable Energy Supply (RES) systems (only solar) in terms of their CAPEX.

GSM BTS and UMTS Node B

•    GSM uses a series of radio transmitters called BTSs to connect the mobiles to a cellular network. They are entrusted with function of channel coding/decoding and encryption/decryption.

•    The Base Transceiver Station (BTS) is generally referred to as the transceivers and antennas that are utilized by every cellular network.


•    A cell site can be positioned in any direction or divided into typically three cellular directions.


•    The Base Transceiver Station is located in the middle of a cell.


•    BTS which comprise of signal encoding, encrypting, multiplexing, modulating, and supplying the radio frequency signals to the antenna, voice via full- or half-rate services.


The figure below shows GSM BTS/UMTS NODE B site components with power rating.

The GSM BTS/UMTS NODE B site components with power rating
The GSM BTS/UMTS NODE B site components with power rating
•    Generator: This is a 15KVA diesel powered soundproof electricity generator that supplies 220V alternating current to the ATS.

•    ATS:    This is short for automatic transfer switch. It switches the generator on or off at the appropriate time as programmed by the engineer.


•    Batteries: The batteries are housed and cooled in a separate cabinet. There are 24 1000AH batteries of 2V each (12 up and 12 down) making 48V DC.


•    Rectifier: This coverts AC (alternating current) to DC (direct current).  It supplies the DC to the BTS. There are 6 50A rectifier modules in the cabinet.


•    BTS: The BTS cabinets have breakers where Radios, BBU, RSU etc. are connected to source their power.

Typical ZTE 3G BTS cabinet

Below is a labelled diagram of ZTE 3G BTS cabinet.


Typical labelled diagram of a ZTE 3G BTS cabinet

Typical labelled diagram of a ZTE 3G BTS cabinet
The table in the figure below shows the descriptions of various parts of a typical ZTE 3G-BTS cabinet.


The descriptions of various parts of a typical ZTE 3G-BTS cabinet

The descriptions of various parts of a typical ZTE 3G-BTS cabinet

BTS Site Daily Load Calculation

The table in the figure below shows the Electrolux ETE24005c 420L, Units, Power Rating (W), Total Power Rating (W), Average Daily Usage (h), Average Daily Energy Used (Whr) for Base Transceiver Station Cabinets, Transmission Cabinet and LED bulb.

BTS Site Daily Load Calculation

BTS Site Daily Load Calculation
Average energy consumption of equipment used in the BTS Case Study Site Kilo-Watt-Hours    = 86640/1000 = 86.640kWh.

Solar Power System Component Specification

•    Solar Module: The PV modules used here is a DM SOLAR 300W 48V of module Size 156mm ×156mm, PV Dimension 1580mm ×808mm × 36mm Cell counts 4×9, weight 12Kg made up of single crystal cell.

•    Solar Charge Controller/Regulator: The voltage obtained from the PV module is used to charge the battery via a solar charge controller. Hence, a 20A-48V Tracer MPPT Solar Charge Regulator is selected to prevent damage to the battery either by overcharging or discharging it.


•    Inverter:    The inverter converts D.C Voltage to AC Voltage for powering domestic appliances like television sets, audio/video players, lighting systems, electric fans etc.

 
•    The source upon which an inverter will run is a 12V/200AH lead acid deep cycle battery, capable of supplying very high currents due to its very low internal resistance.

•    The power need of the flat is 86640Watt load, so choice of an inverter that has at least 3610Watts continuous power rating is accepted. A 4KVA 12V Inverter is ideal.

Solar Power Sizing calculations for BTS site

The next four figure below contains the various BTS site solar power sizing calculations such as the Number of solar panel modules needed, adjusted daily Watt-hour, etc.


Solar Power Sizing calculations for BTS site
Solar Power Sizing calculations for BTS site
Solar Power Sizing calculations for BTS site
Solar Power Sizing calculations for BTS site

Diesel Electricity Generator System Setup and Running Cost Estimate

From the research it is known that servicing a 20KVA, 16KW diesel generator by local mechanics cost about N3000/month. For the duration of 12months (365 days) of used, the amount spent on the 16KW diesel generator will be:

•    Cost of Servicing in 12months = ₦5000/month x 12months = ₦60, 000.00


•    Cost of one Perkins soundproof 20KVA diesel generator = ₦1,840,200


•    Miscellaneous maintenance = ₦3000


•    Cost of diesel fuel price = ₦160.00 for 1litre


•    Consumption of diesel fuel for 16KW in a day = 60 litres


•    Consumption of diesel fuel for 16KW in 1hr = 2.5 litres


•    Cost of operating the 16KW diesel generator for 1hr = ₦400.00 Cost of operating the 16KW       diesel generator for one day i.e 24 hours of operation  = ₦400 per hour x 24 hour = ₦9,600/day.


•    Therefore, for the period of one year (365 days),

The total consumption of petrol: =  ₦9600/day x 365 days = ₦ 3,504,000.00

•    Hence, the total cost of running a 16KW Generator

= 3,504,000 + 60,000 + 1,840,200 + 3000  = ₦ 5,407,200.00 

Public Mains Power System Setup and Running Cost Estimate

The table in the figure below shows the components, number of items, cost of items and total of public mains power system setup.


Public Mains Power System Setup and Running Cost Estimate

Public Mains Power System Setup and Running Cost Estimate
•    BTS AC total Average wattage usage = 86640Whr

•    Diversity factor = 40% of the AC Average loads = 40/100 x 86640/1 = 34656Whr


•    Total watt-hour of load not in use = 34656Whr


•    Total watt hour of load in use = 86640 – 34656 = 51984Whr


•    Since, NEPA measures loads consumptions in KW


•    1kw = 1000w


•    Thus 51984Whr = 51984KWh/1000 = 51.984kwh


•    For an industrial building value  = ₦26.42


•    The amount PHCN will charge 51.984kwh in 24hrs = 51.984 x26.42 = ₦1,373.42/day


•    For the period of 12months (365 days) will be  = 1,373.42/dayx365 days = ₦ 501,297.31

Comparative Analysis of Results

The table in the figure below shows a Solar Powered inverter system cost estimate including the number of items, unit cost of items and total cost.

Solar Powered inverter system cost estimate

Solar Powered inverter system cost estimate

Summary of Results

The figure below shows the BTS\NodeB Site Power consumption Opex (₦)
BTS\NodeB Site Power consumption Opex

BTS\NodeB Site Power consumption Opex

Power Sizing Analysis Using Microsoft Basic Software 

The figure below shows a sample of power sizing analysis using Microsoft Basic software.


A sample of power sizing analysis using Microsoft Basic software

A sample of power sizing analysis using Microsoft Basic software

Conclusion

•    To power telecommunications BTS sites, from the result summary table the best option remains public mains power supply (PHED).

•    However the best alternative from this study is the solar panel system.


•    The diesel electricity generators wasteful and inefficient, and is clearly a major factor increasing OPEX.

Recommendations

•    A hybrid system of either a combination of solar and public mains or for remote sites solar and diesel generators is recommended to strike some economic balance.

•    Standard laboratories and facilities should be established in Nigeria since needed raw materials are readily accessible for the manufacture of photo-voltaic cells for solar panels and its location favours the testing and its use.


•    Producing these cells will definitely minimise the cost and the availability of these modules.


•     The government should increase the funding allocated to the energy sector in the country, so that other kinds of power generation like solar can be fully harnessed.


•    Productive research for the utilization of Photovoltaic science in Nigeria, by integrating it into our existing grid system, should be made to assist in improving energy supply.



By: Tobechukwu Obiefuna
MTN Nigeria 
Email: tobyobiefuna@gmail.com 
OR tobecho@mtnnigeria.net

Click the link to download the PDF copy of  this article for free: HOW TO USE SOLAR ENERGY TO POWER BASE STATIONS

See Also: How to Integrate Photo Voltaic Solar Systems As an Alternative Energy Source

See Also: How to Implement Control Systems

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