Techno-economics of solar PV array-based hybrid systems for powering telecom towers

Abstract

An attempt has been made to evaluate the financial feasibility of hybrid power supply option during real-time grid power unavailability (continuous and intermittent) conditions and determine the optimal hybrid power supply configurations for outdoor telecom towers in India. As grid power availability is highly dependent on locations, a review of real-time hourly grid power supply availability for telecom towers at 36 locations in different parts of India has also been presented. Ten different locations across different climatic zones were analyzed, and it was found that duration and continuity (continuous and intermittent) of power outages considerably affect the LCOE of different configurations. So it is imperative that these factors be taken into account when determining the optimal hybrid power system. Solar PV-based hybrid power supply systems were found to have lower LCOE for all power outage conditions both in continuous as well as intermittent with their values in the range of Indian rupees (INR) 6.76–INR 26.32 (US $0.095–US $0.371) per kWh for the optimal cases (1 US$ =  INR 76.28 (As on April 27, 2020)). While solar PV with battery is found to be the least cost hybrid power supply options for the telecom towers located in areas with continuous grid power unavailability up to 4 h, a diesel generator also needs to be included for larger hours of continuous grid unavailability.

Appendices

Appendix 1: Monthly average daily values of global solar radiation and clearness index for different locations considered in the study

See Fig. 7.

Fig. 7

Monthly average daily values of global solar radiation and clearness index: a Hyderabad, b Bhopal, c Jaipur, d Vadodara, e Ambala, f Belgavi, g Pune, h Mohali, i Angul, j Varanasi

Appendix 2

$${\text{OUT}}_{{{\text{PV}}}} = {\text{RC}}_{{{\text{PV}}}} {\text{df}}_{{{\text{PV}}}} \left( {\frac{{R_{T} }}{{R_{{{\text{Tstc}}}} }}} \right)\left[ {1 + \gamma_{t} \left( {T_{{{\text{pv}}}} - T_{{\text{pv stc}}} } \right)} \right]$$

(3)

where ${\text{OUT}}_{{{\text{PV}}}}$ represents the output of PV array;${\text{RC}}_{{{\text{PV}}}}$ the rated capacity of the PV array (power output under standard test conditions (kW)); ${\text{df}}_{{{\text{PV}}}}$ the derating factor of PV array (%); $R_{T}$ the solar radiation incident on the PV array in the current time step (kW⁄m²); $R_{{{\text{Tstc}}}}$ the incident radiation at standard test conditions (1 kW/m²); ${\gamma }_{t}$ the temperature coefficient of power (%/C);$T_{{{\text{pv}}}}$ the PV cell temperature in the current time step (°C); and ${T}_{pv stc}$ the standard PV cell temperature in the current time step (25 °C).

$${\text{EFF}}_{{{\text{dg}}}} = \left( {\frac{{3.6 {\text{DG}}_{{{\text{ele}}}} }}{{{\text{AD SG}}_{d} {\text{LHV}}_{{{\text{fuel}}}} }}} \right)$$

(4)

where ${\text{Eff}}_{{{\text{dg}}}}$ represents the average annual average efficiency of DG; ${\text{DG}}_{{{\text{ele}}}}$ the total annual electrical production (kWh/year) of DG; ${\text{AD}}$ the annual amount of diesel consumption (Liter/year) by DG; ${\text{SG}}_{{\text{d}}}$ the specific gravity of diesel and ${\text{LHV}}_{{{\text{fuel}}}}$ the lower heating value of the fuel (MJ/kg).

$$A_{{{\text{bat}}}} = \left( {\frac{{N_{b} V_{{{\text{nom}}}} C_{{{\text{nom}}}} \left( {1 - \frac{{{\text{SOC}}_{m} }}{100}} \right)\left( {24 h|{\text{d}}} \right)}}{{L_{{{\text{Avg}}}} \left( {1000 {\text{Wh}}|{\text{kWh}}} \right)}}} \right)$$

(5)

where $A_{{{\text{bat}}}}$ represents the autonomy (hours) of battery bank; $N_{b}$ the number of batteries in the storage bank; $V_{{{\text{nom}}}}$ the nominal voltage of a single battery (V); $C_{{{\text{nom}}}}$ the nominal capacity of a single battery (Ah); ${\text{SOC}}_{m}$ the minimum state of charge of the battery bank (%); and $L_{{{\text{Avg}}}}$ the average telecom load (kWh ⁄day).

Appendix 3: Net present cost of different constituents of each power supply configuration analyzed

See Figs. 8, 9, 10, 11.

Fig. 8

Net present cost of different constituents of “grid, PV and battery” power supply configuration at different hours of power unavailability under (a) continuous and (b) intermittent mode

Fig. 9

Net present cost of different constituents of “grid, PV, DG and battery” power supply configuration at different hours of power unavailability under (a) continuous and (b) intermittent mode

Fig. 10

Net present cost of different constituents of “grid with battery” power supply configuration at different hours of power unavailability under (a) continuous and (b) intermittent mode

Fig. 11

Net present cost of different constituents of “grid, DG and battery” power supply configuration at different hours of power unavailability under (a) continuous and (b) intermittent mode