|
| Parameter definition | Variable | Value | Remark/reference |
|
| Battery life (years) | | 5 | [22, 23] |
| Inverter-charger life (years) | | 10 | Typical [24] |
| Solar PV module life (years) | | 25 | Typical warranty period [25–27] |
| Battery round-trip efficiency (initial), % | | 85% | [22] |
| Battery round-trip efficiency in year , % | | — | Computed for various years (9) |
| Battery depth of discharge, % | | 70% | Authors’ assumption |
| Days of autonomy | | 1 | Authors’ assumption |
| Annual degradation rate of battery round-trip efficiency, % | | 1% | [22] |
| Efficiency of inverter-charging system (initial), % | | 90% | Assumed based on 80% average loading [28] |
| Efficiency of inverter-charging system in year , % | | — | Computed for various years (10) |
| Combined efficiency of power conversion and storage system (initial), % | | 72% | Computed for year 1 (12) |
| Combined efficiency of power conversion and storage system in year (%) | | — | Computed for various years (8) |
| Annual degradation rate of inverter-charging system efficiency (initial), % | | 1% | Authors’ assumption |
| Total annual energy supplied by utility grid in year , kWh | | — | Computed (14) |
| Total annual energy requirement from grid (preinstallation), kWh | | 7200 | Based on monthly consumption of 600 kWh |
| Total annual energy requirement by load, kWh | | — | Computed based on (1) |
| Daily energy requirements of load, kWh | | — | Computed |
| Average annual power demand, kW | | — | Computed based on (4) |
| Annual load (i.e., energy) directly supplied from grid, kWh | | — | Computed (3) |
| Annual energy supplied to load from battery system, kWh | | — | Computed (2) |
| Annual energy input to battery system in year , kWh | | — | Computed for various years (6) |
| Cost of electricity from grid, /kWh | | 0.18 | Table [20] |
| Economic life of investment, years | | 5 | Based on assumed battery life |
| Unit installed cost of battery, /kWh | | 250 | Market prices in Ghana [29] and from [22] |
| Capacity of battery, kWh | | 28.18 | Computed (19) |
| Unit installed cost of inverter and charging system, /kW | | 700 | Market data in Ghana [29] |
| Capacity of inverter, kW | | 0.51 | Computed based on (20) and (26) |
| Discount rate, % | | 5% | Authors’ assumption (tested for sensitivity) |
| Annual grid downtimes, as proportion of total yearly hours (8760 hours), % | | 50% | Based on published load-shedding schedule [14] |
| Proportion of regular load (kW) powered when grid is off, % | | 50% | Authors’ assumption |
| Proportion of annual load supplied through battery-inverter system | | — | Computed based on (17) |
| Salvage value, | | — | Computed (22), (27), and (28) |
| Peak sunshine hours, h/day | PSH | 4.5 | Typical for Ghana [30] |
| Array derating factor | | 80% | Authors’ assumption |
| Array size, kW | | — | Computed (23) |
| PV module cost, /kW | | 2000 | Typical values for Ghana [29] |
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