# State-of-Charge Effects on Standalone Solar-Storage Systems in Hot Climates: A Case Study in Saudi Arabia

^{*}

## Abstract

**:**

## 1. Introduction

^{2}), a considerable number of communities, villages, and rural areas are powered by diesel generators through an isolated grid given that connecting these remote locations to the main grid with transmission lines is prohibitively costly [1,2]. According to 2016 data, over 50 remote locations kingdom-wide were diesel-powered. In addition, nearly 19,000 homes were relying on on-site diesel generation for their energy needs as per the 2017 Saudi household energy survey. Some of these homes would obtain their diesel from gas stations, which means that they use (subsidized) diesel that is allocated for the transportation sector. Renewable technologies hold potential in providing energy for these remote locations cost effectively, and this includes solar photovoltaics (PV).

## 2. Review and Motivation

## 3. Methodology

#### 3.1. Financial Assumptions

#### 3.2. Load, Irradiation, and Temperature Profiles

#### 3.3. Technical Assumptions

#### 3.3.1. Overall System Assumptions

#### 3.3.2. PV Assumptions

#### 3.3.3. Battery Assumptions

^{−4}and 1.169, respectively. From Equation (1), an estimated throughput is derived via the Rainflow Counting Algorithm as detailed previously [50]. Note that the throughput is different from the calendar lifetime. The replacement of the battery will occur when the throughput or lifetime is reached, whichever comes first.

_{0,1,2}are the fitted parameters based on the data available, and T

_{c}is the temperature in degrees Celsius. Based on the provided data sheet, the fitted parameters were calculated as: δ

_{0}= 0.706, δ

_{1}= 0.0113, δ

_{2}= −6.3981 × 10

^{−5}.

_{1,2}are fitted parameters, and T

_{k}is the temperature in degrees kelvin. Based on the typical characteristics of lifetime of lead acid batteries versus temperature [51], μ

_{1}and μ

_{2}were calculated as 71,165.2 and 7234.3 respectively.

## 4. Results and Discussion

#### 4.1. Diurnal Load Results

#### 4.2. Nocturnal Load Results

## 5. Discussion and Policy Implications

#### 5.1. Nocturnal Load Results

#### 5.2. The Diesel Alternative

## 6. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## Disclaimer

## Appendix A

Appliance/Load | Quantity | AC Watts | Hours On per Day | Wh/Day |
---|---|---|---|---|

Coffee maker | 1 | 800 | 0.2 | 160 |

Microwave | 1 | 1300 | 0.15 | 195 |

Iron | 1 | 900 | 0.25 | 225 |

TV | 1 | 130 | 4 | 520 |

Dishwasher | 1 | 1500 | 0.4 | 600 |

Washing machine | 1 | 500 | 0.4 | 200 |

Vacuum cleaner | 1 | 700 | 0.25 | 175 |

Air conditioner (Room) | 1 | 1500 | 10 | 15,000 |

Ceiling fan (AC) | 2 | 50 | 5 | 500 |

Laptop | 1 | 50 | 3 | 150 |

Lights (25 W) | 8 | 25 | 6 | 1200 |

Refrigerator (22 ft^{3}) | 1 | 68 | 24 | 1632 |

Toaster | 1 | 1300 | 0.08 | 104 |

Blender | 1 | 300 | 0.08 | 24 |

Total | 20,685 |

## References

- Rehman, S.; Al-Hadhrami, L. Study of a solar pv-diesel-battery hybrid power system for a remotely located population near Rafha, Saudi Arabia. Energy
**2010**, 35, 4986–4995. [Google Scholar] [CrossRef] - Rehman, S.; El-Amin, I. Study of a solar pv/wind/diesel hybrid power system for a remotely located population near Arar, Saudi Arabia. Energy Explor. Exploit.
**2015**, 33, 591–620. [Google Scholar] [CrossRef] - Renewable Energy Network for the 21st Century (REN21). Renewable 2017 Global Status Report; REN21: Paris, France, 2017. [Google Scholar]
- Eckhouse, B. Battery Storage Still Needs Solar for Growth. Available online: https://www.bloomberg.com/news/articles/2017-09-21/-new-and-cool-battery-storage-still-leans-on-solar-for-growth (accessed on 16 November 2018).
- Ralon, P.; Taylor, M.; Ilas, A. Electricity Storage and Renewables: Cost and Markets to 2030; IRENA: Abu Dhabi, UAE, 2017. [Google Scholar]
- Curry, C. Lithium-Ion Battery Costs: Squeezed Margins and New Business Models. Available online: https://about.bnef.com/blog/lithium-ion-battery-costs-squeezed-margins-new-business-models/ (accessed on 16 November 2018).
- Soulopoulos, N. Cost Projections: Batteries, Vehicles, and TCO; Bloomberg New Energy Finance (BNEF): New York, NY, USA, 2018. [Google Scholar]
- Mandelli, S.; Barbieri, J.; Mereu, R.; Colombo, E. Off-grid systems for rural electrification in developing countries: Definitions, classification and a comprehensive literature review. Renew. Sustain. Energy Rev.
**2016**, 58, 1621–1646. [Google Scholar] [CrossRef] - Ahmad, G. Photovoltaic-powered rural zone family house in Egypt. Renew. Energy
**2002**, 26, 379–390. [Google Scholar] [CrossRef] - Bhuiyan, M.; Asgar, M.A. Sizing of a stand-alone photovoltaic power system at Dhaka. Renew. Energy
**2003**, 28, 929–938. [Google Scholar] [CrossRef] - Jordan, D.C.; Kurtz, S.R. Photovoltaic degradation rates—An analytical review. Prog. Photovolt. Res. Appl.
**2013**, 21, 12–29. [Google Scholar] [CrossRef] - Meydbray, J.; Dross, F. PV Module Reliability Scorecard Report 2016; DNVGL: Høvik, Norway, 2016; pp. 1–18. [Google Scholar]
- Topan, P.A.; Ramadan, M.N.; Fathoni, G.; Cahyadi, A.I.; Wahyunggoro, O. State of charge (soc) and state of health (soh) estimation on lithium polymer battery via kalman filter. In Proceedings of the 2016 2nd International Conference on Science and Technology-Computer (ICST), Yogyakarta, Indonesia, 27–28 October 2016; pp. 93–96. [Google Scholar]
- Alsaidan, I.; Khodaei, A.; Gao, W. Determination of optimal size and depth of discharge for battery energy storage in standalone microgrids. In Proceedings of the North American Power Symposium (NAPS), Denver, CO, USA, 18–20 September 2016; pp. 1–6. [Google Scholar]
- Vidal Faez, A.M.; Ruvalcaba Velarde, S.A. Feasibility Study of Photovoltaic Microgrids and Their Application in Powering Remote Onshore Oil and Gas Surface Instrumentation. In Proceedings of the SPE Saudi Arabia Section Annual Technical Symposium and Exhibition, Al-Khobar, Saudi Arabia, 21–23 April 2015. [Google Scholar]
- Kaabeche, A.; Ibtiouen, R. Techno-economic optimization of hybrid photovoltaic/wind/diesel/battery generation in a stand-alone power system. Sol. Energy
**2014**, 103, 171–182. [Google Scholar] [CrossRef] - Dufo-López, R.; Lujano-Rojas, J.M.; Bernal-Agustín, J.L. Comparison of different lead–acid battery lifetime prediction models for use in simulation of stand-alone photovoltaic systems. Appl. Energy
**2014**, 115, 242–253. [Google Scholar] [CrossRef] - Jossen, A.; Garche, J.; Sauer, D.U. Operation conditions of batteries in PV applications. Sol. Energy
**2004**, 76, 759–769. [Google Scholar] [CrossRef] - Rehman, S.; Alam, M.M.; Meyer, J.P.; Al-Hadhrami, L.M. Feasibility study of a wind–pv–diesel hybrid power system for a village. Renew. Energy
**2012**, 38, 258–268. [Google Scholar] [CrossRef] - Shaahid, S.; Al-Hadhrami, L.; Rahman, M. Review of economic assessment of hybrid photovoltaic-diesel-battery power systems for residential loads for different provinces of Saudi Arabia. Renew. Sustain. Energy Rev.
**2014**, 31, 174–181. [Google Scholar] [CrossRef] - Shaahid, S.; El-Amin, I. Techno-economic evaluation of off-grid hybrid photovoltaic–diesel–battery power systems for rural electrification in Saudi Arabia—A way forward for sustainable development. Renew. Sustain. Energy Rev.
**2009**, 13, 625–633. [Google Scholar] [CrossRef] - Shaahid, S.; Elhadidy, M. Economic analysis of hybrid photovoltaic–diesel–battery power systems for residential loads in hot regions—A step to clean future. Renew. Sustain. Energy Rev.
**2008**, 12, 488–503. [Google Scholar] [CrossRef] - Aslam, S.; Javaid, N.; Khan, F.; Alamri, A.; Almogren, A.; Abdul, W. Towards efficient energy management and power trading in a residential area via integrating a grid-connected microgrid. Sustainability
**2018**, 10, 1245. [Google Scholar] [CrossRef] - Baker, J. New technology and possible advances in energy storage. Energy Policy
**2008**, 36, 4368–4373. [Google Scholar] [CrossRef] - Bahramirad, S.; Reder, W.; Khodaei, A. Reliability-constrained optimal sizing of energy storage system in a microgrid. IEEE Trans. Smart Grid
**2012**, 3, 2056–2062. [Google Scholar] [CrossRef] - Ma, T.; Yang, H.; Lu, L. Feasibility study and economic analysis of pumped hydro storage and battery storage for a renewable energy powered island. Energy Convers. Manag.
**2014**, 79, 387–397. [Google Scholar] [CrossRef] - Li, X.; Chalvatzis, K.; Stephanides, P. Innovative Energy Islands: Life-Cycle Cost-Benefit Analysis for Battery Energy Storage. Sustainability
**2018**, 10, 3371. [Google Scholar] [CrossRef] - Dufo-López, R.; Bernal-Agustín, J.L. Techno-economic analysis of grid-connected battery storage. Energy Convers. Manag.
**2015**, 91, 394–404. [Google Scholar] [CrossRef] - Riaz, S.; Chapman, A.C.; Verbic, G. Comparing utility and residential battery storage for increasing flexibility of power systems. In Proceedings of the Power Engineering Conference (AUPEC), Wollongong, NSW, Australia, 27–30 September 2015; pp. 1–6. [Google Scholar]
- Yang, Y.; Ye, Q.; Tung, L.J.; Greenleaf, M.; Li, H. Integrated Size and Energy Management Design of Battery Storage to Enhance Grid Integration of Large-Scale PV Power Plants. IEEE Trans. Ind. Electron.
**2018**, 65, 394–402. [Google Scholar] [CrossRef] - Charfi, S.; Atieh, A.; Chaabene, M. Modeling and cost analysis for different PV/battery/diesel operating options driving a load in Tunisia, Jordan and KSA. Sustain. Cities Soc.
**2016**, 25, 49–56. [Google Scholar] [CrossRef] - Hossain, M.; Mekhilef, S.; Olatomiwa, L. Performance evaluation of a stand-alone PV-wind-diesel-battery hybrid system feasible for a large resort center in South China Sea, Malaysia. Sustain. Cities Soc.
**2017**, 28, 358–366. [Google Scholar] [CrossRef] - Eteiba, M.; Barakat, S.; Samy, M.; Wahba, W.I. Optimization of an off-grid PV/Biomass hybrid system with different battery technologies. Sustain. Cities Soc.
**2018**, 40, 713–727. [Google Scholar] [CrossRef] - Yahyaoui, I.; Yahyaoui, A.; Chaabene, M.; Tadeo, F. Energy management for a stand-alone photovoltaic-wind system suitable for rural electrification. Sustain. Cities Soc.
**2016**, 25, 90–101. [Google Scholar] [CrossRef] - Ardani, K.; O’Shaughnessy, E.; Fu, R.; McClurg, C.; Huneycutt, J.; Margolis, R. Installed Cost Benchmarks and Deployment Barriers for Residential Solar Photovoltaics with Energy Storage: Q1 2016; National Renewable Energy Laboratory (NREL): Golden, CO, USA, 2016.
- Lai, C.S.; McCulloch, M.D. Levelized cost of electricity for solar photovoltaic and electrical energy storage. Appl. Energy
**2017**, 190, 191–203. [Google Scholar] [CrossRef] - Pawel, I. The cost of storage—How to calculate the levelized cost of stored energy (LCOE) and applications to renewable energy generation. Energy Procedia
**2014**, 46, 68–77. [Google Scholar] [CrossRef] - Boovaragavan, V.; Methakar, R.N.; Ramadesigan, V.; Subramanian, V.R. A mathematical model of the lead-acid battery to address the effect of corrosion. J. Electrochem. Soc.
**2009**, 156, A854–A862. [Google Scholar] [CrossRef] - Jacob, A.S.; Banerjee, R.; Ghosh, P.C. Modelling and simulation of a PV battery grid backup system for various climatic zones of India. In Proceedings of the 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), Portland, OR, USA, 5–10 June 2016; pp. 1807–1812. [Google Scholar]
- Khasawneh, H.J.; Mondal, A.; Illindala, M.S.; Schenkman, B.L.; Borneo, D.R. Evaluation and sizing of energy storage systems for microgrids. In Proceedings of the 2015 IEEE/IAS 51st Industrial & Commercial Power Systems Technical Conference (I&CPS), Calgary, AB, Canada, 5–8 May 2015; pp. 1–8. [Google Scholar]
- Arun, P.; Banerjee, R.; Bandyopadhyay, S. Optimum sizing of photovoltaic battery systems incorporating uncertainty through design space approach. Sol. Energy
**2009**, 83, 1013–1025. [Google Scholar] [CrossRef] - Kaushika, N.; Gautam, N.K.; Kaushik, K. Simulation model for sizing of stand-alone solar PV system with interconnected array. Sol. Energy Mater. Sol. Cells
**2005**, 85, 499–519. [Google Scholar] [CrossRef] - Celik, A.; Muneer, T.; Clarke, P. Optimal sizing and life cycle assessment of residential photovoltaic energy systems with battery storage. Prog. Photovolt. Res. Appl.
**2008**, 16, 69–85. [Google Scholar] [CrossRef] - Kaldellis, J. Optimum technoeconomic energy autonomous photovoltaic solution for remote consumers throughout Greece. Energy Convers. Manag.
**2004**, 45, 2745–2760. [Google Scholar] [CrossRef] - Meunier, J.; Knittel, D.; Collet, P.; Sturtzer, G.; Carpentier, C.; Rocchia, G.; Wisse, J.; Helfter, M. Sizing of a photovoltaic system with battery storage: Influence of the load profile. In Proceedings of the International Conference CISBAT 2015 Future Buildings and Districts Sustainability from Nano to Urban Scale, Lausanne, Switzerland, 9–11 September 2015; pp. 711–716. [Google Scholar]
- Jülch, V. Comparison of electricity storage options using levelized cost of storage (LCOS) method. Appl. Energy
**2016**, 183, 1594–1606. [Google Scholar] [CrossRef] - Mundada, A.S.; Shah, K.K.; Pearce, J.M. Levelized cost of electricity for solar photovoltaic, battery and cogen hybrid systems. Renew. Sustain. Energy Rev.
**2016**, 57, 692–703. [Google Scholar] [CrossRef][Green Version] - Obi, M.; Jensen, S.; Ferris, J.B.; Bass, R.B. Calculation of levelized costs of electricity for various electrical energy storage systems. Renew. Sustain. Energy Rev.
**2017**, 67, 908–920. [Google Scholar] [CrossRef] - Belderbos, A.; Delarue, E.; Kessels, K.; D’haeseleer, W. Levelized cost of storage—Introducing novel metrics. Energy Econ.
**2017**, 67, 287–299. [Google Scholar] [CrossRef] - Manwell, J.F.; McGowan, J.G.; Abdulwahid, U.; Wu, K. Improvements to the Hybrid2 battery model. In Proceedings of the Windpower 2005 Conference, Denver, CO, USA, 17 May 2005. [Google Scholar]
- PowerThru. Lead Acid Battery Working—Lifetime Study. Available online: http://www.power-thru.com/documents/The%20Truth%20About%20Batteries%20-%20POWERTHRU%20White%20Paper.pdf (accessed on 1 December 2018).
- Feron, S.; Cordero, R.; Labbe, F. Rural electrification efforts based on off-grid photovoltaic systems in the Andean Region: Comparative assessment of their sustainability. Sustainability
**2017**, 9, 1825. [Google Scholar] [CrossRef] - Barman, M.; Mahapatra, S.; Palit, D.; Chaudhury, M.K. Performance and impact evaluation of solar home lighting systems on the rural livelihood in Assam, India. Energy Sustain. Dev.
**2017**, 38, 10–20. [Google Scholar] [CrossRef] - Upadhyay, T.P.; Shahi, C.; Leitch, M.; Pulkki, R. Economic feasibility of biomass gasification for power generation in three selected communities of northwestern Ontario, Canada. Energy Policy
**2012**, 44, 235–244. [Google Scholar] [CrossRef] - Schmidt, O.; Hawkes, A.; Gambhir, A.; Staffell, I. The future cost of electrical energy storage based on experience rates. Nat. Energy
**2017**, 2, 17110. [Google Scholar] [CrossRef] - Wang, Z.; Chen, B.; Wang, J.; Begovic, M.M.; Chen, C. Coordinated energy management of networked microgrids in distribution systems. IEEE Trans. Smart Grid
**2015**, 6, 45–53. [Google Scholar] [CrossRef] - Noel, L.; Brodie, J.F.; Kempton, W.; Archer, C.L.; Budischak, C. Cost minimization of generation, storage, and new loads, comparing costs with and without externalities. Appl. Energy
**2017**, 189, 110–121. [Google Scholar] [CrossRef][Green Version] - Buchman, A.; Lung, C. State of Charge and State of Health Estimation of Lithium-Ion Batteries. In Proceedings of the 2018 IEEE 24th International Symposium for Design and Technology in Electronic Packaging (SIITME), Iasi, Romania, 25–28 October 2018; pp. 382–385. [Google Scholar]

**Figure 1.**The average load profiles that will be considered for the analysis. Note the diurnal and nocturnal trends.

**Figure 2.**The average monthly temperatures in the city of Riyadh, Saudi Arabia. Note that for the purposes of the model, 8760 temperature data points were used for the year (not shown for brevity). Further, the bars show the maximum and minimum temperatures experienced.

**Figure 3.**The number of cycles of the battery versus the depth-of-discharge (DOD) (DOD = 1ߞstate of charge (SOC)) based on data provided by the manufacturer. Note that the lower the battery discharges, the shorter the lifetime is.

**Table 1.**Review of papers that designed photovoltaic-battery system (PVBs). The cell with ‘Yes’ are highlighted in gray.

Reference | Has the Paper Considered Temperature Effects on Battery Capacity? | Has the Paper Considered Temperature Effects on Lifetime, i.e., Calendar Life and Cyclical Degradation? | Has the Paper Considered Different MSOC Levels for Sizing Optimization? | Has the Paper Tested for Differed Load Profiles? | Was the System Fully Standalone, i.e., No Grid and No Diesel Generation? |
---|---|---|---|---|---|

[39] | Yes | Yes | No | No | No |

[9] | No | No | No | No | Yes |

[10] | Yes | No | No | No | Yes |

[40] | Yes | No | No | Yes | No |

[41] | No | No | No | No | Yes |

[42] | No | No | No | No | No |

[1] | No | No | No | No | No |

[43] | No | Yes | No | No | No |

[20] | No | No | No | No | No |

[21] | No | No | No | No | No |

[44] | No | No | No | No | Yes |

[15] | No | Yes | No | No | Yes |

[14] | No | No | Yes | No | No |

[45] | No | No | No | Yes | No |

This work | Yes | Yes | Yes | Yes | Yes |

Parameter | Value |
---|---|

Discounting rate | 5 percent |

Inflation rate | 2 percent |

System lifetime | 25 years |

Supply shortage | 0 percent |

Parameter | Value |
---|---|

CAPEX (excluding inverter) ($/W) | 1.8 $/W |

Inverter CAPEX | 0.2 $/W |

Module efficiency (%) | 16 percent |

Annual panel degradation (%) | 0.5 percent |

Temperature power loss coefficient (%/C) | 0.4%/°C |

Nominal operating cell temperature | 47 °C |

Maintenance costs ($/kW/year) | 10 $/kW/year |

Derating factor (including inverter losses) (%) | 85 percent |

Panel slope from the horizontal | 25° |

Azimuth degree from the north | 180° |

Solar irradiation | Hourly irradiation data for Riyadh |

Parameter | Value |
---|---|

Battery model | Trojan SIND 061225 (lead acid) |

Battery cost (including installation) | $2205 (300 $/kW h) |

Nominal voltage | 6 V |

Energy rating | 7.35 kW h |

Capacity (current rating) | 1225 Ah |

Bus voltage | 24 V |

Days of autonomy | 2 days |

Allowable throughput | 14,598 kW h (see text for details) |

Degradation limit | 20 percent |

Round trip efficiency | 85 percent |

Temperature effect on capacity | See text for details |

Temperature effect on calendar lifetime | See text for details |

**Table 5.**Optimum size of the PVB minimizing the net present cost (NPC) for a diurnal load profile based on different minimum allowable state of charge (MSOC) constraints. Any slight discrepancies are due to rounding.

Results Incorporating Temperature Effects | |||||||

MSOC (%) | PV Size (kW) | Total Number of Batteries in the Bank | Average Cost of Energy ($/kW h) | Net Present Cost ($) | Initial Capital ($) | Number of Battery Replacements | Total Number of Batteries Used throughout Project Lifetime |

20 | 6.7 | 8 | 0.435 | 69,985 | 31,025 | 3 | 32 |

30 | 8.0 | 8 | 0.453 | 72,898 | 33,566 | 3 | 32 |

40 | 9.9 | 8 | 0.480 | 77,315 | 37,529 | 3 | 32 |

50 | 7.1 | 16 | 0.728 | 117,287 | 49,499 | 2 | 48 |

60 | 9.4 | 20 | 0.908 | 146,165 | 62,913 | 2 | 60 |

70 | 10.8 | 108 * | 4.208 | 677,471 | 259,781 | 2 | 324 |

Results without Incorporating Temperature Effects | |||||||

MSOC (%) | PV Size (kW) | Total Number of Batteries in the Bank | Average Cost of Energy ($/kW h) | Net Present Cost ($) | Initial Capital ($) | Number of Battery Replacements | Total Number of Batteries Used throughout Project Lifetime |

20 | 6.2 | 8 | 0.244 | 39,306 | 29,961 | 1 | 16 |

30 | 6.9 | 8 | 0.254 | 40,928 | 31,421 | 1 | 16 |

40 | 8.5 | 8 | 0.277 | 44,549 | 34,682 | 1 | 16 |

50 | 11.7 | 8 | 0.321 | 51,655 | 41,082 | 1 | 16 |

60 | 6.6 | 20 | 0.488 | 78,637 | 57,225 | 1 | 40 |

70 | 13.9 | 20 | 0.590 | 94,992 | 71,954 | 1 | 40 |

**Table 6.**Optimum size of the PVB minimizing the NPC for a nocturnal load profile based on different SOC constraints. Any slight discrepancies are due to rounding.

Results Incorporating Temperature Effects | |||||||

MSOC (%) | PV Size (kW) | Total Number of Batteries in the Bank | Average Cost of Energy ($/kW h) | Net Present Cost ($) | Initial Capital ($) | Number of Battery Replacements | Total Number of Batteries Used throughout Project Lifetime |

20 | 6.8 | 12 | 0.615 | 99,044 | 40,023 | 3 | 48 |

30 | 7.2 | 12 | 0.622 | 100,192 | 40,880 | 3 | 48 |

40 | 6.9 | 16 | 0.751 | 120,992 | 49,061 | 3 | 64 |

50 | 7.8 | 20 | 0.906 | 145,879 | 59,631 | 3 | 80 |

60 | 10.2 | 28 * | 1.231 | 198,166 | 82,161 | 2 | 84 |

70 | 7.0 | 148 * | 5.653 | 910,114 | 340,321 | 2 | 444 |

Results without Incorporating Temperature Effects | |||||||

MSOC (%) | PV Size (kW) | Total Number of Batteries in the Bank | Average Cost of Energy ($/kW h) | Net Present Cost ($) | Initial Capital ($) | Number of Battery Replacements | Total Number of Batteries Used throughout Project Lifetime |

20 | 8.8 | 8 | 0.281 | 45,188 | 35,258 | 1 | 16 |

30 | 11.1 | 8 | 0.312 | 50,195 | 39,767 | 1 | 16 |

40 | 7.8 | 12 | 0.347 | 55,859 | 42,149 | 1 | 24 |

50 | 7.5 | 16 | 0.422 | 68,011 | 50,374 | 1 | 32 |

60 | 9.4 | 20 | 0.528 | 84,953 | 62,913 | 1 | 40 |

70 | 10.7 | 36 * | 0.864 | 139,118 | 100,818 | 1 | 72 |

Parameter | Value for Independent Generator | Value for Microgrid Generator |
---|---|---|

Capital cost | 0.70 $/W | 0.20 $/W |

Fuel cost | 0.10, 0.50, 1.00, 1.50 $/L | 0.10, 0.50, 1.00, 1.50 $/L |

Lifetime of generator | 2500 h | 15,000 h |

Minimum load ratio | 25 percent | 25 percent |

Maintenance intervals | Every 400 h of operation | Every 400 h of operation |

Maintenance cost | $25 | $400 |

Operation cost | 0.10 $/h of operation | 0.45 $/h of operation |

**Table 8.**Net Present Cost, in millions of dollars, of delivering energy to 1000 homes using individual diesel generators provided for each home, a microgrid powering the whole community, and individual PVB systems.

Scenario | Diesel Price ($/L) | Diesel Consumption Per Year (Million Liters) | Carbon Emissions Per Year (Thousand Tons) | Comments | |||
---|---|---|---|---|---|---|---|

0.10 | 0.50 | 1.00 | 1.50 | ||||

Individual generator for each home | 111 | 133 | 159 | 185 | 3.03 | 7900 | - No grid investment or maintenance costs required - Model run for two generators each with a capacity of 2 kW |

Microgrid powering complete community | 91 | 105 | 122 | 139 | 1.94 | 5100 | - Cost of supplying diesel, maintaining and upgrading grid, and externalities not included - Model chooses two generators with capacities of 1 MW and 1.75 MW to meet the load |

PVB: 30% MSOC with temperature effects incorporated | 99 (maximum) | 0 | - No grid investment or maintenance costs required - Learning curve of battery technology not considered | ||||

PVB: 30% MSOC with temperature effects NOT incorporated | 50 (maximum) |

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Elshurafa, A.M.; Aldubyan, M.H. State-of-Charge Effects on Standalone Solar-Storage Systems in Hot Climates: A Case Study in Saudi Arabia. *Sustainability* **2019**, *11*, 3471.
https://doi.org/10.3390/su11123471

**AMA Style**

Elshurafa AM, Aldubyan MH. State-of-Charge Effects on Standalone Solar-Storage Systems in Hot Climates: A Case Study in Saudi Arabia. *Sustainability*. 2019; 11(12):3471.
https://doi.org/10.3390/su11123471

**Chicago/Turabian Style**

Elshurafa, Amro M., and Mohammad H. Aldubyan. 2019. "State-of-Charge Effects on Standalone Solar-Storage Systems in Hot Climates: A Case Study in Saudi Arabia" *Sustainability* 11, no. 12: 3471.
https://doi.org/10.3390/su11123471