# Impact of Multi-Year Analysis on the Optimal Sizing and Control Strategy of Hybrid Energy Systems

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## Abstract

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_{2}emissions from 7581 kg/year to 7379 kg/year. The results also show that the optimization results are highly affected by the variations of some critical parameters, such as solar radiation, average load, and battery degradation limits. The achievements indicate the higher effectiveness of the multi-year effects and control strategy on the optimal design of HESs.

## 1. Introduction

## 2. Methodology

#### 2.1. Location and Electric Load Data

#### 2.2. Meteorological Data

^{2}/year [18]. HOMER used the monthly average temperature and global horizontal radiation as input parameters. The average ambient temperature varies between 9.28 °C in January to 36.97 °C, with an annual average temperature of 23.81 °C (Figure 4). The monthly average solar radiation and clearness index is depicted in Figure 5. The yearly average solar radiation at the site is 5.16 kWh/m

^{2}/day, and it varies from 2.64 kWh/m

^{2}/day in December to 7.94 kWh/m

^{2}/day in June. Data on the ambient temperature and solar radiation are taken from NASA [19].

#### 2.3. Configuration of the HES

#### 2.4. Multi-Year Module

#### 2.5. Mathematical Model of the System

#### 2.5.1. PV Panels

_{D}: PV derate factor [%]. P

_{C}: PV-rated capacity [kW]. I

_{S}: Incident radiation on the PV array [kW/m

^{2}]. I

_{S,STC}: Standard radiation [1 kW/m

^{2}]. T

_{C}: PV cell temperature [°C]. T

_{STC}: PV cell temperature under standard test conditions [25 °C]. δ

_{T}: Temperature coefficient [%/°C].

#### 2.5.2. Battery

_{batt,rt}: Battery round-trip efficiency [%].

#### 2.5.3. Estimation of NPC

_{A}: Annualized cost [$/year]. CRF: Capital recovery factor. d: Real discount rate [%]. T

_{project}: Project lifetime [year].

#### 2.6. Control Algorithm

## 3. Results and Discussion

#### 3.1. Optimal Design

#### 3.2. Technical and Environmental Evaluations

_{2,}which makes up most of greenhouse gas emissions [29,30]. In this study, the national grid is the only source of emissions. The environmental analysis shows that the LF strategy is more environmentally friendly than the CC strategy. This is mainly due to the high grid purchases in the CC strategy compared to the LF strategy. The CO

_{2}emissions for LF and CC with multi-year effects are calculated as 3928 and 7379 kg/year, respectively [31]. On the other hand, for a system without multi-year effects, these values are estimated as 3981 and 7581 kg/year.

#### 3.3. Year–Year Analysis

_{2}do not show any variation for the project’s lifetime. On the other hand, when considering the multi-year effects, PV production decreases over the years, mainly due to the effects of degradation. This leads to increasing the grid purchases and hence increasing the CO

_{2}emissions. For the LF strategy, the PV production decreases from 34,882.46 to 31,713.61 kWh/year after 20 years, leading to an increase in grid purchases from 6188.8 to 6241.54 kWh/year and CO

_{2}emissions from 3911.2 to 3944.65 kg/year. In the case of the CC strategy, the PV production decreases from 10,616.4 to 9651.97 kWh/year, leading to increased grid purchases from 11,483.6 to 11,771.9 kWh/year and CO

_{2}emissions from 7286.29 to 7439.84 kg/year with some fluctuations among years. Moreover, the results show that the battery output energy decreases for certain years due to the battery degradation and then suddenly increases again, which relates to the battery replacement.

#### 3.4. Sensitivity Analysis

## 4. Conclusions

_{2}emissions by 2.66%. While, for the LF strategy, considering the multi-year effects leads to an increase in the required PV size from 19 kW to 23 kW and the required number of batteries from 30 to 36, resulting in an increase in the net present cost from $40,607 to $55,113 and decrease the CO

_{2}emissions by 1.33%. Variations in some critical parameters, such as solar radiation, average load, and battery degradation limits, affect the optimization results dramatically. The findings of this work show the importance of the multi-year effects and control strategy in the optimal design of HES.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

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**Figure 11.**Year-year analysis for; (

**a**) PV production; (

**b**) Grid purchases; (

**c**) Battery output energy; (

**d**) CO

_{2}emissions, using LF strategy.

**Figure 12.**Year–year analysis for (

**a**) PV production; (

**b**) Grid purchases; (

**c**) Battery output energy; (

**d**) CO

_{2}emissions, using CC strategy.

**Figure 13.**Effects of critical parameter variations on the NPC using (

**a**) LF strategy and (

**b**) CC strategy.

Parameter | Description |
---|---|

1. PV | |

Type | Flat plate |

Nominal efficiency | 18% |

Nominal operating cell temperature | 47 °C |

Tracking system | No tracking |

Ground Reflectance | 20% |

Lifetime | 25 years |

2. Battery | |

Type | Generic 1 kWh Li-Ion |

Maximum Capacity | 276 Ah |

Nominal capacity | 1.02 KWh |

Round trip efficiency | 90% |

Nominal voltage | 3.7 V |

3. Converter | |

Rectifier capacity | 100% |

Efficiency | 93% |

Lifetime | 15 years |

Cost Type | PV | Battery | Converter |
---|---|---|---|

Cost of capital | $640/kW | $500/battery | $645/kW |

Annual O & M cost | $10/kW | $10/battery | $10/kW |

Cost of replacement | $500/kW | $450/battery | $500/kW |

Electricity Consumption Per Month (kWh) | Price ($ Per kWh) | Price (IQD Per kWh) |
---|---|---|

>4000 | 0.0827 | 120 |

3001–4000 | 0.0550 | 80 |

1501–3000 | 0.0240 | 35 |

1–1500 | 0.0069 | 10 |

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

Project lifetime | 20 | Year |

Maximum annual capacity shortage | 1 | % |

Battery minimum SOC | 25 | % |

Real discount rate | 4 | % |

Description | Unit | With Multi-Year Effects | Without Multi-Year Effects | ||
---|---|---|---|---|---|

LF | CC | LF | CC | ||

HES components | |||||

PV | kW | 23 | 7 | 19 | 6 |

Battery | - | 36 | 20 | 30 | 18 |

Converter | kW | 4 | 4 | 4 | 4 |

Grid purchases | kWh/year | 6215 | 11,675 | 6299 | 11,995 |

Economic optimization | |||||

NPC | $ | 55,113 | 33,102 | 40,607 | 26,750 |

Description | Unit | With Multi-Year Effects | Without Multi-Year Effects | ||
---|---|---|---|---|---|

LF | CC | LF | CC | ||

PV production | kWh/year | 33,274 | 10,127 | 28,816 | 9100 |

Renewable fraction | kW | 69.6 | 37.6 | 68.7 | 34.7 |

Unmet load | kWh/year | 114 | 121 | 155 | 129 |

Battery autonomy | hour | 13.2 | 7.23 | 11.8 | 7.06 |

Battery life | year | 9.92 | 7.75 | 15 | 10.2 |

CO_{2} emissions | kg/year | 3928 | 7379 | 3981 | 7581 |

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## Share and Cite

**MDPI and ACS Style**

Al-Khaykan, A.; Al-Kharsan, I.H.; Ali, M.O.; Alrubaie, A.J.; Fakhruldeen, H.F.; Counsell, J.M.
Impact of Multi-Year Analysis on the Optimal Sizing and Control Strategy of Hybrid Energy Systems. *Energies* **2023**, *16*, 110.
https://doi.org/10.3390/en16010110

**AMA Style**

Al-Khaykan A, Al-Kharsan IH, Ali MO, Alrubaie AJ, Fakhruldeen HF, Counsell JM.
Impact of Multi-Year Analysis on the Optimal Sizing and Control Strategy of Hybrid Energy Systems. *Energies*. 2023; 16(1):110.
https://doi.org/10.3390/en16010110

**Chicago/Turabian Style**

Al-Khaykan, Ameer, Ibrahim H. Al-Kharsan, Mohammed Omar Ali, Ali Jawad Alrubaie, Hassan Falah Fakhruldeen, and J. M. Counsell.
2023. "Impact of Multi-Year Analysis on the Optimal Sizing and Control Strategy of Hybrid Energy Systems" *Energies* 16, no. 1: 110.
https://doi.org/10.3390/en16010110