# Thermodynamic Analysis and Optimization of the Micro-CCHP System with a Biomass Heat Source

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## Abstract

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## 1. Introduction

_{2}capture. The results of these numerical investigations showed that the system supplied net power of almost 22.23 MW, a 34.13 MW heating effect, a cooling effect of 96.40 MW, plus hydrogen generation of 124 kg/h. Additionally, the rate of CO

_{2}capture was 4.32 kg/s. The exergy efficiency and energy efficiency of the system were estimated to be 17.87% and 79.47%, respectively. In addition, the plant had a total product cost rate of 1.162 USD/s and a sustainability index of 1.218. Wang et al. [11] presented the bi-level sizing optimization of a distributed solar hybrid CCHP system considering economic, energy and environmental objectives. Delgado et al. [12] presented an integration of cycles via absorption for the production of desalinated water and cooling. Askari et al. [13] presented the exergo-economic analysis of two novel combined ejector heat pump/humidification–dehumidification desalination systems.

## 2. Materials and Methods

#### 2.1. Analysis of the Proposed System

- Minor changes in pressure were ignored.
- All modeling was checked in stable conditions.
- All processes were one-dimensional and adiabatic, and nothing was carried out during the process.
- The velocity of entering and leaving the fluid in the ejector was equal.
- Kinetic and potential exergy was omitted.
- The power required for pumping or suctioning fluid into the desalination system was omitted.
- The temperature of fresh water leaving the dehumidifier was equal to the average temperature of the air entering and exiting the dehumidifier.
- The state of the output flow from the condenser and evaporator was saturated.

_{3}and LiBr in NH

_{3}-H

_{2}O and LiBr-H

_{2}O solutions. Energy balance:

**Table 1.**ARS cycle validation results with reference [17].

Parameter | Calculated Value | [17] | Error % |
---|---|---|---|

COP | 0/535 | 0/5654 | 5/3 |

f | 4/438 | 4/33 | 2/4 |

${\mathrm{m}}_{\mathrm{g}}^{\dot{}}$ (kg/s) | 12/24 | 12/5 | 2/08 |

${\mathrm{Q}}_{\mathrm{g}}^{\dot{}}$ (kW) | 392/9 | 384/41 | 1/41 |

${\mathrm{Q}}_{\mathrm{a}}^{\dot{}}$ (kW) | 232/8 | 241 | 3/4 |

${\mathrm{Q}}_{\mathrm{e}}^{\dot{}}$ (kW) | 210/2 | 225/57 | 6/8 |

${\mathrm{Q}}_{\mathrm{c}}^{\dot{}}$ (kW) | 370/3 | 378/87 | 2/2 |

#### 2.2. Desalination System

- The lowest temperature of the system: the temperature of the salt water entering the dehumidifier has the lowest temperature of the desalination system.

#### 2.3. Ejector

## 3. Results

#### 3.1. Validation

#### 3.2. Parametric Study Results

#### 3.3. The Effect of Evaporator 1 Temperature on the Energy Efficiency and Exergy of the System

#### 3.4. The Effect of Ammonia Concentration on the Energy Efficiency and Exergy of the System

_{3}increases, the heat capacity of the Kalina cycle agent fluid (NH

_{3}-H

_{2}O) decreases; as a result, with the increase in NH

_{3}concentration, the production power and cooling load produced in CCHP and the amount of heat transferred to the HDH system and the exergy of the product are reduced and irreversible. The number of systems increases. As a result, the energy efficiency and exergy of the system decrease. Changes in ammonia concentration will not affect the production cooling load in the absorption refrigeration cycle.

#### 3.5. Effect of Absorber Temperature on Energy Efficiency and Exergy of the System

#### 3.6. Effect of Heater Temperature Difference on Energy Efficiency and Exergy of the System

#### 3.7. The Effect of Generator Pressure on Energy Efficiency and Exergy of the System

#### 3.8. The Effect of Heat Source Temperature on Energy Efficiency and Exergy of the System

#### 3.9. Optimization Results

_{1}= w

_{2}= 0.5}, EEOD, TEOD) were examined.

- Comparing the optimization results between the basic study and TEOD shows that in the TEOD mode, energy efficiency and exergy efficiency improved by 24.15% and 9.9%. In this case, from the point of view of the first law, the results are very satisfactory.
- The comparison of the optimization results between the basic study and EEOD shows that in EEOD, the energy efficiency and exergy efficiency improved by 21.32% and 11.43%. Compared to the TEOD mode, this mode is very satisfactory from the point of view of the second law of results.
- The comparison of the optimization results between the basic study and MOOD shows that in MOOD, the energy efficiency and exergy efficiency improved by 24.37% and 11.23%. In this case, the net production power, the heat of the evaporators and the amount of freshwater produced increased compared to the initial state.

## 4. Conclusions

- The maximum amount of energy efficiency and exergy of the whole system in the range of heat source temperature between 740 and 750 is equal to 74.2 and 47.7.
- The dehumidifier plays an important role in the freshwater production system. By increasing the dehumidifier performance coefficient (HCRd), the performance of the water softener system (GOR) increases.
- By increasing the temperature of the thermal pool, the temperature of the evaporator improves the overall system performance and increases the energy efficiency and exergy of the system.
- An increase in the concentration of ammonia in the Kalina cycle agent fluid solution and an increase in the temperature difference in the heater (decreasing the efficiency of the heater) will decrease the energy efficiency and exergy of the overall system.
- The flow rate of fresh water produced in the optimal conditions of the overall system was calculated as 0.5 g/s. For future work, the following topics could be addressed:

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 3.**Validation of the diagram of the efficiency changes of the second law of the CCHP cycle according to the temperature changes of the heat source with reference [24].

**Figure 4.**Validation of the ARS cycle coefficient of performance (COP) graph regarding the evaporator temperature with reference [17].

**Figure 5.**Validation of the graph of GOR changes relative to HCRd with reference [25].

**Figure 9.**Effect of heat exchanger temperature change on energy and exergy efficiency of the system.

**Table 2.**Kalina cycle validation with reference [22].

Parameter | Calculated Value | [22] | Error % |
---|---|---|---|

${\mathrm{Q}}_{\mathrm{g}1}^{\xb7}$ (kW) | 3982 | 3905 | 1/9 |

${\mathrm{W}}_{\mathrm{net}}^{\xb7}$, Kalina | 287/5 | 285/6 | 0/66 |

X [12] (%) | 95/43 | 99/97 | 4/5 |

ɳ_{t}, Kalina | 7/219 | 7/17 | 0/68 |

**Table 3.**Validation of ERC and VCHPC cycle in the CCHP system with reference [23].

Parameter | Calculated Value | [23] | Error % |
---|---|---|---|

${\mathrm{Q}}_{\mathrm{eva}}^{\xb7}$ (kW) | 4/367 | 4/3 | 1/5 |

${\mathrm{W}}_{\mathrm{com}}^{\xb7}$ (kW) | 1/6 | 1/52 | 5/2 |

Parameter | Base Case | TEOD Case | EEOD Case | MOOD Case |
---|---|---|---|---|

${w}_{1}$ | - | 1 | 0 | 0.5 |

${w}_{2}$ | - | 0 | 1 | 0.5 |

$TT{D}_{heater}$ | 3 | 4.469 | 2.547 | 3.367 |

${x}_{inletturbine}$ | 0.9 | 0.873 | 0.8705 | 0.8716 |

${T}_{eva}$ (k) | 280 | 274.5 | 274 | 274.6 |

${T}_{cond}$ (k) | 293.2 | 290.7 | 295.3 | 294.8 |

${T}_{outletboiler}$ (k) | 750 | 750 | 750 | 750 |

${T}_{absorber}$ (k) | 308.2 | 305.2 | 305.7 | 305.2 |

${P}_{inletturbine}$ (bar) | 50 | 50.84 | 51 | 51 |

$\dot{{W}_{net}}$ (kw) | 661.4 | 738.9 | 743 | 724.3 |

$\dot{{Q}_{eva}}$ (kw) | 4.367 | 4.25 | 7.239 | 4.251 |

$\dot{{m}_{pw}}\times $ ${h}_{fg}$ | 1.185 | 1.088 | 1.218 | 1.1618 |

${\dot{{Q}^{\xb7}}}_{biomass}$ (kw) | 1339 | 1357 | 1357 | 1357 |

$\dot{{Q}_{absorber}}$ (kw) | 1339 | 1357 | 1357 | 1357 |

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**MDPI and ACS Style**

Harahap, T.H.; Candra, O.; Sabawi, Y.A.; Kareem, A.K.; Mohsen, K.S.; Alawadi, A.H.; Morovati, R.; Mohamed, E.M.; Khan, I.; Madsen, D.Ø.
Thermodynamic Analysis and Optimization of the Micro-CCHP System with a Biomass Heat Source. *Sustainability* **2023**, *15*, 4273.
https://doi.org/10.3390/su15054273

**AMA Style**

Harahap TH, Candra O, Sabawi YA, Kareem AK, Mohsen KS, Alawadi AH, Morovati R, Mohamed EM, Khan I, Madsen DØ.
Thermodynamic Analysis and Optimization of the Micro-CCHP System with a Biomass Heat Source. *Sustainability*. 2023; 15(5):4273.
https://doi.org/10.3390/su15054273

**Chicago/Turabian Style**

Harahap, Tua Halomoan, Oriza Candra, Younis A. Sabawi, Ai Kamil Kareem, Karrar Shareef Mohsen, Ahmed Hussien Alawadi, Reza Morovati, Ehab Mahamoud Mohamed, Imran Khan, and Dag Øivind Madsen.
2023. "Thermodynamic Analysis and Optimization of the Micro-CCHP System with a Biomass Heat Source" *Sustainability* 15, no. 5: 4273.
https://doi.org/10.3390/su15054273