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ABSTRACT
The pollution produced by power purchased from electrical network and the extensive effort of Iranian government toward the elimination of energy subsides are the encouraging factors in Iran for employing hybrid green power system (HGPS) to produce power. Therefore, in this study, the effect of current and future energy prices as well as energy budget on optimal design of an HGPS is studied. Three cases are considered to examine the optimization problem thoroughly: (i) autonomous HGPS; (ii) nonautonomous HGPS, but HGPS cannot sell electricity to electrical network; and (iii) nonautonomous HGPS and HGPS is allowed to sell electricity to electrical network. The results for Case 2 and Case 3 show that with the increase of energy price from three to five times (0.7 and 0.5), budgets for Cases 2 and 3 (0.6 and 0.2,, respectively) are required to ensure that the design is economical.
Nomenclature
| Budget | = | Coefficient for budget |
| C | = | Cost function |
| = | Average cost of loss due to unmet load ($/kWh) | |
| = | Initial investment cost equipment i ($/unit) | |
| CD(mt) | = | Demand cost for month m and at time step t ($/kWh) |
| CP(t) | = | Cost of power purchase at time step t ($/kWh) |
| Ctotal | = | Total cost |
| = | Equivalent loss factor | |
| = | Index of equipment | |
| = | Loss of energy expectation | |
| = | Loss of load expectation | |
| = | Probability of power supply probability | |
| = | Counter | |
| = | Mass of stored hydrogen in HST (kW) | |
| = | Operation and maintenance cost of equipment i ($/kWh) | |
| = | Number of units of equipment i in HGPS (kW or kg) | |
| = | Total number of PV | |
| = | Total number of WT | |
| = | Net present cost of equipment i ($/kWh) | |
| = | Net present cost of unmet load ($/kWh) | |
| NPCnetwork | = | Net present cost of electrical network |
| NT | = | Coefficient of price |
| = | Cost for CO2 ($/kg) | |
| = | Output power of electrolyzer (kW) | |
| = | Fuel cell output power (kW) | |
| = | Input power to electrolyzer (kW) | |
| = | Injected power to inverter from renewable resources (kW) | |
| PHGPS(t) | = | Produced power by HGPS in time step t (kW) |
| = | Power of the HST injected to fuel cell (kW) | |
| = | Injected power to the load (kW) | |
| = | Load demand in time step t (kW) | |
| Pnetwork,max | = | Maximum power of electrical network (kW) |
| Pnetwork,max(mt) | = | Maximum power of electrical network at month m, time step t (kW) |
| Pnetwork(t) | = | Purchase power of electrical network at time step t (kW) |
| = | Output power of PV array (kW) | |
| = | Output power of wind turbines (kW) | |
| Pd | = | Price of demand ($/kWh) |
| Pr(t) | = | Price of power from electrical network in time step t ($/kWh) |
| = | Interest rate | |
| = | Replacement cost of equipment i ($/unit) | |
| = | Time step index | |
| = | Inverter efficiency | |
| = | Angle of incident solar irradiation (rad) |