University of South Wales Master of Sciences Thesis
Standalone hybrid generation system for the remote area of Thar, Pakistan
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Standalone hybrid generation system for the remote area of Thar, Pakistan 2.5.3. Battery sizing Batteries are the main components of the PV-wind system used to store energy at times when there is surplus of supply, which can be used to supply the load at times of more demand from the load. Many factors affect the sizing of the battery system and the most important are [11, 12]: - Daily energy demand - Number of days of storage - Maximum depth of discharge The battery voltage is that of a fully charged battery. It depends up on the number of cells and voltage per cell [11]. 2.38 N cells = the number of cells in series V /cell = voltage per cell The battery capacity is the total Ampere-hour required to support the load requirement and is given by [11, 12]: 2.39 Where, BC = Battery capacity (Ah). Ebat= energy required from the battery per discharge. η disch =efficiency of discharge path (including inverters, wires, diodes, etc). Ncell = Number of series cells in one battery. Vdisch = average cell voltage during discharge. DOD= maximum allowed Depth of Discharge for required life cycle. Npar = number of parallel batteries. Batteries are generally not allowed to be discharged fully. The minimum value to which a battery can be discharged before it is recharged is called maximum depth of discharge, DOD. Deep discharge batteries can discharge up to 30- 40% of their state of charge, SOC [11]. The total energy required from the battery to supply the required loads is the sum of energies consumed by each load, which is the product of the duty ratio and peak energy consumption. It is given as follows [11, 12]: 2.40 Ebat = Wh energy of battery during discharge when all loads (i=1, 2…n) are connected Ebi = Wh energy of battery during discharge when load-i is connected Dbi= Duty ratio for load-i during battery discharge Pbi = Peak power consumption by load-i during battery discharge in watts Tri = repetition period for load-i in hrs. |