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4. Energy Management 277

FIGURE 8.14
Batteries depth of discharge when using PV and battery storage bank only.

FIGURE 8.15
Batteries depth of discharge for hybrid renewable energy system.

4. ENERGY MANAGEMENT OF HYBRID PHOTOVOLTAIC/
BATTERIES BANK/DIESEL GENERATOR SYSTEM

Using only solar energy to supply electricity to the load in an off-grid system is not
viable due to lack of continuous and stable supply of renewable energy all the times
during the day. Consequently, supplement energy sources like DGs and batteries
storage bank are recommended in these cases to cope with a lack or insufficient
availability of solar power. DGs with small output powers up to 20 kW usually oper-
ate from cold start. Therefore, they require sometime to reach stable output power
levels. In addition, batteries stored energy is not totally used to supply energy to
the load. In fact, batteries typically operate in a dod ranging from 20% to 80%.