The inherent irony of using non-renewable energy sources such as oil, gas and coal to power Electric Vehicles (EVs) is not lost on two engineers from India. In their paper “A PV-Wind Based EV Charging Station under Dynamic Weather Conditions,” they explore a charging station method that captures and stores solar and wind energy to charge an EV and test the method in seven cases of differing weather conditions.

The proposed model includes several components: harnessing solar power (PV), harnessing wind power (WECS), maximizing energy extraction (MPPT), storing the energy in an energy storage unit (ESU), and charging the EV. The result is an efficient EV charging station with MPPT and current control techniques to ensure smooth power transfer from solar and wind energy, and energy storage units to the electric vehicle in the charging station.

Schematic diagram of proposed EV charging station

 

Solar Power (PV)

The process of converting sunlight into electricity directly using semiconductors is called photovoltaics or PV. 

Wind Power (WECS)

A Wind Energy Conversion System (WECS) uses turbines to take the kinetic energy of wind and convert it into mechanical energy, which then powers a generator to produce electricity. 

Maximum Point Power Tracking (MPPT)

Maximum Point Power Tracking (MPPT) is a technology used in solar and wind systems to maximize energy extraction. In solar power, it works by dynamically adjusting the voltage and current from the solar array to match the battery voltage and optimize power transfer. This process ensures that the solar panels are operating at their peak power output, regardless of fluctuating light conditions, temperature, or other factors.  In wind power, MPPT optimizes energy extraction by continuously adjusting the generator’s speed and voltage to match the wind’s energy availability. This ensures optimal operation of the wind turbine so it can produce the most power, thereby maximizing the amount of energy harnessed. 

Energy Storage Unit (ESU)

An energy storage unit (ESU) is needed in renewable energy-based EV charging stations. With green energy sources like solar and wind, availability is irregular, so energy production can be inconsistent. ESUs can store excess energy when production exceeds requirement and release it when the requirement is high or the natural sources are not producing electricity, ensuring a stable and reliable supply of energy. ESUs offer backup power when there is little or no renewable energy available in remote or off-grid renewable energy installations. A bi-directional DC-DC converter allows the ESU to get charged from the power source (solar or wind) in a forward direction. When energy is transferred from the ESU to the EV, the stored power moves in a backward direction.

Diagram of ESU with Bi-Directional DC-DC converter

 

Testing

The authors outlined seven scenarios that illustrate how the PV-Wind-based EV charging system can be relied upon in variable weather conditions.

  1. Sunny day: Solar energy directly powers the EV with unused power stored in the ESU.
  2. Partly sunny day: Solar energy and stored energy from the ESU power the EV.
  3. Windy day: Wind power directly powers the EV, with unused power stored in the ESU.
  4. Mildly windy day: Wind power and stored energy from the ESU power the EV.
  5. Sunny and windy day with wind more powerful than the sun: Solar and wind power directly charge the EV with unused power stored in the ESU.
  6. Sunny and windy day with the sun more powerful than the wind: Solar and wind power directly charge the EV with unused power stored in the ESU.
  7. Cloudy day with no wind: Stored energy from the ESU is used to charge the EV.

The scenarios were then simulated with a MATLAB/Simulink environment. MATLAB is a programming language and numerical computing environment used for data analysis, scientific computing, and visualization in engineering applications. Simulink creates visual representations of multi-component models. When combined, they allow researchers to analyze the results of their simulations.

Conclusion

Researchers concluded that their proposed charging station can be used flexibly to charge EVs constantly, irrespective of environmental conditions, guaranteeing a stable energy supply. This finding has positive implications for the scaling of EV use, which is currently constrained by the availability of reliable charging stations powered by sustainable energy. In addition, the PV-wind-powered proposed model can be used in remote areas, far from large cities and grid-based charging points.

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