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Hybrid System

SOLAR PV HYBRID SYSTEM

Hybrid_System

Highlights

  • The largest wind + PV hybrid system installed in Maharashtra
  • Meets the power requirements of all PCs and peripherals at the MEDA office
  • Serves to demonstrate the effectiveness of using solar and wind energy
  • wind systems

    Project Background

    Maharashtra Energy Development Agency (MEDA) is an autonomous body of the Government of Maharashtra formed with objective of promoting the use of renewable energy and energy efficiency in the state. MEDA is headquartered in Pune. MEDA realized early on the large potential for off grid wind+PV hybrid systems, especially in rural unelectrified regions. With a view to demonstrate the proof of concept to potential customers and investors, MEDA decided to install one such system at its own office in Pune.

    The systems size was decided at 5 kWp, comprising of a 3.2 kWp wind turbine and a 1.5 kWp solar PV array.

    The electricity generated was to power lights and some computers in the office.

    However it was soon realized that the wind resource at the site was inadequate, as a result of which the hybrid system was never able to deliver the rated back up. Solar resource at the site was however adequate and available almost throughout the year

    In early March 2003, MEDA decided to augment the capacity of the hybrid system by the further addition of solar PV.

    wind systems

    The Challenge

    Having drawn lessons from their previous difficult experiences of the wind+PV hybrid, the capacity addition had to be done within the following constraints:

  • Installed wind generator or wind energy charge controller were not be disturbed
  • Existing system components were to be reused to the maximum extent possible.
  • Module installation was required to be done on the terrace within a designated area only with the added provision that the area below the modules was not only accessible but also usable.
  • The project was required to be completed in a tight budged within a tighter time frame.
  • SVAM Electronics assisted MEDA in first carrying out the scoping study and was then subsequently awarded the contract to install the system.

    Drawing upon the knowledge of its experienced staff, SVAM Electronics offered MEDA a value engineered solution. The project was completed within 5 weeks.

    wind systems

    Project

    The total capacity of the wind + PV hybrid system is 11.2 kW with 3.2 kW of wind and 8 kWp of solar PV.

    The PV modules are mounted on a specially fabricated structure at a height of 4 m above the ground.

    The installed peak power is 8 kWp consisting of 35 & 75 Wp c-Si modules. The array is electrically split into two arrays of 4 kWp each, so done with a view to increase system reliability and offer redundancy. Array wiring terminates in two junction boxes, and cables run from the junction boxes to the control room, located below the solar module array.

    wind systems

    A system voltage of 144 VDC was chosen. System voltage for the earlier 5 kWp system was 48 VDC. Merits of choosing higher system voltage:

  • Since the current handled reduces, operation of inverter and charge controller is efficient and far more reliable at higher DC input voltages
  • Cost of the inverter and charge controller reduces
  • Reduced load on the ventilation system inside the control room since heating reduces
  • The system is designed such that in case of excess energy generated, provision is made to charge the batteries of the UPS operating at 120 VDC.
  • A Bergey 3.2 kW 2-bladed wind generator, with a nominal power of 3.2 kW is installed on a tower next to the MEDA office building.

    The PV charge controller consists of two PWM controlled MoSFET based 4 kW modules. The PV charge controller works in conjunction with the wind energy charge controller. The rated operating voltage of the wind generator is 48V which is raised to 144 VDC by means of a 3.2 kW DC - DC converter.

    The battery storage consists of 24 flooded electrolyte tubular plate batteries of 12V 200 Ah each. The battery bank is rated at 144V 400 Ah.

    A 15 kVA true sine wave inverter converts battery power to 230V 50 Hz AC supply.

    Performance

    The wind PV hybrid system is presently operating 33 computers and assorted peripherals at the office.

    Daily operation of the system is presently being monitored by means of a metering panel provided for the system. The metering panel indicates input / output voltages & currents, wind speed, wind direction, solar isolation and the energy consumed. Performance figures are determined by manually correlating the data obtained from the metering panel.

    Addition of a data logger is proposed for the near future.

    The system is delivering on an average 33 units per day on the demand side with an uptime of over 90%. This shows that the system is well designed to meet the requirements of the office.

    The system is designed to operate online, i.e. the connected load operates directly off the solar modules and/or wind generator without draining the battery bank.

    Environment

    The wind+PV hybrid system produces an average of 12045 kwh /year. Compared with the usual sources of electricity in India, this equates to an annual CO2 emission saving of around 7500 kg/year (Indicative figure only considering diesel substitution).

    Installation of the system has also helped MEDA safeguard itself against power cuts, which are often frequent during the summer months.

    The system has obviated the necessity for the installation of a back up generator that would have had negative environmental and cost impact.

    The project is a good example of how a well designed, technically optimized off grid renewable energy system can effectively meet the electricity requirements of even a site located in an urban environment.

    The location at a reputed government office has the added advantage of demonstrating to the public the effectiveness of small energy production systems using two natural sources - viz. sun and wind.

    Ever since the system was commissioned in June 2003, it has proved to be a source of attraction for visitors to MEDA. Pune is a fast growing city where energy demand has outstripped supply by a large margin. A live, working wind + PV hybrid system is helping raise awareness of renewable energy in Pune and beyond.

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