First net metering project in West Bengal: BRWS Hospital, Patuli

Location: Patuli
Department: Hospital

Overview – Net-Metered Solar Rooftop Power Plant

The BRWS hospital in Patuli is said to be the first project in West Bengal that implemented the net metering policy. Net Metering is essentially a system that gives solar energy owners “credits” for the power that they add to the grid. When the solar panels produce excess power, that power is sent to the grid. And this power can be ‘taken back’ when the solar plants are not functioning – for example, during the night. When a unit of solar energy that has been ‘net metered’ is called back for use, the bi-directional electricity meter will run backward. That is, customers are billed only for the ‘net’ energy use.

Every state electricity board has its terms and conditions while implementing ‘net metering.’ In West Bengal, the minimum requirement of plant size is 5kWh with 3 phase power to implement net Metering. All institutional consumers like govt. Private or charitable hospitals and health centers, government offices and institutions, government, government-aided or private academic institutions, or any housing complex under govt. Schemes for development are eligible for this policy, barring any domestic users.

For the standard structural design in this project, only 3.5 kWh was possible due to the small roof space available. For this reason, all the other PV system integrators rejected the work for the space issue. SunShell came up with a splendid solution to make the project eligible to meet the requirements for Net Metering. They decided on a uniquely elevated structural design to accommodate the whole 5kWh Net-Metered Solar Rooftop Power Plant on the same roof. Thus the 1st net-metered grid-connected solar rooftop power plant was finally commissioned in West Bengal


Technical Details

The 5kWh plant is grid-connected with the first-ever net metering policy. The 20 units of 250Wp solar PV modules produce enough energy to run the whole hospital. The inverter used in this model is of a Kaco variety of 5kWh with a DC switch present. While working in commercial sectors, it is crucial to pay attention to protective measures. For this reason, SunShell has also introduced AJB with SPD of Type II 1000V 40kA on PV string fuse 1000V 15kA. To protect against high voltage and load failures, the structure has ACDB with LED indication on AC side SPD and suitable MCB. Also, a termination system of 415V is present on the LT side. For additional safety, lightning arrestors with dedicated earthing and required earthing protection in compliance with IS 3043 guidelines are also fitted into the structure for optimal operation.


Technical Features

  • Plant type: Grid-connected
  • Net metering: Yes
  • Solar PV Module: 250Wp x 20 nos
  • Inverter: Kaco 5kWp with DC switch
  • AJB: yes, with SPD Type II 1000V 40kA, PV string fuse 1000V 15A
  • ACDB: yes with AC side SPD, Indication LED, and Suitable size MCB
  • Termination: At LT side 415V
  • Lightning arrestor: Yes, with dedicated earthing
  • Earthing protection: yes, complied with IS 3043
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