grid connected solar pv power plant technology and ... connection 2 captive power-two meters...

Grid Connected SPV

Rooftop Power Plant

Technology and Policy

Solar Policy for MaharashtraRound Table Conference

Urja Prabodhan Kendra, Mumbai

May 13, 2014 13/5/2014Vaman Kuber, Sol2Sys

Address by Dr. Farooq Abdullah

• National consultation in New Delhi on net metering in grid solar projects on Dec. 20, 2011.

• “Prepare an action plan for introducing net metering in commercial and residential roof top solar projects.”

• “With solar power cost coming down from Rs. 18/- per unit in 2010 to Rs. 8/- per unit in 2012, it should be possible to allow consumers feed extra power to the grid.”

• “Come out with practical solution to facilitate the process.”

13/5/2014Vaman Kuber, Sol2Sys

Large Scale SPV Power Plant

PV Array D.C Protection and

SwitchgearsInverter

A.C Protection and

Switchgears

Distribution/Transmission Grid

MV/HV Transformer13/5/2014Vaman Kuber, Sol2Sys

Rooftop SPV Power Plant

PV D.C Protection and

SwitchgearsInverter

A.C Protection and

SwitchgearsAC Electrical Loads

LT Distribution Grid

Main LT Panel


Rooftop SPV Power Plant Operation

Source: GPCL


Energy Metering and Feed-in-Tariff

PV Array

Loads

InverterDistribution

Panel

Controller

Grid

Load Meter

PV Meter

Net Meter

• AC electrical output of inverter consumed by loads or AC current is fed back to grid

• For generation > consumption, PV - Load = Net Export

• For generation < consumption, Load – PV = Net Import

• Feed-in-Tariff (FIT) paid to customer based on Net Export


Grid Connection 1Power Export/Import-Two Meters

21Load Meter PV Meter

Inverter

PV

AC Isolator

Fuse Box

Building Loads

Single phase LT Grid Supply13/5/2014Vaman Kuber, Sol2Sys

DOMESTIC APPLICATION

Grid Connection 2Captive Power-Two Meters

Inverter

PV

1Net

Meter

Three Phase LT Grid Supply

Fuse Box

Industrial Loads

2

Generation

Meter


INDUSTRIAL/COMMERCIAL APPLICATION

Grid tied System with Battery backup


Grid tied Battery backup Operation

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Distributed Solar PV Generation

• Use available roof/terrace space.

• Overall performance ratio to point of utility is 10-15% higher due to reduced transformer and cable losses.

• Feed local load and meet peak day time demand.

• Potential to improve local power quality.

• Reduce additional investment and on-going maintenance for DG sets, Batteries and UPS.

• Higher installation cost of Rs. 7-8 Cr/MW.

• LV grid interface is a challenge.


Germany Rooftop Program

• 20% energy produced by renewable sources.

• 80% of >1GWp PV installations are rooftop in Germany.

• FIT introduced by law and scaled back in phase wise manner to allow market growth.

• Feed-in-tariff: € 0.30-0.40/kWh for 10kWp to 1MWpPV size (€ 0.95 in 2005)9% digression from 2011.

• Average Electricity Cost approx. 25 Euro Cents/kWh.


Gujarat Rooftop Program

• GPCL has launched 5MWp distributed rooftop PV power plant program in Gandhinagar.

• Build, Own, Operate and Maintain model. (BOOM/BOOT)

• Rooftop owners to lease rooftop space to project developers.

• Torrent Power to purchase clean electricity from project developers at Rs. 11-12.5/unit. (25 year average)

• Project developers to pay green incentives to rooftop owners based on solar generation.

• Green incentives to cover major % of electricity bills for rooftop owners.

• Solar PV Energy generated by plant will be monitored by separate meter and fed to LV public grid. (Gross Metering)


IITB 1MW Rooftop PV Plant

Solar potential of average 5.3 peak sun hours per day

PV power plant performance ratio of 78%

Average annual energy of 1.39 million kWh for a period of min. 25 years.

The plant capacity factor (PCF) of 17%.

Supply up to 50% of the peak load demand of the academic area.

Generate up to 25% of the total energy requirement of the academic area.


IITB 1MW Rooftop PV Plant

The total Life Cycle Cost (LCC) estimated at Rs. 10 Cr.

Unit leveled energy cost estimated at Rs 5.0 over a period of 25 years.

Up to 5% net annual savings in IITB electricity costs.

Payback period- 5-6 years with 30% subsidy


Utility and User Considerations

• Power quality of grid should not be reduced by grid fed solar power.

• LV grid interface standard will ensure power quality is maintained.

• Personnel safety in the event of mains failure or instability is ensured by anti-islanding operation.

• Automatic protection device recognizes grid failures and cut-offs as well as voltage and frequency fluctuations.

• Manual Switching Devices sensing grid impedance jumps may be used for LV single phase feed-ins.

• PV plant feed-ins to rural grid branch lines can increase line voltage and support weak grid when large loads are present.

• Load consumption and grid feed-in need to be synchronizedduring day time by tailoring usage patterns to avoid excessive increase in line voltage.


Islanding Protection

• Islands are small sections of grid network.

• When grid fails, powering of island can pose risk to workers.

• Inverter output can be incompatible with equipment connected to island when grid fails.

• Anti-islanding operation: Inverter output is isolated from grid network in the event grid fails or is unstable.

• This presents a challenge with LV grid in India in terms of PV capacity utilization.

• Intentional Safe Islanding Policy is required


LV Grid Interface Standard

• G83-1/1 (EN 50438) UK Engineering Recommendation for small embedded generator feeding power to domestic grid.Voltage and Frequency Range: 207-264V, 47-50.5 HzMax. Export: 5.75kW-1 phase, 11kW-3 phase,Power Quality: Flicker, DC Injection, Harmonics and PF,Loss of Mains Test.

• IEC 61727: PV Systems Characteristics of the Utility Interface for PV systems <10kW connected to low voltage grid.

• IEC 62116: Islanding prevention methods

• CEA-Draft Standard for Connectivity of Distributed Energy Resources-issued 2013

• Customize LV grid interface standard for India.Voltage and Frequency Range for synchronization,Time to connect and disconnect PV generator,Metering configuration.


Rooftop Policy-Central Vs. State

Parameter SECI Kerala Maharashtra

Capacity 10MW in each phase

50% of Distribution Transformer (DT) Capacity, Max. 3MWp

15-30% of DT Capacity on case to case basis

PPA Offtaker State DISCOMs

KSEB (RPO allowed) MSEB/ThirdParty(RPO allowed)

Incentives 30% subsidy, FiT not specified

APPC (Rs. 1.99/unit) for excess energy fed to grid after banking statement

FiT at par with Electricity Rates (Attractive for allsectors unlike GBI)

Connection Voltage

>=33kV <5kW-240V SPLT5-100kW-415V TPLT>3MW-11kV HT

<10kW-240V SPLT10-100kW-415V TPLT100kW-1MW-11kV HT1MW-5MW-33kV HT


Rooftop Policy-Central Vs. State

Parameter SECI Kerala Maharashtra

Metering Net Meter and Generation Meter

Net Meter and Generation Meter

Generation and Load Meters for single phase systems up to 10kW, Net Meter and Generation Meter for 3 phase systems >10kW

Max.Generation

No upper cap Upto 200% of averageyearly consumption

Energy Banking

No upper cap Allowed for 1 year, yearly payments

Sharing Allowed, 5% wheeling charge

Allowed, Concessional wheeling charge


Rooftop Program Challenges

• Requires LV grid interface standard. CEA draft standard “Connectivity of Distributed Energy Resources” is effective 2013.

• Large Voltage and Frequency range of operation is required.

• Power quality issues: PF, DC Injection, Harmonics, EMI, Surge Currents, Voltage Dips.

• Anti-islanding Protection and Intentional Islanding.

• Battery Operation when grid is not available.

• Dual Mode Inverter is complex and adds to cost.

• Requires Solar energy meter and Net energy meter in addition to Load energy meter.

• Net Metering/ABT (Availability Based Tariff) Meter infrastructure is complex and expensive.


Benefits of Rooftop Program

• Improving reliability of grid and distribution transformers.

• Deferring grid investments-DTs and Switchgear.

• Improve power quality (Voltage and Phase) at load end of grid.

• Reduce peak power purchase cost of utilities.

• Reduced transmission and distribution losses.

• Offset central power generation capacity.


Rooftop Program Recommendations

• High efficiency C-Si technology for limited space on rooftop to enhance local manufacturing.

• Distributed PV architecture for improved performance.

• Customized LV grid interface standard for India.

• Grid interactive battery backup operation to improve plant availability when grid is not available.

• Standardize support structures for rooftop power plants to reduce cost and time to install.

• Develop low cost dual inverter and net energy meter.

• Develop means to harness thermal energy and enhance PV output (PVT Technology).

• Large scale manufacturing of plug and play AC modules for direct grid interface.



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