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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
13/5/2014Vaman Kuber, Sol2Sys
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
13/5/2014Vaman Kuber, Sol2Sys
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
13/5/2014Vaman Kuber, Sol2Sys
INDUSTRIAL/COMMERCIAL APPLICATION
Grid tied Battery backup Operation
AP0004 Rev 01
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13/5/2014Vaman Kuber, Sol2Sys
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.
13/5/2014Vaman Kuber, Sol2Sys
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.
13/5/2014Vaman Kuber, Sol2Sys
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)
13/5/2014Vaman Kuber, Sol2Sys
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.
13/5/2014Vaman Kuber, Sol2Sys
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
13/5/2014Vaman Kuber, Sol2Sys
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.
13/5/2014Vaman Kuber, Sol2Sys
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
13/5/2014Vaman Kuber, Sol2Sys
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.
13/5/2014Vaman Kuber, Sol2Sys
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
13/5/2014Vaman Kuber, Sol2Sys
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
13/5/2014Vaman Kuber, Sol2Sys
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.
13/5/2014Vaman Kuber, Sol2Sys
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.
13/5/2014Vaman Kuber, Sol2Sys
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.
13/5/2014Vaman Kuber, Sol2Sys