Issues and Challenges with Grid Integration of Renewable Energy in India

Abstract

World is witnessing significant growth of the renewable energy sector due to environmental issues and increased cost of fossil fuels. However, as S&C’s Troy Miller recently wrote for Powergrid International, integrating renewable energy supplies to the power grid poses significant challenges to broader adoption of renewable energy generation. Variable output, resource variability, and bidirectional power flows will impact Power system stability and reliability, as well as quality of service to end users. In this paper, we have reviewed some of the challenges resulting from the grid integration of Renewable Energy and tried to suggest the possible solutions in Indian context.

Foreword

Conventional sources of Electricity Generation are capital cost intensive and situated far from the load centers. The ever increasing demand, dearth of fossil fuels, corresponding pollution & GHG emissions have paved the path for development of Renewable Energy sector.

By the word Renewable, we understand something, which can be replenished without affecting the surrounding much. Renewable sources are widespread across the geographical area, so the concept of Distributed & Decentralized Generation is associated with Renewable Energy generation. Across the Globe, distributed generation is encouraged due to the following major advantages;

- Being located at the Load centre, it helps the Utility in reducing stress on Grid, Peak Demand and T&D loss

- Real time Demand side management reduces burden on conventional generation- Reduced Electricity bill, provides backup power & use of spare roof area - Consumer can earn revenue through Export of Power to the Grid- Reduction in Carbon footprints of the Nation

Power Sector Scenario in the Country

Installed Plant capacity as on Oct. 2015;

Sector MW %ageState 96,646 34.5Central 74,171 26.5Private 1,09,512 39.1

Total 2,80,328

Sl. No. Fuel MW %age1 Thermal 1,95,604 69.8a) Coal 1,70,138 60.7b) Gas 24,473 8.7c) Oil 994 0.4

2 Hydro (Renewable) 42,473 15.23 Nuclear 5,780 2.14 Renewable Sources (Other) 36,471 13.0

Total 2,80,328

Plant Load Factor (Thermal):

Sl. No. Year Target (%) Actual (%) Sector-wise ActualCentral State Private

1 2009-10 77.2 77.5 85.5 70.9 83.92 2010-11 72.1 75.1 85.1 66.7 80.73 2011-12 68.7 73.3 82.1 68.0 69.54 2012-13 70.0 69.9 79.2 65.6 64.15 2013-14 69.6 65.6 76.1 59.1 62.16 2014-15 65.52 64.46 73.96 59.83 60.587 2015-16 66.27 61.78 72.23 55.34 59.35

Power Supply Position:

Sl. No.

YearEnergy Peak

Requirement Availability Surplus(+)/Deficit(-) Demand Peak Met Surplus (+)/Deficit (-)

MU MU MU % MW MW MW %

1 2009-10 8,30,594 7,46,644 -83,950 -10.1 1,19,166 1,04,009 -15,157 -12.7

2 2010-11 8,61,591 7,88,355 -73,236 -8.5 1,22,287 1,10,256 -12,031 -9.8

3 2011-12 9,37,199 8,57,886 -79,313 -8.5 1,30,006 1,16,191 -13,815 -10.6

4 2012-13 9,95,557 9,08,652 -86,905 -8.7 1,35,453 1,23,294 -12,159 -9.0

5 2013-14 10,02,257 9,59,829 -42,428 -4.2 1,35,918 1,29,815 -6,103 -4.5

6 2014-15 10,68,943 10,30,78 -38,138 -3.6 1,48,166 1,41,160 -7,006 -4.7

7 2015-16 6,62,204 6,46,223 -15,981 -2.4 1,53,366 1,48,463 -4,903 -3.2

Summary:

Presently, Renewable constitute around 13% of the total installed capacity. India has set an ambitious target of adding 175 GW of Renewable Energy (i.e. 35-40% of the installed capacity) by 2022. Table below depicts the sector wise break up of 175 GW.

Solar Wind Small Hydro Bio Mass & Others100 60 5 10

Out of the 100 GW Solar, 60 GW is targeted from land based Solar Plants and 40 GW from Grid connected Roof Top Solar. In comparatively saturated Countries in terms of Renewable Energy, the percentage of Roof Top Solar as against Total Solar PV installed capacity is shown below;

CountrySolar PV Installed Capacity (~in GW)

Share of Solar Roof Top (~in %)

Germany 38 60US 20 40Japan 24 35Australia 4 80

Mass scale integration of Power generated through Rooftop Solar PV panels needs implementation of Micro Grids. However, certain issues are associated with such integration with Utility Grid, which are discussed in this paper.

A) Metering and Energy Accounting

Metering arrangements for Rooftop Solar PV projects in use are Gross metering and Net metering

i) Gross Metering: The entire energy generated by Rooftop Solar PV system is fed directly into the Grid and the system owner is benefited by feed-in-tariff based on sale of power to the utility

ii) Net Metering: The excess/surplus is either sold to or banked with the utility, thus, combine elements of captive consumption and exchange of power with the utility

Net Metering Vs Gross Metering

The fundamentals of Net metering principle are;

- A billing methodology allowing customers with self generation to “Net” the amount of generated electricity against the energy used from the Grid.

- Usually requires the use of a single meter that “spins backward” when customers are generating more than they are consuming or two meters; a system use meter and an excess generation meter.

- For the netted energy, customers are billed on applicable retail tariff, which acts as an incentive.

Net Metering Concept & Schema

Issues & Challenges

a) Non availability of standard, model for Net metering schemes

b) Absence of Net meter specifications, specifically for 1 Ph. connections.

c) Code of practices for use of different class of import, export meters and generation meter.

d) Lack of clarity on role of different entities in bilateral/ tripartite arrangements in projects developed by owner/ third party.

e) Non availability of provisions towards TOD settlements as to how to align energy settlement under Net metering with the existing framework.

B) Interconnection Arrangements

When a consumer is privileged to export surplus power to the Grid, issues related to the point of connectivity, level of voltage of interconnection, limit of power export & most importantly the safety concerns comes into the picture.

While the “draft CEA Technical standards for connectivity of distributed generation resources regulation 2012” recognizes the issues in interconnectivity but has left on the Utility/Licensee to address the same.

Whereas, international codes like NEC, IEEE 1547 & UL 1741 takes care of Reliable Power Grid Operation, Protection against Faults, Power Quality, Impact on Utility Monitoring and Switching Equipment, Testing facilities and Quality Assurance etc. ANSI specifies the product specification of inverter, its installation and safety.

Issues & Challenges

a) Existing power systems are designed to support only one way power flow from the point of generation through a transmission system to distribution level loads. These systems were not originally intended to accommodate the back feed of power from distributed generations at the distribution level.

b) For the safe system operations of an interconnected distribution generation following is important:

- Self islanding in the event of Grid faults i.e. protection from distribution system faults.

- Cease to feed power to Grid in the event of internal PV system breakdown and/or Grid fault automatically.

- Protection to People (Public & Utility workers) and Property- Protection from abnormal Voltage & Frequency levels, - Protection while synchronization with Grid- Protection against injection of Harmonics, DC supply & Flicker etc. to the Grid

c) Inverter of Solar PV system and Meters need to have inbuilt disconnect switch & supply imbalance sensing device.

d) Indian standards need to reflect provisions related to various product specifications, installation and testing in line with international equipment standards issued by International Electro technical Commission (IEC).

e) Capacity building of Utility Officials is required on the testing & operation of new technologies.

C) Commercial Settlement Process

Grid penetration of roof top solar projects will require clarity on the energy accounting & Commercial settlement for electricity consumed from such system as well as excess energy injected into the Grid. Commercial settlement depends upon:

a) Definition of eligible consumerb) Generation capacity limitsc) Interconnection voltaged) Energy Accountinge) Net metering settlement periodf) Restrictions on level of overall or local Grid penetrationg) Renewable Purchase Obligation (RPO)h) Application of other charges & incentives (fixed charge, connectivity charge,

TOD, ABT, GBI) etc.

Though CERC Forum of Regulators (FOR) working on Renewable Energy addressed these issues but these are yet to be incorporated in the Codes.

D) Applicability of Regulatory Instruments

As stated above, Regulatory infirmities are still persisting. Non availability of clearly defined technical standards and guidelines for Grid connectivity, metering, safety and security etc. are major barriers in implementation of such projects.

Available Standards and Codes like ‘CERC model guidelines for Rooftop Solar Grid interactive system based on Net metering’ and ‘CEA technical standards for connectivity of the distributed resources regulations 2012’ etc. are still under draft form and lacks adequate clarity. The main technology constraint lies with the specification of meters which necessarily has to be export import type smart meter with disconnection facility from remote.

Current Regulatory framework also lack in addressing the charges related to wheeling, open access, cross subsidy etc. Many States have laid regulations covering Net metering, LT connectivity etc. but restricted the Grid penetration and usage of Renewable Energy by the Consumers.

E) Other Issues

a) Generation from Renewable sources of Energy is possible, only when the resources are available. RE Power integration with the Grid requires dis-patchable Plants which can compliment RE generation during off hours.

b) Flexibility of Generation and Load dispatching is required, so that quick balancing can be done between Renewable Generation, Conventional Generation and Load.

c) Real time balancing of variation between load & supply and to manage unscheduled outages, a spread in operating frequency band, deviation settlement mechanism along with storage capacity/spinning reserve etc. is necessary.

d) On account of the Price competitiveness of RE power as against Conventional sources of Energy, Off-taker for Renewable power is not readily available.

Conclusion

Presently Renewable Purchase Obligations (RPO), Feed-in-Tariff, Competitive bidding, Tax policies, fiscal & regulatory incentives are being provided to boost the Sector. Enabling large scale Renewable integration into the Utility Grid requires, evolution of appropriate regulations, policy and a market driven mechanism. A road map need to be framed accommodating regulatory, policy, institutional, capacity building & market alterations to support the integrated Power system in future with following provisions;

a) Must Run status of Renewable Energy powerb) Methodology of Estimating RE generation accuratelyc) Ensuring 100% RE power off-take through Trading/PPAs (Power Purchase Agreement)d) Incentives for achieving Flexible Generation & Load and Grid Discipline, & e) Capacity Building/Skill Development of Agenciesf) Introduction of low cost financing mechanism

Implementation of following solutions is also proposed for addressing the issues with Grid Integration of Renewable Energy;

a) Reactive compensation solutions: Reactive compensation mitigates the impacts of varying RE output on power systems. Fast-compensating dynamic static compensators are effective at providing VAR support.

b) Volt/VAR Optimization: Variable output from RE generation impacts supply voltage levels for utility customers, and in turn affect power quality. Volt/VAR optimization technology can help address such voltage swings in real time by optimizing voltage profiles for all distribution feeders served by a substation.

c) Energy storage: It can address problems such as smoothing rapid variations in output from renewable energy generation, levelling output from renewable energy plants to align actual output with scheduled output, and storing electricity for use when demand is high but renewable energy generation output is low.

The implementation of Smart grid technology is the answer to many technical problems discussed above. Smart Grid integrates all the Power system components (Generation to Demand management) with the help of advanced communication infrastructure and information technology.