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Friday, 23 October 2015

Issues with large scale Renewable Energy integration and the way out

Renewable Energy (RE) particularly Wind and Solar have huge potential and going to be the dominant energy sources in near future. Their large scale integration into the grid is going to cause certain serious issues which need to be addressed. 

Intermittent and Variable in nature:

As we know wind and solar are intermittent and variable in nature, their output depends on the availability of wind and sunlight. Variation in the output may cause significant change in power flow over the transmission and distribution lines, affecting the reliability and security of the power system. 

Most of these RE power plants are located far away from the major load centres and existing transmission lines. Usually these RE plants are connected to the grid at a voltage of 33 kV, 66 kV, 132 kV or 220 kV depending on the capacity of the plant and its location.

Sluggish development of Transmission Infrastructure:

Normally the gestation period of these RE plants are 6 to 12 months, whereas the development of a transmission infrastructure takes some 4 to 5 years depending on the conditions like Right of Way (RoW) requirement, clearances from various government organizations, financial condition of the executing agencies etc.

Limited Reactive Power support:

Currently many of the wind turbines have induction generators which either have no or limited reactive power support, thus causing issues like voltage regulation. Same is the case with line commutated solar PV systems.

Thus, the large scale integration of RE into the grid along with insufficient transmission facility is going to cause serious issues like congestion, voltage regulation, nodal price, supply reliability and security of the system. 

Mitigation methods: 

Some mitigation methods for the above said issues are:
1.   Variation and intermittency in power supply can be better handled by a strong interconnected transmission system.
2. Reactive power support in the form of Static VAr Compensator (SVC) or STATCOM can be provided at the RE power plants or some strategic locations to take care for the reactive compensation and voltage regulation.
3.   Private participation in the transmission sector will help to enhance the execution capability.
4.  Strong weather and hence output forecasting technique along with a strong real time interaction with the System Operator (SO) with help in mitigating certain grid code issues.
5. Some form of storage capacity whether it’s the pumped storage hydro plant or large scale battery storage, will also help to counter a variety of issues discussed earlier.
6.  New energy market structures incorporating special ancillary services such as reactive support services, spinning reserves, flexible generation etc is also going to strengthen the grid operation in the advent of large scale RE penetration.   
7. A separate Renewable Energy Management Centre (REMC), with advanced communication and control techniques, should be planned for the enhanced security and reliability.

So in near future we are going to witness a new and much eco-friendly power system, particularly in the developing countries like India.