Ensuring grid readiness for renewable energy

Pakistan is working to achieve up to 60% of electricity generation from renewable energy in line with UN SDG 7. For a country with a historic reliance on expensive, imported fuels whose prices are sensitive to USD/PKR parity, this is welcome news.

However, while an abundance of renewables in the energy mix may be beneficial for the environment, this addition also requires close attention to investments in the grid for stability and reliance.

Unstable grids can cause large scale power outages, such as that experienced by Pakistan’s national grid on 23rd January 2023. According to Nepra’s (National Electric Power Regulatory Authority’s) own investigation report of the incident, 500MW of wind generation resulted in overloading of the transmission lines in the southern part of Pakistan.

Lower hydel generation in the northern section of the country also had a cascading effect across Pakistan’s electrical network, eventually shutting it down. Interestingly, the report highlights that NTDC (National Transmission and Dispatch Company) issued dispatch instructions without adequate consideration of the prevailing network conditions.

Balancing generating units and channelling the energy to respective power consumption centres is a delicate act. A critical component is maintaining “grid inertia.” Apart from the HVDC lines the electrical network in Pakistan mostly operates at a frequency of 50Hz.

Grid inertia ensures stability by maintaining this constant frequency. Changes or fluctuations in the system frequency can trigger loss of connectivity and interruption of power.

Over the course of a day, power generation is increased according to the merit order to cater to growing daytime demand. Increased demand without adequate supply causes system frequency to drop. The converse can also have a negative impact.

NEPRA’s Performance Standards for Transmission state that the system frequency should stay between 49.5Hz and 50.50Hz. Any frequency swings beyond the tolerance limits results in activation of protection devices which isolate power plants from the electrical grid.

When we focus on adding renewable energy sources, we must ensure that there is adequate inbuilt protection so that grid operates at safe frequency levels. For renewable energy – particularly solar and wind – we must also consider including Battery Energy Storage Systems (BESS). These can store surplus energy from the grid and release when demand is low, creating a “synthetic inertia” acting as a stabilizing influence.

Nepra recently concluded a hearing on NTDC’s PKR 510 billion transmission upgrade plan, which also involved the addition of BESS technology at its 220 kV Jhimpir Grid Station with a completion date of February 2024. Nepra has also held a public hearing on open competitive bidding for four renewable energy projects for which K-Electric will be the power purchaser.

The company envisions significant addition of renewable energy by 2030 and has also outlined an investment plan of PKR 484 billion to bolster the capacity of its transmission and distribution infrastructure supporting Karachi and its adjoining areas. An additional opportunity to secure the grid for both NTDC and KE lies in the exploration of BESS technology on the part of those project developers who are building renewable projects.

In this regard, KE is conducting an ongoing VRE study which will facilitate the incorporation of renewables as well. Simultaneously, increasing network visibility is part of KE’s strategic goals for the future. Further integration of network management technologies such as SCADA will further add to the resilience and flexibility of the network.

Power sector planning is a complex process with multiple moving parts. Addition of generation capacity must be conducted in a systematic, balanced manner to maintain grid stability. We often focus on the potential cost impacts of renewable energy addition, but a prudent approach is required to ensure the grids fully equipped to handle the inflow as well.

Copyright Business Recorder, 2023