• Sudden surges in RE could result in serious system failure
• Only proposed battery storage RE plant in Poonakary under review

The Ceylon Electricity Board (CEB) faces a serious risk of system failure during holidays due to the sudden influx of solar-based Renewable Energy (RE) into the grid, particularly when electricity demand is low.

CEB Chairman Dr. Tilak Siyambalapitiya, addressing this concern, revealed plans to mitigate such risks through an incentive-based electricity tariff system. This mechanism will encourage industries to operate on holidays, thereby stabilising demand and reducing strain on the system, according to Dr. Siyambalapitiya.

Last Thursday (23), the CEB’s power generation data highlighted the variability in electricity demand, with a peak at 7 p.m. reaching 2473.3 MW of active power and a low at 3.45 a.m. of 1328.2 MW. Total energy generated for the day amounted to 46.19 GWh. 

Solar and wind energy, though significant, accounted for only 7.04% (3.25 GWh) and 1.41% (0.65 GWh) of the total generation, respectively. The contributions from hydro and thermal sources remained dominant, with key inputs from Mahaweli hydro (12.02 GWh), CEB coal (12.94 GWh), and CEB oil (2.08 GWh).

According to power sector experts, the system’s vulnerability stems from the intermittent nature of RE sources like solar and wind, particularly during holidays when demand is unusually low. 

At the night peak, the grid relied heavily on hydro (823.6 MW), coal (541.5 MW), and oil (283 MW) to meet demand, underscoring the challenge of integrating RE during off-peak hours. 

Reservoir levels, which influence hydroelectric output, showed moderate rainfall on Friday (24), with key reservoirs like Castlereagh at 1093.09 metres above sea level (masl) and Maussakelle at 1164.59 masl. While these conditions support hydro generation, they further highlight the challenge of balancing RE sources with conventional generation during low-demand periods.

As learnt by The Sunday Morning, to address these risks, the CEB is planning to propose tariff incentives aimed to align industrial activity with the availability of renewable energy to ensure grid stability and minimise the potential for system failures.

Addressing vulnerabilities 

Speaking to The Sunday Morning, a senior official at the CEB, who wished to remain anonymous, clarified why the system faced risks when renewable energy flooded the local grid, explaining that the lack of RE storage facilities was a significant factor.

The official highlighted that rooftop solar generation at the household level surged into the system during long holidays when energy consumption was low.

“As of now, we manage the system by controlling firm energy capacities, but since RE generation is unpredictable, sudden surges can still pose a risk to the entire system,” the official explained.

When asked for further clarification, the official stressed that shortages could be managed by generating more electricity, but excess rooftop solar generation flowed directly into the system without any control, creating a risk of failure.

“This is a very tricky issue. We cannot control rooftop solar supply as all units are directly connected to the system. These units act like small power plants, but the CEB doesn’t have access to them. Solar energy generation is also highly variable. In such situations, we currently de-load some firm power plants, but that is not always practical,” the official stressed.

The CEB official further warned that if this issue was not addressed, the country could face outages due to sudden power failures.

The official cited the root cause of the system’s vulnerability as the ad hoc inclusion of RE projects without considering the variable energy capacities that the grid could handle.

“Renewable energy should be integrated into the system in a scientific way. At present, there are limitations due to transmission line and grid capacities. RE without storage technologies can disrupt the system. This is why we insisted that the previous administration follow a systematic approach instead of adding RE projects haphazardly,” the official said.

LTGEP 2022-2041

As stated in the Long-Term Generation Expansion Plan (LTGEP) 2022-2041, reaching the 70% RE target by 2030 and maintaining it beyond that period requires numerous interventions from a long-term planning perspective. 

Apart from introducing flexible thermal generation, the plan also identifies other grid support interventions such as implementation of utility-scale Battery Energy Storage Systems (BESS) primarily for energy shifting purposes, which is essential in order to accommodate high levels of variable renewable energy in the system. 

Furthermore, BESS shall be required to provide other ancillary services such as fast frequency response and frequency regulation. BESS are proposed to be developed as standalone systems as well as integrated solutions coupled with large-scale fully facilitated solar PV parks.  

Furthermore, the Pumped Storage Power Plant (PSPP) essentially acts as an energy storage, providing the same services as BESS. Due to the longer implementation timeline, BESS are introduced in the initial stages of the planning horizon while PSPP is introduced from 2029 onwards in phase development. 

An early introduction of a ‘Renewable Energy Desk’ to the system control centre is mandatory with controlling and monitoring facilities to separately manage RE capacities that are going to be integrated in large proportions. Introduction of solar and wind forecasting too is essential to go with the RE Desk.

Sole battery storage RE project 

Nevertheless, as learnt by The Sunday Morning, the only battery storage RE project proposed in Sri Lanka was the large-scale floating solar project which was proposed for Poonakary. However, the project is currently under review. In addition, no other solar projects that are currently proposed or commissioned have battery storage mechanisms.

However, as stated in the LTGEP, the battery energy storage applications in power systems are expanding globally and technology costs are declining notably. 

Even though the scale of battery energy storage applications in power systems are small compared to pumped storages, battery energy storages have a wide array of applications in all generation, transmission, distribution, and consumer endpoints. Given the range of applications, battery energy storages are employed to enhance the quality and reliability of supply of electricity. 

The battery storage systems provide services in different time frames ranging from fast frequency support to energy arbitrage with economic dispatch. It also provides various support services for renewable energy grid integration. 

Lithium-ion types of batteries in power system applications are growing at present compared to other forms of chemical batteries such as flow batteries, lead-based batteries, and sodium sulphur batteries. Techno-economic assessment of the type of battery storage application and the type of battery technology is essential to identify effective storage solutions. 

The CEB in its latest renewable energy grid integration study has assessed the requirement of grid-side application of battery energy storages with the introduction of large amounts of intermittent and non-synchronous generation into the power system.