Storage Series: Mauritius

Just completed a trip to Mauritius and learned about the countries three-phase approach to energy transition

Phase 1: Ancillary Services, Phase 2: Arbitrage Phase 3: Round the clock power

Background

The Republic of Mauritius is an island state of about ~1.37 million people located off the southeast coast of Africa in the Indian ocean. In addition to the main island of Mauritius, the national territory includes the island of Rodrigues and the more distant St. Brandon and the Agaléga Islands. The Mauritius island is around 61 km long and 45 km wide, with an area of 1,864 km2. The total area of the country is 2040 km2. The capital and largest city is Port Louis.

The challenge

The Mauritius economy is dependent on agriculture products (e.g. sugarcane, poultry, pumpkins etc.), financial services and industries such as food processing, textiles, mining, chemicals, tourism etc. The Russia Ukraine war has led to significant rise in the price of coal imports from 90 USD to 400 USD thereby denting the profitability and economics of electric utilities in the country. With an estimated GDP growth of ~3.40%, the country is determined to phase out coal power plants leaving the transition towards clean energy even more critical. The country aims to achieve ~60% of electricity generation mix from renewable energy sources by 2030. The peak electricity demand is approx. 500 MW in the present scenario. Like any other SIDS, large scale deployment of renewable energy (approx. 115 MW) has made the Mauritius grid more vulnerable for intermittency issues.

Systematic response

The Government plans to install a total of 38MW of battery energy storage system (BESS) by 2024 to stabilize the frequency of the grid and to allow the absorption of at least 350MW of intermittent power, including the 115MW already installed.?

In phase 1, 18 MW of battery energy storage capacity at four different locations (district level) provides ancillary services and act as spinning reserves. Despite lying idle for much of the time, battery storage is a critical back up to manage unplanned shut down of coal power plants, sudden demand surge and cloud cover affecting solar power generation. This capacity also enables frequency and voltage regulation, VRE integration and with high state of charge (80-90%) can kick in when the frequency goes down.

In the phase 2, 20 MW battery storage capacity can enable Firm RE Capacity or Peaking Capacity. System operators must ensure they have an adequate supply of firm RE generation capacity to reliably meet demand during the highest-demand periods or the peak demand. This peak demand is typically met with intermittent RE generators that have parabolic generation curve. Battery storage can transform this generation curve into a trapezoid shape to ensure adequate firm peaking generation capacity. While VRE resources can also be used to meet this requirement, these resources do not typically fully count toward firm capacity, as their generation relies on the availability of fluctuating resources and may not always coincide with peak demand. But system operators can improve VRE’s ability to contribute to firm capacity requirements through pairing with BESS. Pairing VRE resources with BESS can enable these resources to time shift their generation to be coincident with peak demand, improving their capacity value and system reliability.

In phase 3, RE plus storage projects can be planned to further accelerate RE capacity addition towards 60% targeted mix by 2030. Hybrid PPAs may provide 12 hours of base load power generation from 9 am to 9 pm on daily basis. The peak demand occurrences at 10:30 am, 2 PM and 7 pm can be explored from other available RE sources such as bagasse/biomass systems sourced from sugarcane. Seasonal variations in renewable power generation can also be planned with co-firing bagasse in coal power plants.