TREP 01 – Grid Stability BESS at Popua Power Station, Tongatapu (7.2 MW/3.8 WH)
The component is leading by Tonga Power Limited. The civil and mechanical scopes are completed. Experts are being mobilized from NZ for the HV installation works. Due to border restrictions, experts from Europe will arrive when a repatriation flight allows them to arrive in Tonga.

bess trep 1

BESS at Popua Power Station for TREP 01

TREP 02 – Load Shifting BESS at the Villa, Tongatapu (6W/20.88Wh)
The installation is leading by Tonga Power Limited. The civil and mechanical construction is completed. The contractor (Akuo Energy of France and Infratech of NZ) currently working out a remote commissioning plan which may have financial and performance guarantee impacts. An expert from NZ has arrived in Tonga while the European staff is currently unable to mobilize but will be able to in the foreseeable future. PMU and key stakeholders are working on the remote commissioning plan and mobilization of critical staffs.


BESS at Villa for TREP 02


Battery Energy Storage Systems (BESS) is a technology developed for storing electricity with the underlying idea being that this stored energy can be utilized at a later time.
We are currently working alongside the Tonga Renewable Energy Project to construct Tonga’s first ever Battery Energy Storage Systems to store Renewable Energy Generation from our Solar & Wind Farms, to be used at the most suitable time. There are two types of BESS that are currently being constructed, Power BESS & Load Shifting BESS. 
Battery Energy Storage Systems are a vital component to reaching Tonga’s 50% Renewable Energy target by end of year 2020. Battery Energy storage systems will be able to store renewable energy generated from our existing solar and wind generation sites and distribute it to the people of Tonga when required. This second Battery Storage system main function will be load shifting which will facilitate increasing capacity of renewable generation in the grid by storing solar generation during the day for use during evening peak and at night.
This project is funded through the TREP project which is co-financed through ADB, GCF fund and DFAT along with contributions from government of Tonga and TPL.

Popua Power Station Bess

Batteries: 5.333 MWh / 10.66 MW


  • Spinning Reserve
  • Smooth Variations in load on diesel generators
  • Manage short term power imbalance in the system (active and reactive power)'
  • Potentially allow diesel off operation (ZDO) of the system by setting grid frequency and voltage

Villa Load Shifting BESS


Batteries: 23.846 MWh / 11.9 MW


  • Manage daily power imbalance in the system, by capturing excess renewable generation during the day for release at night, and into the evening peak load. This reduces "spill" of renewable generation and increases the percentage of renewable energy generation of the power system.