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Graciosa | Island microgrid system

Introduction

Graciosa is an island in the Atlantic Ocean which is part of the Portuguese Azores.

Graciosa has a population of more than 4700 inhabitants and the economy is mainly built on agriculture and dairy industries.

Graciosa’s electricity supply today is purely based on diesel generators requiring the shipping of diesel fuel which makes the cost of energy high.

Renewable energy to displace diesel

The annual electricity consumption on Graciosa is 13.5 GWh with a peak load of 2.3 MW. As a result on Graciosa 3.3 million litres of diesel are burnt every year.

Battery on | Diesel generators off

The major part of the energy during the day will be generated by the solar panels. The annual yield of the solar and wind part is over 9 GWh covering over 60% of the need. However the challenge with renewable energy is that they are intermittent, clouds will reduce the yield of the solar panels suddenly while winds may pick-up or drop away in just a few seconds.

The Lithium Ion battery system plays a crucial role to smoothen the effects of sudden fluctuations in electricity production. Without a battery, diesel generators will have to run permanently to provide ‘spinning reserve’, with the battery they can be switched off.

By combining solar PV power generation with wind turbines and a Leclanché Lithium Ion battery storage system, the consumption of diesel is reduced by over 60%.

The business case

On Graciosa the total renewable energy system is being installed and will be operated to generate power and sell this in a Power Purchase Agreement (PPA) to the local utility.

In the PPA a mechanism is built in that the utility and through them the end customers will benefit from the cost reduction. In reverse, there is an incentive built in for the system operator to increase the efficiency and the savings of diesel providing them a better return on investment.

Depending on the development of the cost of diesel the payback time for this project is between 5 to 8 years.

The technology

The total system on Graciosa comprises of the following main components:

  • The Leclanché Battery Energy Storage System consisting of a 3.2 MWh Lithium Titanate battery bank and inverters
  • A solar PV plant of 1000 kWp with tri-phase solar inverters
  • A wind park with a total output of 4.5 MW
  • An Energy Management System to control the total system and make all components work together harmoniously