30 September 2020


Hybrid Systems Solar PV Wind Storage Operations & Maintenance

Realising Isolated Grids’ Potential

Author: Wärtsilä & Jason Deign, Contribution Writer

Around 11% of the world’s population lives on islands. These 730 million or so people frequently live surrounded by abundant natural energy resources, ranging from solar and wind to tidal and geothermal. Yet they typically have to make do with energy from imported fossil fuels, which pushes up electricity prices and the cost of living generally. According to some estimates, islands could cut energy costs by up to 75% by transitioning from diesel to renewables.

However, while the case for using clean energy on such isolated grids is clear, the mechanics for enabling this transition are complex. Isolated grids are often particularly fragile because of their small size and lack of interconnection. Adding intermittent generation to the hybrid plant mix can exacerbate challenges associated with grid safety and stability. That is why it is important not only to take care with system design and engineering, but also to rely on an advanced control system when optimising the energy potential of microgrids.

Island Grid+

The Wärtsilä Island Grid+ GEMS solution is a comprehensive package that empowers the renewable modernisation of isolated grids using a variety of generation assets. The solution allows isolated grid operators to:

  • Minimise the levelised cost of energy by reducing fuel consumption and maximising renewable generation.
  • Predict energy generation using load and renewable energy generation forecasting.
  • Enhance grid safety by optimising asset dispatch and maintaining reserve levels.
  • Improve grid quality by adding fast-responding battery assets to the island grid.
  • Manage and optimise various assets under a single portfolio.

Total Control 

Due to the delicate nature of many isolated grids, it is important for operators to have as much control as possible over the electricity network. The Wärtsilä Island Grid+ GEMS solution covers all the functions required for reliable grid operations, including: 

  • Tertiary control, dispatching engines, batteries and renewable generation at any given time to achieve the best possible economic optimisation and meet grid safety reserve requirements while observing the operational constraints of all assets. 
  • Renewable energy forecasting, using weather forecasts, statistical models, non-parametric machine learning and advanced parametric regression techniques to compute the expected power generation from solar and wind assets. 
  • Primary response, provided via engine governors and Wärtsilä energy storage systems. Electronic control allows batteries to regulate frequency and voltage when facing large load steps or renewable power ramps. 
  • Load forecasting based on residential and industrial loads. Machine learning is used to predict the load, which enables predictions to get progressively more accurate over time. 
  • Emergency handling in response to plant failures, unexpected renewable generation interruptions or load changes to ensure grid reliability. Secondary control, maintaining high grid quality by distributing real and reactive powers across all running engines and energy storage units.

Case study: the island of Graciosa

The small island of Graciosa, in the Azores, has a predominantly agricultural economy but has been working to foster tourism for the last 10 years. In tandem with this economic development, the island has sought to reduce its dependence on diesel fuel and in 2020 inaugurated a hybrid renewable power plant combining 1 MW of solar, 4.5 MW of wind power and a 6 MW/3.2 MWh energy storage system.

GEMS management 
The entire island’s energy management is monitored, integrated and optimised by Wärtsilä’s GEMS advanced software system. GEMS software uses artificial intelligence and machine learning technology to optimise multiple energy generation assets based on load patterns and weather forecasting. GEMS's computing technology and logic also accommodates intermittent renewable sources such as solar and wind. 

Asset control 
Particularly unique to the project is that GEMS carries out individual asset control as well as system balancing to maximise renewable energy penetration. This is traditionally done by system operators. GEMS allows the island system to perform at its best while decreasing the cost of diesel generation.

Hybrid plant 
The Azores, much like other island communities, have traditionally had no option but to depend on external fuel sources for their energy. This involves importing fossil fuels to power the grid, which exposes the islands to high fuel costs and potential unreliability of supply. But now, with its hybrid renewable power plant and Wärtsilä technology solution, Graciosa has the potential to eliminate approximately 190,000 litres of diesel fuel per month, while increasing the use of renewables from 15% to 65%. 

100% renewables
The aim is to reach a stage where all of the island’s diesel generators can be turned off and the island runs on 100% renewable energy. This could be done for up to several successive days in some cases, depending on the solar and wind conditions. If that happens, the savings—depending on fuel costs—could be as high as USD $3.15 million a year.

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