El Hierro Displays A Classic Example Of Renewable Energy Usage

ABB, the Swiss Engineering firm, have designed and implemented a project in a small Spanish island of El Hierro to tap the energy from wind, hydro and solar plants. This will make El Hierro self reliant as far as energy requirement is concerned. Presently, the island depends exclusively on diesel generators to meet its energy need. The present annual import of diesel just to power the generators is around 40, 000 barrels. The carbon emissions of 18,200 tones due to power generation via diesel are expected to reduce drastically after the successful implementation of this interconnected grid based renewable energy source generation scheme.

The wind farm along with hydro power plant is going to fulfill about 80% of the total energy necessity. The hydro plant is of pumped storage type and has the capacity to produce 11.3 MW.  There is also a wind farm of 11.5 MW supplementing the hydro plant in generating electricity. Solar thermal units will provide rest of the 20% of the energy and these will form a grid-connected system. All the power plants are grid connected and hence the power system will be more stable and function to its optimum efficiency.

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ABB and the Spanish government have used the natural demographic features in the island excellently. For the installation of the hydro plant, a crater of extinct volcano was selected. The hydro plant is of pumped storage type. The difference between a normal hydro plant and pumped storage plant is the recycled flow of the water to drive the turbines as and when the need arises. When the energy requirement is been fulfilled via solar and wind plants, the water will remain stored in the crater. As soon as energy generation from wind and solar plants reduces, water will be released and the difference in energy adjusted from the power generated from turbines. Thus, the hydro plant will operate only when energy demand increases and cannot be satisfied by wind and solar farms.

The island’s main substation will receive power generated from five wind turbines and hydro power plant. The transfer of power from the remote generating plants to the main substation is done via distribution transformers. The major difficulty encountered during the application of grid-based system employing renewable power plants is maintaining plant frequency and voltage in stable margins. This stability is achieved by sharing of reactive and active power demand in transmission lines and generators. ABB has installed Automatic Generation Control (AGC) to maintain the stability of the power system. The control over hydro turbines, pumped storage process, new interconnected substation and the existing substation and the communication between all these entities will be governed by ABB’s Distributed Control System.  

The project is valued at €54 million and Icaria, a Greek island has already planned to model their energy generation structure similar to El Hierro. Fully operational by end of 2011, this project will not only make this hot tourist destination self reliant in energy but also provide power for three water desalination facilities.

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