Bonaire: Island of green dreams

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The relatively unknown Caribbean island of Bonaire is harbouring a secret. It is in the process of building what will be the world’s largest hybrid wind-diesel power plant, which will ultimately see its population enjoying 100 per cent of its electricity from renewables within five years.

Heather Johnstone, Chief Editor

A biofuel engine at the wind-diesel hybrid project on the Caribbean island of Bonaire

Revolutions can often happen in the most unexpected of places. This is certainly true for the small Caribbean island of Bonaire, which is in the process of revolutionizing its energy infrastructure from one primarily based on fossil fuels to another that utilizes 100 per cent renewable energy resources to meet all of its electricity needs.

The island of Bonaire, which covers an area of 250 km2 and is part of the Dutch Antilles, is located approximately 80 km north of the Venezuelan coast. In the past it has been a plantation island, as well as a salt producer.

Today, the island attracts around 100 000 tourists annually ” primarily divers drawn by its stunning marine environment. The island’s local population totals in the region of 14 500 and has a peak electricity demand of 12 MW or 75 GWh per year.

This demand is currently being met by a set of rented container diesel generator systems supplied by Aggreko, which feed power into the grid. However, this is a short-term measure.

Bonaire’s only power plant burnt down in 2004 and the government then made the bold decision to restore generation but to achieve this using 100 per cent renewable sources.

Subsequently, a consortium called EcoPower Bonaire BV won the contract to develop the government’s ambitious plan, which included investment in wind power R&D, as well as the construction of a facility to produce biodiesel from algae.

In November 2007, the consortium signed a contract with its project partner the Water and Energy Company of Bonaire (WEB) to build and operate what will be the world’s largest hybrid wind-diesel power plant. WEB, which is the state-owned water and energy company, also signed a power purchase agreement with the consortium to buy all the electricity produced by the hybrid plant.

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Consortium partners

EcoPower Bonaire is a Dutch-German consortium. The project developer Econcern of the Netherlands was the project’s major stakeholder, with a 90 per cent stake, and was responsible for project development, contracting and financing, as well as the operation of the plant. However, in June 2009 Econcern declared bankruptcy, and the developer’s core activities were taken over by Dutch energy company, Eneco.

The other consortium members are Enercon, a German wind turbines and system supplier, with a five per cent stake, and the German engine manufacturer, MAN Diesel & Turbo (formerly MAN Diesel) holding the remaining five per cent.

The Bonaire project is now managed by the administrators of Econcern/Evelop. In May, the project will start commercial operation and at the same time the administrators will offer the project for sale. Currently, the administrator holds 100 per cent of the shares. MAN has a convertible loan which gives it the right to convert this loan to five per cent of the shares.

To finance the project, Rabobank of the Netherlands provided non-recourse financing; 20 per cent equity and 80 per cent debt. The cost to build the new wind-diesel system is expected to be $55-60 million, with an anticipated return of $15 million a year. Part of this investment is also expected to be recouped through carbon credits.

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Project Timeline

The project comprises two distinct implementation stages. The main objective of the project’s first phase was for EcoPower Bonaire to gain operating experience with wind power on Bonaire and to reduce the island’s immediate power generation costs.

Ecopower Bonaire, a 100 per cent renewable wind-biodiesel system

The island’s inhabitants paid relatively high electricity costs because of the island’s reliance on diesel, which is expensive to transport to Bonaire.

In 2007, Enercon installed a single 300 kW E-33 wind turbine at Sorobon, on the southeast coast of the island, which replaced an obsolete wind turbine that had not been in use since 1996.

The Sorobon site was chosen because good wind data were already available, and it was characterized by very stable wind conditions and an average wind speed of over 9 m/s. The existing grid cable connection also has sufficient capacity to accommodate one medium-sized wind turbine.

The second phase of the project involves the construction of the hybrid wind-diesel power plant itself, comprising an 11 MW wind farm supplemented by a 14 MW diesel power plant. It also includes a 3 MW energy storage system.

The main role of the energy storage system, which is supplied by Saft of France, is to maintain power quality and continuity of supply in critical situations, such as a sudden increase in demand or failure of one of the wind turbines or diesel generators, preventing the possibility of a blackout on the island. The battery system will be able to deliver over 3 MW for more than two minutes, providing sufficient time for an additional diesel generator to be brought online.

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Hybrid wind-diesel technology

The wind farm is located on the northeast coast of Bonaire and comprises twelve 900 kW E-44 turbines. Each turbine is expected to operate at a high capacity factor, with 3000-3500 full load hours annually.

Enercon’s E-44 has been developed as a strong-wind system for the international market in the medium power range. As all other Enercon wind turbines, the E-44 is provided with an efficient rotor blade design and has a rotor diameter of 44 metres.

Twelve wind turbines are utilized for the Bonaire project, totalling 11 MW

Transport logistics and maintenance reasons dictated that only turbines of sub-megawatt size would be used in the wind farm. All installation and maintenance activities can be performed with a 500-tonne crane. Under ideal conditions, the wind farm alone can fully meet the island’s current electricity requirements.

The diesel plant is located near to the BOPEC oil terminal in the northwest of the island, approximately 10 km away from the wind farm. The plant consists of five MAN Type 9L27/38 diesel engines, each of 2.8 MW power output, which have the advantage that they have a very short start-up time and essentially become available at the ‘flick of a switch’.

The number and size of diesel engines was a result of studies and load simulations. The diesel power plant has to be operated on a very wide power range from 0 MW to the full capacity of 14 MW to cover always just the load that cannot be delivered at that moment by the wind turbines.

To allow the diesel engines to be operated always at their most efficient ” between 70 and 100 per cent load of each diesel engine ” it was calculated that more smaller diesel engines would be more efficient than fewer larger ones.

Initially, the diesel plant will be run on conventional diesel and HFO, but an important part of the project is to ultimately produce bio oil from algae to run the power plant. The diesel power plant will therefore be equipped to burn both mineral and biofuels.

Bonaire has a number of large saltpans suitable for growing saltwater algae. However, it is anticipated that between three to five years of research and development will be needed before a bio fuel producing facility is up and running. The consortium estimates that 10 000 tonnes of algae will be needed to run the power plant. Enercon is also in charge of the wind-diesel load balancing management system.

The company already commercially markets a sophisticated wind powered water desalination system and a wind-diesel system. Besides a wind turbine and diesel generator, the latter comprises an in-house developed flywheel system, a containerized energy storage battery pack, and a so-called ‘black start’ unit. This device is necessary to create operational grid conditions in an island-type grid system during start-up.

According to Enercon, a wind penetration rate of 90 per cent is achievable with this system. A demonstration system comprising a 600 kW E-40 turbine and an additional hydrogen production and storage unit delivered by Hydro (formerly Norsk Hydro) of Norway, was installed and commissioned on the Norwegian island Utsira in 2004.

A second test and demonstration wind-diesel system comprising a 330 kW turbine operates in the vicinity of Enercon’s company headquarters in Aurich, Germany. A third and larger wind-diesel was installed on one of the Falkland/Malvinas islands during the second quarter of 2007.

However, the Bonnaire wind-diesel project initially will not include flywheel technology, and the initial aim is a wind penetration rate of 40-45 per cent. However, an option to boost the wind penetration rate may be considered at a later stage.

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Bonaire’s benefits

When the new system is up and running, power consumers on Bonaire are expected to be able to look forward to a between 10-20 per cent reduction in their electricity bills. Further, the island’s dependence on highly fluctuating (and steadily rising) oil prices will be substantially reduced and electricity will be more reliable.

Finally, the island’s CO2 neutral electricity is expected to save in the region of 70 000 tonnes of greenhouse gases. The combination of algae production, the wind turbines, and the biodiesel plant is also expected to give a major boost to the island’s employment.

What is unique about the Bonnaire project is that it will serve as a very useful test bed for the high penetration of wind energy onto the electricity grid at a time when there is a growing integration of intermittent renewable energy on the world’s grids.

Potentially, the Bonaire project can also become a model for bringing a stable and reliable electricity supply to other islands or remote regions.

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