The power of many

Contact Newsletter +49 221/ 82 00 85 - 0
Reading time: 6 min
by Christian Sperling / 27 December 2018
Windfarm in the country site on an island.

Renewable Energy Island – Part 1

Somewhere in the big blue ocean, there lies an island that can serve as a blueprint for the approach to tackle the challenges of climate change with a self-sufficient supply through renewable energies.

Somewhere in the big blue ocean, there lies an island that can serve as a blueprint for the approach to tackle the challenges of climate change with a self-sufficient supply through renewable energies. 

Enabling a reliable and climate-friendly supply based on decentralized energy supply is one of the major goals of Next Kraftwerke. Unfortunately, this cannot yet be achieved on a very large, nation-wide scale – politics and the energy industry are still too caught up in the paradigm of large fossil-fuel power plants, and the development towards a decentralized energy supply is moving slowly.

But what is not possible on a large scale yet,can already be achieved on a smaller scale: Islands and island groups are well suited forself-sufficient energy systems. Why don’t we have a look how this might work?

Cutting off islands from fossil energy production on the mainland

Generally speaking, the power supply of islands is usually based on one of the two following concepts: Either the island has its own power generation facilities or the electricity is transported from the mainland or a neighboring island via submarine cables. A lot of times, smaller offshore islands, which are situated further away from the mainland, are equipped with medium to large diesel generators; larger offshore islands tend to have oil or coal-fired power plants. This is where the first problem occurs: Diesel, oil or coal need to be shipped to the islands. This not only poses a problem in times of bad weather, but it is also very expensive and worsens the CO2 balance due to the energy consumption of the ships responsible for the transport.

Additionally, even transporting power via submarine cables may be problematic. The Greek Cyclades are a good example: Being relatively close to the mainland, these islands are all supplied with electricity generated in large fossil-fuel power plants on the Greek mainland via a network of submarine cables. In case of a malfunctioning cable the islands are without power except for the supply from a few smaller emergency generators. History has shown, that these power failures can last for several hours, depending on the type of disturbance. Plus, voltage fluctuations, short outages and voltage sags are also commonplace on the island due to the poor condition of the distribution and low-voltage networks.

Almost all islands are surrounded by directly usable energy sources

So why shouldn’t they uses sources that are already directly available?. Nearly every island has great potential for onshore and offshore wind parks. And if the island is not situated in polar regions, chances are high that solar power is also a good option for generating power. 

Cogeneration units and power storage units can support this power generation and help provide a steady supply in times of low wind and solar power feed-in. In order to maintain such a system, an intelligent and central management of the energy supply is required. This can be quite difficult to achieve with the often decades-old energy infrastructure on islands.

Reliable power supply with additional ecological benefits

The major challenge is that electricity produced by volatile energy sources such as wind and photovoltaics cannot be produced in an exactly targeted manner. But through the aggregation of power producing and consuming units in a Virtual Power Plant, this challenge can be met. Feed-in schedules as well as exact forecasting for weather, production and consumption help a lot. Consumption can be shifted to periods with oversupply, cogeneration and power-to-x-technology can be used for transforming power into heat or gas.

Balancing seasonal effects

With the exception of tropical latitudes, islands are subject to seasonal effects invarying degrees. While electricity consumption on predominantly tourism-oriented islands tends to fall in the winter months due to the lack of tourists, it rises on islands without a tourism-oriented character due to the larger demand for heating and lighting. 

While solar energy supply is reduced to the seasonal minimum during these periods,wind power plants, biomass CHPs and pumped storage power plantstake over the island’s power supply. Andin cases of neccessity – on cloudeddays without wind, for example – gas CHPs and emergency generators can provide the needed power.

Existing projects, application examples and initiatives

Island projects with electricity from 100 percent renewable energies are currently rather the exception than the norm. A lot of times, conventional electricity producers still have to support the power production based on renewables. Nevertheless, there are already promising approaches – such as the projects on the Danish island of Samsø or the Canary Island of El Hierro, which have already come quite close to the goal of 100 percent renewable energies for self-sufficient island power supply, using various ways.

Caribbean - Sint Eustatius: The PV battery diesel hybrid power plant

On 24 March 2016, SMA Solar Technology AG (SMA) commissioned a photovoltaic battery/diesel hybrid power plant on Sint Eustatius, a 21 km² Caribbean island belonging to the Netherlands with 4,000 inhabitants. As a supplement to the existing 5 MVA diesel power generation plant, the first expansion stage of the hybrid power plant with a peak output of 1.89 MWp and a 1 MW battery storage system was already able to significantly increase the renewable energy share on the island.

The second expansion stage, with an increase in PV capacity to 4.15 MW and a battery capacity of 5.9 MWh, will now be able to supply the entire island with electricity from renewable sources as long as the PV feed-in is high enough.

Canaries - El Hierro: Wind and pumped-storage systems create energy independence

El Hierro is located 1,500 kilometers from the Spanish mainland. With only 11,000 residents, it is the smallest and most remote island of the Canary Islands. Until June 2014, power was supplied exclusively by a diesel generator, whose fuel supply had to be delivered to the island by ship – resulting in 18,200 tons of CO2 emissions annually. The classification of El Hierro as UNESCO Biosphere Reserve in 2000 marked the start of an ambitious project aimed at supplying the island exclusively with electricity from renewable sources. The project was funded by the Spanish government, the EU and the Spanish energy supplier Endesa. However, its goal has not yet been fully achieved by 2017, partly because of unforeseen geological problems and partly because of the project’s pioneering nature.

Due to the island’s mountainous topography and the high amount of wind present on the island, the idea for this project was to install a pumped-storage power plant that is fed by a windfarm. The Gorono des Viento wind farm opened in 2014 and it feeds the pumped-storage plant located above. The installed wind energy capacity of 11.5 MW, combined with the 11.32 MW capacity of the pumped-storage power plant, is sufficient to supply El Hierro completely with electricity from renewable sources and to operate the seawater desalination plants, also helping the island with its low fresh water supply. However, the diesel generator is currently required as a backup to compensate for power fluctuations. 

Endesa web portal on the El-Hierro project

Denmark – Samsø: The island with a negative CO2 fingerprint

20 years ago the inhabitants of the Danish island of Samsø located in the Baltic Sea decided to completely supply their island with electricity and heat from renewable energies by 2030 - by 2017 already, this goal has almost been achieved. In order to do so, the residents combine nearly all renewable technologies: CHPs fired with biogas, wood and straw, a 2,500 m² solar heat plant, various PV plants and eleven onshore and ten offshore wind power plants, with an installed capacity of 34 megawatts in total – all in all producing an abundant energy surplus.

Furthermore, the turbines are not owned by a single investor or the Danish state, but are distributed to many individual private owners on the island, who have personally committed themselves to the 100 percent renewable energy target. Currently, the people of Samsø are already generating negative CO2 emissions of minus 12 tons per inhabitant. Since 2007, the experience and results have also been documented in an in-house energy academy (Energitjenesten Samsø).

More information on the project at

GREIN: Global Renewable Energy Islands Network

Under the auspices of the United Nations, IRENA (International Renewable Energy Agency) launched the GREIN project. The aim is to exchange ideas and have practical discussions on how to create viable roadmaps for the expansion of renewable energies on islands. Important topics are grid integration, the question of resources, the requirements of tourism, sustainable seawater desalination, and techniques for clean waste incineration. In the meantime, the first roadmaps for Barbados and Kiribati have been developed. In Cape Verde and Vanuatu, the GREIN project has been active in an advisory capacity. 

More information on the GREIN web portal at the United Nations

Christian Sperling

Christian Sperling

Content Marketing Manager