Big footprint on a small island

46 km off the coast of Italy, the small island of Ventotene is installing a new hybrid energy solution that has the potential to make a big impact. The solution uses a Microgrid Controller to combine the existing diesel motors with renewables and an innovative storage system, reducing fuel, costs and emissions – and raising the quality of life.


by Claudia Flisi

Isolation, as well as seasonal volatility, was a problem for the island, aptly named Ventotene, “swept by the wind”. Once used as a place of exile by Roman rulers it is located 46 kilometers from Italy’s western coastline, about halfway between Rome and Naples, and is so remote that even today, its 700-plus permanent residents are not connected to Italy’s national electric grid.


Where does energy come from on a small, isolated island in the Mediterranean? Four diesel generators, with each producing 600 kVA, had met the island’s energy needs for years. The motors struggled to cope with load variations and were not working in the optimal operating range. The result was a decrease of asset service life.

This initiative has improved our way of life on the island. It is the beginning of a new way to live, a new co-existence with and respect for our environment.
Long-time resident Pietro Pennacchio

The advent of tourism in recent years has changed Ventotene’s needs and expectations. Reports Pietro Pennacchio, director of the island’s Mezzatorre Hotel: “I have seen this place transform from a state of quasi-abandonment when I came in the 1970’s to what it is today.” One example: buildings that were used as dwellings for exiled prisoners centuries ago have become vacation homes for summer visitors today – visitors with modern energy demands.

Incorporating existing infrastructure

The Italian energy utility, ENEL, took a look at the situation in Ventontene in 2014. As elsewhere in Italy and other countries where they are present, Enel is pursuing sustainable actions aimed at decreasing greenhouse gas emissions and increasing asset efficiency, flexibility and reliability. The goal for Ventotene was to support power generation and the distribution of their isolated network, thereby lowering fuel consumption as well as emissions and energy supply costs, and increasing their grid hosting capacity for new renewable energy systems. According to ENEL, the company planned to do this by developing a new hybrid solution that would integrate existing infrastructure (the diesel motors) and innovative storage systems (lithium batteries) to maximize plant efficiency, reduce emissions, and increase system reliability and asset lifetime, allowing for higher renewable penetration.

Thanks to Enel’s intervention in the power station, many of the island's homeowners and businesses have had the opportunity to install photovoltaic panels over the last years, reports Pennacchio. ENEL has seen large savings in their energy costs during this transition. According to the company, it is a great satisfaction for them to use the sun's renewable energy – consuming less and polluting less. Solar panels currently produce 90 kW of energy for the island. They are useful for water heating and cost saving. But the problem was that the energy produced was inherently unstable and existed independently of the energy from the diesel motors.

Turnkey storage and grid management

Flexibility and storage capability were going to be key to the new system. According to ENEL, the company was interested not only in pricing but in competence, reliability, and sustainability. And it was looking for a partner who shared its values. Since ENEL had worked with Siemens on a storage system that was later installed in it’s distribution network, the Italian utility asked Siemens to participate in the project.

The partners proposed a customized turnkey solution that included building a Siestorage battery energy storage system with an output of 500 kW and a storage capacity of 600 kWh, managed by a Microgrid Controller. The advanced control system, developed by Enel and Siemens, ensures that the diesel generators can be used more efficiently because short-term peak loads are covered by power from the storage system and not from the generators.

When solar power is the prime energy source, it is supplied by lithium ion batteries that compensate foreseeable fluctuations in the power of the island’s photovoltaic generators, ensuing stability of the network. Lithium ion batteries were chosen specifically because they combine high performance and a high number of charge and discharge cycles. The batteries alone can supply energy to the network when they are sufficiently charged and demand is “normal” – that is, in all but peak periods. According to ENEL, Ventotene’s energy comes only from the batteries about 25 percent of the time.

Seamless integration of resources

Modularity and flexibility are the other key elements of the hybrid system. It is designed to allow proper functionality even when part of the battery is disconnected or when there is a breakdown in one of its inverters. Its flexible design ensures that renewable sources, such as the island’s solar panels, can be integrated into the network seamlessly.

The Microgrid Controller manages supply and demand intelligently, reducing the problems of seasonal volatility and fluctuations inherent in solar energy sources. Its intelligence also means optimal functioning of the diesel motors, turning them off when demand is low as well as allowing them to work with maximum efficiency. The result is a savings in annual fuel costs of around 15 percent; because a motor functioning at full load consumes less fuel, reduces emissions, and experiences less wear and tear.

Consequently, the island’s grid stability increased, allowing more distributed PV panels to be installed. Constant monitoring of electrical frequency and tension has virtually eliminated blackouts in the summer.

A renewed way of life

Additional benefits include decreased maintenance costs due to fewer hours of operation of the diesel motors, and an improvement in environmental sustainability because CO2and NOX emissions are drastically reduced. The upshot is a reliable system for the entire life of the installation, satisfying to both ENEL and the islanders.


The implications extend beyond one little island. Ventotene may be a small project but it has a potentially large footprint. It represents on a small scale what could be accomplished more and more frequently in the future, in Italy and beyond: the integration of pre-existing energy solutions, such as diesel motors, with sustainable implementations that are technologically advanced and tap renewable energy sources.


Claudia Flisi is an independent journalist based in Milan, Italy.

Picture credits: Siemens AG

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