Let’s try to imagine that the energy system was already exclusively run on renewable energy. If we would turn the switch on a sultry summer evening, something would not work as expected: in fact, grid-connected wind farms or solar PV fields would not be producing energy at that time. Obviously, in order to switch the light on or turn the washing machine on, we cannot wait for the wind to blow or the sun to shine. Therefore, in order to carry out the ‘green revolution’, the main limitation of some renewable sources – their scarce predictability - must be solved.
Presently, in order to avoid blackouts, this variability is compensated for by grid-injecting energy generated by thermal electric plants or by programmable renewables such as hydropower and geothermal. Now the last step can finally be made, with the development of batteries for energy accumulation when there’s peak production (windy or very sunny days), avoiding its dispersion and reinjecting it into the grid when it’s most convenient.
In fact, there are some days in which renewable energy generation is capable of meeting the total energy needs of entire areas. As distributed generation grows, the grid will need to become increasingly flexible. Storage is an essential tool to this end. Thanks to accumulation systems, generation can actually be adjusted to the needs of the grid, avoiding the dysfunctions - instability of voltage or frequency levels - caused by load or generation excess: additionally, this way a more flexible and efficient management of a more or less broad portion of the grid is made possible.
There are various types of accumulation systems. Thermal storage uses energy from sun radiation, pumping storage harnesses hybrid basins downstream of hydropower plants, while electro-chemical storage involves the use of batteries. Already some interesting storage tests are ongoing also with inertial flywheel systems and with the so-called ‘ultracapacitors’. The Enel Group has been aware of this technology’s potential for years, having started to test its first experimental models in Italy and Spain.
In 2014 in Chile we have provided electricity around the clock to the small mining village of Ollagüe, located at a height of 3,660 metres. The hybrid system we built there consists of 1,539 solar PV panels, a small-wind plant equipped with accumulation batteries, an emergency diesel generator and two Trinums (concentrated solar co-generation systems) that can simultaneously generate electricity and thermal energy. Many areas in South America have weak electricity grids and a great abundance of renewable sources, and in these cases storage can solve serious powering problems.
In Italy – specifically in Catania – we inaugurated in September a 1MW/2MWh storage system, connected to a 10 MW solar PV plant, which uses the Durathon "sodium-metal halide" technology developed by General Electric. On the other hand, at the Potenza Pietragalla facility, storage is embedded into the pre-existent wind farm. This 2MW/2MWh system is the first to use Samsung SDI ion-lithium technology, which can ensure extremely high performances. Also in Italy, on the island of Ventotene we have completed the tests aimed to verify the 300 kW and 600 kWh ion-lithium technology-based battery, which will integrate the island’s generation system. In fact, Ventotene is powered by a storage system achieved by Enel that allows to store the electricity generated by the small local generators, thus avoiding waste in the wintertime and blackouts in the summertime (when the island is densely inhabited by tourists) and reducing the use of fuel and related emissions.
In Spain, again in the islands - where the depth of the seabed hinders the connection to the domestic grid - we are developing the STORE - Storage Technologies of Reliable Energy - project. On the Canary islands three storage plants are already online: a lithium battery system on the Gran Canaria, an inertial storage system on La Gomera, an ultracapacitor bench on La Palma.
Within this technological innovation context we have signed a partnership with Tesla Motors, a US-based manufacturer of top-of-the-range electric vehicles, to test the integration of their storage systems into our wind farms and solar PV fields. Test results will provide information on production growth at facilities and renewable integration into the electricity grid. Besides Tesla, our projects involve partnerships with other large sector global players such as Fiamm, General Electric, Samsung SDI and Toshiba, and we are evaluating the possibility of introducing storage in other countries in which we are present.
Over the last few years renewable technologies have advanced at an extremely fast pace. Storage is the final piece to complete the puzzle for a zero-emissions future: a scenario which will find the Enel Group at the forefront due to its large-scale development.