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Interview: Behind Spanish island’s ‘100% renewable energy’ project headlines

The International Renewable Energy Association (IRENA) recently released its electricity storage technology roadmap, looking at how electricity storage can support the increased deployment of renewable energy.

The roadmap highlighted the necessity of electricity storage in remote areas and on islands, but also cited this as an economic opportunity.

For some time IRENA and other experts have said that islands could act as test cases and models for energy storage in the wider market.

Last week, PV Tech Storage reported that Spain’s El Hierro, the most southerly of the Canary Islands, managed to use a combination of only wind, hydro and energy storage to meet the energy needs of all of its 10,000 locals for a total of four hours.

The island has an EUR80 million (US$91 million) facility with five wind turbines, whose excess energy is stored by raising water via a pump system into an artificial reservoir. When there is an energy shortfall, the water is channeled back through turbines to produce more electricity.

Meanwhile, back in January, Chilean authorities received plans from developer Valhalla Energy for a 600MW PV project to be connected to a 300MW pumped hydro energy storage plant. The US$1 billion project was earmarked for the northern Tarapaca region and it was claimed that the plant’s combined technologies would allow electricity generated to be used 24 hours a day.

In light of this, PV Tech Storage spoke to Emanuele Taibi, Island Roadmaps Analyst for IRENA, about the specifics El Hierro’s storage technology and what factors could help it to run on 100% renewable energy and storage for even longer than four hours.

Dinorwig pumped hydro storage facility in Wales, UK. According to IRENA's Emanuele Taibi, the El Hierro project - and others - represent a new paradigm for the established technology. Image: flickr user: Dennis Egan.
How significant is this development?

The project is indeed very significant. IRENA has been invited to the commissioning of this unique system, and it is a first for an island to rely mostly on wind and pumped hydro storage for its electricity supply and we hope that greater visibility of innovative projects like these can encourage others to act. Globally, the vast majority of energy storage is pumped hydro. In the case of El Hierro, unlike most of the existing pumped storage systems worldwide, the reservoir has been created artificially just for storage purposes, instead of using an existing hydro power plant with a typical dam on a river used to create the reservoir.

What are some other notable examples of successful island-based storage projects?

Successful cases of islands with large shares of variable renewable energy, enabled by storage solutions, exist in every region. From King Island in Australia, to Tokelau in the Pacific, to Pellworm in Germany, Samso in Denmark, Jeju in Korea, etc. An important element is that new systems will often experience challenges, and careful planning can help in reducing these. Having experts to support islands, as living laboratories for the energy transition, in finding solutions for the operations of these systems would create the knowledge base for replicating these models elsewhere. In the case of King Island, several technical challenges were encountered and solutions have been developed. Now King Islands is a global training centre that hosts a workshop for owners and operators of remote area power systems.

The pumped hydro plant on El Hierro. This and cover image: Gorona del Viento
How can we increase reliance on renewables and storage to much longer durations?

What is crucial is to understand storage requirements for a specific system in view of designing a minimum cost system. When it comes to islands that use batteries, a combination of different technologies is sometimes used to address short term, in minutes, and long term, in hours, of storage, to ensure that grid operation is reliable, and that electricity is available also when the sun does not shine and the wind does not blow.

In the case of El Hierro, where the storage solution is a water reservoir purpose-excavated for the system, the easiest way to increase the duration of the storage would be to make the grid smarter, so that electricity is mostly consumed when wind is blowing. Then if the electricity is produced by releasing water from the reservoir, most non-critical electricity uses are postponed.

When electricity is being produced from wind, a smarter grid could be used to activate appliances, such as washing machines, dishwashers and hot water boilers, via remote control. When running on pumped hydro storage, however, the appliances could be deactivated.

Storage can also be on the demand side, using chilled water and ice storage for air conditioning and refrigeration, in addition to electric water heater. In this way it is possible to make the best out of the wind resource, reducing curtailment of excess production, and at the same time maximise the duration of storage.

A smarter grid could also inform the user about the current price of electricity. This would be determined instantaneously based on marginal generation cost. Electricity from storage has the highest cost and excess electricity that would otherwise be curtailed would almost be free.

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