Spain completes testing of Europe’s largest research vanadium BESS
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Summary
Spain's Fundación Ciudad de la Energía (Ciuden), a government energy research foundation, has completed operational testing of a 1 MW/8 MWh vanadium redox flow battery (VRFB) system at its Cubillos del Sil technology center, which it says is the largest vanadium flow battery in Europe dedicated to applied research.
<p class="p1"><span class="s1">Spain's Fundación Ciudad de la Energía (Ciuden), a government energy research foundation, has completed operational testing of a 1 MW/8 MWh vanadium redox flow battery (VRFB) system at its Cubillos del Sil technology center, which it says is the largest vanadium flow battery in Europe dedicated to applied research.</span></p><p><strong>From <a href="https://www.pv-magazine.es/2026/03/23/hibridan-22-mwp-fotovoltaicos-con-sistemas-bess-de-flujo-de-vanadio-ion-litio-y-sodio-azufre-y-dos-electrolizadores/" rel="noopener" target="_blank">pv magazine Spain</a></strong></p>
<p class="font-claude-response-body break-words whitespace-normal leading-[1.7]">Ciuden, a body under Spain's Ministry for Ecological Transition and the Demographic Challenge, has completed testing of a VRFB system at its Technology Development Center in Cubillos del Sil, northwestern Spain.</p>
<p class="font-claude-response-body break-words whitespace-normal leading-[1.7]">The 1 MW/8 MWh system includes a dedicated 100 kW/800 kWh module for R&D testing under controlled conditions. The contract was awarded to Spanish company CYMI for €6.4 million ($7.4 million), incorporating technology from South Korean firm H2 Inc.</p>
<p class="font-claude-response-body break-words whitespace-normal leading-[1.7]">The VRFB system joins two storage technologies already deployed at the site during 2025: a sodium-sulfur (NaS) battery rated at 1 MW/5.8 MWh and a lithium-ion system rated at 600 kW/1.3 MWh. The three systems are hybridized with a 2.2 MWp solar installation, bringing total storage capacity to close to 15 MWh – sufficient to absorb the daily output of the solar plant during periods of high generation. The installation also incorporates two electrolyzers commissioned at the end of 2025: a 300 kW proton exchange membrane (PEM) unit and a 250 kW solid oxide electrolyzer cell (SOEC) operating at high temperature.</p>
<p class="font-claude-response-body break-words whitespace-normal leading-[1.7]">Ciuden said the VRFB system offers more than 15 hours of storage autonomy, making it the longest-duration battery system available in Spain for demonstrative-scale R&D testing. The technology uses the redox reaction of vanadium across four oxidation states in liquid electrolytes stored in independent tanks, enabling a service life of more than 20 years and modular capacity expansion by decoupling power and energy ratings.</p>
<p class="font-claude-response-body break-words whitespace-normal leading-[1.7]">The project's primary objective is to generate technical and operational data to support industrial scalability, analyzing efficiency, degradation, integration with renewables, and response to different load profiles.</p>
<p class="font-claude-response-body break-words whitespace-normal leading-[1.7]">Ciuden said the multi-technology configuration – combining solar generation, three distinct storage chemistries, and two electrolyzer types – represents a singular experimental environment at European scale for validating advanced storage and green hydrogen solutions.</p>
<p class="font-claude-response-body break-words whitespace-normal leading-[1.7]">The initiative is funded under the NextGenerationEU program within Spain's Recovery, Transformation and Resilience Plan (PRTR).</p>