CITYSOLAR · Project

Transparent Solar Windows That Generate Electricity Without Blocking Light

energyPrototypeTRL 4

citysolar-h2020.eu

Imagine if your office windows could generate electricity while still letting daylight through — that's exactly what this project built. Regular solar panels are dark and opaque, so you can't put them on windows. CITYSOLAR combined two types of advanced solar cells — one that captures near-ultraviolet light and another that captures near-infrared — stacking them together so visible light passes through while invisible light gets turned into power. The result is a see-through solar window prototype that aims to boost transparent solar performance by 50% compared to what was previously available.

By the numbers

50%

Targeted performance improvement over existing transparent PV technologies

EUR 3,779,242

EU funding for development

Consortium partners across 7 countries

Industrial partners in the consortium

40%

Industry participation ratio in consortium

The business problem

What needed solving

Buildings in cities have vast glass surfaces that waste solar energy potential. Conventional solar panels are opaque and cannot replace windows, leaving urban buildings dependent on the grid even when surrounded by sunlight. Meeting nearly zero-energy building regulations in dense cities requires a way to generate renewable energy from vertical glass facades — not just rooftops.

The solution

What was built

The project built a working prototype of a transparent solar window that embeds a tandem perovskite-organic solar cell device into a building-integrated PV module. This demo unit was designed to show how the technology could work in a real window application, targeting a 50% performance improvement over existing transparent photovoltaic solutions.

Audience

Who needs this

Commercial property developers building or retrofitting large glass-facade office towersArchitectural glass manufacturers looking to add energy-generating products to their catalogSmart city planners and municipal energy offices targeting urban renewable generationBuilding facade engineering firms designing high-performance building envelopesGreen building certification consultants helping clients achieve NZEB compliance

Business applications

Who can put this to work

Commercial Real Estate & Property Development

enterprise

Target: Property developers and building owners managing large glass-facade office buildings

If you are a property developer dealing with rising energy costs and pressure to meet nearly zero-energy building standards — this project developed transparent solar window modules that generate electricity from your existing glass surfaces without sacrificing natural light. With a 50% performance improvement over previous transparent photovoltaic technologies, this could turn every window into a power source and reduce your grid dependency.

Glass & Facade Manufacturing

mid-size

Target: Architectural glass manufacturers and facade system integrators

If you are a glass manufacturer looking to differentiate your product line with energy-generating glazing — this project built a working prototype of a solar window embedding tandem perovskite-organic solar cells into building-integrated PV modules. The technology uses advanced light management to maintain transparency while maximizing energy capture, giving you a next-generation product to offer architects and developers.

Smart Building & Energy Management

any

Target: Building energy system integrators and smart building technology companies

If you are a building energy integrator struggling to find renewable generation options for dense urban environments where rooftop space is limited — this project demonstrated window-integrated multi-junction solar cells designed specifically for city buildings. With 10 partners across 7 countries and 4 industrial players involved, the technology was designed with real integration requirements in mind.

Frequently asked

Quick answers

What would it cost to integrate these transparent solar windows into a building?

The project did not publish specific cost-per-square-meter figures. As a Research and Innovation Action with EUR 3,779,242 in EU funding, the focus was on proving the technology works rather than optimizing production costs. Commercial pricing would depend on manufacturing scale-up by industrial partners.

Can this technology be manufactured at industrial scale?

The project delivered a BIPV prototype — a solar window embedding the tandem device in its structure — aimed at bringing the technology close to a real product application. However, scaling from prototype to industrial production would require additional engineering. The consortium included 4 industrial partners, which suggests manufacturing considerations were part of the project scope.

What is the intellectual property situation — can I license this technology?

The project description notes that some consortium members hold key intellectual property. IP generated during the project is governed by the Horizon 2020 grant agreement, which typically allows partners to license results. You would need to contact the coordinator (Consiglio Nazionale delle Ricerche, Italy) to discuss licensing terms.

How much more efficient is this compared to existing transparent solar panels?

The project objective explicitly states a target of increasing the performance of available transparent photovoltaic technologies by 50%. This was pursued through multi-junction architecture combining perovskite and organic solar cells with advanced light management techniques.

Does this comply with building energy regulations in Europe?

The technology directly supports the EU's nearly zero-energy building requirements mentioned in the project objectives. Transparent photovoltaics are designed to be embedded in building applications to reduce CO2 emissions. Specific building code certifications would still need to be obtained for commercial deployment.

How long before this could be installed in actual buildings?

The project ended in April 2024 with a completed BIPV prototype. The deliverable description states the aim was to bring the technology close to a real product application, suggesting further development and certification steps remain before commercial installation. Based on available project data, a realistic timeline to market would depend on the industrial partners' commercialization plans.

Consortium

Who built it

The CITYSOLAR consortium is well-balanced for a technology development project: 10 partners spread across 7 countries (Canada, Switzerland, Germany, Denmark, France, Italy, Saudi Arabia), with a 40% industry ratio — meaning 4 out of 10 partners come from the private sector. The coordinator is Italy's National Research Council (CNR), one of Europe's largest public research organizations. The mix of 4 universities, 2 research institutes, and 4 industrial players (including 1 SME) suggests the project was designed with eventual commercialization in mind, though led by a research institution. The inclusion of non-EU partners from Mission Innovation countries adds access to specialized materials expertise. For a business looking to adopt this technology, the industrial partners are the most likely path to commercial products or licensing arrangements.

CONSIGLIO NAZIONALE DELLE RICERCHECoordinator · IT
UNIVERSITA DEGLI STUDI DI ROMA TOR VERGATAparticipant · IT
FRIEDRICH-ALEXANDER-UNIVERSITAET ERLANGEN-NUERNBERGparticipant · DE
ELECTRICITE DE FRANCEparticipant · FR
ENI SPAparticipant · IT
KING ABDULLAH UNIVERSITY OF SCIENCE AND TECHNOLOGYparticipant · SA
SYDDANSK UNIVERSITETparticipant · DK
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRSparticipant · FR

How to reach the team

Consiglio Nazionale delle Ricerche (CNR), Italy — contact via CORDIS project page or project website

Order a report on this consortium See CONSIGLIO NAZIONALE DELLE RICERCHE profile →

Next steps

Talk to the team behind this work.

Want an introduction to the CITYSOLAR team to discuss licensing or pilot integration? SciTransfer can arrange a direct connection with the right consortium partner for your needs.

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