Solar windows are one of the latest cutting-edge renewable energy products. They can help generate free electricity anywhere a pane of glass is placed.
Traditional solar power generation requires installing solar panels on your roof. Solar windows generate electricity by harnessing the daylight passing through them.
These innovative solutions combine the functionality of traditional glass with the ability to harvest sunlight and promise to redefine how we think about building design and sustainability.
But what are solar windows, and how do they work?
Quick Takeaways:
- Solar windows are similar to regular windows but have photovoltaic cells to capture and convert sunlight to electricity
- They range from transparent and semi-transparent to quantum dot solar windows, solar film and solar window coatings, organic photovoltaic solar windows, and smart solar windows
- Estimated prices range between £175 and £250 per square metre of solar glass
What Are Solar Windows?
Solar windows are simply solar panels that resemble semi-transparent or transparent glass panes. They can function similarly to conventional windows but feature photovoltaic glazing that contains solar cells to convert sunlight into renewable electricity.
They’re a kind of building-integrated photovoltaics (BIPV), a technology that is integrated within the building rather than installed on it.
This direct integration into infrastructure creates a more seamless approach to energy generation, making them suitable for application in urban areas where space is limited.
However, they have only been installed in a few projects, most of which are commercial rather than domestic. Solar windows are currently undergoing a lot of research and development, so they could be worth considering if you love the idea of solar panels but don’t like how they look on top of the roof.
How Do Solar Windows Work?
Solar windows work similarly to solar panels but can allow light to pass through them. The photovoltaic glazing acts like the silicon wafers on traditional solar panels.
Traditional panels capture every single photon of sunlight that lands on the surface. Solar windows allow visible photons to penetrate the glass and capture invisible light like ultraviolet and infrared waves.
The invisible light excites electrons within the solar cells, creating an electric current that moves through a tiny wire that exits out of the window and connects to the building’s wiring, just like a standard solar system.
Types of Solar Windows
Transparent Photovoltaic Solar Glass
These windows utilize transparent photovoltaic (PV) cells to capture sunlight and convert it into electricity.
In 2014, researchers at Michigan State University developed a new type of solar concentrator that could be placed over a window to generate solar electricity while allowing people to see through the window.
The researchers quickly brought the development onto the solar market through a company called Ubiquitous Energy, which now produces transparent solar cells and electricity-generating alternatives to traditional windows.
Features
- Absorb non-visible light (UV and infrared) while allowing visible light to pass through, ensuring transparency.
- Maintain the appearance of traditional windows.
- Efficiency ranges from 5–10%, depending on the materials used.
Applications
- Residential and commercial buildings.
- Suitable for maintaining aesthetic appeal while generating energy.
Semi-Transparent Solar Glass
Semi-transparent solar glass strikes a balance between energy generation and light transmission. They are partially tinted, which allows them to absorb more sunlight while letting some visible light through.
Features
- Higher efficiency compared to fully transparent solar windows due to increased light absorption
- Slightly tinted appearance
- Often utilize thin-film solar technologies.
Applications
- Office buildings and high-rise structures with extensive glass façades
- Greenhouses that need controlled light levels and energy generation
Solar Window Coatings
Solar coatings can be applied to existing windows to give them solar energy-harvesting capabilities. NEXT Energy Technologies developed a proprietary transparent photovoltaic (PV) coating that transforms commercial windows into energy-generating windows. NEXT estimates that the windows can produce up to 30% of the power of traditional solar panels.
Features
- Consists of a thin layer of photovoltaic material or quantum dots
- Retrofitting option for buildings with installed windows
- Cost-effective compared to replacing entire window panes
Applications
- Older buildings or infrastructure where replacing windows is impractical
- Temporary solutions for testing solar technology
Quantum Dot Solar Glass
Quantum dots are microscopic semiconductor particles that absorb sunlight and emit it at a different wavelength, directing it toward solar cells at the edges of the window.
They’re usually nano PV cells implanted directly into the glass. U.S. manufacturer UbiQD developed a solar window with laminated glass and luminescent solar concentrators based on copper indium sulfide and zinc sulfide quantum dots and is testing pilot installations in Nevada.
Features
- High efficiency in capturing light and directing it to PV strips
- Maintain transparency while maximizing energy output
- They’re applicable as coatings or embedded directly into glass
Applications
- Modern commercial buildings and urban infrastructure
- Smart windows with integrated solar capabilities
Solar Film Windows
Solar films are thin, flexible layers of photovoltaic material that can be applied to window surfaces. In 2011, 3M developed a see-through film that turns ordinary windows into solar panels.
The solar film is arrayed in narrow, translucent green strips with clear gaps between them. It is glued to windows in large patches and can generate around 20% of the electricity of a traditional silicon solar panel.
Features
- Lightweight and easy to install
- They can be used on existing windows or in conjunction with other solar technologies
- Lower energy generation compared to embedded PV cells
Applications
- Retrofitting homes and businesses
- Temporary installations for energy testing
Organic Photovoltaic (OPV) Solar Glass
Organic photovoltaics use carbon-based materials to create solar cells. These materials are flexible and can be integrated into window designs. A group of researchers at the University of Michigan developed an organic solar cell with an efficiency of around 10% and a transparency of 40%.
Features
- Lightweight and highly customizable
- Less energy-intensive to produce than silicon-based PV cells
- Lower efficiency but more sustainable manufacturing
Applications
- Eco-friendly building projects
- Lightweight structures or mobile applications
Dynamic Solar Glass
These combine energy generation with dynamic tinting, allowing them to adjust their transparency in response to sunlight.
Features
- Integrated solar cells with light-sensitive materials for shading control
- Reduce energy costs for cooling and heating in addition to electricity generation
- Advanced features like smart home integration
Applications
- High-tech office buildings and luxury homes
- Greenhouses that need precise light and heat control
What are their Advantages?
Dual Functionality
They can act as both standard windows and power generators. This dual purpose ensures they serve practical and energy-efficient roles simultaneously.
Aesthetic Appeal
One of the standout features is their ability to blend seamlessly into a building’s design. Unlike traditional solar panels, which can be visually intrusive, solar windows maintain a sleek and modern appearance.
Space Efficiency
In densely populated urban areas, where rooftop space is often limited, solar windows provide an innovative way to generate renewable energy without requiring additional real estate.
Lower Carbon Footprint
By harnessing sunlight, solar windows reduce reliance on fossil fuels, help to lower harmful emissions and combat climate change.
Energy Savings
Buildings equipped with solar windows can generate their own electricity, significantly reducing utility bills over time. While the initial investment may be high, the long-term savings often justify the cost.
Versatility
Solar windows are not limited to residential or office buildings. They can be used in vehicles, greenhouses, public infrastructure, and more, showcasing their adaptability.
What Are Their Disadvantages?
While solar windows hold great promise, they also come with challenges that must be addressed.
Lower Efficiency
Solar windows currently have lower efficiency rates than traditional solar panels, typically ranging from 5–10%. This is due to the transparent design, which limits the amount of sunlight that can be absorbed.
High Upfront Costs
The advanced technology in manufacturing makes them more expensive than traditional glass or solar panels. This cost barrier can deter widespread adoption, especially for homeowners and small businesses.
Durability Concerns
They must withstand environmental concerns like weather changes, wind, and debris while maintaining transparency and functionality. Ensuring long-term durability remains a challenge for manufacturers.
Regional and Seasonal Limitations
Solar windows are most effective in sunny regions. Their energy generation capabilities may be limited in areas with frequent overcast weather or during shorter winter days.
Complex Installation
Installation requires specialized skills and equipment, which can increase the overall cost of implementation.
Are There Real-world Applications of Solar Windows?
Solar windows are already making their mark across various sectors. Here are some notable applications:
Commercial and High-Rise Buildings
Skyscrapers with large glass façades are ideal for solar glass. These buildings can generate significant electricity to power their operations while maintaining a modern, sleek appearance.
For example, the Future Business Centre in Cambridge adopted transparent solar panels in its curtain walls. The Gloucestershire County Council Hall also includes a curtain wall with over 380 solar glass panels.
Canopies in Homes
They’re an excellent choice for energy-conscious homeowners with garden canopies. They’re applied as semi-transparent solar glass canopies over patio areas and ponds, allowing the integration of renewable technology naturally to provide shade and electricity for the home.
Greenhouses
In agricultural settings, they allow light to pass through for plant growth while simultaneously generating electricity. This creates a self-sustaining energy system for farmers.
Public Infrastructure
Bus shelters, train and petrol stations, and airports can integrate solar windows to power lighting, ticketing machines, and other electronic systems.
For example, Sainsbury’s petrol stations in Weymouth and Leicester all feature a canopy with integrated transparent solar glass, providing both shelter and renewable electricity generation.
Vehicles
Car manufacturers are exploring solar glass as a way to power onboard electronics or extend the range of electric vehicles.
How Do Solar Windows Compare to Traditional Solar Panels?
| Feature | Solar Windows | Traditional Solar Panels |
| Appearance | Transparent and visually appealing | Visible and utilitarian |
| Energy Efficiency | Lower (5–10%) | Higher (15–22%) |
| Space Requirements | Fits into existing windows | Requires rooftop or open space |
| Cost | Higher upfront investment | Relatively affordable |
| Applications | Ideal for urban buildings and vehicles | Best for rooftops and open areas |
How Much Do Solar Windows Cost?
Solar windows are an emerging technology, and the potential costs of installing them may be higher than those of traditional solar panels.
Estimated prices range between £175 and £250 per square metre of solar glass. With limited supply and installation complexities, you can expect the prices to be higher.
Who Offers Solar Windows in the UK?
Polysolar
Polysolar is Based in Cambridge and has developed a portfolio of innovative transparent solar glass solutions.
Founded in 2007 to develop the next generation of photovoltaic materials, Polysolar has developed and commercialised a range of transparent photovoltaic glazing materials for integration into an extending variety of solutions, including canopies, carports, facades, and other bespoke applications.
Onyx Solar
Onyx Solar is a global leader in photovoltaic glass solutions and has undertaken over 500 projects in 60 countries. The company was founded in 2009 and manufactures solar glass suitable for curtain walls, building facades, atriums, walkable floors, and canopies.
It offers solar glass with ample customization options, including various colours, shapes, sizes (up to 4000mm x 2000mm), and transparency levels, making it easy to integrate the most advanced solar technology into any architectural design.
Solarshield
Solarshield is a leading UK supplier and installer of window films. They’re 3M’s only UK Master Window Film Dealer and approved, accredited installers for the world’s largest window film manufacturers.
The company offers a nationwide survey, supply, and installation service for a full range of high-performance window films, glass containment systems, window graphics, and commercial and residential blinds.
They have also been involved with high-profile projects throughout Greater London, the South East, and across the UK.
Final Thoughts
Solar windows can help transform everyday glass into power-generating surfaces, offering a unique way to harness solar energy without compromising functionality or aesthetics.
They work similarly to solar panels but feature lower efficiencies. They range from transparent and semi-transparent to quantum dot solar windows, solar film and solar window coatings, organic photovoltaic solar windows, and smart solar windows.
Sources and References
- https://msutoday.msu.edu/news/2014/solar-energy-that-doesnt-block-the-view
- https://www.patagoniaworks.com/press/2023/1/19/next-energy-technologies-installs-energy-generating-windows-on-outdoor-retailer-patagonias-headquarters#:~:text=NEXT’s%20windows%20are%20created%20by,used%20onsite%20in%20the%20building.
- https://www.pv-magazine.com/2021/11/09/quantum-dot-solar-window-with-3-6-efficiency/
- https://www.computerworld.com/article/1425042/3m-film-turns-windows-into-transparent-solar-panels.html
- https://www.pv-magazine.com/2021/09/16/semi-transparent-organic-solar-cell-for-window-applications/