Building-Integrated Photovoltaics in Smart Windows: Your Guide to Sustainable Facades

BIPV Smart Facades: Benefits for Sustainable Buildings

Building-Integrated Photovoltaics (BIPV) delivers clean renewable power to the building sector, an industry responsible for 30% of global energy consumption and 26% of energy-related emissions.

Smart glass facades can also facilitate cleaner, greener buildings by dynamically reducing solar heat gain and glare, thus minimizing HVAC and lighting costs.

Therefore, the combination of BIPV and smart glass facades represents the Holy Grail for sustainable construction, with the following benefits for net zero buildings:

• Power the smart glass directly via clean and renewable sunlight
• Reduce operational carbon and HVAC / lighting costs, thanks to dynamically tintable layers
• Control glare and privacy for enhanced occupant safety, comfort and productivity
• Remove cable routing costs, material costs and cable maintenance overhead
• Facilitate drop-in window replacements in building retrofits, which reduce electrical installation costs

But first, let’s take a step back and review some of the basic terms relevant to this article.

What is Photovoltaics?

Photovoltaic technology converts light into clean electricity. 

We describe this energy as ‘clean’, since the process produces zero carbon emissions during its operational phase, while relying on an infinitely renewable source: i.e. the sun.

The diagram below shows the ‘photovoltaic effect’, where incident sunlight creates electrical charge, which powers an electrical load (the lightbulb). Anti-reflective coatings increase the light throughput.

Photovoltaics offer a renewable energy source on roofs, walls, floorings and facades, as well as powering parking lots, traffic lights and air-conditioned bus stops in smart cities.

You can read more about transparent photovoltaic glass in our deep-dive article.

What is BIPV?

Building-Integrated Photovoltaics (BIPV) incorporates photovoltaic layers directly into traditional building materials, such as facades, roofs and flooring. 

This turns a material expense into a sustainable income stream by generating clean energy, either for direct use in the building, or by selling excess energy back to the grid.

As BIPV systems are both construction products and electrical components, in the European Union they are subject to:

• the European Union Construction Product Regulation (CPR 305/2011),
• the Low Voltage Directive (LVD 2014/35/EU), and
• the Electromagnetic Compatibility Directive (ECD 2014/30/EU).

In the European Union, the reference standard for BIPV products and systems is EN 50583.

In 2020, a similar international standard was introduced: IEC 63092.

What is Smart Glass?

Smart glass is a family of glazing materials that enhance the optical, thermal or electrical properties of traditional glass by way of surface coatings, internal laminations or embedded circuits inside the glass.

This includes energy-filtering smart glass, energy-generating smart glass and display smart glass for construction, transportation and consumer devices.

More in our article about the basics of Smart Glass.

Why Combine Smart Glass with Photovoltaics?

Photovoltaic layers can power smart glass directly and sustainably, avoiding mains electrical connectivity, which reduces cable routing costs, material costs and maintenance costs.

The combination becomes a cable-free, drop-in replacement for existing windows, which minimizes electrical installation costs, since the whole job can be completed by a glazier.

Is it realistic to power Smart Glass using Photovoltaics?

Short answer: yes.

Photovoltaic layers produce direct-current (DC) electricity. 

Some smart glass technologies, such as electrochromic and electrophoretic smart glass run on DC electricity.

This means that PV layers can power the smart glass directly, without requiring electrical conversion or transformation components.

How can Photovoltaics be combined with Smart Glass?

As smart glass end-product manufacturers since 2009, we typically design and fabricate smart glass IGUs as a laminated structure, with multiple interlayers. 

Some interlayers dynamically absorb visible light, and some reflect solar heat and secondary heat to keep temperatures stable in the building. 

It is an ‘obvious next step’ to include a photovoltaic layer in the window frame (or in the IGU) to power the smart glass directly. 

This avoids the costs of mains electrical components, such as isolation transformers, inverters and power factor correction circuitry, as well as their respective installation and maintenance costs.

The laminated IGU often has a thickness of 12-22 mm, with exit cables that need routing inside wall cavities or window / door frame enclosures. The cables connect directly to the smart glass controller or isolating transformer.

If we power the smart glass directly from integrated (or attached) PV modules, we avoid this complexity entirely, reducing build and maintenance costs.

What is the difference between BIPV and BAPV for Smart Glass Facades?

In a nutshell:

Building-Integrated Photovoltaics (BIPV)

BIPV replaces the traditional building material, becoming a structural part of the architecture, and is designed-in from the concept stage.

BIPV integrates PV layers inside the roof, wall, window frame or the IGU itself.

Building-Applied Photovoltaics (BAPV) 

BAPV modules are retrofitted onto an existing structure (roof, facade or window) using mounting hardware. 

The modules can be removed without affecting the underlying materials. BAPV modules in smart glass windows attach onto the outside of the frame.

Here is a summary comparison of both solutions:

Let’s now look at the solutions that combine photovoltaics with smart glass, and the pros and cons of each.

Photovoltaics and Smart Glass: A Technical Comparison

The table summarises the key combinations:

Let’s now explore how these solutions deliver on the benefits.

1. Opaque PV layers inside Smart Glass IGU

As shown in the image below, the opaque PV modules are fabricated inside the glass and spaced apart, which gives a customisable level of transparency at the time of fabrication. 

This does not, however, allow for dynamic modulation of light during building operations, unless the glass has a tintable layer.

This solution typically uses mono-crystalline silicon (mc-Si) with an efficiency of about 20%, which offers excellent power generation capacity. 

For example, under Standard Test Conditions (STC), we have:

• Solar irradiance, G_STC = 1000 W/m²
• Cell temperature, T_cell = 25ºC
• Air Mass (AM1.5G) global solar spectrum (as per IEC 60904–1), which defines how much sunlight reaches the Earth’s surface after passing through an atmosphere thickness of 1.5 times the vertical path, at a total irradiance of 1,000 W/m².

Given an efficiency of η_STC= 20%, we would see a maximum power generation capacity of:

P_MAX = η_STC x G_STC

P_MAX = 20% x 1000 W/m2 = 200 W/m²

The obvious detractors however are the reduced VLT (typically 30%-50%, depending on the PV cell density) and the shadows cast on the interior by the opaque PV modules.

Combining opaque PV layers with tintable smart glass would allow variable VLT, but the overall VLT will be lower due to the dark PV modules.

While these installations represent the current standard in BIPV, their aesthetics and functional limitations demonstrate that the industry has significant room for innovation.

2. Translucent (Thin-Film) PV inside Smart Glass IGU

Translucent (thin-film) PV layers are coated onto glass, which gives a customisable level of transparency at the time of fabrication.

The manufacturing process for thin-film PV is similar to low-emissivity (low-e) hard-coated glass.

At the time of writing, thin-film PV accounts for approximately 5% of globally-installed solar capacity.

Thin-film PV can be made from different semiconductor materials such as:

• amorphous silicon (a-Si)
• copper indium gallium selenide/ sulfide (CIGS)
• cadmium telluride (CdTe)

While amorphous silicon cell efficiency is lower (6-8%), CIGS and CdTe efficiencies are now catching up (16%).

As a result, CdTe now dominates the thin-film sector, with about 90% of market share.

Combining translucent thin-film PV with dynamic tint glass would allow us to vary the VLT, better suiting the needs of building occupants.

However, the most prevalent technology (CdTe) has a lower efficiency (η_STC= 16%).

Running the same calculations under Standard Test Conditions (STC), we would see a maximum power generation capacity of:

P_MAX = η_STC x G_STC

P_MAX = 16% x 1000 W/m2 = 160 W / m²

This solution provides improved and variable daylighting, but the reduced efficiency results in lower power generation, which delays the Payback Period.

3. BIPV Frame with Smart Glass IGU

This solution embeds PV modules inside a translucent (non-switchable) glass frame which powers the smart glass IGU directly.

The frame diffuses incident sunlight onto the PV cells located underneath, but does not reveal their structure, improving the aesthetics of the facade.

This solution requires a glass frame with high VLT to maximise PV power output, and high haze factor to improve the frame aesthetics.

In the diagram, we show a low-power, low-voltage smart glass technology, such as electrochromic (EC) or electrophoretic (EP) smart glass, allowing direct activation via the PV cells, since both operate at around 3-5 Vdc.

Key Features:

• Cable-free, drop-in window replacement
• Powered by renewable, clean energy
• Dynamic VLT, fast switching time, responsive to changing user needs
• Electrochromic (EC) glass switches in seconds to minutes, whereas electrophoretic (EP) glass can switch in just a few seconds
• The frame houses an optional rechargeable battery to store electrical charge collected during the day for use at night
• The IoT light sensor on the frame automates dynamic switching based on sunlight levels
• The wireless module allows for remote control via a building management system.

4. BAPV Frame with Smart Glass IGU

The corresponding BAPV solution is identical, but places the PV cells on the front surface of the window frame (rather than inside the frame).

This results in greater power generation, but has poorer aesthetics as the PV cells are visible on the frame, as you can see in the representative image.

Since the PV modules are located on the exterior of the frame, we must route the power cables to the smart glass, which might complicate the design in some cases.

The BIPV and BAPV solutions separate the PV from the smart glass, but there are two technologies that combine the layers more intelligently:

• PhotoElectroChromic device (PECD)
• PhotoVoltaChromic device (PVCD)

Let’s now take a deeper look at each.

5. PhotoElectroChromic device (PECD) Smart Windows

Photoelectrochromic device (PECD) technology for smart windows is still in the prototype stage and is not yet ready for mass-market commercialization. 

Nevertheless, it is worth mentioning as a future game-changer that combines clean energy generation with dynamic tint directly within the glass.

An example PECD device is shown below:

A PECD device features an electrochromic (EC) layer, powered by a dye-sensitized solar cell (DSSC) which converts sunlight into clean electricity.

The EC layer modifies the transmittance of visible and near-infrared light, without requiring an external power supply, resulting in net-zero energy consumption.

• Sunlight passes through the glass and hits a semiconductor layer (like titanium oxide), sensitized with a special photoactive dye
• The dye absorbs light, elevating electrons into the conduction band of the titanium oxide, which transport them into an external circuit
• These photogenerated electrons travel into the neighboring electrochromic layer
• Lithium ions from an electrolyte migrate into the electrochromic film to balance the charge, which causes the glass to darken
• With no sunlight, the ions flow back, returning the window to a clear state

All generated electricity is consumed internally, so this technology cannot export power to the building. All power is used exclusively to change its transparency.

6. PhotoVoltaChromic Device (PVCD) Smart Windows

Likewise, photovoltachromic (PVCD) technology for smart windows is also in the prototype stage and not ready for mass-market commercialization. 

PVCD devices split their output to partially tint the glass, sending surplus electricity to power external building electronics.

As shown below, a PVCD device generates clean electricity from sunlight but requires an external switch to connect / disconnect the EC layer.

For architects and facade engineers, the energy efficiency of PVCD smart windows depends on several environmental and design factors.:

Climate-Specific Performance:

Hot & Tropical Climates: According to this academic study which references the Koppen-Geiger Climatic classifications, PVCD windows are most effective at reducing cooling loads and offering efficiency gains of up to 32% in BWh regions (Hot Desert Climate), and gains of 6–20% in sub-tropical (C category) regions.

Temperate Climates: Active control systems in these regions can save 2–12% in energy, primarily by modulating lighting consumption rather than just thermal loads.

Cold/Cool Climates: While PVCD windows can offer energy savings (up to 20%), designers must balance these against potential increases in heating demand, as reduced light absorption can negatively impact passive solar heat gain.

Design & Orientation Strategy:

Orientation Impact: In hot-summer moderate climates in the southern hemisphere, north-facing windows deliver the highest energy reductions (23–25%), followed by east/west orientations (19–20%) and south-facing (8–10%).

Window-to-Wall Ratio (WWR): Higher WWRs typically correlate with maximum energy efficiency in hot climates.

Technological Evolution:

Visual Aesthetics: Early drawbacks, where opaque PV sections blocked vision, are being addressed by new designs utilizing transparent, efficient PV cells to power electrochromic layers.

Net Zero Integration: PVCD windows can serve as a vital component in Net Zero building strategies, generating the power required for their own functionality while offsetting building electricity demand.

Comparison of PECD vs PVCD Smart Windows

Conclusion

Combining BIPV technology with smart glass facades represents a transformative solution for sustainable architecture, turning building envelopes into cable-free, energy-generating systems. 

By embedding PV layers directly inside IGUs or into frames, we can eliminate cable routing costs and grid connectivity, offering a drop-in replacement for traditional glazing that reduces both labor and material overhead. 

These systems provide dynamic glare and privacy control, reducing operational carbon and HVAC cooling loads to support Net Zero buildings. 

Implementing this technology requires balancing aesthetics with climate and orientation goals.

Options range from standard BIPV integrations, using opaque or translucent PV layers, to advanced photoelectrochromic (PECD) and photovoltachromic (PVCD) devices that combine light-harvesting with tinting functions. 

Architects and engineers should prioritize sun-facing facades for maximum energy efficiency, selecting the device type based on whether the project requires passive tint or an active solution that can export surplus electricity.

References

“Building-Integrated Photovoltaics: A Technical Guidebook”, Nuria Martín Chivelet; Costa Kapsis; Francesco Frontini.