How do Solar Windows Work? [Definitive Guide]
There’s more to windows than illumination. Today, you can save money by producing solar energy using your building’s windows!
In a mission to make buildings energy-efficient and self-sufficient, a solar power production technology that leverages window surfaces has been invented.
Solar panels or organic photovoltaic molecules can be installed on the edges or the entirety of a building’s window, automatically turning it from a conventional one to a solar power-producing window.
But the real question is:
How do solar windows work?
Solar windows collect invisible light (Infrared and Ultraviolet) and transform it into usable electricity. A solar panel receives the light through tiny solar cells, which convert it into an electric current and are then fed to a conventional solar PV system.
This post aims to help you understand how solar windows work, how much they cost, the benefits they bring to a home or commercial buildings, and much more.
But before that, let me introduce you to solar windows first.
What are Solar Windows?
Solar windows are a special type of windows integrated with tiny solar cells that harness sunlight then convert it to electricity.
Solar cells for solar windows are extremely tiny and hidden, but they perform their intended role– producing solar power from sunlight. Currently, most common solar windows are transparent and harness invisible light such as UV and Infrared.
Commonly installed in tall buildings with large glass surfaces, solar windows are an innovative technology that perfectly complements power produced by solar roof mounts.
Solar window technologies came to be thanks to the collaborative efforts of chemists, engineers, and solar specialists. It’s not distinct who invented solar windows, but Physee was among the pioneer companies (more on that later).
In the meantime, let’s check out the main types of solar windows.
Types of Solar Windows
Sunlight windows fall into three distinct categories:
- Fully- opaque solar windows
- Semi-transparent solar windows
- Fully transparent solar windows
The fully opaque solar windows are the oldest solar window designs. They are typically what they sound like: opaque solar cells embedded on the surface of windows. The main weakness of opaque solar windows is low solar production efficiency.
Today, opaque solar windows are not as common as they once were due to their inefficiency in producing solar power. They also decrease the quality of light a room gets, which defies a window’s primary purpose– to illuminate a room.
Please note: It’s still crucial to protect your belongings from destructive UV rays and excessive heat. Solar-powered roller shades serve this purpose perfectly.
Next came semi-transparent solar windows. These leverage semi-transparent solar cells and come at a much higher solar efficiency (around 10%).
Today, modern solar window technologies allow for the installation of fully transparent solar cells on windows. As of now, transparent solar windows mainly generate electricity from invisible light.
Though transparent solar windows have low theoretical efficiency, they’re better than opaque and semi-transparent solar windows.
How Solar Windows Work?
In this section, we will explore how the current generation of semi-transparent and transparent solar windows works.
How do semi-transparent solar windows work?
Semi-transparent solar windows collect near-infrared rays. To achieve this, the solar cells for semi-transparent windows have non-fullerene acceptors.
Since non-fullerene IR acceptors have weak bonds, they’re easily destroyed by UV rays. For this reason, a buffer material is used to block them.
On hitting the solar cells, the IR rays are converted to an electric current. After that, a zinc oxide solar panel film is used to conduct the electrons to an electrode and later to an inverter of a solar PV system.
From the inverter, the solar power can be stored in a battery bank or used to power devices in the building.
As highlighted earlier, the efficiency of semi-transparent solar windows is in the 10% range. Researchers from the University of Michigan developed solar cells with 43.3% transparency and a record efficiency of 8.1%.
How do transparent solar windows work?
Transparent solar panels installed on windows are embedded with organic molecules– usually nanomaterials– that absorb wavelengths of light on the invisible spectrum (infrared and UV light).
On collection of the infrared and ultraviolet light, it’s channeled to the contour of the solar panels.
The last step is converting this light to electricity through the help of tiny solar cells also embedded on the transparent solar panels.
Transparent solar windows are both aesthetically pleasing and more practical in producing solar power than other types of solar windows.
With this knowledge, we can now analyze solar window efficiency and performance.
A Performance Analysis of Solar Windows
Due to the fact that solar windows work with infrared and UV light, their power production efficiency is limited to a theoretical maximum of 20%.
With this kind of solar window efficiency and considering the current solar window technologies leveraged, a single solar window should produce around 10 W daily. This can, of course, vary depending on the amount of light harnessed.
10W is enough to charge two phones a day; thus, it’s a decent amount of power.
With an extensive area of solar windows, you can produce a good amount of energy that can be fed to the main PV solar systems to boost what roof PV mounts produce.
According to Freedonia Group, 8.3Billion square meters of flat glass were to be installed in new buildings globally by 2020. Assuming this glass area was installed and lined with solar cells, it’s enough to produce 2000+ TWh of power– around a tenth of the global electricity consumption in 2020.
This is enough evidence that solar glass could boost the solar production of buildings to a great extent if maximally leveraged.
Solar Windows Cost
According to Tesla, a square foot of solar windows should cost around $21.25.
The cost of solar windows is usually 20% higher than that of conventional windows.
Solar cells on windows may seem like a huge investment at first, but the energy benefits you’ll reap in the long run make it a worthwhile investment.
For every dollar you invest in a solar window, you should expect to get a $3 benefit when the project is done and much more cost benefits in the long run.
Due to the high initial investment and low efficiency of solar power, installing solar windows for homes is uneconomical.
However, solar windows are an excellent investment for commercial buildings despite their efficiency problem.
Find out why below.
Solar Windows for Commercial Buildings
Large commercial buildings are, no doubt, heavy energy consumers. Unlike residential buildings, a commercial building’s roof area may never produce enough energy to meet the establishment’s energy demands.
Therefore, installing solar windows is a brilliant solution for meeting the substantial power needs of commercial buildings.
Solar panels can be installed on the window edges as described above or applied as organic PV molecules. Despite the ease of installation, these panels provide some impressive energy benefits for commercial buildings.
Examples of Solar Windows Projects/Technologies
Physee’s PowerWindow installed in a Dutch bank is one of the world’s most popular solar window projects.
This is a 300 square feet solar window project made of small solar panels that are installed in the glass pane’s window.
Physee solar windows are very useful in the bank’s setting as employees can charge their phones by plugging them into the windows using USB cables.
What a great discovery!
SolarWindow uses a liquid organic photovoltaics technology for solar windows.
With this spray-on solar windows technology, a thin transparent coating is applied to transparent glass or standard plastic window panes. On application, the liquid mixture produces tiny solar cells films on the window.
When light hits these solar cells, they generate an electrical charge that’s transported by ultra-small wires to a larger output wire and into a conventional solar power system.
SolarWindow coating produces electricity when exposed to:
- indoor light
- reflected light
- shaded light, and
SolarWindow technology is feasible for tall office buildings and skyscrapers with extensive glass pane surfaces that can generate a huge amount of solar power.
Ubiquitous Energy ClearView Power Windows
Ubiquitous Energy, a California-based startup, has its unique solar windows called ClearView Power Windows.
These windows use an organic dye that is applied to the surface of window glass. The dye allows visible light to pass through, just like in a standard window but captures infrared light.
The infrared light is then converted into electricity and channeled to a pre-installed solar system.
Ubiquitous Energy has installed these solar windows on its headquarters buildings in Redwood City.
Solar windows vs. Conventional Rooftop Solar Panels
|Factor||Solar windows||Conventional solar panels|
|Type of light converted||Non-visible light (Infrared and UV)||Visible light|
|Photovoltaics used||Organic photovoltaics||Silicon solar cells|
|Maximum theoretical efficiency||20%||30%|
|Cost per square foot||$20-$25||$4-$10|
|Lifespan||20-30 years||15-30 years|
|Watts per square foot||2.5-3.5W||8-10 W|
|Size and design of the solar panels||Sleek, thin, and hidden||Large and conspicuous|
Note: Solar windows are meant to complement solar roof panels rather than replace them.
Advantages of Solar Windows
Eliminates the need for wiring
If your conventional windows are to be powered by the grid, you will need a lot of cabling and wiring. In contrast, solar windows do not need any of this as the glass panels themselves will generate energy. This is beneficial because it offsets both the cost and the negative visual impact of highly cluttered wires or cables.
No need for encapsulation
When solar panels are installed on a surface, they need to be covered by glass panes–encapsulation. Unlike solar tiles for roofs, where encapsulation is a distinct process, the glass of a high-performance window doubles as encapsulation. Such an innovative approach significantly lowers the cost of installing solar windows.
More practical in producing solar power
As mentioned earlier, windows take up a considerable section of the vertical surface of a building. So, installing solar windows would mean decent solar energy production, which is hard to achieve with solar panel rooftop mounts.
Residents of apartments can produce solar power
Most apartment owners won’t allow you to install solar tiles on the roof. Since solar windows will barely affect the apartment’s design, you won’t encounter any problems with your landlord installing them, and you’ll still produce renewable solar energy while there.
Disadvantages of Solar Windows
Despite their incredible benefits, solar windows have two major drawbacks: low efficiency and the high initial cost of installation.
The power conversion efficiency of solar windows is just a third of what you’ll get from conventional solar panels. This is a significant hurdle affecting solar windows since it means that a vast glass area is needed to produce a decent amount of solar power.
High initial cost
As evident from the comparison table above, the cost of installing solar windows is more than double what you’d spend on a conventional roof solar panel mount. This means that even if you have the space, it’s pricey to install solar windows.
Hopefully, the cost and efficiency problems currently affecting solar windows will be sorted as solar windows technology evolves.
Our hope is that solar windows will be feasible to install in every home one day.
What is a switchable solar window?
A Switchable solar window is a special type of window that tints at warmer temperatures. In a tinted “switched state”, the window collects sunlight and converts it to electricity just like a typical solar panel would do.
An excellent example of a switchable solar window is SwitchGlaze, an innovation by the National Renewable Energy Laboratory.
What is a solar door?
A door is one of the fittings in your home that can run on solar. A solar door is an automatic door powered by solar power. Usually, solar panels are mounted on the door to capture sunlight and produce electricity.
The electricity is tapped into the door’s opening and closing mechanism. Due to the intense stress of opening and shutting a door, solar panels for a solar door need to be solid and sturdy enough. Solar doors, just like solar windows, save the environment from pollution since they leverage clean solar energy.
Are solar windows a good investment?
If you have a decent glass surface on your building, solar windows are definitely a worthy investment.
For now, it may not be economical to install solar windows in a building with a few windows due to their low efficiency. Hopefully, the efficiency of solar windows will be improved to make it an all-around worthy investment.
What are solar gaps?
Solar gaps are a special type of solar blinds that track the sun (with the help of a built-in tracker), produce DC with photovoltaics, and convert it to AC with an inverter.
According to SolarGaps, a Ukraine-based company and the pioneer for this unique solar window technology, a square meter of solar gap blinds can produce 100W per day.
This translates to about 22.4%, which is higher than the theoretical solar window efficiency of 20%. Other than producing solar power, solar blinds can also keep your building cool.
Make the most of your building with solar window technologies
Solar window technologies are here to automatically transform your conventional windows from lighting structures into solar energy collectors.
With a solar window, solar energy will be captured and converted into electricity that can be used to power devices in your home or business establishment.
Currently, most solar windows work with invisible light. Going forward, though, you should expect to see solar windows that can even convert visible light to electrical energy.
Renewable energy production is an essential aspect of any building. The good thing is, you can transition to renewable energy by simply turning your windows to solar.