Solar windows have glass designed to convert sunlight into electricity. Find out how they work and which are their benefits
The term solar windows refers to transparent photovoltaic panels that can be used as windows. This is still a little-known solution that not only improves efficiency but also has little impact aesthetically, unlike traditional systems.
Before proceeding with the installation of solar windows, it is necessary to evaluate two factors: “transparency” and “effectiveness”. Solar windows, in some cases, can offer transparency comparable to that of traditional windows. Therefore, before making a choice, it is important to consider the lighting needs of the environment (which can change depending on the presence of other windows).
As for “effectiveness”, solar windows produce much less energy than photovoltaic panels. There is therefore the risk of installing an element with specific expectations and obtaining a different and less satisfactory result.
To evaluate these aspects, you may find it useful to use professional solar design software, which allows you to design any type of installation, obtain in-depth economic analyses on the actual profitability of the system, and assess the real benefits of the investment.
What are solar windows and how do they work
Solar windows are real windows made up of photovoltaic glass capable of absorbing solar radiation to generate the electrical energy needed to meet the needs of a housing unit.
They are made up of two glass sheets between which optically active materials are inserted: amorphous silicon, monocrystalline, or polycrystalline photovoltaic cells. Their visual impact is imperceptible as a “transparent gel containing amorphous silicon” is applied. This gel can be applied to the surface of each glass or inserted into the cavity of an insulating glass unit. This process transforms the panels into semiconductors, giving them a transparency that makes them suitable for use as windows.
The choice of where to apply the gel significantly affects the results in terms of productivity. In fact, if the gel is applied directly to the glass surface, the solar window can generate up to 100 watts per square meter. If, instead, it is applied in the cavity, the production can reach up to 300 watts per square meter, almost tripling the efficiency.
Types of solar windows
A solar window can be classified based on the degree of transparency into:
- window with transparent glass: guarantee the performance of a traditional window and allow both light and heat to pass through;
- window with semi-transparent glass: allow the passage of relatively dark light but ensure a high production of electrical energy. They prevent the absorption of heat and infrared rays;
- window with colored glass: capable of giving the building a different touch of elegance while maintaining the same performance.
In addition to the degree of transparency, a solar window can also be differentiated based on the material used. In this context, the following types of windows with photovoltaic cells are distinguished:
- crystalline: have a double tempered glass sheet with monocrystalline or polycrystalline silicon cells in their cavity. In some cases, they may also include thin film amorphous silicon cells. A layer of polyvinyl butyral keeps the cells separate from the glass, acting as a resin designed to retain fragments in case of breakage. The result is a transparent glass;
- amorphous silicon: appear darkened, but the light that filters through is sufficient to illuminate the interior. The photovoltaic cells used are amorphous silicon with a thickness of 0.3 microns;
- organic solar cells: are composed of light-reactive polymers thanks to the presence of carbon. Organic cells are printed on very thin rolls and can be applied to different surfaces.
Solar windows: advantages and disadvantages
Solar windows contribute to improving the energy efficiency of the home and integrate harmoniously with a home automation system. Furthermore, they do not compromise the natural irradiation of the residence, especially if crystal clear glass is chosen.
However, like any device, solar energy windows have some disadvantages:
- by maintaining a fixed vertical position, their energy production is lower compared to traditional photovoltaic panels positioned on the roofs;
- inability to orient and tilt the glass based on solar irradiation, effectively reducing the potential for electricity production;
- inability to manage shading;
- need to replace the entire solar window in case of breakage of a solar cell;
- higher cost compared to traditional photovoltaic panels.
How much do solar windows cost?
Transparent photovoltaic glass has a cost ranging from €0.90/Watt to €7/Watt. The cost is influenced by the quality and type of photovoltaic glass, which can be based on amorphous silicon, organic, graphene, etc. In contrast, a traditional 350 Watt photovoltaic panel has a cost ranging from €200 to €400, depending on the quality of the cells used.
This results in a cost per photovoltaic module ranging from €0.50/Watt to €1.15/Watt, which is significantly lower than that of solar windows.
Both costs must be integrated with those of installation, which can vary depending on the complexity of the installation and the structure required to support windows and panels.