Transparent solar cells
We have developed a way to print windows with built-in solar panels. Solar light is 53% composed of infrared light, which we do not see, but feel like heat. This infrared light is separated from visible light when it enters the window and is directed to solar cells, where convert into electricity with 11 % efficiency. Visible light passes inside. The optical system practically does not distort light, distortions can be minimized
In this case, an optical system is used to divide and redirect infrared light and solar cells with enhanced absorption in the IR region.
Measurements of power versus angle were also carried out, at angles of about 20 degrees the power drops by 15%
The conversion efficiency of infrared light is 11%, it can be increased to 16-17%. This is about 110 watts per square meter of double-glazed windows. Transparency for visible light is 90.5% perpendicular, and about 78% at an angle of 45-60 degrees, the window changes its color from blue to burgundy at an angle. You can make a drawing that will not be visible at small viewing angles to the window, but visible on reflection when looking obliquely at the glass. In the future, we plan to increase transparency for visible light.
If we take the area of Burj El Khalifa, an area of 334,000 m², then, considering that on average only half the building, then 110x334000 / 2, there will be 18.37 MW, and for the light day there will be 367.400 kWh.
The peak consumption of the tower is 30-50 MW, that is, the window can provide up to 50% of the energy of the glass building.
The usual cost of a solar battery is about 80-100 dollars per square meter, about the same cost have energy-saving windows
I think this is profitable in places with small available and expensive space, where we cannot built solar power station. For example this is Singapore, Hong-Kong, Dubai, or center of San-Francisco agglomeration. If we use transparent solar cells, we can cover up to 30 % of energy in building. If cost is 150 $ for sqr meter , investments returned in 3-4 years.
Window integrated solar cell concentrator. Photo-sensitive mirror always concentrate infrared on solar cells, visible light depends on intensity of light
Parameters for transparent solar cells arrays:
Efficiency: 9.8-10.8 %. 90-110 Watts from sqr meter
Transparency for Sun direct light, visible 90%, Invisible light (ultraviolet + infrared) 10-15%.
Cloudy weather, shaded area, visible light 90 % , invisible light (ultraviolet +infrared ) 10 %
So by adopting the said technology, the output power yield is expected up to 150 W on maximum lighting from 1 sqr . meter panel.
At the end of development, we should get a clear transparent sheet of large area in which is built-in an array of reflectors directing sunlight into an array of solar panels . The array of reflectors, and solar cells must be manufactured in a single process using additive manufacturing. The degree of reflection will depend on the intensity of sunlight: the more light passing inside reflects more infrared light. Hence, transparent solar panels can be used instead insulating glass in skyscrapers.
Semi-transparent solar cells
The most spread on the market semi-transparent solar cells based on cadmium telluride. Maximum efficiency is about 11-12% with a transparency of 10%. Transparency can be adjusted by changing the thickness of the solar panel. With a transparency of 90%, the efficiency will be about 1%, but in market reality, the maximum transparency is about 50% and the efficiency is about 5-6%
Semitransparent cells based on dyes (due to sensitized solar cells), brown, red, yellow and green colors that can be used similar stained glass windows. They assembled a group of Michael Gratzel from the Lausanne Polytechnic School. The efficiency of such cells is about 5-7%. They absorb a part of the visible light, and the other part is passed. In this case, the infrared part is captured only partially.
Full transparent solar cells
There are also solar cells on quantum dots that absorb mainly the infrared part of the light, but the efficiency of such batteries is only about 2-4%.
Also, there are batteries based on luminescent solar concentrators, where the light falls on the luminophore and is re-emitted to solar batteries along the perimeter of the window. The efficiency of such systems also does not exceed 3-5%. For example - Physee of Delfts University
It should be noted the Spanish Onyx Solar and American Ubiquitous energy. Ubiquitous Energy states that efficiency was about 2.5% in last published data (2016). They did not publish complete data on transparency, efficiency, size and did not show their samples to the public and independent experts. Also in the tau structure there is the problem of transparent electrodes - there should be 2 of them, and each has an average transparency of 95%, and a total of 90%. At the same time, the battery itself has a transparency of 90%, thus a total of about 80% or less.
Also there were windows where the lens is built, but they distort the visible picture.
Energy efficiency glass
There are glasses that reflect infrared light to the street (in summer) or back to the room (in winter). They can also be considered as competitors in the construction market. Usually they have a layer of thin metal films and have a visible light transparency of about 75-85%. Manufacturers say that they allow to keep up to 20% of heat and the temperature in the summer is 3-10 degrees lower, and in the winter it is 2-5 more.