Background Research

The sun:

For this project, the outermost layer of the window moves through various positions to maximize the amount of sunlight and solar energy it gains each day. This outer pane is powered by a small motor and is also connected to a timer which determines its position at any given time throughout the day.

The timer needs to be set in a way that when solar noon occurs, the lay of the windows containing the solar cells are perpendicular to the side of the building. Solar noon is defined as when the sun crosses the celestial median or the highest point the sun reaches each day [1]. On average for the entire year, the sun rises around 6:19am each day and sets at 6:28pm each night [2]. Again, it is known that at solar noon the window will be perpendicular to the building, forming an angle of 90 degrees. Due to the fact that the window will start at rest, or 0 degrees, each morning, it is determined that each hour the window's position needs to change by increments of 15 degrees each hour. Doing this should maximize the amount of light the solar cells are able to absorb.

[1]"Measure Your World - Solar Noon", Windows2universe.org, 2017. [Online]. Available: http://www.windows2universe.org/citizen_science/myw/meas_solarnoon.html. [Accessed: 14- Apr- 2017].
[2]"Sun or Moon Rise/Set Table for One Year", Aa.usno.navy.mil, 2017. [Online]. Available: http://aa.usno.navy.mil/cgi-bin/aa_rstablew.pl?ID=AA&year=2017&task=0&state=PA&place=philadelphia. [Accessed: 15- Apr- 2017].

Solar Energy, Solar Cells, and the Sun:

Photovoltaics is defined as the direct conversion of light into electricity at the atomic level [1]. A photovoltaic cell is better known to the non scientific world by another name: solar cell. Each solar cell contains a thin semiconductor wafer, anti-reflective coating, front contact and back contact. The bottom layer of the cell is usually doped with boron and the top layer with phosphorus, bonding with the silicon to create a negative charge [2]. When light hits the cell, electron are loosened in the layers and create an electric current that can be used to power an object.

For this experiment, multiple Polycrystalline solar cells will be wired together, forming an array. Theses are square pieces made from a molten silicon cast.  In general, the larger the module or array, the larger the amount of electricity that can be produced.

According to the Light Research Center at Rensselaer Polytechnic Institute, altering the orientation of the panel throughout the day to maximize its exposure to the sun will optimize the collection efficiency [3]. For a fixed panel, the climate and location of an area will affect its positioning.

[1]G. Knier, "How do Photovoltaics Work? | Science Mission Directorate", Science.nasa.gov, 2017. [Online]. Available: https://science.nasa.gov/science-news/science-at-nasa/2002/solarcells. [Accessed: 15- Apr- 2017].

[2]"How Solar Panels Work", Union of Concerned Scientists, 2017. [Online]. Available: http://www.ucsusa.org/clean-energy/renewable-energy/how-solar-panels-work#.WO5pHBiZO8U. [Accessed: 15- Apr- 2017].

[3]"How does the tilt angle and/or orientation of the PV panel affect system performance? | Photovoltaic Lighting | Lighting Answers | NLPIP", Lrc.rpi.edu, 2017. [Online]. Available: http://www.lrc.rpi.edu/programs/NLPIP/lightingAnswers/photovoltaic/14-photovoltaic-tilt-angle.asp. [Accessed: 15- Apr- 2017].

Lighting for Plant Growth, Greenhouse:

With the increased demand for food as a result of growing populations, farmers have increasingly turned to greenhouses. This enables year round growth of produce in addition to growth of plants in areas whose climate’s could not sustain them previously. Growing plants outside of their usual climate or time of year require two things: warmth and sunlight. Greenhouses fix the problem of temperature simply by the way they are built, generally out of glass or some other clear material. These materials are able to heat the insides of the greenhouse despite much colder temperatures outside. This is accomplished due to the fact that the ground absorbs radiation emitted by the sun throughout the day [1]. The heat absorbed is then spread out between the ground as well as a large amount of air. This dilutes the heat enough that temperatures are kept at a level which is acceptable for human and other kinds of life. When a greenhouse is created, however, the amount of air above the ground that needs to be heated is reduced to just the air within the greenhouse. Greenhouses are then able to be heated up much more quickly and the real problem comes from ventilating them properly so it does not overheat, thus killing the growing plants.

The issue of sunlight is generally addressed by using LED lights as an artificial source of sunlight. A study done at the China Jiliang University, looked at the best combination of LED lighting to maximize capture of light energy by plants. Since natural light is a varied mix of wavelength, a single wavelength LED would not be a suitable replacement. The study found that a combination of three wavelengths, 660±30 nm, 460±20 nm, and 400±20 nm, result in the best fit for the plants [2]. These wavelengths correspond to the LED light, blue LED light, and purple LED light and when combined in the ratio of two red, one blue, and one purple LED lights, the plants are able to absorb the maximum amount of light.

[1] S. Bowling, “How Do Greenhouses Work?,” Article #817. University of Alaska Fairbanks. http://www2.gi.alaska.edu/ScienceForum/ASF8/817.html

[2] S. Wang, H. Ji, et al., “An Intelligent Controlling System for LED Plant Supplemental Lighting Greenhouse”. China. http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6270920

Previous Inventions:

After thoroughly researching the product market, a couple of previous inventions were found that are similar to the proposed design but nothing that is exactly the same. One invention is a solar cell blind. These blinds are mainly used in homes since they reduce glare and also make the sun more manageable. They are less for the reuse of energy that is collected and more for managing sunlight that is coming into homes. This product is also very expensive with each unit costing $300 at a minimum.

Another similar invention is the totally transparent solar cell, which makes every window and screen a power source. The invisible cell is a solar concentrator and makes any window or piece of glass a solar cell, which is capable of producing a lot of energy [1]. Although this invention is not on the market yet, it is expected to become available soon. One company that is looking into these transparent solar cells is Solar Window Technologies, INC. Their mission statement is to “produce extraordinary amounts of clean electricity, financially reward our customers, and benefit the environment,” which is a similar idea to the proposed solar window. The main difference between the two designs is that the frame in this group’s design will be lined in solar cells while Solar Window Technologies’ has invisible cells.

There are also researchers in the Center for Advanced Solar Photophysics at Los Alamos National Laboratory. This team is looking to incorporate solar cells and panels onto buildings and windows without having them be blocking the whole view [2]. They plan to use quantum dots on windows to provide solar energy on the windows to get energy. There are also 3M Window Films which is a sun control window film [3]. The films protect against improved comfort, improved energy savings, increased privacy, increased fade protection, reduced glare, and increased safety. This is a good alternative to not having the solar cells directly on the window. There is also a patent on a window that has a solar cell window fitting. Solar cells are applied and mounted in a window fitting. The website says that the design has solar cells placed on the blind to be exposed to the sunlight.

[1] TLending, Jamie. "This fully transparent solar cell could make every window and screen a power source." Extreme Tech. April 20, 2015. Accessed April 12, 2017. This fully transparent solar cell could make every window and screen a power source.
[2] Klimov, Victor. "Turning Windows Into Solar Panels." Energy.gov. March 7, 2017. Accessed April 12, 2017. https://www.energy.gov/articles/turning-windows-solar-panels.
[3] "3M™ Commercial Window Film – Comfort, energy savings, safety & security for your building." 3M United States. Accessed April 12, 2017. http://www.3m.com/3M/en_US/building-window-solutions-us?WT.term=%2Bsolar %2Bwindows&WT.source=google&WT.campaign=Energy&WT.medium=cpc&WT.content=text&WT.srch=1&WT.mc_id=3MWindowFilms_Paid_Search&cshift_ck=d857f2e1-48bf-4259-b6b1-04197dcc01e0cs.