As more residential communities are making the decision to use the energy from the sun to power their everyday household activities, the level of advancements that are occurring has provided a brand-new meaning to the terms, effectiveness, and efficiency. As studies conducted by the United States Department of Energy (DOE) have shown, the amount it will cost an average household to make the change to solar energy is steadily decreasing from year to year. Due to the vast applications for solar technology in modern day residences, certain advancements in solar energy systems have different benefits as households vary. Therefore, understanding these new developments will help residents to plan for not only a personal solar energy system, but to be able to withstand and equip future technology as it evolves. 

Upward Trajectory of Solar Panel in Residential Neighborhoods

Since the end of the Industrial Revolution, solar energy has become one, if not, the cheapest source of energy that is able to generate small size power plants, such as residential neighborhoods with specially designed windows. Within residential neighborhoods, homeowners are beginning to utilize solar panels that are complementary to the design of their homes. There are new technological advancements that allow for solar panels installations to become more efficient while being able to extract more of the sun's rays to generate more energy. As time moves forward many communities are enacting upon the solar power sector continual growth. They are looking to set sustainability goals and have home improvements resemble the solar energy direction countries are turning to. Since the increased flux in solar energy during the last three years, many solar energy companies are competing to design and build more effective and efficient solar panels that can conserve the most energy. 

During the second quarter of 2021, the United States Congress passed to prolong the twenty-six percent Investment Tax Credit that would support solar energy innovation and increase the likelihood of residential homeowners and companies adding solar panels to their homes for two more years. The extension of the Investment Tax Credit had a vast growth within the storage component of the solar energy systems. This system has allowed for an eligible tax credit due to the on-site renewable energy systems. Not only did the U.S. Congress take part in making solar panels affordable, so did the U.S. DOE [1]. The U.S. DOE has pledged millions of dollars to allow researchers to discover brand new solar techniques and technologies, along with lessening the cost of solar panel energy. 

Transparent Solar Cells

Currently, silicon is the most widely used material in solar technology but having non-transparent windows can often be difficult in residential design and construction. In residential buildings, regardless of size, windows can be considered the face, considering that windows allow sunlight in, and that the homes’ facade can absorb and reflect light. By designing and creating solar cells that are translucent, University of Michigan researchers were able to establish a record setting 8.1 efficiency rating. Instead of using the traditional silicon material, the team used a carbon based organic which ultimately increased the transparency to 43.3% [2]. This is important especially in residential homes because it has the possibility to exchange conventional cells to cells that resemble car windows or sunglasses, whether being in the new phase of construction or the existing infrastructure.

The diagram below illustrated by MIT researchers, Vladimir Bulović, Miles Barr and Richard Lunt, displays the inner workings of a transparent photovoltaic system, which is designed to increase efficiency while providing visual clearance, unlike other solar cells. These cells can provide a resident apartment building, as high as a skyscraper, with more than enough electricity to reduce the cost by nearly 25%, without altering the face of the building itself.

Residential Breakthroughs

Ground Mount Solar: When roofs are not adequate locations to place solar panels, for instance when the slope of a roof is not at the angle to attract solar rays or other obstructions hinder installation, ground-mounted solar photovoltaic systems can be used. The limitations provided by roofs are not the same for ground level structures, therefore the installation process of these panels allow for any height, orientation, and angle of tilt to be obtained, as long as the spacing is provided at ground level to produce maximum sunlight [3]. When dealing with ground-mounted solar panels, there are two structural designs that are commonly used: the standard ground mount and the pole-mounted system. The difference between the two is that the standard system is anchored directly to the ground at various locations on the system using steel framework, while the pole system is a single mast, anchored in the ground and the panels are placed in rectangle or square frames. Homeowners have also found this system to be easier to maintain in terms of the cleaning process and the ability to maintain their own solar panel without having the installation team provide maintenance. 

Community Solar Gardens: These solar technology systems provide features of clean energy without having to go through the process of having to install solar panels on the roof or ground level. A solar facility consists of multiple systems of solar panels connected with the ability to share with multiple residential areas at one time, whether they be single family, multiple family, or apartment style living. Even though many people are interested in establishing solar technology and clean energy for their residences, there are still many factors hindering them from making the conversion. Therefore, many communities design and implement various solar facilities that help generate electricity to the local electric grid, which help bring credit benefit to personal electricity bills. These areas must be placed in areas that are well lit and experience a large amount of sunlight exposure. Once energy is generated from the local solar garden, it is then transferred out to the local electricity grid that is then shared with surrounding residents. It is important to note that many of these gardens utilize ground mount solar technology in different available lots and open spaces around neighborhoods. Solar community gardens are categorized in the following three programs.

• Utility Sponsorship - This program is always under the operation of a utility company looking to increase their investment and services in renewable energy, for a neighborhood that traditionally cannot afford to establish technological advancement on their own.

• Private Company - This program falls under those who are interested in solar power generating investment on a small-scale project site. For example, buying or investing in this company will allow you to utilize their solar power systems as clean energy, where local companies do not offer solar technology utilities.

• Subscription Program - Within this program, a company had used their private funds to install a solar community garden within the residential neighbors. Residents are then responsible to pay a monthly or yearly fee to the ratio of solar panels it would take to supply electricity to their residence. 

Solar Shingles. The two types of solar shingle created to match the small roofing shingles of a normal roof and are integrated into the concept design of the asphalt roofing are the silicon shingle or the copper-indium-gallium-selenide (CIGS) photovoltaic shingle. Many people have started to use shingles mostly for the aesthetic, as many homeowners want something that matches their home design instead of having the large traditional roofing. These can take the form of a single panel or a group of shingles that can shape into either tile, concrete, or any other form of roofing, while allowing the conversion process of solar energy into home electrical energy. A well-known process in which the solar shingles generate energy is by way of the photovoltaic system, which is said to last over thirty years. These photovoltaic system shingles are used on sloped roofs. 

• Silicon Solar Singles - The solar shingles are interchangeable with the common non-solar roofing since they are made of a strong metal with a film of amorphous silicon that can be used in any weather condition. 

• Copper-Indium-Gallium-Selenide (CIGS) - the newest advancement of solar shingles that are made to be more durable, flexible, and lighter in weight to hold all forms of weather and still be able to hold enough solar energy. 

Solar Skins. With solar technological advancements pushing forward, the use of solar skins is becoming more receptive to homeowners due to solar skins being able to change to any color or pattern that would fit the needs of the home. For example, solar skins can be placed anywhere on the homeowner’s property and can change to resemble the roof, side panels, grass, etc. These skins can be used to wrap around everything in an individual’s home. The solar skins provide homeowners with the flexibility of low roof options, unlike the traditional solar panels or solar shingles. The solar skins are made from metal brackets and fixtures that utilize the rail-free racking system that uses a thin transparent material. 

Cell Division and Breakdown of Solar Panels to Increase Efficiency

Contactless Dispensing Process. During the process of contactless dispensing, a metal component is applied onto the solar cells using perovskite-silicon tandem solar cells. This is a process that many companies are trying to aim to commercialize. 

Passivated Emitter Rear Cell (PERC). Originally created in the 1980, the Passivated Emitter Rear Cell is still used today to help increase energy absorption and conversion into electricity for solar cells of the first generation. The PERC is composed of a traditional silicon cell covered with layers that can attract the layer of sunlight to pass through each cell, so the energy can be stored for the consumption of household energy. These cells are made of crystalline silicon that can be used in extreme elevated temperatures [5].

Design Specifications: Within the design of the PERC solar cell, the passivation surface is a dielectric surface. This cell was designed to limit the amount of contact for the conductor-metal area while increasing the reflection of the rear surface. This was accomplished by allowing photons to be absorbed while passing in and out of the cell itself. This technology also helps to reduce the levels of heat absorption on panels. 

Heterojunction Technology (HJT): Also in the 1980s, to increase power output and electricity efficiency, the HJT was created. This is an amorphous layer made of a non-crystalline substance applied to both sides of the cell-like wafer structure called the mono-Si or multiple being the poly-Si - allowing for more sunlight to be converted. The heterojunction technology is not used solely on its own but with the common solar panel as a cover to increase the durability and efficiency [6].

Design Specifications: The HJT Solar Module, is one of the more common models that are able to achieve an average module efficiency of 21.4%. The materials used to design these panels are Crystalline Silicon (c-Si), Amorphous Silicon (a-Si), and Indium Tin Oxide (ITO). This technology uses a combination of wafer-based photovoltaic technology and thin film technology to create their solar cells. This technology can achieve an efficiency as high as 26.7% with a price range of around $0.34/W. 

Bifacial Solar Panels: Similar to the single sided HJT process, there is a double-sided exposure to sunlight that can soak up the sunlight on all sides with an increase of 40% in efficiency as opposed to the mono-facial panels. With these panels, they can move depending on the angle of the sunlight. 

Design: In comparison to the conventional panel also known as Monofacial panels, Bifacial panels are designed to generate energy from the back and front of the panel. By attracting the sunlight from the front of the panel and harvesting reflected light from the back this panel can produce a greater output of power. The source for reflection comes from a series of photovoltaic modules placed in a nearby row. These panels have a symmetric cell structure that can also obtain and hold extra sunlight and are n-type wafers whereas the conventional panel is a P-type Wafer [7]. The front irradiance is projected towards the first layer which is front passivation & AR, and then to the second layer which is an emitter (p + Si). The rear irradiance is projected towards the first layer known as rear passivation and then to the BSF (n + Si). Just as conventional PV modules use a white back sheet, the bifacial uses a transparent back sheet or a glass. Therefore, the energy generates or produce by this panel can be calculated using Equation 1, which helps in the design for percent gains.

Total Produced Energy = Energy from Front + Energy from Rear

Equation 1. Bifacial PV Energy Equation

Cost Benefits from using Bifacial Panels depend on what is known as the Bifacial gain which is the ratio of additional rear energy (kWh) to front energy (kWh) at specific standard test conditions, as shown in equation 2. 

Bifacial Gain (BG) = EnergyrearEnergyfront

Equation 2. Bifacial Gain (BG) Ratio 

When designing these panels, they must be designed for the best Albedo range, see Equation 3, as possible which describes the ratio of light that is able to be reflected based on different surface materials, such as ice, sand, snow, water, grass, and concrete to name a few. In simpler terms, to not be confused with reflectance, albedo is the complete solar radiation reflectance for the full spectrum of light. This ratio is the main factor when determining the energy generated from the back panel. For example, snow has a much higher range of albedo in comparison to water and asphalt.

Albedo = Reflected light Incident Light

Equation 3. Albedo Ratio

The next major factor in designing bifacial panels is the elevation, which results in a more efficient BG. When the module is placed at a certain elevation above ground level, more sunlight can be reflected. The best module elevations are those that are designed with at a maximum height of 1m (39.37 in) above ground level. The relationship between module elevation and BG can be shown as a liner representation until it reaches 1m. As the module elevation increases, the BG also increases. 

Deployment of Solar Panel Advancements

According to the United States Department of Energy Solar Energy Technologies Office, the increased use of solar panels would likely decrease the amount of carbon gasses used in households. Their primary model states that moving forward until 2050, with businesses and homes enhancing their electrical capabilities, the use of clean energy fuel, the transportation using more electric buses and the use of industrial energy, the energy consumption will reach as high as thirty-two gigawatts-AC (GWac). 

If the technological advancement of solar panels continues to grow with the expected rate of solar panel installations, they are expecting to not have an increase in electricity for household bills. The anticipated growth has a lot to do with the increased employment of those in the solar energy industry and those who are looking to study the trends of solar panel uses in various neighborhoods. Many of these employees are exploring where low-income neighborhoods can best be suited for a solar panel garden that can help to cut down the cost for the installation in their homes. These gardens may need to be placed on top of an apartment building that is located in a central part of the district. In these homes, not only will this affect the electricity but may allow homeowners to convert to electric appliances such as stoves or/and dryers. [8]

About Dr. Raj Shah
Dr. Raj Shah is a Director at Koehler Instrument Company in New York, where he has worked for the last 27 years. He is an elected Fellow by his peers at IChemE, CMI, STLE, AIC, NLGI, INSTMC, Institute of Physics, The Energy Institute and The Royal Society of Chemistry. An ASTM Eagle award recipient, Dr. Shah recently coedited the bestseller, “Fuels and Lubricants handbook”, details of which are available at ASTM’s Long-Awaited Fuels and Lubricants Handbook 2nd Edition Now Available (https://bit.ly/3u2e6GY). He earned his doctorate in Chemical Engineering from The Pennsylvania State University and is a Fellow from The Chartered Management Institute, London. Dr. Shah is also a Chartered Scientist with the Science Council, a Chartered Petroleum Engineer with the Energy Institute and a Chartered Engineer with the Engineering council, UK. Dr. Shah was recently granted the honorific of “Eminent engineer” with Tau beta Pi, the largest engineering society in the USA. He is on the Advisory board of directors at Farmingdale university (Mechanical Technology ) , Auburn Univ ( Tribology ) and Stony Brook University ( Chemical engineering/ Material Science and engineering). An Adjunct Professor at the State University of New York, Stony Brook, in the Department of Material Science and Chemical engineering, Raj also has over 500 publications and has been active in the alternative energy industry for over 3 decades. More information on Raj can be found at https://bit.ly/3sayVgT

Ms. Nicole Turner is a student at Hofstra University, Hempstead NY and is a part of a thriving  internship program at Koehler Instrument company  which encourages students to take a deep dive into alternative energy technologies.  

References

1. Solar Energy Technologies Office. “Solar Energy in the United States.” Energy.gov, Sept. 2021, https://www.energy.gov/eere/solar/solar-energy-united-states. 

2. Moore, Nicole Casal. “Transparent Solar Panels for Windows Hit Record 8% Efficiency.” University of Michigan News, 21 Aug. 2020, https://news.umich.edu/transparent-solar-panels-for-windows-hit-record-8-efficiency/.

3. Cbsolar, CBSolar, and Cbsolar. “2021 Home Solar Technology Advances.” Cool Blew Electric & Solar, 30 Apr. 2021, https://coolblewsolar.com/blog/2021-home-solar-technology-advances/#:~:text=%202021%20Home%20Solar%20Technology%20Advances%20%201,energy%20via%20a%20photovoltaic%20system%20like...%20More%20. 

4. Toussaint, Kristin. “Community Solar Garden Coming to the South Bronx.” Metro US, 26 Feb. 2020, https://www.metro.us/community-solar-garden-coming-to-the-south-bronx/. 

5. Green, Martin A. “The Passivated Emitter and Rear Cell (Perc): From Conception to Mass Production.” Solar Energy Materials and Solar Cells, North-Holland, 16 July 2015, https://www.sciencedirect.com/science/article/abs/pii/S0927024815003244. 

6. Pickerel, Kelly, et al. “What Are Heterojunction Technology (HJT) Solar Panels?” Solar Power World, 24 Sept. 2020, https://www.solarpowerworldonline.com/2019/11/what-are-heterojunction-technology-hjt-solar-panels/. 

7.  Bifacial Design Guide - LG Electronics. LG Electronics. (2017). Retrieved April 2, 2022, from https://www.lg.com/global/business/download/resources/solar/Bifacial_design_guide_Full_ver.pdf 

8. Dec 1, 2021, by Darrell Proctor. “New Materials, Efficiency Upgrades Advancing Solar Technologies.” POWER Magazine, 1 Dec. 2021, https://www.powermag.com/new-materials-efficiency-upgrades-advancing-solar-technologies/. 

9. Stauffer, Nancy. “Transparent Solar Cells.” Main, 24 Oct. 2017, https://energy.mit.edu/news/transparent-solar-cells/. 

10. *, N. (2022, March 6). A complete guide to PERC solar panels (vs. other techs). Solar Magazine. Retrieved April 8, 2022, from https://solarmagazine.com/solar-panels/perc-solar-panels/ 

The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag

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