History of Solar Technology

For centuries sunlight provided and enabled life on our planet. Whether directly or indirectly the sun had allowed for the creation of almost all known energy resources such as fossil fuels, hydro, wind, biomass, and more. As civilization grows the energy needed to support our lifestyles increases daily, requiring us to find new innovative ways to use our renewable resources such as the sunlight to create more energy for our society to continue making progress. 

As early as the ancient world we have been able to use the sun's energy to survive, the use of sunlight as energy originated with an architecture that was built over 6000 years ago, whereby the orientation of the home was adjusted so that sun rays passed through openings to act as a form of heating. After a few thousand years the Egyptians and the Greeks used the same technique to keep their homes shaded from the sun in the summertime, in order to keep their homes cool [1]. Windows where large single pane windows were used as solar heat treats, allowing the entry of the heat from sunlight but trapping the heat inside. Not only was sunlight essential for the heat it exerts in the ancient world, but it was also used for food preparation and conservation through salting. In salting, the sun was used to evaporate the toxic sea water and obtain salt which was collected in solar ponds [1]. Later in the Renaissance era, Leonardo da Vinci had proposed the first industrial application of a concave mirror solar concentrator to be used as a water heater, later Da Vinci also proposed the technology of welding copper using solar radiation and allowed for the technical solutions to operate textile machines [1]. Soon enough during the industrial revolution, W. Adams created what is now known as a solar oven. This oven had eight symmetrical silver glass mirrors creating an octagonal reflector. The sunlight was concentrated by the mirrors into a glass covered wooden box where the pot would be placed, allowing it to boil [1]. Fast forward a couple hundred years and the solar steam engine was constructed around 1882 [1]. Abel Pifre used a concave 3.5m diameter mirror and had it focus on a cylindrical steam boiler, this engine produced enough power to operate a printing press. 

In 2004 the world's first commercial concentrating solar power plant which was named the Planta Solar 10, was set up in Seville, Spain. The sunlight was reflected but about 624 meters to a tower where the solar receiver was set up with a steam turbine and a generator. This was able to produce energy to power over 5500 homes. About ten years later in 2014 the world's largest solar power plant was opened in California, USA. This plant had over 300,000 controlled mirrors used and allowed for the production of 377 MW, which provides energy for about 140,000 homes [1].

Wearable Solar Cells

Not only are there plants being built and used but new technology made for consumers in retail stores are being created as well. Solar panels have made their debut and even solar-powered cars have started to come into play but one of the newest advances that has yet to be released is the new solar wearable technology. With the integration of USB connection or another device it allows for the connection from clothing to a source, devices such as phones and earbuds etc. which can be charged on the go. Just a few years ago a group of Japanese researchers at Riken Research Institute and Torah industries Inc. have described the development of a thin organic solar cell that will be heat printed onto pieces of clothing allowing the cells to absorb the sun's energy and be used as a power source [2]. The tiny solar cell is an organic photovoltaic cell that holds a thermal stability of up to 120℃ as well as the ability to be flexible [2]. the members of the research group based the organic PV cell on a material called PNTz4T [3]. PNTz4T is a semiconductor polymer which was previously developed by Riken which an excellent environmental stability as well as high efficiency of power conversion, the cells were then covered on both sides by an elastomer, a rubber like material [3]. In the process they used two pre-stretched 500 micrometer thick acrylic elastomers which allows light to enter the cell but prevents water and air to enter into the cell. This elastomer used helps decrease the degradation of the cell itself and gives it a longer lifetime [3].

One of the most significant disadvantages to this industry is the water. The degradation of these cells can be caused by multiple factors but the largest is water, with any technology water is the common enemy. Any excessive moisture and prolonged exposure to air can negatively impact the efficiency of organic PV cells [4]. While with computers or phones water is avoidable in most situations, with clothing it is impossible to avoid. Whether it be the rain or the washer machine, water is unavoidable. After a variety of tests comparing the freestanding organic PV cells to the double side coated organic PV cells, in figure 1 where both organic PV cells were dipped in water for 120 minutes it was concluded that power conversion efficiency only reduced by 5.4% while the freestanding cell was reduced by 20.8% [5].

Figure 1. Normalized power conversion efficiency as a function of the dipping time. The error bars on the plots indicate standard deviations normalized by the average of the initial power conversion efficiency in each structure [5].

Figure 2 depicts another development by Nottingham Trent University, a mini solar cell that can be embedded into yarn that would then be woven into textiles [2]. Each cell that is included in the products are held to a certain criterion in order for it to be used such as the 3mm long and the 1.5mm wide requirement [2]. Each cell is laminated with a waterproof resin for the purposes of washing the clothing in the laundry or due to the weather [2]. The cells have also been tailored for comfort, each cell is installed in a way that the cells don’t stick out or irritate the wearer’s skin. In further research, it was found that a in a small section of clothing similar to a 5cm^2 section of fabric can contain just over 200 cells and in ideal condition can produce 2.5 – 10 volts of energy and has been concluded that only 2000 cells are needed to be able to charge a smartphone [2].

Figure 2. Miniature solar cell of 3 mm long and 1.5 mm wide (Photo provided by Nottingham Trent University) [2].

The photovoltaic fabric merges two lightweight and low-cost polymers to create energy producing textiles. The first of two components is the mini solar cell that gathers the power from the sunlight and the second component consists of a nano-generator that converts the mechanical energy into electricity [6]. the photovoltaic section of the fabric is composed if polymer fiber which is then coated with layers of manganese, zinc oxide which is a photovoltaic material and copper iodide which is used to harvest the charges [6]. the cells are then woven together with a small thin copper wire and integrated into clothing. 

The secret behind these innovations lies with the transparent electrodes for the flexible photovoltaic device. The transparent conductive electrodes are one of the parts on a photovoltaic cell, it allows the travel of light into the cell improving the light collection rate. Used to make these transparent electrodes is the indium-doped tin oxide (ITO), this material is used because of its ideal transparency (>80%) and fine sheet resistance with an excellent environmental stability [7]. ITO is vital because of the almost perfect proportions of all its components. The thickness combined with the transparency and resistance are in a proportion that maximizes the results of the electrode [7]. Any fluctuation in the proportions can cause a negative effect on the electrode that affects the performance. For example, increasing the thickness of the electrode will decrease transparency and resistance causing performance to decrease. However, the ITO is a finite resource that being consumed quickly. There has been ongoing research to find a replacement that not only measures up to the ITO but hopefully surpass the performance of ITO  [7].

As of now materials such as polymeric substrates that have been modified with transparent conductive oxides are rising in popularity. Unfortunately, these substrates  have been proven brittle, rigid, and heavy which considerably decreases flexibility and performance [7]. Researchers have offered the solution of using flexible fiber-shaped solar cells as a replacement for the electrodes. The fiber-shaped cells consist of electrodes with two diverse metal wires twisted and combined with active material as a replacement for the electrodes [7]. It has shown promise due to the solar cells being lightweight, yet the issue is the lack of contact areas between the metal wires which decreases the contact area which led to the decrease of photovoltaic performance [7].

The environmental factor was also a big motivation to continue researching. The world currently heavily relies on non-renewable energy sources such as fossil fuels, coals, and oils. Shifting focus away from non-renewable energy sources and towards renewable energy including solar energy is a necessary investment for the future. Millions of people charge their phones, computers, laptops, smart watches, and all electronic devices daily, with the ability to charge these devices with our fabric when simply taking a walk it can reduce our use of fossil fuels. While this may seem insignificant on a small scale such as 1 or even 500 people, when scaled up to tens of millions of people it can significantly reduce our fossil fuel use.  

Floating Solar Farms

It is known that the solar panels in the solar plant farms including panels that are installed on top of homes have contributed to the use of renewable energy and caused a decrease in the use of fossil fuels, yet fossil fuels are still significantly being used across the USA. One of the main issues in this industry is acquiring land to build these farms. An average home can only support a certain number of solar panels and the solar farm estates are limited. In regions where there is ample space, most people are always hesitant to create a new solar plant because it permanently shuts down the possibility and potential for other opportunities on that land such as a new business. Recently there have been large installations of floating photovoltaic panels of which can generate large volumes of electricity, the main benefit of the floating solar farms has been the reduction in cost [8]. Without the use of land there is no more worry centered around the installation cost on top of homes and buildings. Currently all known floating solar farms are on human made bodies of water while in the future it is possible to place these farms on natural bodies of water, the man-made reservoirs have many advantages that are not prevalent atop oceans [9]. The man-made reservoirs are easily managed and have previous infrastructure and roads allowing for a simple installation of the farms. The floating solar farms have also been proven more productive than solar farms on land due to the temperature changes between the water and land [9]. Due to the high specific heat of the water, land usually has a higher surface temperature then a body of water and it has been proven that high temperatures can negatively impact the performance of solar panel conversion rates. While the temperature can’t control how much sunlight a panel receives it does play a factor in how much power you receive from the sunlight. In low energy situations (a.k.a cooler temperatures) the electrons within the solar panel will be at rest then later on when sunlight hits, they reach their excited state [10]. The difference between the rest and excited state is the voltage which is how much energy is produced. Not only can sunlight excite these electrons but so can heat. If the heat around the solar panels give the electrons energy and place them in a low excited state then the voltage won’t be as large when sunlight hits the panels [10]. since land is more susceptible to absorbing and emitting heat than water, the electrons in solar panels on land will most likely be in a higher excited state then of the solar panels were on or near a body of water where temperatures are cooler. Further research has proven that the cooling effect of water around the floating panels helps produce up to 12.5% more energy than if the panels were on land [9].

Figure 3. Floating solar farm at a reservoir in north-west England, Giles Exley [9].

As of now solar panels only cover 1% of the nation’s energy requirements but if these solar farms are planted on at most a quarter of the man-made reservoirs then solar panels would supply almost 10% of energy needs in the USA. In Colorado the floating panels are bring brought in as soon as possible, the two great reservoirs in Colorado have lost large quantities of water due to the evaporation but with the installation of these floating panels it’s possible to save the reservoirs from drying and create power [11].  Even if one percent of man-made reservoirs were equipped with solar farms, it would be enough to generate a minimum of 400 gigawatts which is enough energy to power 44 billion LED light bulbs for over a year.

Figure 4a shows the increase of power that the floating solar cells have provided in correlation with figure 4b. While in the past decade there were very few of the floating solar farms, they still have made such a difference in the power that is generated. In the future when floating solar farms become more abundant the total energy that is produced is said to expand two times reaching a capacity of 1.1TW by the end of 2022 from the 0.5TW in 2018. [12].

Figure 4a. Global capacity of solar PV and its annual addition due to floating PV plants [12]. 

Figure 4b. Total capacity of Floating PV Plants installed around the world [12].

Environmentally speaking these floating solar farms are very beneficial in many more ways than one.  Aside from reducing fossil fuel reliance, solar farms also reduce the amount of wind and sunlight reaching the water surfaces which can potentially help reverse climate change [9]. A floating farm that can reduce the wind speed and direct sunlight to the water surfaces by at least 10% can offset an entire decade of global warming [9].  In terms of biodiversity and ecology there seem to be no large negative impacts that have been found. The panels prevent large wind activity on the water’s surface resulting in the decreasing of erosion of the banks and the protection as well as stimulation of vegetation. [13]. There are no definitive results that prove whether marine life has been affected but measures such as bio huts created by Ecocean which are filled with seashells have been submerged under the PV panels in order to potentially support marine life. [13]. Ongoing research is occurring with one of the main concerns of which being the potential impact of the food chain due to the installation of an infrastructure such as the PV panels on open water rather than the man-made reservoirs. With less sunlight entering the waters, it can lead to decreased rates of photosynthesis causing a great loss of phytoplankton and macrophytes. With the decrease of these plants impact the animals on the next level of the food chain and so on, causing the aquatic life to subsidize [14]. Although it has yet to happen, this can prevent the further, the potential destruction of the ecosystem is a large disadvantage of floating solar farms. 

Conclusion

With the sun being our largest source of energy finding ways to harness that energy and using it in our communities is difficult. The new technology and innovations that are becoming available everyday are making that possible. While there isn’t many wearable solar clothing for purchase currently or many floating solar farms to visit, it doesn’t change the fact that the future of the technology doesn’t have great potential or a promising future. The floating solar cells have still a long way to go in the sense of wildlife before it can be used as common as solar panels on top of homes. Wearable solar cells too have a way to go before becoming as common as the clothes we wear every day. In the future there is hope for evolving solar cells that can be used in everyday life that don’t have to hide between our clothing. As technology advances in the next few decades, the potential for the solar energy industry is endless. 

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 - Jul 15 2020 - David Phillips - Petro Industry News Articles - Petro Online (petro-online.com)

A Ph.D in Chemical Engineering from The Penn State University and 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 Dept. of Material Science and Chemical Engineering at State University of New York, Stony Brook,  Raj also has over 475 publications and has been active in the energy arena for over 3 decades. More information on Raj can be found at ​Koehler Instrument Company’s Director elected as a Fellow at the International Institute of Physics Petro Online (petro-online.com)

Ms. Mariz Baslious  and Mr. Blerim Gashi are students of Chemical Engineering at the State University of New York, where Dr. Raj Shah is the chair of the external advisory board of directors.  Mariz and Blerim are part of a growing internship program at Koehler Instrument company, in Holtsville, NY which encourages students to learn more about the world of alternative energy technologies.

 

References

1. Szabo, Lorand. “The History of Using Solar Energy.” 2017 International Conference on Modern Power Systems (MPS), 2017, https://doi.org/10.1109/mps.2017.7974451.  

2. Electropages. “Wearable Solar Technology Breakthrough.” Electropages, https://www.electropages.com/blog/2019/11/wearable-solar-technology-breakthrough.  

3. “A Solar Cell You Can Put in the Wash.” RIKEN, https://www.riken.jp/en/news_pubs/research_news/pr/2017/20170919_2/. 

4. “RF Wireless World.” Advantages of Organic Solar Cell,Disadvantages of Organic Solar Cell, https://www.rfwireless-world.com/Terminology/Advantages-and-Disadvantages-of-Organic-Solar-Cell.html. 

5. Jinno, Hiroaki, et al. “Stretchable and Waterproof Elastomer-Coated Organic Photovoltaics for Washable Electronic Textile Applications.” Nature Energy, vol. 2, no. 10, 2017, pp. 780–785., https://doi.org/10.1038/s41560-017-0001-3. 

6. Gallowayjim54. “Solar Power Fabric.” SolarPowerCampingGear.com, SolarPowerCampingGear.com, 11 Jan. 2021, https://solarpowercampinggear.com/solar-power-fabric/

7. Hashemi, Seyyed Alireza, et al. “Recent Progress in Flexible–Wearable Solar Cells for SelfPowered Electronic Devices.” Energy & Environmental Science, vol. 13, no. 3, 2020, pp.685–743., https://doi.org/10.1039/c9ee03046h.

8. “Floating Solar: Can Solar Farms Thrive on Water?” Solstice Community Solar, 26 July 2021, https://solstice.us/solstice-blog/floating-solar/.  

9. Giles Exley Associate Lecturer of Energy and Environment. “Floating Solar Farms Could Cool down Lakes Threatened by Climate Change.” The Conversation, 28 Apr. 2021, https://theconversation.com/floating-solar-farms-could-cool-down-lakes-threatened-byclimate-change-157987. Author: Casey McDevittCasey communicates Solstice's mission through social media, et al.

10. “Does Temperature Affect the Amount of Energy a Solar Panel Receives?” UCSB Science Line, http://scienceline.ucsb.edu/getkey.php?key=2668.

11. “Floating Solar Is a Win-Win Energy Solution for Drought-Stricken US Lakes.” The Guardian, Guardian News and Media, 30 June 2016, https://www.theguardian.com/environment/2016/jun/30/floating-solar-is-a-win-win-energy-solution-for-drought-stricken-us-lakes. 

12. Gorjian, Shiva, et al. “Recent Technical Advancements, Economics and Environmental Impacts of Floating Photovoltaic Solar Energy Conversion Systems.” Journal of Cleaner Production, vol. 278, 2021, p. 124285., https://doi.org/10.1016/j.jclepro.2020.124285. 

13. Garanovic, Amir. “First Insights into Floating Solar Show No Adverse Environmental Impacts.” Offshore Energy, 18 May 2021, https://www.offshore-energy.biz/first-insights-into-floating-solar-show-no-adverse-environmental-impacts/.

14. “Solar Projects on Water Could Come at a Cost to the Environment, Alert Experts.” Mongabay, 14 Mar. 2021, https://india.mongabay.com/2021/03/solar-projects-on-water-could-come-at-a-cost-to-the-environment-alert-experts/. 

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

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