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It’s the Sun, Son

I think of myself as a pretty knowledgeable person. I work hard in school, learn outside

the classroom, and keep up with the news. However, I had absolutely zero idea how a solar panel

works until very recently. How does a flat slab of blue glass create electricity from sunlight? It

seemed like it should be simple, but when I really tried to figure out how it all works, I came up

empty handed. I even tried using my AP Chemistry knowledge to deduce it with some advanced

“3-D chess” level logic, but that led nowhere. Eventually, I looked it up on YouTube, and was

presented with a short video describing the process. I was amazed. For a system so

straightforward, photovoltaics are a vastly misunderstood technology. The beauty of the design

inspired me to investigate photovoltaics further through my senior project.

I have been around solar panels almost everyday for the last twelve years. Every one of

my campuses from elementary school through high school has featured a massive array of these

“photovoltaics.” The roof of my house has solar panels to heat the pool. I even used to use a

solar powered calculator! Despite this constant exposure, I never thought too deeply about how

solar panels work or the process that brought them into the mainstream. Solar panels have always

just seemed like normal aspects of life to me, like zippers. When you ask most people how a

zipper works, they will probably struggle to give an accurate answer since nobody really thinks

about how they work. They just exist and we all accept it without really considering them. In this

way, we have taken them for granted.

I hope we never take solar power for granted because there is perhaps nothing more

incredible than deriving electricity directly from the Sun, the original source of all of Earth’s

energy. The illusion of knowledge that leads people to feel confident in their understanding of

zippers also leads them to overlook solar power, even when it can be found all around them.

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Despite the obvious intellectual value in solar technology, many people question whether the

shift towards renewable energy sources is worthwhile. Solar’s position as the most visible of

such begs the question: How well does it work? In other words: How effective are photovoltaic

solar panels in producing energy efficiently and economically?

Before addressing the efficacy of photovoltaics, it is important to understand how they

work. Most know that solar panels convert light to electricity, but the true genius of the

mechanism lies in the thin wafers underneath the glass. These “solar cells” are composed of

semiconductive layers of silicon. The topmost layer is doped with small amounts of phosphorus,

an element with one more valence electron than silicon in its ground state. This seemingly

minute difference in the composition of these elements leads this layer of the semiconductor to

hold a surplus of electrons, all of which repel each other in an attempt to reach a more stable,

balanced electric state. This layer is referred to as the n-type layer, as its excess of electrons gives

it a negative net charge. The silicon layer beneath this one is doped with boron, an element with

one fewer valence electron than silicon in its ground state. Thus, this layer has a deficiency of

electrons and also wishes to reach a more stable, balanced electric state. Therefore, this layer is

referred to as the p-type layer, as its shortage of electrons gives it a positive net charge. In the

region where these layers meet, called the junction, electrons in the n-type layer cross the border

to the p-type layer, creating a barrier of stable electric charge. When photons from sunlight strike

the solar cell, they displace electrons in both layers, ushering them into the n-type layer by the

electric field surrounding the junction. Connecting a circuit to both layers allows these electrons

to flow down the wire into the p-type layer, generating an electric current that is pooled together

with that of several other solar cells to form a photovoltaic solar panel. (“How”).

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Now that the mechanism behind photovoltaics is clear, their efficiency can be addressed.

Some of the most important factors in efficiency are sustainability and safety. Renewable energy

sources like solar power have a much less harmful impact on the environment than fossil fuels,

and the statistical evidence can be overwhelming. A study conducted by Hannah Ritchie and

Max Roser of data collection organization Our World in Data supports this idea, as they report

that clean energy sources like solar, wind, and hydropower each cause fewer than 0.07 deaths per

TWh of electricity they produce, compared to 18.4 and 24.6 per TWh by oil and coal,

respectively. This finding can mainly be attributed to renewables’ low greenhouse gas emissions,

which amount to as little as about 1/200th per GWh of those produced by fossil fuels (Ritchie &

Roser). The burden these energy sources place on the global ecosystem is unsustainable, as it

kills people and eliminates natural resources.

This destructive process repeats until all of the raw materials used to produce this energy

are exhausted. If this were to take place, the disruption to the global electricity chain would be

catastrophic, as coal, oil, and natural gas currently comprise 79% of the world’s energy

production (Ritchie & Rosen). Renewable energy sources do not face this challenge, as they rely

on eternal functions of the Earth in its natural state, such as the shining of the Sun or blowing of

the wind. Additionally, solar power requires little regular maintenance or hands on operation,

allowing for the reallocation of other energy sources’ inputs into other tasks. In this sense, solar

power conserves labor and capital resources when compared to non-renewable alternatives like

oil and coal.

The National Renewable Energy Laboratory’s (NREL) solar calculation tool PVWatts

can estimate that an array of solar panels covering the roof of an average house in Walnut Creek

would generate greater than 10 MWh of electricity per year, which is roughly equivalent to the

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average electrical consumption of an American household according to the U.S. Energy

Information Administration. By relying on solar energy, such a household would help contribute

to this conservation of resources, demonstrating the impact of minor energy shifts. If every house

in a neighborhood relied on solar panels as their main source of energy, the area’s reliance on

fossil fuels would be significantly reduced. However, just 14% of electricity is used to power

residences in America, compared to the 52% used to power industrial practices, according to a

study by professors at Penn State (Alley et al.). For this reason, major changes in energy

sourcing will likely not come from personal solar implementation, but shifts in corporate

practices and manufacturing processes.

Another way to measure the efficiency of an energy source is its conversion rate. The

conversion rate of a mechanism is the ratio of its energy output to its energy input, expressed as a

percentage. The conversion rates of most photovoltaic cell designs lie between 22% and 28%

(Center). On the high end of this spectrum is the most popular design, monocrystalline silicon

cells. The distinction “monocrystalline” denotes the makeup of the silicon wafers, as these cells

are cut from a single silicon crystal, lab-grown specifically for use in solar panels (Wallender).

These sport a greater conversion rate than polycrystalline cells, which are produced by melting

down silicon fragments to be cubed and cut into wafers (Wallender). Polycrystalline cells only

boast a conversion rate of 23%, as the fragmented silicon is not as effective as a semiconductor

(Center).

These efficiency rates may appear disappointing. People would certainly wish to convert

all, or as close to all the energy available to be collected by these devices. However, this is

currently an unattainable standard. A study conducted by Sam Nierop and Simon Humperdinck

of the Dutch environmentalist company Ecofys found that in 2016, fossil fuels converted energy

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at an average of just 40% efficiency, a far cry from some expectations. For this reason,

conversion rates in the 20-30% range are much more competitive than they appear. These rates

are also much more impressive when considering that these cells generate electricity 400% as

efficiently as the first photovoltaic cells made by Bell Laboratories 1954 (“Photovoltaic”).

Despite the tremendous strides these silicon cells have made over the years, some other

solar cell designs greatly exceed the aforementioned benchmarks. For example, multijunction

gallium arsenide cells boast conversion rates greater than 45%. The leap in their efficiency can

be attributed to the use of more than two semiconductor layers within the cells. Standard

single-junction silicon cells only employ a single junction between the n-type layer and p-type

layer. This layer can only absorb photons of a specific energy level, limiting the amount of

energy that runs through the system. This principle, known as the Shockley-Queisser Limit,

inspired the design of multijunction cells, which escape this pitfall by passing photons through

several layers of semiconductors with high, decreasing bandgaps. This ultimately increases the

conversion rate, because photons of higher voltages can be harvested before they pass all the way

through the solar panel and are lost as heat. (Solar Energy Technologies).

While multijunction cells generate electricity at nearly twice the conversion rate of single

junction ones, they are also much more expensive. In an interview, solar technologist Gregg

Higashi, a member of the Alta Devices team that broke multiple photovoltaic efficiency records,

pointed out that multijunction technology costs hundreds of dollars per Watt to manufacture,

compared to single junction’s price tag of less than a dollar per Watt. These cells are still in their

infancy and need much more time in design to become profitable and worthwhile for use beyond

satellites and other aerospace technology. Higashi described multijunction as “the holy grail,” but

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the challenge facing engineers is producing it at a low cost. For now, firms will have to push

through an unprofitable period of development before achieving viability on the open market.

While evaluating the efficiency of energy production, energy storage must also be

considered. This issue is particularly important for photovoltaics due to their most obvious

limitation: the night. When the Sun cannot shine, solar panels are minimally effective, meaning

that they experience regular periods of high and low energy yields. An overload of energy during

the day can lead to economic losses for energy providers when that electricity is not used, or as

Yale’s Cheryl Katz quoted Wesley Cole of the NREL, “One of the challenges of renewable

energy is the more you put on the grid, the more the value declines.” To solve this issue and

provide a reliable and consistent supply of electricity, battery facilities can store vast amounts of

solar energy for use at times of low Sun exposure. 2020 saw a record total of industrial battery

capacity installation in the U.S, reaching 1.2 GW. This trend is spearheaded by the development

of lithium-ion batteries, which are being manufactured on a massive scale to meet growing

energy needs. The Moss Landing Power Plant in Monterey was recently converted into a

renewable energy storage facility housing multiple lithium-ion batteries. These collectively total

400 MW, more energy storage than in the entire rest of California. Similar projects are becoming

more common around the world and are often tied directly to solar power. Storing excess solar

energy with improved battery technology like that in the Moss Landing Power Plant will enable

lower energy waste and higher energy use in the future (Katz).

Recent years’ massive investments in energy storage also highlight a potential challenge

for the growth of the solar industry, and the energy industry at large. Charles Marino, an

executive at solar development company Ubiquity Solar, shared in an interview that much of the

electrical infrastructure currently used in the U.S. was built between the 1930s and 1950s. This

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infrastructure, including power lines and electrical towers, has not been overhauled in many,

many years, and some estimates suggest that most fossil fuel power plants will cease operations

by 2035 (Katz). The lack of modern, sustainable infrastructure in America has contributed to the

slow advances of clean energy, as there is currently not enough high capacity energy

transportation to supply electricity to the entire country. Marino noted that America’s energy

needs are outpacing its supply, which could lead to more rolling blackouts like those seen in the

Bay Area in recent years.

Despite the challenge failing infrastructure poses, a new status quo in the electricity

business could emerge rather seamlessly. Higashi pointed out that if individual communities

were to house their own renewable energy plants like solar farms, they could abandon the

infrastructure built to transport electricity over long distances. Batteries can help localize energy

production and storage, so the threat of grid overload could be largely avoided with thoughtful

community planning and investment in renewable technology. Higashi mentioned that lots of

solar technology is already being manufactured with clean energy, as most firms build their

factories in Washington to harness cheap hydroelectric power. This evergreen production strategy

could help America “boot-strap itself into being completely carbon-free,” in Higashi’s words.

Solar power is positioned as an attractive solution in this scenario. Its highly sustainable

mechanisms and ease of residential application make it an attractive choice for widespread

implementation. One idea that Marino confirmed was in the works was a fleet of photovoltaic

cars. These vehicles would not only derive functional electricity using the solar panels mounted

on their roof, but could also carry lithium-ion batteries beneath their floor. This would allow

these cars to collect and store solar energy throughout the day, which could then be used to

power a home during the night. This model of “plugging your house into your car, not the other

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way around,” as Marino put it, could revolutionize the electrical industry. This would allow

consumers to stay “in front” of the grid, meaning they would not be reliant upon it for all of their

electricity. Higashi also proposed manufacturing thin-film solar panels that consumers could roll

out over their roofs, and tiles with built in solar cells for which consumers could easily swap out

their existing shingles. These options would decrease the expense of installation, a more

prominent factor in the cost of photovoltaics now that cells’ prices have plummeted in recent

years. Doing so would decrease their household energy costs and contribute to global

sustainability goals.

This economic incentive for consumers to invest in solar panels also stems from the Solar

Investment Tax Credit (ITC). This is a federal program allowing individuals and businesses to

deduct purchases of photovoltaic technology from their tax sheet at a rate of 26% (Solar Energy

Industries). Marino called the ITC, “the lifeblood of this industry. People think we’re selling the

panels but we’re actually selling the tax credit. We wouldn’t be in business without it.” The

credit was renewed in 2020 before the more than a decade old policy was set to expire,

stimulating the solar industry’s growth and continuing to bring photovoltaics into the

mainstream. Residential areas today are covered in solar panels, from homes, to parking lots, to

schools and businesses. They can all save money by investing in solar, a trend that shows no

signs of stopping soon. As was touched on earlier, industrial interests will drive the change in

energy sourcing, consuming over half of America’s electricity (Alley et al.). By incentivizing

businesses to take the leap in renewable energy, the ITC hits the energy industry where it matters

most, fueling change in the present and future.

Much of the solar industry’s growth can also be attributed to an economic phenomenon

known as “economies of scale.” When a market experiences this state, the price of its product

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declines as more of it is made. The solar industry has been undergoing economies of scale for

decades due to the learning curve in its production. As more solar modules are produced, new

manufacturing techniques are discovered, improved technology is developed, and the extraction

of raw materials becomes more widespread and less expensive. These all drive down the cost of

photovoltaic technology, encouraging more investment and leading to increased production and

lower prices. This cycle of improvement caused the price of solar electricity to decrease by

99.6% from 1976 to 2019, including 89% from 2009 to 2019, a greater reduction than that of any

other major energy source in that timeframe. In fact, photovoltaics now hold the lowest levelized

costs of energy (LCOE) of any energy source. LCOE is a metric that accounts for plant

construction and operation, as well as fuel costs. Solar power relies on a free and abundant

resource as its fuel, which cannot be said of other energy sources like fossil fuels. This is the

primary reason why these sources do not currently experience economies of scale, as fuel costs

fluctuate and operational costs rise with slower improvements in technology and stricter

regulations. As Katz mentioned while describing expanded energy storage, a study by Ritchie

shows that the battery market also experiences a learning curve, which has led to a 97% price

decline since 1992. These indicators of prolonged growth suggest that new advancements in both

photovoltaic and battery technology will continue to drive down their prices moving forward,

making solar power even more economically competitive in the future (Ritchie & Roser).

These findings demonstrate that the evolution of energy technology will allow

photovoltaics to continue to become more affordable and find a long-term home firmly within

the American energy sector. Not only do consumers benefit economically from photovoltaics,

but they share in the benefits of a sustainable, environmentally conscious society. This moral

argument for solar power is supported by their competitive efficiency and unmatched

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affordability. However, in order to accommodate this shift, the U.S. will need to continue

investing in the ITC and upgrades to its electrical infrastructure. China now dominates the solar

industry due to its massive investments in photovoltaics before the technology experienced

economies of scale. Higashi explained that “China did the world a favor, but also drove almost

every other solar company out of business. Competition is really, really fierce.” Without strong

domestic solar power, America will struggle to compete with other countries that rely on

renewable sources of energy and incorporate sustainability into their energy policy.

A vast amount of energy is available to be harnessed from the sun - a grand total of 173

billion MW of power at all times (Center). This largely untapped resource is one of humanity’s

most powerful tools against global warming, and must be taken seriously by consumers and

producers alike. Photovoltaics have a low environmental impact, their efficiency is competitive

with other sources, and they are cheaper than any other options on the market. Individuals should

purchase solar for their homes and cars, and businesses should purchase solar for their offices

and factories. However, traditional single-junction polycrystalline photovoltaics are not the only

option. Multijunction cells are becoming more viable by the day, and other clean technologies

like hydropower and wind turbines are experiencing similar economies of scale to photovoltaics.

A united effort behind a diverse palette of energy sources is the only way to reduce the world’s

carbon footprint and prevent irreparable damage to our planet. Innovation will continue to

provide these novel solutions at lower and lower prices, so the sooner renewables like solar are

embraced, the safer our global climate will become. In his most powerful statement about the

solar industry, Marino spoke on behalf of himself and his colleagues, explaining that “We all

believe your generation is going to be the one to solve the problem.” With minds facing towards

the future and solar panels facing towards the Sun, any goal is within reach.

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Works Cited

Alley, Richard B., et al. “Global Energy Uses.” EARTH 104: Earth and the Environment

(Development), The Pennsylvania State University,

https://www.e-education.psu.edu/earth104/node/1346. Accessed 18 April 2022.

Center for Sustainable Systems - University of Michigan. “Photovoltaic Energy Factsheet |

Center for Sustainable Systems.” Center for Sustainable Systems,

https://css.umich.edu/factsheets/photovoltaic-energy-factsheet. Accessed 22 March 2022.

Higashi, Gregg. Solar Technologist. Personal Interview. 23 April 2022.

“How solar panels generate power.” SaveOnEnergy, Save On Energy, 2022,

https://www.saveonenergy.com/solar-energy/how-solar-panels-work/. Accessed 8

February 2022.

Katz, Cheryl. “In Boost for Renewables, Grid-Scale Battery Storage Is on the Rise.” Yale E360,

15 December 2020,

https://e360.yale.edu/features/in-boost-for-renewables-grid-scale-battery-storage-is-on-th

e-rise. Accessed 22 March 2022.

Marino, Charles. Solar Developer Executive. Personal Interview. 3 March 2022.

National Renewable Energy Laboratory. “NREL's PVWatts Calculator.” PVWatts Calculator,

U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, 2022,

https://pvwatts.nrel.gov/index.php. Accessed 15 March 2022.

Nierop, Sam, and Simon Humperdinck. “International comparison of fossil power efficiency and

CO2 intensity - Update 2018.” Guidehouse, 2018,

https://guidehouse.com/-/media/www/site/downloads/energy/2018/intl-comparison-of-fos

sil-power-efficiency--co2-in.pdf. Accessed 22 March 2022.

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"Photovoltaic Cell Developed, May, 1954." Historic U.S. Events, Gale, 2014. Gale In Context:

High School,

link.gale.com/apps/doc/BT2359030418/SUIC?u=wal55317&sid=bookmark-SUIC&xid=

e2927755. Accessed 16 Feb 2022.

Ritchie, Hannah and Roser, Max. “Why did renewables become so cheap so fast?” Our World in

Data, 1 Dec 2020, https://ourworldindata.org/cheap-renewables-growth. Accessed 16

February 2022.

Solar Energy Industries Association. “Solar Investment Tax Credit (ITC) | SEIA.” Solar Energy

Industries Association, https://www.seia.org/initiatives/solar-investment-tax-credit-itc.

Accessed 22 March 2022.

Solar Energy Technologies Office. “Multijunction III-V Photovoltaics Research.” Department of

Energy, https://www.energy.gov/eere/solar/multijunction-iii-v-photovoltaics-research.

Accessed 22 March 2022.

U.S. Energy Information Administration. “Frequently Asked Questions (FAQs) - US Energy

Information Administration.” EIA, 7 October 2021,

https://www.eia.gov/tools/faqs/faq.php?id=97&t=3. Accessed 22 March 2022.

Wallender, Lee. “Monocrystalline vs Polycrystalline Solar Panels – Forbes Advisor.” Forbes, 25

February 2022,

https://www.forbes.com/advisor/home-improvement/monocrystalline-vs-polycrystalline-s

olar-panels/. Accessed 22 March 2022.

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