What Resource Is Solar Energy?

1. What is Solar Energy?

At its basic definition, solar energy is the radiant energy from the sun that reaches the Earth. Solar energy is generated from sunlight and then converted into useful forms of energy such as heat and electricity (https://ei.lehigh.edu/learners/energy/solar/solar1.html). The sun produces energy through a process called nuclear fusion, where hydrogen atoms fuse together under intense heat and pressure to form helium. This fusion process releases energy in the form of photons or light particles. Some of these photons travel the 93 million miles from the sun to Earth to provide our planet with solar energy (https://www.sunrun.com/go-solar-center/solar-articles/solar-energy-definition-what-is-solar-energy).

There are two main ways to utilize solar energy: solar photovoltaics (PV) and solar heating or thermal technology. Solar PV systems directly convert sunlight into electricity using solar cells made of semiconductor materials. The solar cells absorb the photons and release electrons, generating an electric current that is collected and turned into usable electricity. Meanwhile, solar heating/thermal systems collect the sun’s warmth through panels or tubes and concentrate that thermal energy to heat water or spaces (http://solarenergyfactsblog.com/define-solar-energy/).

History of Solar Energy

Solar energy has been harnessed by humans for thousands of years. The earliest uses of solar energy date back to 7th century BC, when people used magnifying glass to concentrate the sun’s rays to make fire [1]. Solar energy continued to be used passively for heating, cooking, and drying. In the 1860s, Auguste Mouchout invented the first solar-powered engine. He demonstrated that solar power could be used as a viable energy source [2].

However, it was not until the 1950s that solar energy technologies became more practical and widespread. In 1954, Bell Labs introduced the first modern silicon photovoltaic (PV) cell. This led to the mass production and commercialization of solar panels. The oil crisis of the 1970s further drove investment and adoption of solar energy. The cost of solar power has declined dramatically since then, making it more affordable and accessible globally [3].

Benefits of Solar Energy

solar energy is a renewable resource

One of the biggest benefits of solar energy is that it is a renewable resource. The sun provides an unlimited, inexhaustible supply of energy that will continue shining for billions of years (1). This means solar energy can be harnessed over and over again without depletion. In contrast, fossil fuels like coal, oil, and natural gas are finite resources that will eventually dwindle over time.

By switching to solar energy, reliance on fossil fuels is reduced. Solar power systems generate clean, emissions-free electricity from sunlight. As homes, buildings, and facilities adopt solar energy, demand decreases for non-renewable energy from oil, coal, and natural gas (2). This helps combat climate change and improve public health by reducing air pollution and greenhouse gas emissions associated with burning fossil fuels.

Solar energy can lower electricity bills, especially with net metering programs that allow excess solar electricity to flow back to the grid (2). Installing solar panels provides on-site power generation, reducing dependence on the utility company. Solar energy systems can provide electricity for decades with very little maintenance or intervention after the initial setup.

The emissions-free electricity generated from solar energy helps decarbonize the electricity sector. Solar PV systems produce no carbon dioxide or air pollutants while operating, allowing clean energy generation. This helps cities, states, and countries work toward achieving zero-emissions targets.

Limitations of Solar Energy

While solar energy has many benefits, it also comes with some limitations. One of the main drawbacks is its intermittent nature. Solar panels only produce energy when the sun is shining, so they do not generate any electricity at night or on cloudy days. This inconsistency can make it challenging to rely solely on solar power. Adding energy storage, like batteries, can help mitigate this issue but also increases costs (Constellation, 2022).

Another limitation of solar is the high upfront costs. Installing a solar energy system requires a significant initial investment. According to one source, residential solar panel systems cost $15,000-$25,000 on average in the U.S., while commercial and utility-scale systems are even more expensive (Nachi, 2022). The payback period can take many years, even though savings are realized over the system’s 25+ year lifetime.

Solar arrays also require adequate space and sunlight exposure for optimum energy production. The panels must be oriented properly and avoid shading from buildings, trees or other obstructions. Rooftop systems may not have ideal conditions, especially in dense urban settings. Overall placement constraints can limit solar’s applications (Nachi, 2022).

Solar Energy Economics

The cost of solar panels has declined significantly over the past decade, making solar energy more affordable. According to the Solar Energy Industries Association (SEIA), the average cost of solar panels in 2010 was $7.34 per watt, compared to just $0.994 per watt in 2022, an 86% reduction.[1] This dramatic decrease is attributed to improvements in technologies, manufacturing processes, and economies of scale as the solar industry has expanded.

The levelized cost of energy (LCOE) from solar photovoltaics has also become cost-competitive with conventional energy sources. The U.S. Energy Information Administration found the LCOE for solar PV declined from $359 per megawatt hour in 2010 to just $37 per megawatt hour in 2021.[2] This positions solar favorably against the average LCOE for natural gas ($56/MWh) and coal ($109/MWh).

Federal and state incentives have also helped reduce the upfront costs of solar installation for homeowners and businesses. The federal Solar Investment Tax Credit (ITC) offers a 26% tax credit for systems installed in 2022-2023, which will step down to 22% in 2024.[3] Many states and utilities also offer additional rebates, performance-based incentives, and net metering programs.

With solar energy costs continuing to fall, analysts forecast strong near-term growth. SEIA and Wood Mackenzie project over 40% annual growth in the U.S. over the next 5 years, reaching over 200 GW of total installed capacity by 2026.[4]

[1] https://www.seia.org/solar-industry-research-data

[2] https://www.eia.gov/outlooks/aeo/pdf/electricity_generation.pdf

[3] https://www.energy.gov/eere/solar/solar-investment-tax-credit-itc

[4] https://www.seia.org/us-solar-market-insight

Major Solar Energy Technologies

There are several major technologies used to harness solar energy, the most common being photovoltaics and concentrated solar power.

Photovoltaics (PV) convert sunlight directly into electricity using solar panels made up of solar cells containing photovoltaic material. When sunlight shines on the solar cells, the energy from the photons in the light knocks electrons free from the atoms, allowing electricity to flow. PV panels are modular and scalable, making them useful for powering anything from small gadgets up to entire buildings (1).

Concentrated solar power (CSP) systems use lenses or mirrors to concentrate sunlight onto a receiver, heating up a thermal transfer fluid that is used to drive a turbine to generate electricity. There are different types of CSP technologies that concentrate solar energy in different ways, such as parabolic troughs, linear Fresnel reflectors, power towers, and dish/engines (2).

Solar thermal technologies harness the sun’s heat energy rather than converting it to electricity. Common uses include solar water heating systems for residential and commercial buildings and concentrated solar thermal plants that focus sunlight to heat fluid and drive steam turbines (3).

(1) https://www.energy.gov/eere/solar/how-does-solar-work
(2) https://www.solaracks.com/what-are-the-different-types-of-solar-energy-technologies/
(3) https://www.trvst.world/renewable-energy/different-types-of-solar-energy/

Leading Countries in Solar Energy

China has emerged as the global leader in solar energy capacity over the past decade. According to a report by Nationmaster, China ranked 1st in solar energy capacity in 2019 with 175 gigawatts installed. The United States ranked 2nd with 75 gigawatts of solar capacity. Other top countries include Japan (56 GW), Germany (49 GW), and India (34 GW) (Nationmaster).

The United States has long been a leader in solar technology and deployment. It has a diverse range of solar installations, from large utility-scale solar farms to residential rooftop solar panels (E3 Solar). The solar industry has grown rapidly in the US, aided by federal tax credits and state policies supporting renewable energy.

China surpassed the United States in solar capacity starting around 2015. One study found that China’s dominance is partly due to its centralized, state-driven approach to developing solar versus the more decentralized, market-driven approach in the US (Chen, 2019). China has invested heavily in solar panel manufacturing, driving down costs.

Solar Energy Storage

As solar energy is produced intermittently, storing the energy is crucial for providing continuous renewable power. There are three main ways to store solar energy: batteries, thermal storage, and mechanical storage.

Batteries are the most common method of solar energy storage. Lithium-ion, lead-acid, and flow batteries can store surplus solar power during the day and discharge it when needed at night (https://aurorasolar.com/blog/storing-solar-energy-everything-you-need-to-know/). While battery costs are dropping, batteries remain one of the largest expenses of a solar system.

Thermal storage involves heating a material during peak production and using the trapped heat to generate electricity after sunset. This allows solar thermal plants to operate even when the sun isn’t shining. Molten salt and phase change materials are common thermal storage mediums (https://codibly.com/news-insights/solar-energy-storage-what-are-your-options/).

Mechanical storage converts electricity into kinetic or gravitational potential energy, often using flywheels or pumped hydro. These technologies can respond quickly to changes in supply and demand to help balance the grid.

A combination of storage solutions, demand response programs, overbuilding solar capacity, and grid interconnections can provide reliable, round-the-clock renewable energy despite sunlight’s intermittency.

Future of Solar Energy

The future of solar energy looks bright, with projections for massive growth in solar deployment globally. According to the International Energy Agency (IEA), solar is expected to become the number one source of power generation globally by 2050, supplying up to 25% of electricity demand. IEA.

Several key innovations and improvements are expected to drive growth in solar energy. Researchers are working to improve solar cell efficiency, with predictions that efficiency could reach over 50% by 2050 compared to around 20% for most panels today. New solar cell materials like perovskites and organic PV also show promise for better efficiency and flexibility. On the storage side, batteries and other solutions are advancing to better store solar energy for overnight or cloudy day use.

Solar will play a major role in the global energy transition away from fossil fuels. As solar costs continue to decline, it is expected to reach and surpass parity with conventional energy sources like coal and natural gas in more markets, accelerating its growth. With solar’s environmental benefits like zero emissions, it is being rapidly adopted by countries and corporations with clean energy commitments. If key innovations materialize and supportive policies are enacted, some analysts predict solar could supply up to 50% of global electricity by 2050.

Solar Energy and Sustainability

Solar energy plays a critical role in supporting sustainability efforts around the world. According to the U.S. Energy Information Administration, solar energy accounted for just 3% of total U.S. electricity generation in 2020, but it is the fastest growing renewable energy source with an average annual growth of 42% over the past decade (1). The rapid growth and adoption of solar power brings major sustainability benefits.

First and foremost, solar energy helps reduce greenhouse gas emissions that contribute to climate change. Whereas fossil fuels like coal and natural gas release carbon dioxide into the atmosphere when burned to generate electricity, solar panels produce clean, emissions-free renewable power. The Solar Energy Industries Association estimates that solar generation avoided over 55 million metric tons of carbon dioxide emissions in 2020 alone (2). Widespread implementation of solar could significantly curb emissions and help mitigate climate change.

Solar energy also promotes energy independence and security. By harnessing the sun’s rays rather than imported fossil fuels, solar helps reduce reliance on finite resources controlled by other nations. Local and regional solar generation reduces the need for long-distance transmission lines. With solar technology advancements like battery storage, the intermittent nature of solar becomes less problematic, further increasing energy reliability and resilience.

In addition, solar is now one of the leading sources of job creation in the energy sector. The Solar Foundation’s National Solar Jobs Census found there were over 231,000 solar workers in the U.S. in 2020, with installations increasing 45% from 2019 to 2020 (3). Solar jobs increased in 46 of 50 states,showing the technology’s job creation potential across diverse geographies.

With solar energy’s emissions reduction capabilities, limited environmental impact, and job growth opportunities, solar serves as a critical tool for sustainable development around the world.


(1) https://energy5.com/saving-the-planet-one-panel-at-a-time-the-environmental-impact-of-solar-energy-production

(2) https://www.mdpi.com/2071-1050/13/11/6295

(3) https://optiononesolar.com/solar-energy-and-sustainability/

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