What Can Solar Radiation Be Converted Into?

Solar radiation refers to the radiant energy emitted by the Sun in the form of electromagnetic waves. Harnessing solar radiation is critical as it is the original source of energy that drives life on Earth. By converting solar radiation into other forms of energy, we can utilize this abundant renewable resource for various applications to meet our energy needs in a sustainable manner. There are a number of ways solar radiation can be converted or harnessed, which we will explore in this article. These include photovoltaics, concentrated solar power, solar thermal systems, solar fuels, solar sails, as well as direct uses in agriculture and industry.

Table of Contents

Photovoltaics

Photovoltaic cells, also known as solar cells, are devices that convert sunlight directly into electricity using the photovoltaic effect. PV cells are made from semiconductor materials such as silicon that when exposed to sunlight, absorb photons and create an electric current (How do solar panels work?, 2022).

PV cells are assembled together into solar panels or modules. When sunlight strikes the semiconductor material of a PV cell, the photons knock electrons loose from their atoms, allowing the electrons to flow through the material and produce electricity. PV cells contain electric fields that act to force electrons freed by light absorption to flow in a certain direction, creating a DC current. An inverter is then used to convert the DC into AC electricity for practical use (How do solar panels work?, 2022).

Some key materials used for PV cells include mono-crystalline silicon, poly-crystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide. Mono-crystalline silicon is the most efficient but also most expensive. Applications for PV panels include rooftop solar on homes and buildings, solar farms, space vehicles, consumer electronics, and more.

Source: https://www.livescience.com/41995-how-do-solar-panels-work.html

Concentrated Solar Power

Concentrated solar power (CSP) systems use mirrors or lenses to concentrate sunlight onto a small area, generating high temperatures that can be used to produce electricity. The concentrated sunlight is converted into heat, which is then used to drive a steam turbine or heat engine connected to an electrical power generator.

There are four main types of CSP technologies:

Parabolic trough systems use long, U-shaped mirrors to focus sunlight onto a receiver tube running along the focal point, heating up a transfer fluid inside it to 290–550°C.
Power tower systems, also known as central receiver systems, use many large, flat or slightly curved mirrors called heliostats to reflect and concentrate sunlight onto a central receiver on top of a tower. The receiver contains a fluid that can be heated up to over 1,000°C.

Parabolic dish systems are dish-shaped reflectors that concentrate sunlight onto a receiver at the focal point of the dish. The concentrated heat is transferred to an engine or generator to produce power.
Linear Fresnel reflector systems use multiple long, thin segments of flat or slightly curved mirrors placed at different angles to concentrate sunlight onto elevated receivers.

The heat generated by CSP systems can be used to produce electricity via a steam turbine, or it can be stored to produce power on demand or at night. CSP plants are best suited for areas with high direct solar radiation. The modular nature of CSP technology allows plants to be tailored to meet specific energy demands.

According to the IEC (https://medium.com/e-tech/saving-sunshine-for-cloudy-days-a94a098b098f), CSP represented less than 2% of global solar capacity in 2021 but is one of the fastest growing solar technologies. Key applications include supplementing electricity generation, providing grid stability services, and supplying process heat for industrial purposes.

Solar Thermal

Solar thermal systems convert sunlight into heat energy. They utilize solar thermal collectors, often mounted on rooftops, which absorb sunlight and transfer the heat to a fluid like water or air.

There are two main types of solar thermal collectors:

Flat plate collectors – These are insulated, weatherproof boxes with a dark absorber plate under one or more glass or plastic covers. They can heat fluid up to about 66°C.
Evacuated tube collectors – These feature parallel rows of transparent glass tubes, each containing a glass outer tube and metal absorber tube attached to a fin. The vacuum between the two tubes traps heat. These can heat fluid up to 93°C.

Typical applications of solar thermal technology include:

Heating water for residential and commercial use
Heating swimming pools
Space heating of buildings

Industrial process heating
Power generation when coupled to an engine or turbine
Desalination of seawater

Air conditioning via absorption chillers

Solar thermal systems offer a clean, renewable way to meet hot water and heating needs. Costs have fallen in recent years, and government incentives can make installation affordable. With thermal energy storage, systems can provide hot water even when the sun isn’t shining.

Solar Fuels

Solar fuels are energy carriers like hydrogen and carbon-based fuels that are produced by converting solar energy, through artificial photosynthesis. Artificial photosynthesis involves using sunlight to split water into hydrogen and oxygen, in a process called photoelectrochemical water splitting^[1].

The hydrogen produced can then be used as a fuel source or combined with carbon dioxide to produce renewable synthetic fuels like methanol or ethanol. These solar fuels offer a way to store solar energy in the form of chemical bonds, providing renewable alternatives to fossil fuels.

However, artificial photosynthesis faces significant challenges. Efficient and cost-effective materials for absorbing sunlight and catalyzing fuel-producing reactions need to be developed and engineered into integrated systems. Storing, transporting and using the fuels produced at large scales must also be addressed^[2].

If these obstacles can be overcome, artificial photosynthesis offers tremendous potential. Solar fuels could provide storable, transportable energy on demand, offering a carbon-neutral alternative to fossil fuels and aiding the transition to renewable energy systems^[3].

Continued research and development is focused on improving efficiency, lowering costs, and scaling up artificial photosynthesis systems to make solar fuels a viable energy solution for the future.

^[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4410565/
^[2] https://royalsocietypublishing.org/doi/10.1098/rsfs.2015.0014
^[3] http://www-reisner.ch.cam.ac.uk/docs/solar_fuels_report.pdf

Solar Sails

Solar sails, also known as light sails or photon sails, are a proposed method of spacecraft propulsion using radiation pressure exerted by sunlight on large mirrors. According to How can you use solar sails for spacecraft propulsion? (https://www.linkedin.com/advice/0/how-can-you-use-solar-sails-spacecraft-propulsion-a9b6f), solar sails use sunlight to propel spacecraft in a similar way to the wind pushing a sailboat forward. Solar sails would work by reflecting sunlight off a large, mirror-like sail made of lightweight reflective material like Mylar or Kapton film.

As sunlight hits the sail, the radiation pressure from the photons transfers momentum to the sail and provides thrust to propel the spacecraft. This thrust is minimal but acts continuously over long periods of time to gradually accelerate the spacecraft to high velocities. Solar sails can potentially reach speeds over 100,000 mph, ideal for long voyages across the solar system and beyond. Unlike rockets, solar sails do not require propellant so they can accelerate indefinitely without using fuel.

Solar sails have been proposed for a variety of applications according to research by The mission’s design of solar sail spacecraft based on multi-objective optimization (https://ui.adsabs.harvard.edu/abs/2018AIPC.2046b0100S/abstract). Potential uses include long-term space observation missions, asteroid reconnaissance, solar system escape trajectories, and using the sun as a gravitational slingshot for interstellar travel. While solar sails remain a developing technology, recent progress shows promise for enabling unique deep space missions not possible with conventional chemical rockets.

Agriculture

Solar radiation can be used in agriculture for a variety of applications, including crop drying, water treatment, and irrigation systems.¹ Crop drying is an important post-harvest process that removes moisture from crops after harvesting using solar radiation as a heat source. This extends the shelf life of crops and prevents spoilage.²

Solar water disinfection uses solar radiation to inactivate pathogens in water used for crop irrigation and livestock. Exposure to UV radiation from sunlight kills bacteria, viruses, and parasites in contaminated water.¹

Solar-powered irrigation utilizes solar photovoltaic panels or solar thermal collectors to power water pumps that provide irrigation for crops. This provides a clean, renewable energy source for irrigation in areas with scarce water resources.²

Industry

Concentrated solar power (CSP) can be used to provide heat for various industrial processes that require high temperatures, including food processing, chemical production, and materials treatment. CSP uses mirrors or lenses to concentrate sunlight onto a receiver, heating up a transfer fluid that can then be used to generate steam.

Steam is essential for many industrial processes like drying, preheating, cleaning, boiling and more. Traditionally, fossil fuels have been used to produce this steam. However, CSP offers a renewable way to generate high temperature steam (up to 565°C) for these applications.

According to the Solar Thermal World organization, over 1,100 CSP plants were in operation globally for industrial process heat applications as of 2020, with a total capacity exceeding 1 GWth. Countries with significant CSP industrial process heat capacity include Mexico, India, Spain, and China ^[1].

Replacing fossil fuels with CSP for industrial process heat can significantly reduce greenhouse gas emissions. CSP with thermal energy storage can also provide steam on demand, even when the sun isn’t shining. With thermal storage, CSP offers a clean, dispatchable source of high temperature process heat for industry.

Electricity Generation

Utility-scale solar power plants are large installations designed to provide renewable electricity at scale. The two main types of utility-scale solar technologies are photovoltaics (PV) and concentrated solar power (CSP). PV converts sunlight directly into electricity using semiconducting materials, while CSP uses mirrors to concentrate sunlight to heat a transfer fluid that drives a generator

Solar electricity generation has been growing rapidly in recent years. According to the International Renewable Energy Agency (IRENA), global solar PV capacity increased over 200-fold between 2000 and 2020, from 1.5 gigawatts to over 760 gigawatts. In 2021, new solar PV installations reached a record high of over 160 gigawatts. This growth is expected to continue as solar electricity costs continue to fall dramatically.

To integrate large amounts of solar onto the electric grid, additional investments in grid infrastructure, storage, and flexible generation are needed. Solar generation peaks at midday and drops off in the evening when demand is still high. Areas with high solar penetration sometimes have to curtail solar output during periods of oversupply. Solutions for better grid integration include upgraded transmission lines, advanced inverters, battery storage, hybrid PV-plus-storage plants, and improving solar forecasting. With the right policies and technologies, high levels of solar penetration have been successfully implemented in regions like California and South Australia.

Overall, utility-scale solar power is one of the most rapidly expanding renewable energy sources with great potential to provide clean electricity at low cost. Continued technology improvements and grid integration strategies will enable solar to become a major pillar of the global energy system.

Conclusion

Solar radiation is a powerful source of renewable energy that can be harnessed in many ways. Technologies like photovoltaics and concentrated solar power convert sunlight into electricity to power homes, businesses, and the grid. Solar thermal captures heat to provide hot water and steam for heating and industrial processes. Technologies like solar fuels and artificial photosynthesis use solar energy to create renewable fuels like hydrogen. Solar radiation can also directly enable agriculture and industrial processes like drying and evaporation.

Overall, solar radiation is an abundant, renewable resource with the potential to generate massive amounts of clean energy to power our society. Advances in solar technologies like thin-film photovoltaics, concentrated solar farms, and solar thermal storage will enable solar to become an increasingly significant portion of the energy mix. With solar costs continuing to fall dramatically, the future is bright for widespread solar deployment. Harnessing solar radiation will help tackle climate change, reduce pollution, and enable a clean energy transition.