Solar Panels

Introduction

The Earth receives a significant amount of solar energy: 173 thousand terawatts. This amount is ten thousand times greater than the power consumed by the planet's population. Therefore, could it be feasible for the world to eventually depend entirely on solar power?

How it works

To address the query, let us first explore the process by which solar panels convert solar energy into electrical energy. Solar panels consist of smaller units known as solar cells. These cells are commonly composed of silicon, a semiconductor and the Earth's second most abundant element. Within a solar cell, crystalline silicon is positioned between conductive layers. Each silicon atom forms four strong bonds with its neighboring atoms, which effectively restrict the movement of electrons and prevent the flow of current. However, the crucial element lies in the utilization of two distinct layers of silicon in a silicon solar cell. The first layer, known as n-type silicon, contains an excess of electrons, while the second layer, referred to as p-type silicon, possesses extra spaces for electrons, or "holes." At the junction where these two layers meet, electrons are able to migrate across, creating a positive charge on one side and a negative charge on the other.

Light can be considered as the movement of small particles known as photons, emanating from the Sun. When a photon collides with a silicon cell with sufficient energy, it has the ability to dislodge an electron from its bond, creating a vacancy called a hole. The negatively charged electron and the positively charged hole are now free to move. However, due to the presence of an electric field at the p/n junction, they can only move in one direction. The electron is attracted to the n-side, while the hole is drawn towards the p-side. The mobile electrons are gathered by thin metal fingers located at the top of the cell. Subsequently, they flow through an external circuit, performing electrical work such as powering a lightbulb, before returning through the conductive aluminum sheet at the back. While each silicon cell generates only half a volt, multiple cells can be linked together in modules to increase the power output. Twelve photovoltaic cells are sufficient to charge a cellphone, whereas numerous modules are needed to power an entire house. In a solar cell, electrons are the sole moving components, and they always return to their original positions. As a result, there is no wearing out or depletion, enabling solar cells to endure for decades.

So what's stopping us from being completely reliant on solar power?

The distribution of solar energy across the planet poses physical and logistical challenges. Certain areas receive more sunlight than others, making solar energy unevenly distributed. Moreover, solar energy is inconsistent, with reduced availability on cloudy days and at night. To fully rely on solar energy, efficient methods for transporting electricity from sunny locations to cloudy ones and effective energy storage are necessary. The efficiency of solar cells is also a challenge. If sunlight is reflected instead of absorbed, or if dislodged electrons return to a hole before going through the circuit, the energy of that photon is lost. Currently, the most efficient solar cell only converts 46% of available sunlight into electricity, while commercial systems typically operate at 15-20% efficiency.

So what will be next?

Despite these limitations, it is feasible to generate enough power to meet the global energy demand using present-day solar technology. However, substantial funding for infrastructure development and a significant amount of space would be required. Estimates suggest that tens to hundreds of thousands of square miles would be necessary, which may seem extensive, but considering the Sahara Desert alone spans over 3 million square miles, it is a viable proposition. Furthermore, solar cells are continuously improving in terms of efficiency and cost-effectiveness, making them a competitive alternative to grid electricity. Moreover, innovative solutions like floating solar farms have the potential to revolutionize the solar energy landscape. Additionally, it is crucial to acknowledge that more than a billion people lack access to a reliable electric grid, particularly in developing nations with ample sunlight. In such areas, solar energy is already a more affordable and safer option compared to alternatives like kerosene. However, for regions like Finland or Seattle, effective utilization of solar energy may still require further advancements.