J. Solar Energy is a multi-disciplinary journal that covers significant contributions to the field of solar energy from both fundamental and applied perspectives. The journal was established in 2008 and is published by Elsevier. The editor-in-chief is Joshua L. Andrews (University of Michigan).
This year marks the 110th anniversary of the solar energy era, as the technology was first developed in the U.S. in 1907. Since then, solar power has grown from a small cottage industry to a significant economic and industrial force that now supplies about 19% of our energy needs. Today, there are more than 300 different technologies that can be used to convert solar energy into various forms of electricity, including direct current (DC), alternating current (AC), and nuclear fusion. (The largest of which is the International Hybrid Electric Vehicle Energy Storage System Project (I.H.E.V.E.S.T.)).
During this period of sustained growth, solar energy has undergone several evolutions, including advancements in material science, engineering, and economics that have enabled greater energy generation at lower cost. For example, silicon photovoltaics (PV) – the original solar cell technology developed in the early 20th century – still form the basis of most solar energy systems, yet today’s cells are significantly more efficient and less costly.
However, despite its significant contributions to our modern society, solar energy still has several hurdles to overcome before it can achieve its true potential. These challenges are both scientific and economic, and they range from the need for more research and development to improve efficiency and lower costs to the need for more sustainable, environmentally-conscious energy sources.
To help address these issues, this article presents an appraisal of the past and future of solar energy, as well as a summary of the various scientific and technical challenges that currently stand in the way of the technology.
The Evolution Of Solar Energy
As previously stated, the U.S. was the first country to successfully utilize solar energy for commercial use around the turn of the century, although large-scale power generation did not occur until the 1950s and 1960s.
The major turning point came about in the mid-1920s, when the oil industry turned to coal and subsequently nuclear power generation as a result of the Great Depression. This led to a significant decline in the use of oil, particularly for transportation, and effectively put a stop to economic growth for several decades. While the demand for oil declined, the need for electricity increased, and power stations using oil or coal as fuel became standard. In these days, the only option for homeowners and businesses was either an oil or coal-fired power station.
However, during this time, solar power gained interest among those seeking green energy sources. In the early 1930s, the construction of the Boulder Canyon Dam on the Colorado River led to the generation of about 20 MW of power that was transmitted through a high-voltage direct current line to the Los Angeles area. This marked the beginning of commercial use of solar power in the U.S., with the potential to supply about 10% of the nation’s energy needs. For several years, large-scale solar energy systems were built in California and other parts of the country, as the Great Depression continued and electricity was seen as a luxury item.
Since its inception, solar energy has faced several scientific challenges that have prevented it from becoming a practical and sustainable energy source. These challenges fall into three major categories: 1) Efficiency; 2) Cost; and 3) Scalability.
Efficiency is the measure of output compared to input, and as in any other form of energy, increasing efficiency generally leads to greater energy generation and lower costs. With respect to solar energy, this means improving the materials used in the photovoltaic cells and reducing the amount of energy lost through conversion processes (e.g., in transmitting electricity through wires).
Cost is another major factor that prevents solar energy from being widely used. The cost of solar panels has decreased over the years, yet the price of electricity generated by the technology still remains high due to technical hurdles such as efficiency and transmission cost. This has effectively made solar energy a luxury item that those who can afford it can enjoy, while those who cannot afford it must rely on traditional energy sources.
Finally, scalability is one more hurdle that solar energy must overcome. As the population increases and more people become industrialized, the demand for electricity increases, putting pressure on our existing power grids. Most experts predict that we will need to create more decentralized power generation systems, such as solar energy, to effectively meet this demand.
Like any other new energy source, solar energy also faces several technological challenges that must be overcome if it is to reach its full potential. These challenges fall into five major categories: 1) Transmission & Distribution; 2) Resource- and Material-Scarcity; 3) Regulation; 4) Market Infrastructure; and 5) Social Inequity.
Transmission & Distribution refers to the process of getting solar power from where it is generated to the places where it is needed. This process involves connecting large areas of solar panels through a combination of wires and solar roads, along with the building of more power plants and the replacement of older, legacy power lines. (Transmission lines for electricity are usually made of metal and/or fiber optics, with the voltage being transformed from high to low as the power passes from plant to consumer.)
In terms of solar energy, there are several different technological approaches that can be used to improve transmission and distribution, including using more efficient materials and technologies, increasing the efficiency of power plants, and implementing more efficient power grids. One approach is to use solar roads, which are essentially concrete pavement markings that are used to generate electricity. (Think of them as power lines in the sky.)
Resource- and Material-Scarcity describes the limited availability of resources (e.g., land, labor, and capital) for the purpose of generating electricity. When discussing solar energy, this usually means that there are not enough photovoltaic materials (e.g., silicon or compound semiconductors) to generate enough electricity for the entire world’s needs. One way of combating this problem is to re-purpose existing buildings and infrastructure for energy generation, such as by incorporating photovoltaic cells or using solar hot-tubs for water heating.
Even more significant than the resource- and material-scarcity issue is the problem of market infrastructure. When it comes to selling solar power to end-consumers (e.g., businesses and individuals), the power companies that generate the energy usually sell it at a cheap price to large corporate entities, who in turn sell it at a cheap price to end-consumers. This is because power companies must cover the cost of generating the energy (usually through expensive fuel) and the cost of transmitting the energy through expensive wire.
However, if the end-consumers want to purchase solar power at a premium (e.g., using solar credit), then the power companies have no choice but to increase their prices, thus creating a higher barrier to entry for new solar power producers.
Finally, social inequity describes the situation where those who can afford access to energy (e.g., through paid employment or through large purchases of goods and services) enjoy a distinct social advantage over those who cannot afford access to energy or those who are energy deprived (e.g., due to social isolation or lack of appropriate infrastructure). One example of social inequity is the global energy system, which is largely dependent on fossil fuels and is thus accessible only to those who can pay for it. (The European Union is working to reduce this kind of social inequity by supporting renewable energy alternatives.)
The cost associated with generating electricity from solar power is higher than the cost of electricity from traditional power sources due, in part, to the higher initial investment cost (e.g., for solar equipment) and, in part, to the expense of producing more energy (i.e., the so-called “external cost” such as the cost of fuel and/or the cost of generating more energy at another location). This leads to the question of whether or not this form of energy is cost-effective on a case-by-case basis. The answer, however, depends on a number of different factors, including the location of the electricity consumer, whether or not carbon-free power generation is a policy issue, etc.