This is Part 7 of a paper written about the projected US Energy profile in the year 2050. In this chapter, we take a look at solar energy as an energy source.

History of Solar Energy

One of the most intriguing renewable technologies is solar energy. Throughout history, the power of the sun has long fascinated humans. Many ancient civilizations, such as the Egyptians and Aztecs, worshipped the power of the sun. The Greeks, and later the Romans, harnessed passive solar energy in much of their architecture (Alternate). Through the use of passive solar buildings, ancient civilizations were able to create effective heating and air conditioning effects.

Solar energy has long fascinated humans; in fact, energy from the sun is directly responsible for the vast majority of all other energy resources. Through photosynthesis, energy from the sun is stored in plants and other biomass across the globe. The human body and all life on earth are also driven by solar energy, as we get our energy from biomass. Similarly, fossil fuel resources (coal, natural gas, and oil) all derive their energy through carbon burial of ancient solar energy.

The vast majority of the earth’s energy is derived directly from the sun’s power. The use of the term “solar energy” today typically refers to directly harnessing the energy of the sun’s radiation to produce electricity. While there is such limitless potential in solar energy, the great challenge is to harness this potential into an economically viable resource that is competitive in the energy marketplace. 

Current Use of Solar Energy

Currently, approximately 0.1% of the United States’ yearly electricity is supplied by solar energy. While there has been significant discussion about the potential and importance of solar resources, entrenched fossil fuels and the comparatively high prices of solar energy have restricted any significant progress.

Once of the main reasons solar energy is so fascinating is because of its tremendous potential. Each day, more solar energy is absorbed by the earth than the entire world uses in a whole year (Globe).

The United States has been slow to capitalize on its solar potential (Carlin). However, internationally, many nations have achieved much greater success with solar energy. In particular, the European Union has achieved tremendous success in increasing solar capacity.  In Germany, solar power meets approximately 1% of total electricity demand and this number is rapidly rising (US Lags). In Spain, this number is 2.8% (Sawin).  . In fact, for several days last year, over 50% of Spain’s electricity demand was powered by solar energy (Wind Energy consolidated).

Recently, China has also developed a significant solar presence, in both consumption and production of solar panels (Watts). As these countries invest greater resources and technology into the rapidly developing solar market, prices will decrease and, ultimately, allow for non-subsidized solar technologies to achieve success. The United States has much to learn from the example set by these countries. 

How Solar Energy works

There are two main methods for harnessing the energy of the sun for electricity production: solar thermal energy and photovoltaic cells.

Solar thermal energy is the most traditional form. Through a series of concentrated panels, the heat of the sun is concentrated on a very small area, creating a significant amount of heat. This heat is then transferred to water, creating steam and spinning a turbine, creating electricity the same way a combustion reaction does.

However, instead of burning fossil fuels to generate heat, thermal energy directly uses the sun’s heat energy. Ultimately, this also accounts for significantly greater efficiency. While fossil fuels receive heat energy from the sun that is stored and then combusted, with a poor rate of return, solar panels attempt to directly harness as much of the sun’s heat as possible.

Consequently, photovoltaic cells work very differently from most traditional forms of energy. Instead of spinning a turbine, PV cells directly convert the sun’s radiation into electricity. In doing so, they take advantage of the photoelectric and photovoltaic effect. The photoelectric effect suggests that when light is shined on to a metal surface, it will emit electrons and start a current. This theory takes advantage of the light’s particle nature.

The current generated through sunlight is then combined with an electric-field produced voltage that is built into a solar cell. Ultimately, through the combination of the electron-stream generated current and the panel-produced voltage, power can be produced. Impure silicon is typically the most effective material used to build solar panels, due to its crystalline structure that can easily generate an electric field. When sunlight is shined directly on a photovoltaic panel, the energy of the sun is converted directly to a current and electricity.

PV cells are extremely attractive, since they do not require any significant structures in the installation process (Toothman and Aldous). Nevertheless, due to the lack of sufficient research and development, most PV technology is still too expensive to be commercially viable.  

Solar Energy Technologies

There are several different technologies prevalent in the solar industry. Since much emphasis on solar has been developed in the past 30 years, many newer technologies are still in the infant stages. The most widespread method for solar thermal power generation is the creation of solar towers.  Instead of relying on just cell angles to attract light, solar towers utilize mirrors, lenses, and other optical equipment to focus as much light on the cells as possible. While the additional infrastructure may sometimes be expensive to build, it ultimately brings down the costs of solar power and allows for much greater generation of electricity ((Toothman and Aldous).

This technology typically requires significant space and sunshine, but has the potential to be competitive with traditional electricity generation; Spain has successfully harnessed solar tower technology in the Andalucían deserts (Jha).

A new form of photovoltaic technology is thin-film solar cells. These are simple, much cheaper solar cells that are not made out of the ideal silicon that is used in the vast majority of panels. While these capture less energy than thicker cells, they are significantly cheaper to create and can be produced in much greater quantities (Toothman and Aldous).

One of the most fascinating future technologies is solar photovoltaic cells in space. For years, astronauts have utilized space solar panels to power satellites and space missions with the greater light intensity found in space; however, the most significant challenge to this technology is transporting it back to Earth.  A recent Japanese project aims to collect much higher-efficiency electricity in space and use a laser to beam it to the Earth (Hornyak).  Pacific Gas and Electric, a California utility, similarly has proposed the conversion of energy to radio waves which are sent to earth and translated to electricity (LaMonica). While this space technology is widely perceived as prohibitively expensive, there has not been any significant research into its potential.

One of the most significant challenges confronting solar penetration of the electricity market is the intermittent supply of the resource. Just like wind, solar energy is very unpredictable and cannot very easily be used as the sole resource in an energy mix. During periods of high energy demand, often at night, solar energy cannot be provided, because the sun is no longer shining. Solar energy is also heavily dependent on weather fluctuations and cannot increase or decrease capacity to match demand, as is possible with most traditional power plants. While some energy can be stored through solar thermal heating in the form of boiling water, significant heat is lost over time.

PV cells often also store energy in the form of batteries, but batteries are extremely expensive (Toothman and Aldous). The most significant potential for solar energy in the near future is as a supplemental resource to other power plants in the electric grid. In January 2008, a combined power plant built in Germany successfully combined solar energy with wind, biogas, and hydropower together to account for any intermittency in energy supplies (Technical Summary). This type of power plant, where many different renewable resources are used together, represents the most realistic plan for the future. 

Solar Energy Environmental Concerns

While solar panels offer significant benefits for reducing dependence on fossil fuels, they also offer significant environmental benefits. First and foremost, solar energy does not produce any carbon emissions. It also does not produce any sort of toxic waste (like nuclear energy) and does not have the potential for any horrible safety accidents (such as the collapse of a coal mine or an oil spill). Providing that a system is properly installed, there are no real risks for safety.

Solar Energy Security

Another significant benefit for solar energy is its importance in energy security. The construction and use of solar panels can all be done using American resources. Instead of relying on Middle Eastern nations for fossil fuels and instead of being dependent on volatile foreign markets, domestically produced solar panels can be instrumental in achieving energy security.

However, in recent years, the vast majority of solar panel production has moved to China (Watts). Throughout the future, it is important for the US government to invest in building domestic production capacity in the solar industry. Unless this happens, we are simply trading dependence on Middle Eastern oil for a dependence on Chinese solar technologies. 

Solar Energy Economics

While solar energy has substantial benefits, the greatest challenge to its successful mass implementation is economics. Solar power is simply much more expensive relative to traditional fossil fuel technologies. In some ways, this is an unfair comparison.

Unlike solar energy, fossil fuel technologies have been around for hundreds of years and significant research and development has been focused on reducing costs. However, in the absence of subsidies or a carbon trading system, solar power must be economically viable enough to compete in the energy marketplace.

For example, while coal costs approximately 2.5-4.5 cents/kwh to produce, many solar technologies cost up to 20 cents/kwh (Understanding the cost of solar energy). In fact, most PV technologies are even more expensive, with costs reaching 40cents/kwh. In the highly competitive power market, these costs are unsustainable. In an effort to support the fledgling solar industry and promote greater research and development, the federal government and several states have initiated subsidy programs.

From an individual perspective, there are several incentive programs that can support homeowners to add solar panels to their houses. On the federal level, the residential federal tax credit gives a tax credit of 30% of the total cost of installation of any solar electric or solar hot water heaters (Solar Government Incentives). In the absence of any comprehensive federal plan on renewable energy, policies concerning solar energy differ greatly from state to state.

One of the most successful of these programs is California’s Million Solar Roofs initiative, which has helped propel California to be the national leader in solar energy. This program focuses on surplus net metering through which consumers can sell back to the utilities any additional electricity generated through their own solar panels (Million Solar Roofs). This same type of program has also achieved significant success across Europe. In fact, in Spain this program was ultimately “too” successful, and the Spanish government was ultimately forced to scale it back to prevent utilities from losing too much money (Gonzalez and Johnson).

While many statewide efforts have been successful in increasing demand for solar energy, much federal guidance is also needed to increase research and development into solar technology. While demand-focused subsidies may be effective in the short-term, a sustainable solar future will only be possible if solar technologies are significantly cheaper.

As recent research developments have demonstrated, increased funding and scale production of solar technology has the potential to dramatically decrease costs. On a federal level, the 2009 stimulus bill gave a significant amount of money to the solar industry (Galbraith). Similarly, the Department of Energy recently provided $168 billion in research funding for 13 industry-led solar development projects (DOE Selects).

While solar energy has significant potential, the technology and funding capacity is not at the same level as traditional fossil fuel resources. Without a more involved government role, along with additional subsidies and tax credits, solar technology will be unable to achieve success in an extremely competitive energy marketplace. 

Solar Political Viability

The most significant political opposition to solar energy has been its high cost. If the costs of solar power are sufficiently decreased, the benefits for environmental sustainability and energy security make solar energy a very politically significant resource.