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| Fig. 1: Photovoltaic solar farm. (Source: Wikimedia Commons) |
Solar energy is one of the most popular forms of renewable energy. In 2010, there were 33.8 terawatt hours of energy produced from solar cells, whilst in 2020 there were 843.9 terawatt hours, an increase of 2397% with a compound annual growth rate of 37.95%. [1]
When sunlight shines on a solar cell, light particles called photons hit the surface of the cell and are absorbed. These photons excite electrons in the cell and they are knocked loose from their atoms; this movement of electrons forms an electric circuit (with the right conditions), creating an electric current, which is electricity. [2] Solar cells are blue because they are made of polycrystalline silicon; an image of a solar farm can be seen in Fig. 1.
Solar cells are not completely efficient (in that they do not convert all of the sun's energy into electricity) due to the generation of heat and light reflection amongst other things. Specifically, crystalline silicon photovoltaic cells are the most popular solar cells, accounting for 85% of sales in 2011, but only have an efficiency of between 20 and 25%. [3]
The Sahara Desert is the largest desert in the world and is largely uninhabited by humans. It is also one of the brightest places on Earth, with over 3,600 hours of bright sunshine per year (82%+ of daylight hours). [4] These facts, coupled with the fact that it extends over 3.5 million miles2, raise the question of why we don't utilize it to expand our solar energy generation. [5]
In 1996, German particle physicist Gerhard Knies, estimated that in just six hours, the world's deserts receive more energy from the Sun than humans consume in a year. [6] Of course, global energy consumption is multiples greater than that of in 1986 and the Sahara is smaller than all of the world's deserts combined. But Knies's estimation would still support the claim that the Sahara could power the world with just a few days of sunshine. Below you can see a calculation of the power of the Sahara. We can calculate the energy of the Sahara using the solar constant and the radius of the Earth. We know that the solar constant is 1.3 × 3 and the Earth's radius is 6.38 × 105 m.
The solar constant is 1300 Watts at midday and we know that the area of the Sahara is 3.6 × 106 mi2, which is equal to 9.2 × 106 km2. We can use this information whilst averaging day and night by dividing by π to calculate energy in the Sahara per year.
| 9.2 × 1012 m2 × 1300 W m-2 × 3600 sec h-1 × 24 h d-1 × 365 d y-1 / π | |
| = | 1.20 × 1023 J y-1 |
Total global energy consumption was 6.35 × 1020 Joules. [7] Hence, the Sahara produces 189 times more energy per year than what is consumed. If we are able to capture even a fraction of this energy, the world will be changed completely.
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| Fig. 2: Concentrating solar farm. (Source: Wikimedia Commons) |
There have been efforts to utilize the Sahara's power such as Noor Ouarzazate Solar Complex in Morocco and the Desertec project - a proposed €400+ billon German-led investment fund. [8] The Desertec project utilized concentrated solar panels as opposed to photovoltaic cells and was designed to transport electricity generated in the Sahara to Europe. An image of concentrated solar panels can be seen in Fig. 2.
One of the issues that Desertec faced was efficiently transporting the electricity: cross-Mediterranean power lines would need to extend to over 3000 km, leading to energy losses - estimated to be 10-15% from North Africa to Europe and greater from central Saharan regions. [8,9] The technology to reduce these losses exists, but is costly and reduces the potential profitability of the project. Another large issue that Desertec faced was having a lack of existing infrastructure in the Sahara. The low population density of the Sahara is positive in that avoiding towns or cities is not an issue but it also brings forth the issue of a lack of available labor to construct solar farms. Furthermore, transportation lines are poor in the Sahara, meaning it is very difficult to transport materials to remote areas, increasing construction costs significantly. [8] Other geopolitical issues presented large obstacles to Desertec's progress and funding from many transnational corporations was resultantly cut. [10]
From the evidence we have seen, it is clear that utilizing the energy of the Sahara is an incredibly difficult challenge. The issue of Western consortiums developing solar plants in the Sahara includes elements of exploitation and neo-colonialism. Hence, it is much more feasible for African nations to develop solar plants in the Sahara. Transportation costs would be minimal and exploitation issues would be non-existent. Successes have been seen with Morocco's Noor Ouarzazate Solar Complex, a four-section facility with a combined capacity of 580 MW. [9] For Western nations to develop solar farms in the Sahara, it is imperative that they do so in collaboration with local governments to reduce inequality and quash any elements of exploitation. Whilst the Desertec project was intended to help domestic nations, there was still significant skepticism as to the scale of distribution. Skepticism is more than granted given the history of European colonization and resource exploitation in Africa - which was often framed in a way to seem as though European nations were helping develop Africa. Hence, there should be a greater emphasis on delivering real positive outcomes to local nations. For example, distributing the generated electricity equally to domestic nations and to Western nations could be a viable option that would improve the sustainability and longevity of the project. The likelihood of this situation occurring in reality is slim but could be a reality if the right conditions are set. For example, an independent regulator could intervene on any European-led solar projects in Africa, ensuring exploitation does not occur and that resources are allocated in a fair and pre-determined manner. Complementarily, European-led solar projects could pledge a specific (and agreed upon) amount of capital into developing local infrastructure in the areas that solar farms exist; this would also be regulated by an independent party to further reduce the possibility of exploitation.
© Jawad Jafar. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Renewable Statistics 2022," International Renewable Energy Agency, 2022.
[2] M. R. S. Shaikh et al., "A Review Paper on Electricity Generation from Solar Energy," Int. J. Res. Appl. Eng. Sci. Technol. 5, No. 9, 1884 (2017).
[3] S. Dubey, J. N. Sarvaiya, and B. Seshadri, "Temperature Dependent Photovoltaic (PV) Efficiency and Its Effect on PV Production in the World - A Review," Energy Procedia 33, 311 (2012).
[4] J. E. Oliver, Encyclopedia of World Climatology, 2nd Ed. (Springer, 2005), p13.
[5] M. Hereher, "The Sahara: A Desert of Change," in Sand Dunes: Ecology, Geology, and Conservation, ed. by C. D. Galvin (Nova Science, 2013).
[6] L. Hickman, "Could the Desert Sun Power the World?," The Guardian, 11 Dec 11.
[7] "BP Statistical Review of World Energy," British Petroleum, June 2022.
[8] T. M. Schmitt, "(Why) Did Desertec Fail? An Interim Analysis of a Large-Scale Renewable Energy Infrastructure Project From a Social Studies of Technology Perspective," Local Environ. 23, 747 (2018).
[9] S. Bohn et al., "A Pan-European-North African HVDC Grid For Bulk Energy Transmission A Model-Based Analysis," IEEE ES Transmission and Distribution Conference and Eposition, IEEE 6863272, 14 Apr 14.
[10] S. Afshar, "Desertec: Harnessing the Energy of the Desert," Physics 240, Stanford University, Fall 2017.
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