|Fig. 1: The photoelectric effect. (Source: M. Ayub)|
Harvesting sunlight has been done for millennia, and current photovoltaic technologies promise to use it in order to produce a sustainable source of electricity and reduce our reliance on fossil fuels.
Most familiar solar energy systems utilize the principle of the photoelectric effect, which is characterized by the emission of electrons by metals when light rays above a frequency threshold are incident on their surface.  Fig. 1 shows a simple diagram of this effect. For large scale applications, however, concentrated solar power (CSP) plants are highly attractive. They use a large number of mirrors to focus the sun's rays at a tower where the radiation is used to extract heat and in turn, convert it to electricity.
Recent advances in the efficiency and cost of photovoltaic cells have made solar energy an attractive source for producing grid electricity. grid solar power cost in the US hit 1$/Watt in 2017, beating government goals by 3 years. 
And the amount of solar energy available is virtually infinite. The Earth receives more solar energy each hour than the total consumption of energy in one year. From another perspective, the total energy needs of the United States can be met by covering a mere 1.7 percent of the land area with solar energy collectors having 10% efficiency, which is roughly the area of New York.  This naturally makes one wonder: what if we did something like that?
Desertec Industrial Initiative (DII) was an effort by several private and public sector organizations in Europe to pursue this idea. The aim of the project was to export solar power from the Sahara desert to electric grids in the European Union. It offered a promising idea for harnessing an untapped resource - the vast uninhabitable deserts of the world. However, there are several technological, economic, and geopolitical hurdles that make it currently unviable compared to other alternatives.
First of all, while deserts are largely uninhabitable, they are not lifeless. Vast ecosystems of diverse flora and fauna thrive in deserts and can be found concentrated near scarce water sources. A major concern against the DII was the strain on local water sources for cleaning and maintenance of the solar farms. Hence, the ecological impact of such a project needs to be properly evaluated.
The next major hurdle is the transmission. A centralized solar panel farm would require extremely long transmission lines over thousands of miles. However, power transmission technology has come a long way; current generation HVDC wires lose as little as 3% of power every 1000 km.
The third and perhaps the most challenging hurdle is the complicated coordination effort required by multiple countries in order to achieve this. These include agreements on how to spread out the large capital investment, how to distribute the electricity, where to lay the transmission lines that would pass through several countries (some of which might be politically unstable), and which companies to award contracts to.
Lastly, several detractors have pointed out that the project is a continuation of the colonialist agenda of exploiting natural resources from Africa to fuel the industrialized first world countries in Europe, with little or no benefit to the local population.
Desertec, despite its initial hiccups with the DII, is moving ahead with the idea. As of the writing of this article, they are facilitating a 4.5 GW CSP project in Tunisia that will supply electricity to European markets. While a centralized solar energy farm shows great promise for grid power generation, there are several socio-economic and ecological concerns that are not being adequately addressed.
© Moe Ayub. 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.
 H. D. Young, R. A. Freedman, and A. L. Ford, Sears and Zemansky's University Physics: With Modern Physics, 13th Ed. (Addison-Wesley, Boston, 2011).
 K. Hao, "Solar Is Now So Cheap in the US It Beat Government Goals By Three Years" Quartz, 14 Sep 17.
 S. Cass, "Solar Power Will Make a Difference - Eventually," MIT Technology Review, 18 Aug 09.