Generating solar energy in the desert is a tempting challenge. The abundance of solar irradiation and the dry air with an almost cloudless sky provide almost perfect conditions for driving PV plants. Not surprisingly, people have thought about this possibility, and some projects have already been proposed which, however, so far have not developed beyond the first planning stages. Furthermore, these projects are still not on financially safe ground. In any case, they will require a tremendous amount of financing and that is, it seems, their most vulnerable point.
One of those futuristic project ideas, called Desertec, provides some insight into its deliverables and may thus be used as a reference. According to planning, it should be able to transmit in 2020 some 60 TWh of electrical energy from the north African desert right away to energy-hungry Europe. This roughly corresponds to the annual production of 6 nuclear plants. Electricity output is expected to grow continuously over the years with a target of 700 TWh annually in 2050.
One may, of course, question whether transmitting electricity over several thousands of kilometers is the smartest way of doing things. The losses in the transmission network will be significant, as discussed in an earlier posting. It´s not only the length of the distribution grid eating up a substantial part of the energy produced by the desert sun. As it does not make sense to transmit electricity during daytime only, part of the generated power would have to be stored for transmission during the night. This, too, consumes some energy which in turn reduces the efficiency of the whole project.
Rather than sending solar power via large distance cables to Europe, one may ask if using it for liquefying hydrogen might be a better option. Given the state-of-the-art technology the expected Desertec output for 2020 could provide some 6 Megatons of liquefied hydrogen annually which may be shipped across the Mediterranean for further useage.
Applying model calculations taking into account the losses during transportation and handling we found that this amount of liquid hydrogen could provide sufficient energy to drive some 3 million cars with an average annual driving distance of 20,000 km. This corresponds to the stock of registered vehicles in a country like Hungary (2008 data).
Going over to the even more optimistic scenario for 2050, then the collective effort of all desert-based PV facilities sould enable the production of at least 70 million tons of liquefied hydrogen. Transferring this figure into cars on the road, we find that this amount provides fuel for not less than 35 million autos. This is reoughly equivalent to the number of registered cars in Italy (2008 data).
In this way solar energy, via its hydrogen derivative, could become a serious competitor to gasoline and diesel. Its advantages are obvious with both, solar energy and hydrogen being available in virtually unlimited quantity. Moreover, the environmental benefits with a substantial reduction in CO2 emissions are equally promising. Bear in mind that the transport sector is responsible for about 25% of all CO2 emissions in Europe.