The future of the Earth as described in the new paper by Ugo Bardi. Image source
A new paper by Ugo Bardi of the University of Florence is in press on the journal "Nature Energy Revolutions." The study was performed with the support of a European financed project under the Horizon 25-25-25. Using sophisticated simulation tools based on system dynamics, the paper builds on previous studies of Ugo Bardi and his coworkers on the market penetration of photovoltaics and other renewable energy systems.
"Our approach in this project," says Bardi, "was to remove some constraints previously considered as unavoidable in the input of the model." The calculations by Bardi indicate that PV plants could replace the current fossil energy production in a very short time: less than 10 years.
Bardi reported that "We started from a concept developed in the 1980s, the "self-replicating lunar factory," an autonomous solar powered machine with the capability of reproducing itself using minerals found in the Earth's crust. From the available data on the energy return of photovoltaic energy, we can assume that the doubling time of the machine can be taken as ca. 2 years. Then, with the assumption of dedicating a "seed" of 1 TW of the current installed global power to bootstrap the first photovoltaic factories, we may calculate that we need just 4 doublings, or 8 years, to reach 16 TW, which is close to the currently installed power of 18 TW."
"The consequences of this innovative approach," continues Bardi, "are more impressive if we examine the longer term. In principle, PV plants could eventually capture the total solar radiation beamed on the Earth surface, about 90,000 TW. With an efficiency of conversion of 15%, the plants could produce a total power of some 15,000 TW, one thousand times larger than the current global power generation. Such a production level could be obtained in less than 30 years from now by the growth of autonomous, self-replicating solar machines." The final result has been described in several comments as the "Bardi Sphere" (even though Bardi doesn't use this term in the paper), in analogy with the older concept of the "Dyson Sphere."
The paper by Bardi goes on to examine the consequences on the Earth's ecosphere of the envisaged rapid growth of PV installations that would result in the whole planetary surface being covered with a uniform layer of PV panels. That would transform the Earth in a different kind of "blue marble." One consequence would be to block the evaporation of water and therefore the formation of clouds.
Bardi's comment on this point is that "Of course, we would see the nearly complete elimination of water in the atmosphere vapor and a considerable cooling as a result. That would be in part compensated by the lower albedo of PV plants which, in any case, work better at lower temperatures, so that the overall effect would be beneficial with respect to energy production. Even better would be a further increase of the solar light reaching the surface as a result of the elimination of the cloud cover. In a longer-term future, the complete elimination of the Earth's atmosphere can be envisaged to increase even more the solar irradiation reaching the surface for further improvement of the energy production rate."
Another source of concern that has been voiced about Bardi's plan is the modifications of the human habitat that would derive from such a large expansion of PV plants. Bardi replies as "Of course, a consequence of the projected expansion of the PV sphere is that planet Earth will not be suitable any longer for vertebrate life. But that's not a problem: with so much power available, humankind and its environment can be easily simulated in the form of a program running in a computer. Virtual humankind wouldn't face the same physical constraints to growth existing in the real world, those limits that humans seem to hate so much. They would surely be happier to live in a virtual world where such constraints can be relaxed to the point that it can be said they don't exist."
h/t Paolo Battinelli
