Saral’s notion that human industrial society cannot operate entirely on renewable energy, because, he claims, to do so would violate the Second Law of Thermodynamics, is incorrect, Indeed it’s a blatant misrepresentation of a basic concept in physics. As originally a physicist and now an interdisciplinary energy researcher who recently published a non-technical article on “The Feasibility of 100% Renewable Energy” in Insurge-Intelligence, I have pointed out that a global 100% renewable energy (RE) system would not violate the Second Law, so long as the Sun continues to shine. You don’t have to be a physicist or engineer to understand the following brief explanation — just to think logically:
1. Fact accepted by Saral: The rate of solar energy received by the Earth is thousands of times the rate of human energy use.
2. Fact accepted by physical scientists but denied by Saral: Solar energy is high-grade energy. As seen from the Earth, the Sun has a black-body temperature of 5777°K (6050°C), which is definitely high-grade in thermodynamic terms.
3. Fact accepted by Saral: Energy tries to flow “downhill”, from high-grade energy to low-grade. Solar energy received on the Earth is degraded into low-grade heat by both natural and human processes. Low-grade heat cannot be efficiently “recycled” into high-grade energy. This is a simplified statement of the Second Law of Thermodynamics, but it is irrelevant to Saral’s argument, because of the next fact.
4. Fact ignored by Saral: Low-grade heat energy, that’s mostly unusable by human society, is continuously replaced by high-grade energy from the Sun, so long as the Sun continues to shine.
QED.
Another way of looking at Fact 2, which Saral is reluctant to accept, is in terms of efficiency of energy conversion, defined to be energy output divided by energy input. A consequence of the Second Law is that pushing energy “uphill”, that is, converting low-grade energy to high-grade, although possible, has a low efficiency. For example, using a solar hot water system, which produces water at about 80°C, to generate electricity (a high-grade form of energy), is technically possible, but its efficiency would be at best a few percent. Compare this with the following efficiencies in generating electricity: large wind turbine in strong winds 42–45%; stacked solar cells (stacked to collect different light wavelengths) 42%; black coal-fired power station 35–40%; lignite-fired power station 20–30%. Clearly solar energy, in both its direct and indirect forms, is high-grade, if fossil fuels are. Indeed, fossil fuels are just solar energy produced and stored naturally over millions of years.
Here is another way of thinking about the whole issue. Life has already existed on Earth for over a billion years based on solar energy. Extending this to human industrial society just needs the following question to be answered: is there enough land and ocean area to collect enough solar energy, in its direct and indirect forms (e.g. hydro, wind and wave), to meet reasonable human demands, without severely destroying photosynthesis and damaging ecosystems and biodiversity? Even most critics and deniers of renewable energy accepting Fact 1 would have to answer “yes, so long as the Sun continues to shine”.
Quite a small total area of desert, including parts in every inhabited continent, could in theory supply all current energy demands of industrial society from the Sun. In practice, we need a mix of different renewable energy sources to balance fluctuations in direct solar energy.
Of course we still must oppose the notion pushed by many neoclassical economists that endless growth is possible on a finite planet.
In addition to obfuscating the issue, Saral illogically introduces another incorrect interpretation of the the Second Law. But this is irrelevant because the Second Law is about energy, not materials — energy only enters indirectly and contingently in terms of the energy source for driving the recycling process. So my response to that (important) side-issue is that far more recycling can be done in future than at present by good design for reuse and recycling, and by using low-cost renewable energy to drive the process, without violating the Second Law.
Unfortunately, Saral seems to be using his audience’s lack of knowledge of basic physics to present pseudo-science.