[NOTE: The author is an energy technology and policy researcher with degrees in engineering and public policy who has worked in the Information Technology field in private- and public-sector, consulting, and academic roles. This essay was originally produced as a non-academic writing sample requested for an application to a job in a quasi-governmental organization.]
The modern world looks and works the way it does only because of a stupendously large and rapid consumption of energy, most of it derived from burning fossil fuels and almost all of it in the last 200 years – only about one one-thousandth of all of human history. Through multiple mutually-reinforcing lines of evidence, scientists now know that civilization’s exploitation of Earth’s particular quirk of having energy-rich combustible carboniferous deposits buried near its surface has contributed greatly to the proportion of carbon dioxide (CO2) in Earth’s atmosphere. That gas, in addition to others such as methane (which is also emitted in high quantities through human activity), plays a large role in the regulation of the planet’s average surface temperature.
The proportion of CO2 in atmosphere, which stayed between about 200 and 280 parts per million (ppm) over the last half-million years, blew past 400ppm in 2013 and has shown no sign of slowing down since. Simultaneously with that rise in CO2 proportion, average Earth surface temperature has increased by about 0.9ºC over the 1950-1980 average and scientists have established with very high confidence that the relationship between the two trends is causal.
0.9ºC doesn’t sound like a huge difference. We almost certainly wouldn’t notice it if our daily high and low surface air temperatures were 0.9ºC warmer from one year to the next, but that’s not the issue. Comprised of the movement of air and water, the transfer of heat among and between them and the land, and the transformation of water between its solid, liquid, and gaseous phases, the Earth’s climate/weather system can be thought of as an engine whose motion is powered by the Sun. The rising proportion of CO2, methane, and other greenhouse gases tips the equilibrium between the radiant energy from the Sun that reaches the Earth and the radiant energy that the Earth reradiates out into space, and so the “engine” runs “hotter” - materials and energy transfer within the climate/weather system at higher rates. At the same time, the allocation of the planet’s water tips away from the colder solid phase toward the warmer liquid and gaseous phases, meaning that ice melts, oceans rise, and water evaporates faster (where it comes back down as dew, frost, or precipitation).
It is those broad changes that scientists refer to when they discuss “climate change” or “global warming;” it isn’t so much changes in surface air temperature as we perceive it as it is differences in the stability and safety of human habitation, the predictability and productivity of agriculture, and the persistence of utility of our built infrastructure. What’s worse, the rise in energy consumption to modern levels and its direct and indirect consequences – practically instantaneous in geologic, climatic, or bio-evolutionary terms – is occurring faster than human society and the natural world can react absent crisis and catastrophe. We see this manifesting today in problems such as built infrastructure being insufficient to handle now-routine runoff water quantities, thousands of buildings destroyed by wind-and drought-aided wildfires, roadways and railways buckling from days on end of extreme heat, and houses damaged by trees that struggle with altered erosion and soil conditions, new insect infestations, and stronger storms.
The premier social and technological challenge of the 21st century, then, will be a combination of both mitigating and adapting to climate change. An adaptation-only response leaves us open to risks we have only begun to contemplate, such as ecosystem destruction on land and in the oceans, assaults to the food system that our present population may not be able to tolerate, and the appearance and expansion of regions where the temperature and humidity conditions are incompatible with human life without some form of artificial support.
We know that it is theoretically possible on a megawatthour-by-megawatthour basis to replace fossil-fuel-based and even nuclear-based electrical generation (both of which involve terrestrial material extraction) with solar and wind sources, but to evaluate the practicality of doing so requires 1) a reckoning of scale between the two broad generation classes 2) an assessment of kind with respect to the good (as economists use the term) each of the two classes produce.
Of all the electric generation in the United States, natural gas, coal, and petroleum products form about five-eighths of the total and nuclear makes up the next one-fifth. Almost all the rest is made up of renewables, of which a little under half is hydropower (7.4% of the total). Almost all of the remainder – comprising 6.3% and 1.3% of the generation total respectively – are wind and solar. Almost all of the latter consists of photovoltaic generation in which solar panels convert sunlight into electricity in a single step.
As a thought experiment, we can take the example of a real hydroelectric facility and establish how large of a solar panel farm we would need to construct to make an equivalent. Chickamauga Dam in Chattanooga,Tennessee impounds a 57-square-mile lake. Its operator, the Tennessee Valley Authority, claims the dam has has a "dependable" generation capacity (i.e., what it can make on an average day) of 119 megawatts. Meanwhile, The Arnedo solar plant in Spain has an area of 70 hectares, cost €181 million, and generates 34 gigawatthours per year. So over long periods of time, the dam generates 31 times the power of the solar farm and the lake is 210 times the size of the farm. Therefore, to make a panel farm that achieves power parity over long periods with the dam, we'd have to build about 31 Arnedos at a cost of $5.5 billion, covering about 1/7th the area of the entire lake.
Our comparison falls a bit short because the dam and the solar farm can’t produce the same good. Although the dam’s operators have to take into account the amount of water available in the lake and due to arrive at the lake from upstream, how much or how little flow into the Tennessee River the dam must allow, and what the demand for electricity is at any given moment to determine how much electricity the dam must generate, the generation is nevertheless fairly reliable. By contrast, the panel farm’s production must go stone dead every night and takes a big hit with every cloud that passes between the farm and the Sun. To make the two generation technologies’ goods equivalent – or better yet, to make the farm’s good equivalent to that of a fossil-fuel plant’s consistency and reliability – we’d have to increase the size of the farm and couple it to some form of storage, be it electrochemical (batteries) or electromechanical (e.g., flywheels).
This difference in good utility hits us awkwardly because our civilization has organized itself with around-the-clock electricity generation as a given. For that particular characterization of business-as-usual to hold, renewable generation’s goods must be adapted in degree and in kind to match those of fossil and nuclear generation. Recall that in the thought experiment above, we attempt to establish how much solar farm it would take to match the generation of a single hydro dam – and we’d need about eight square miles of farm to do it. If we chose to extend the experiment to every hydro plant in the US, it would still only cover 7.4% of all US generation.
The author performed mathematical modeling to determine about how much solar farm and storage it would take to match the electrical demand of the state of Georgia on an hourly basis and arrived at about 1400 square miles of farm (roughly a tenth of what is used in the state for agriculture) and for storage either a cube of batteries a quarter mile on a side or a half-billion-ton flywheel carved into what is now Stone Mountain near Atlanta (not having yet worked out for sure if the solid rock can handle a load of 213 Gs at the outer edge, the flywheel design may have to be revisited). Now imagine doing the same in Texas, where the annual electricity demand is three and a quarter times greater than Georgia’s.
If we are to imagine a post-fossil-fuel civilization that consumes energy at a rate like what we are accustomed to today, it will be one that is absolutely shot through with solar panels, wind turbines, and storage technology. There are serious implications for land use, allocation of industrial production, human labor, access to and acquisition of raw materials, and waste disposal and recycling, yet solving these problems is what it would take to successfully execute a post-fossil energy systems transition while maintaining a civilization that even remotely resembles ours.