# How Much Land Would it Take to Generate All US Electricity With Solar Alone?

## An in-principle calculation demonstrating how little land is really needed

Renewable energy resources are more diffuse than concentrated fossil energy, requiring wind farms spread o’er many leagues, and array upon array of solar panels. But is this a fundamental barrier to employing renewables at scale, as some would have you believe? The answer is nay, and it can be quickly seen from some back-of-the-envelope calculations (and with the assistance of some pretty maps), that no more than 7,000 square miles of photovoltaic panel surface area would be needed to generate 100% of US electricity. This is less than 0.2% of the contiguous US land area, and a small fraction of urban area in the US.

This demand could be satisfied with existing rooftops and other impermeable surfaces, such as parking lots. And of course, no all-renewable portfolio would actually be 100% solar, but this exercise shows that land area is not a limiting factor in scaling solar.

To inform our calculations, let us first introduce some fundamentals concerning solar resources…

# A primer on the origin, extraction, and emissions of everyone’s favorite fossil fuels

Three major forms of fossil energy together provide almost all the world’s energy: coal, oil (and the derived petroleum fuels), and natural gas. Moreover, humanity’s insatiable appetite for these fuels is the major driver of climate change. Therefore, it is essential to understand the fundamentals of these fuels: Where do they come from, what are their properties, and how do we extract them. Furthermore, it is generally understood that natural gas is the “cleanest” of the fossil fuels, while coal is the dirtiest. Again, we must ask why, and provide at least a basic answer. The purpose of this article is to answer (at least broadly) these questions, and to make the reader familiar with some key terms and concepts. In brief, the takeaways are:

• All fossil fuels derive from organic matter buried at great depths and processed under pressure.
• Oil and gas are produced by the same basic geologic processes, and are often present in the same wells/fields. Conventional oil/gas is formed when these hydrocarbons seep from low permeability source shales to collect in “traps,” where they can be pumped by conventional methods.
• Unconventional oil/gas extraction via “fracking” involves drilling into and breaking up source shales directly.
• Coal in the US is most commonly mined via surface mines, especially mountain top removal with valley fill, where whole mountains are blasted away to access coal seams.
• Fossil fuels are mainly a mix of molecules with carbon (C) and hydrogen (H) bonds. Burning oxidizes these molecules to water and carbon dioxide, releasing heat along the way. The more C-H bonds, vs. C-C bonds, the more energy is released per atom of C, and thus the less CO₂ per heat energy released.
• Natural gas, as CH₄, has the most C-H bonds of any fossil fuel (it is the most “reduced”), and burns the cleanest. Coal is the least reduced fossil fuel, and burns dirtiest.

# Why Solar Panels Can’t Get Much More Efficient (And That’s Okay!): Shockley-Queisser and the limits to converting sunlight into electricity

Commercially available solar panels now routinely convert 20% of the energy contained in sunlight into electricity, a truly remarkable feat of science and engineering, considering that it is theoretically impossible for silicon-based solar cells to be more than 32% efficient. This upper bound, known as the Shockley-Queisser Limit, was first calculated by the eponymous scientists (who actually gave 30% as their original limit) in the Journal of Applied Physics in 1961 [1] (see also updates by Rühle [2]).

Now, if we can answer why solar panels are thus limited, we can understand the essentials of photovoltaics (PV), which have their basis in the photoelectric effect, and p-n semiconductor junctions. While many have never heard of it, the photoelectric effect is of monumental importance, and when Albert Einstein received the 1921 Nobel Prize in physics, it was “for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect,” while p-n junctions lie at the foundations of modern electronics, including transistors and LEDs. Indeed, a solar cell is essentially an LED in reverse: Instead of an electric current generating light, light generates electric current!

# Just how many animals do Americans eat? And how many would you save by going meatless one day a week?

(Post also published on medium.com!)

# The many faces of food waste in the time of coronavirus: Discards, biofuels, meat, and opportunities for change

Enjoy here this post, also on medium.com

#### Introduction and effective waste in the food system

The ongoing COVID-19 pandemic has reshaped the patterns of American life in unprecedented
ways and with stunning rapidity, resulting in many unintended, but not unwelcome, environmental benefits, as skies clear and animals venture into newly empty spaces [1]. On the other hand, the pandemic has also resulted in what appears to be (and is) a shocking crisis of food waste: Acute demand shocks from the almost overnight shift away from food consumption in suddenly closed restaurants and large institutional settings (including schools, universities, and many places of business) towards in-home consumption have resulted in the well-publicized farm-level wastage of whole fields of fresh produce, and the dumping of millions of gallons of fresh dairy [2].

Without commercial customers or the means to quickly reorient to retail supply chains,
and with limited on-farm storage capacity, some farmers have been forced to plow crops under,
bury already harvested produce, or dump milk into manure lagoons. With slaughterhouses now
reeling from COVID-19 as well, slaughter numbers are down and the dire prospect of millions
of livestock meeting their end on-farm without ever reaching a plate is raised, and the USDA now projects Americans will actually decrease their meat consumption in the coming year [3].
And yet, shocking images of rotting crops and animal culls belie a US food system that has long
ultimately wasted, in one form or another, the vast majority (perhaps as much as 80-90%) of all
food calories produced at the farm level, with dramatic consequences for the environment and
both animal and human health and well-being, while the pandemic could paradoxically spur beneficial changes that mitigate such waste.

# Electricity Emissions Factors by Region, Part 1: Background and the Western Region

#### Part the First: Brief Background on Emissions Factors

Electricity generation accounts for almost one-third of US territorial greenhouse gas emissions, and the average US residence consumes just under 11,000 kilowatt-hours (kWh) electricity per year (in addition to other fuels, such as natural gas).  Thus, it is essential to understand the impact of electricity use, and especially how changes in use at the household level will affect emissions.

# Oblivion by any other name: “Biological annihilation” and “defaunation” in the “Anthropocene”

Everything that needs to be said has already been said. But since no one was listening, everything must be said again.

André Gide

I too am reduced to repeating what must be said, and given this nascent blog’s readership, it seems rather likely that it will need saying again.  To wit, George Monbiot recently discussed, in a melancholy but extremely important article (see also the version in The Guardian), the vanishing of so much nature and wild life before his own eyes, in his own lifetime.  It is not mere false nostalgia, and he cites much published work that documents the astonishingly rapid and ongoing global loss of animal life, a process that has been variously (and by respectable scientists, no less!) termed “defaunation” in the “Anthropocene” and, more recently, a “biological annihilation.”

# From 17,000 kWh/year to less than zero: my experience with energy-efficiency and rooftop solar in Mesa, AZ

I wrote several hundred pages of a book that amounted to exhorting people to alter their own habits of residential energy consumption (turn down the heat, you rogues!), as well as upgrade their built environment  (e.g. insulate the attic) and appliances, or even, *gasp*, add solar to their roofs.  All this because the numbers, at least in the abstract, showed that such banal acts of conservation (not counting solar) can reduce the carbon footprint of residential energy use by at least 30-50%, from a baseline average of about 12 metric tonnes (1 tonne = 1 metric ton) of CO$_2$-equivalent (CO$_2$e).  But a demonstration of how, over the course of roughly 5 years, the net energy use in my house actually fell progressively from around 17,000 kWh of electricity per year down to less than zero (net) seems in order.

# Amasa Delano, ecologic destruction, and the face of Empire

I should like to highlight here (see also TomDispath.com version) a remarkable essay by Greg Grandin, one that contrasts two of Melville’s characters as faces of Empire: Captain Ahab and the historical sealing captain Amasa Delano, who partook in the massive late eighteenth century extirpation of seal populations in the South Pacific for fur, which was used a luxury item for the wealthy, and who put down a slave rebellion aboard a Spanish slave ship.  Delano viewed himself as a moral man, one “who has a knowledge of his duty, and is disposed faithfully to obey its dictates.”