Galactic Travel Or A Trip To The Mall — It’s All About Energy

By Robert Stewart, Cullen Chair in Exploration Geophysics

Eight of the top 10 highest grossing movies in North America since 1977 have been (perhaps surprisingly) science fiction. There is “Star Wars – The Force Awakens, of course, and “The Martian” is rising.  But really, these films are about energy, both the personal and physical kinds.

On the human side, the characters have profound drives, forceful personalities and perseverance. Then there are interplanetary trips and galactic travels requiring vast amounts of science, engineering and fuel. Our attraction to these stories lies in their combination of magnificent adventure, dazzling technology and people and energy undergoing transformation.

Our fantasies, via the movies, are fueled by energy. But in everyday life, the reality of that energy is naturally more complex, even though filling up at the gas station and driving to the mall seem pretty simple. How we produce, measure and use energy define much about life in the 21st century – and serve as a tribute to human ingenuity.

So, how do we measure energy? A basic unit is the calorie. It’s the physical amount of heat required to raise one gram of water through 1 degree Celsius. In food consumption or dietary realms, the calorie is actually 1,000 physics calories or a kcal. Humans need about 2,000 (female) to 2,500 (male) calories per day for a normal active life. That’s one human power.  It takes about 10 humans to generate one horsepower. Your car thus has the power of about 2,000 humans.

 Alex Epstein has an interesting observation in his book, “The Moral Case for Fossil Fuels,” that given average U.S. energy consumption of 186,000 kcal/day, we effectively have about 90 humans working for us. Fortunately, the workers are actually machines with petroleum, coal, uranium, wind, sun and electricity as their “machine food.”

In the metric system (SI – Système Internationale d’unités), the joule is employed to measure energy. An apple dropped from waist height would have about one joule of energy when it hit the ground. Natural gas is traded in GigaJoules (a billion joules, or one thousand million falling apples) and in Imperial volume units of Mcf (thousands of cubic feet). The “M” is the Roman numeral for one thousand, which is a little confusing as we now use M to denote Mega or one million in SI parlance.

Nonetheless, a GJ of energy is similar to an Mcf of natural gas or a million BTUs (British thermal units). A BTU is the amount of heat required to raise the temperature of one pound of water 1 degree Fahrenheit. When dealing with energy flow (or work or power), we use Watts or a Joule per second.

The United States consumes around 19 million barrels of petroleum products per day (MMbopd) or some 120 PetaJoules per day. According to the Energy Information Administration, we produce about nine million barrels of crude oil per day, so even with the remarkable shale revolution, the country still imports millions of barrels of oil per day. Oil self-sufficiency is challenging. Incidentally, the barrel size itself goes back to a standard container for wine (the tierce) defined in the 15th century. The width of a barrel is about 20 inches. Lining up 3,150 barrels would extend about one mile. From New York City to Los Angeles is around 2,500 miles. Thus, a string of 7.8 million barrels would stretch from New York to LA. Effectively, the U.S. consumes a row of barrels stretching from the east to the west coast and back every day.

Now let’s inquire a little more about energy sources and power generation. Texas, the largest electricity generating state, has seen electrical demand as high as 70 gigaWatts (GW) on a hot summer day in 2015, serving a population of 27 million people. Keeping everyone comfortable and productive is no small task. A reasonably sized power plant of 1 GW could use coal (about one train of 100 cars per day), enriched uranium (150 pounds per day), oil (supplied by one Gulf of Mexico deep-water platform), wind (from about 4,000 one megawatt turbines) or solar (around 20 million panels measuring five feet-by-three feet). Each energy source has advantages and issues, and selecting one source will require considering factors including: availability, cost, reliability, land use and atmospheric impact. Certainly one of our greatest challenges is how to produce more energy with less impact.

Returning to the movies, the highest grossing film in domestic history, “Star Wars – The Force Awakens,” depicts prodigious energy use – that of whole planets and stars. Even Matt Damon’s misadventure to Mars required tons of fuel and billions of dollars. It’s fascinating that most of the blockbuster movies in recent times are science fiction, including “Avatar,” “Jurassic World,” “Jurassic Park,” “Transformers” and “E.T. the Extra-Terrestrial.”

People have voted with their discretionary dollars to see glimpses of the future, suggesting that a large part of tomorrow will involve harnessing immense energy resources. Our health, comfort, security, imagination and destiny demand it.

Robert Stewart is Cullen Chair in exploration geophysics and director of the Allied Geophysical Laboratories in the University of Houston’s College of Natural Sciences and Mathematics. His previous work in the private sector included time at Chevron’s Oil Field Research Lab, ARCO and Veritas Software.


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