Units
This is the standard SI unit of energy used in science and engineering.
What is the joule?
A typical lightning bolt at 1 gigajoule lasting 0.2 seconds delivers this power, in gigawatts.
What is 5 gigawatts?
A human needs roughly this much power, in watts, to survive from food alone.
What is roughly 100 watts?
coal is described as “dirt cheap,” while these three properties make many renewables challenging.
What are storage difficulty, geographic unevenness, and intermittency?
The greatest time-travel movie of all time.
What is Back to The Future?
Food “Calories” on nutrition labels are actually this many small calories.
What is 1,000 calories (one kilocalorie)?
Converting units, 1 kilowatt-hour is equal to about this many megajoules.
What is 3.6 megajoules?
In 2019, average global power production worked out to roughly this many watts per person, about “2.5 hair dryers.”
What is about 2,460 watts per person?
Thin-film CdTe solar cells are limited by the rarity of this element, whose entire world production only supports about 2 gigawatts per year.
What is tellurium?
This international agreement, mentioned in the notes, set a goal to limit warming to well below 2 degrees Celsius.
What is the Paris Agreement?
In February 2011, an average Seattle household used about 61 of these energy units per day.
What are kilowatt-hours?
In the global primary energy supply chart, fossil fuels (coal, oil, gas) contribute about this percentage of the total.
What is about 81 percent?
The notes equate 100 watts of human metabolic power to about this many megajoules per day.
What is about 8.64 megajoules per day?
The notes describe platinum, palladium, and rhodium as excellent fuel-cell catalysts but limited by this shared characteristic.
What is that they are extremely rare (scarce) metals?
To stay below 2 °C warming, the notes describe a carbon budget of about this many billion tons of cumulative CO₂ emissions.
What is about 3,000 billion tons?
Around 2019, world primary energy production was about 606 of these -joule units.
What are exajoules?
As of November 2025, atmospheric CO₂ concentration was about this many parts per million.
What is about 427 ppm?
Around 2010, the human species used about 17 terawatts of power, equivalent to roughly this number of 1-gigawatt power plants.
What is about 17,000 power-plant equivalents?
The same chart groups rare earth elements in blue; these include lanthanides like neodymium, crucial for this type of generator technology in wind turbines.
What are high-strength permanent magnets?
About this fraction of fossil-fuel CO₂ emissions is taken up by the biosphere and oceans.
What is one half?
In 2019, U.S. primary energy consumption was about 100 of these quadrillion-BTU units.
What are quads?
In 2019, total primary energy production of about 606 exajoules corresponds to around this many joules.
What is about 6.06 x 1020 joules?
Solving the energy–climate challenge will require contributions not only from science and engineering but also from these three nontechnical domains.
What are policy, economics, and social/justice fields?
The target cost mentioned for solar PV competitiveness without subsidies is about this many dollars per watt-peak.
What is about $0.50 per watt-peak?
Converting coal’s chemical energy to light in an incandescent bulb yields an overall efficiency of about this percentage.
What is about 1.3 percent?