This course provides an interdisciplinary introduction to the science and technology of energy systems with an emphasis on environmental and societal impacts. Topics include: global energy resources and consumption; fossil fuels (oil, gas, and coal); renewable energy technologies (wind and solar); energy storage systems (batteries, fuel cells, and hydrogen); nuclear energy (fission and fusion); and bioenergetics (photosynthesis, respiration, and biological energy conversion). Through lectures and discussions, the course develops a quantitative and intuitive understanding of energy production, transformation, and sustainability in both natural and engineered systems.