Lesson 1 doesn't have any reading assignments. However, the following readings are optional and recommended.
Links
[1] https://www.eia.gov/energyexplained/index.cfm?page=wind_home
[2] https://www.eia.gov/energyexplained/index.cfm?page=hydropower_home
[3] https://www.eia.gov/energyexplained/index.cfm?page=solar_home
[4] https://www.eia.gov/energyexplained/index.cfm?page=geothermal_home
[5] https://www.eia.gov/energyexplained/index.cfm?page=biomass_home