Click image to open full size
Environmental Science
Grade 6-12
Renewable Energy Sources Comparison Cheat Sheet
A printable reference covering solar, wind, hydropower, geothermal, biomass, capacity factor, efficiency, and environmental tradeoffs for grades 6-12.
Related Tools
Related Labs
Related Worksheets
Renewable energy sources come from natural processes that can be replenished on a human time scale. This cheat sheet compares major renewable sources so students can quickly see how each one works, where it is useful, and what impacts it can have. It helps students connect energy choices to climate, cost, land use, reliability, and local geography. Comparing sources is important because no single renewable source is best in every location.
Key Facts
- Solar energy converts sunlight into electricity using photovoltaic cells, and output is highest when sunlight is strong and direct.
- Wind energy uses moving air to spin turbine blades, and power increases greatly as wind speed increases.
- Hydropower uses moving or falling water to turn turbines, and it can provide steady electricity where rivers or dams are available.
- Geothermal energy uses heat from inside Earth, and it is most practical in areas with hot rock, hot springs, or volcanic activity near the surface.
- Biomass energy comes from recently living material, and it can release carbon dioxide when burned even though the carbon was recently part of the carbon cycle.
- Efficiency = useful energy output / total energy input x 100%.
- Capacity factor = actual energy produced / maximum possible energy produced x 100%.
- A good renewable energy plan often combines sources, such as solar during sunny days and wind or hydropower when solar output is low.
Vocabulary
- Renewable energy
- Energy from a source that is naturally replenished on a human time scale, such as sunlight, wind, flowing water, Earth heat, or biomass.
- Photovoltaic cell
- A device that converts sunlight directly into electricity.
- Turbine
- A machine with blades that spins when pushed by wind, water, steam, or gas to help generate electricity.
- Capacity factor
- The percent of a power source's maximum possible energy output that it actually produces over time.
- Intermittent energy
- Energy that is not available at all times because it depends on changing conditions such as sunlight or wind.
- Carbon footprint
- The total amount of greenhouse gases released by an activity, product, or energy source.
Common Mistakes to Avoid
- Calling all renewable energy pollution-free is wrong because construction, mining, land use, and maintenance can still affect ecosystems and produce emissions.
- Assuming solar panels work at full power all day is wrong because output changes with cloud cover, season, time of day, and panel angle.
- Treating biomass as always carbon neutral is wrong because burning biomass releases carbon dioxide and may cause deforestation or air pollution if not managed well.
- Comparing energy sources only by cost is wrong because reliability, location, storage needs, habitat effects, and emissions also matter.
- Confusing efficiency with capacity factor is wrong because efficiency measures energy conversion, while capacity factor measures how much a system actually produces over time.
Practice Questions
- 1 A solar panel receives 800 J of sunlight and produces 160 J of electrical energy. What is its efficiency?
- 2 A wind farm could produce 1000 MWh in a month if it ran at full power the whole time, but it actually produces 350 MWh. What is its capacity factor?
- 3 A town uses 600 MWh of electricity in a week. If hydropower supplies 240 MWh, what percent of the town's electricity came from hydropower?
- 4 A coastal town has strong winds, moderate sunlight, limited river flow, and strict habitat protections. Which renewable source would likely be most useful, and what tradeoff should planners still consider?