Solar and wind energy
Big idea: Renewable energy can be sustained indefinitely and produces minimal greenhouse gas emissions during operation.
Solar energy
- Photovoltaic (PV): Convert sunlight directly to electricity using semiconductors
- Concentrated solar power (CSP): Mirrors focus sunlight to heat fluid and drive turbines
- Advantages: Abundant, no emissions in operation, decreasing costs, scalable
- Disadvantages: Intermittent (no sun at night), requires storage, land use, manufacturing impacts
- Global growth: Solar is now the cheapest electricity source in many regions
Wind energy
- Onshore wind: Turbines on land; cheaper but visual/noise impacts
- Offshore wind: Turbines at sea; stronger/more consistent winds but higher cost
- Advantages: No emissions in operation, relatively cheap, proven technology
- Disadvantages: Intermittent (wind varies), bird/bat mortality, visual impact, noise
- Global growth: Wind capacity has grown ~15% annually in recent years
Both solar and wind are intermittent — they dont produce power all the time. This creates challenges for grid management and requires energy storage or backup power.
Exam tip: When evaluating renewables, always consider BOTH advantages AND disadvantages. No energy source is perfect!
Hydro, geothermal, and biomass
Big idea: Hydropower, geothermal, and biomass are established renewable sources with different advantages and environmental trade-offs.
Hydroelectric power
- How it works: Flowing water spins turbines; requires dams or run-of-river systems
- Advantages: Reliable, controllable, long lifespan, provides water storage and flood control
- Disadvantages: Habitat destruction, fish migration barriers, displacement of communities, methane from reservoirs
- Note: Large dams are controversial; small-scale hydro has fewer impacts
Geothermal energy
- How it works: Heat from Earths interior drives turbines or heats buildings directly
- Advantages: Reliable baseload power, small footprint, low emissions
- Disadvantages: Location-limited (near tectonic boundaries), can release H₂S and CO₂, induced seismicity risk
- Note: Iceland gets ~25% of electricity and ~90% of heating from geothermal
Biomass energy
- Sources: Wood, crop residues, biogas from waste, biofuels (ethanol, biodiesel)
- Advantages: Can be carbon-neutral if regrown, uses waste, provides baseload power
- Disadvantages: Competes with food production, deforestation risk, air pollution when burned, low EROI
- Note: Sustainability depends heavily on how biomass is sourced
Exam tip: Biomass is only carbon-neutral IF new plants absorb as much CO₂ as burning releases. Unsustainable biomass can be worse than fossil fuels.