6.8 Energy from the Sun

Direct and indirect solar energy

Solar energy reaches Earth as radiation and can be captured directly with photovoltaic (PV) cells (convert sunlight into electricity) or solar thermal systems (heat water/air for use or to drive turbines). It's a renewable, nondepletable resource with no fuel cost once installed, and produces no direct greenhouse gas emissions during operation.

Advantages of solar power

Solar energy is abundant, widely distributed, and reduces reliance on fossil fuels, cutting CO2 emissions and air pollution. It can be used at small scale (rooftop panels) or large scale (solar farms), and passive solar design reduces heating/cooling energy needs in buildings.

Limitations of solar power

Solar is intermittent — dependent on sunlight, weather, latitude, and time of day — requiring energy storage (batteries) or backup power. High initial installation costs, land use for large solar farms, and manufacturing impacts (mining materials, energy use, disposal of panels) are drawbacks.

Key terms

Photovoltaic (PV) cell

A device that converts sunlight directly into electricity using semiconductor materials.

Solar thermal system

A system that uses sunlight to heat water or air for direct use or to generate electricity via steam turbines.

Intermittency (solar)

The variability of solar energy production due to weather, time of day, and season, requiring storage or backup power.

Advantage of solar energy

Renewable, abundant, and produces no direct greenhouse gas emissions during operation.

Limitation of solar energy

High installation costs, intermittent supply, land use concerns, and environmental impacts from manufacturing panels.

Try an AP-style question

How do photovoltaic (PV) cells produce electricity?

1. Wind spins a small turbine inside
2. Sunlight boils water inside the panel
3. Heat melts salt stored in the cell
4. Sunlight frees electrons in semiconductors