Use of Solar Energy for Power (College Board AP® Environmental Science): Study Guide

Photovoltaic solar cells

Basic principles of solar power

• Every hour, the Sun provides enough energy to cover the world's energy consumption for a year

• This energy is transferred from the Sun to the Earth through visible light and infrared radiation

• Solar energy is harnessed from the sun's radiation, providing a renewable and sustainable energy source

• It is a renewable and sustainable source of energy that can be utilized in various ways

• The efficiency of solar energy systems depends on sunlight availability, weather conditions, and geographic location

Photovoltaic (PV) solar cells

• PV cells convert sunlight directly into electricity using semiconductor materials

• Several solar panels connected together can provide power to homes, small businesses, communication devices, and satellites

• Energy generated can be stored in batteries for later use

Advantages of PV cells

• Most places receive a reliable source of solar energy on a daily basis

• No greenhouse gas emissions or air pollutants produced during operation

• Suitable for various scales of application (from house rooftops to very large solar farms)

• Can be integrated into existing buildings and infrastructure

• Solar is progressively becoming less expensive and more efficient due to higher demand

• PV cells can be used to generate electricity in remote places or to power solar street signs

Disadvantages of PV cells

• PV cells are sunlight-dependent and therefore an intermittent energy source

• Solar cells are relatively inefficient (around 20%–40%)

• Individual solar cells produce small amounts of electricity, making it necessary to have many cells in panels to meet energy demand

• Solar panels and equipment require a large initial investment

• Solar farms need a lot of land, which could have been utilized for agriculture

• Energy storage solutions are needed for night-time or cloudy days

• The manufacture and disposal of PV cells have an environmental impact through:

  • mining of rare earth minerals

  • disposal of e-waste

• Some people dislike the appearance of large solar farms (visual pollution)

Active solar energy systems

• Active solar heating systems use solar energy to heat a liquid or air through mechanical and electric equipment

• The system typically includes solar collectors, pumps, and storage tanks

• The system can provide energy even when sunlight is not immediately available, thanks to energy storage capabilities

• Water is stored in a water tank and pumped through small pipes running through the solar panel

• Infrared radiation from the Sun heats the water in the pipes as it flows through them

• The water returns to the tank at a higher temperature

• Further heating may be necessary to reach the desired temperature (e.g. for a shower)

Passive solar energy systems

• This system absorbs heat directly from sunlight without the use of mechanical or electric equipment

• Passive solar systems uses a building's design, location, climate and materials to make the most of heat and light from the sun

• Heat is stored in walls and floors made of materials such as concrete, brick, stone, or tires and is released slowly throughout the day and into the evening

• Buildings often feature large south-facing windows, thermal mass (e.g., concrete, brick), and insulation

• Energy cannot be stored long-term, so passive heating is limited to sunny days and the hours just after sunset