Renewable Energy

Renewable Engery - Power derived from natural sources that replensih themselves continously on a human time scale.


Hydropower:

  • Uses moving water to generate electricity

  • Water is stored in a reservoir behind a dam, usually at a height

  • Water stored at a height has gravitational potential energy

  • When water is released, it flows down a large pipe called a penstock

  • As water flows down, gravitational potential energy is converted into kinetic energy

  • The fast-moving water spins a turbine

  • The turbine is connected to a generator by a shaft

  • The spinning turbine drives the generator, converting mechanical energy into electrical energy through electromagnetic induction

  • Electricity is then transported through power lines to homes and businesses

  • Water flows back into the river downstream

  • The amount of electricity generated depends on the volume of water and the height it falls (head)

  • Can respond quickly to changes in electricity demand

  • Some systems use pumped-storage, pumping water uphill to store energy for later


Energy Pathway:

Gravitational Potential Energy → Kinetic Energy → Electrical Energy


 Pros

Cons 

  • Renewable

  • Low greenhouse gas emissions

  • No fuel needed

  • Reliable electricity generation

  • Can generate electricity on demand

  • Fast response to changes in electricity demand

  • low operating and maintenance costs

  • Long lifespan

  • Water can be stored in reservoirs for later use

  • Depends on water avalibility and rainfall

  • Droughts cna rreduce electricity generation

  • Building dams can require cutting down trees and clearing large areas of land

  • Can destroy natural habitats and disrupt ecosystems

  • Can affect fish migration and river ecosystems

  • Expensive to build dams and infrastructure

  • Limited suitable locations

  • Reservoirs can flood land and displace wildlife and communities

Key Terms:

Hydropower: Generating electricity using the energy of moving water

Reservoir: A large area where water is stored behind a dam

Penstock: A large pipe that carries water to the turbine

Turbine: A rotating machine turned by moving water

Generator: Converts mechanical energy into electrical energy

Head: The height difference between the water reservoir and the turbine

Pumped-storage: Pumps water uphill when electricity demand is low and releases it to generate electricity when demand is high.

Solar Photovoltaic:

  • PV cells convert light directly into electrical energy

  • Light is absorbed

  • Solar panels contain PV cells - Photovoltaic

  • PV cells are made from silicon, a semi-conductor

  • Sunlight hits the solar cells

  • The light energy causes electrons to move, producing an electrical current

  • The electricity produced is initially direct current (DC)

  • An inverter converts DC electricty into alternating current (AC) for homes and electricity grid.

  • The energy from the light enables electrons to move, creating in electrical current

  • Energy transformation: radiant/light energy → electrical energy

  • Some sunlight is reflected


Energy Pathways:

Radiant Energy → Electrical Energy


 Pros

Cons 

  • Renewable

  • Low greenhouse gas emissions

  • No fuel needed

  • Installed on rooftops or large solar farms

  • Low operating and maintance costs

  • Useful in remote locations

  • Needs sunlight

  • Its highly dependant

  • Energy storage might be needed

  • Large solar farms

  • Requires significant land

  • Creating panels requires energy and raw materials

  • No electricity at night

Key Terms:

Photovoltaic Effect: Converting light energy into electrical energy

Solar Cell: A device that converts sunlight into electricity

Inverter: Converts DC electricity into AC electricity

Geothermal Energy

  • Geothermal energy uses heat from inside the Earth

  • Heat from underground can warm water, producing hot water or steam

  • The steam turns a turbine

  • The turbine drives a generator, producing energy

  • In some systems, geothermal heat is used directly for heating buildings

  • Water can often be returned underground to be reheated and reused

  • Production well brings hot fuild to the surface

  • The hot fluid produces steam

  • The steam turbine which is connected to a generator

  • After cooling water can be returned underground through an injection well

  • Some geothermal systems use about exhanger and a separate working fluid


Energy Pathways:

Thermal Energy → Kinetic Energy → Electrical Energy


 Pros

Cons 

  • Renewable

  • Produces electricity continuously

  • Not dependent on weather

  • Produces relatively low greenhouse gases

  • Requires little land in comparison to other options

  • Needs suitable geological conditions

  • Expensive

  • Difficult

  • Can release underground gases

  • Resources can be locally depleted

  • Cost of drilling

  • Suitable underground heat and fluids needed


Key Terms:

Geothermal: Relating to heat from inside the Earth

Turbine: A machine turned by moving steam or fluid

Generator: Converts mechanical energy into electrical energy

Wind Energy

  • Wind is moving air caused mainly by uneven heating of Earth’s surface by the Sun

  • Wind pushes the blades of a wind turbine

  • The blades rotate

  • The rotation drives a generator

  • The generator converts the movements (kinetic/mechanical energy) into electrical energy

  • Electricity is then sent to homes or the electricity grid

  • Airflow over rotorblade causes them to rotate

  • A shaft connects the rotating blades to the generator

  • Generator converts the movement into electrical energy


Energy Pathways:

Kinetic Energy (Moving Air/Wind) → Kinetic Energy (Spinning Blades and Gears) → Electrical Energy


 Pros

Cons 

  • Renewable

  • Low greenhouse gases

  • No fuel

  • Large amounts of energy

  • Can still be used for farming

  • Costs are low after turbines are installed

  • Needs wind

  • Outputs can vary depending on wind speed

  • Very large and visually intrusive

  • Loud

  • Affects birds and bats if poorly located

  • Needs a good location

  • Variable output because wind speed changes


Key Terms:

Wind Turbines: Captures the kinetic energy of wind

Kinetic Energy: Energy of movement

Generator: Converts mechanical energy into electrical energy

Intermittent: Not continously avalible