Read the notes, then try the practice. It adapts as you go.When you're ready.
Session Length
~17 min
Adaptive Checks
15 questions
Transfer Probes
8
Renewable energy refers to energy derived from natural sources that are replenished at a rate faster than they are consumed. Unlike fossil fuels, which take millions of years to form and release stored carbon when burned, renewable energy sources such as solar, wind, hydroelectric, geothermal, and biomass harness ongoing natural processes to generate electricity and heat. The fundamental appeal of renewables lies in their potential to provide virtually limitless energy while dramatically reducing greenhouse gas emissions and air pollution.
The rapid expansion of renewable energy technologies over the past two decades has been driven by steep cost declines, supportive government policies, and growing awareness of climate change. Solar photovoltaic module prices have fallen by more than 99% since 1976, and onshore wind turbine costs have dropped by roughly 70% since 2009. These cost reductions, combined with improvements in energy storage and grid integration, have made renewables cost-competitive with or cheaper than fossil fuels in most markets worldwide. As a result, renewables accounted for the majority of new electricity generation capacity added globally in recent years.
Beyond electricity generation, the renewable energy transition encompasses broader systemic changes including the electrification of transportation, the development of green hydrogen for industrial applications, and the redesign of energy grids to accommodate variable generation sources. This transition presents both technical challenges, such as intermittency management and long-duration storage, and socioeconomic opportunities, including job creation, energy independence, and improved public health outcomes from reduced air pollution.
One step at a time.
Technology that converts sunlight directly into electricity using semiconductor materials that exhibit the photovoltaic effect. When photons strike a PV cell, they knock electrons loose from atoms, generating a flow of electricity.
Example: Rooftop solar panels on homes use photovoltaic cells made of silicon to convert sunlight into electricity, reducing household reliance on grid power and lowering electricity bills.
The conversion of kinetic energy from wind into electrical power using wind turbines. Modern turbines use aerodynamic blades to spin a rotor connected to a generator, with power output proportional to the cube of wind speed.
Example: Offshore wind farms in the North Sea use turbines with blade spans exceeding 200 meters to generate electricity for millions of homes, taking advantage of stronger and more consistent ocean winds.
Technologies that capture energy produced at one time for use at a later time, essential for balancing the intermittent nature of solar and wind power. Major technologies include lithium-ion batteries, pumped hydro storage, and emerging solutions like compressed air and flow batteries.
Example: Tesla's Hornsdale Power Reserve in South Australia uses a large-scale lithium-ion battery to store excess wind energy and release it during peak demand, stabilizing the regional grid.
The point at which the cost of generating electricity from renewable sources equals or falls below the cost of purchasing power from the conventional electricity grid. Once grid parity is achieved, renewables become economically competitive without subsidies.
Example: Solar power reached grid parity in many sunny regions by the mid-2010s, meaning homeowners could generate solar electricity more cheaply than buying it from their utility company.
The variability in power output from renewable sources caused by natural fluctuations in weather conditions. Solar panels produce no power at night and reduced power on cloudy days, while wind turbines depend on variable wind speeds.
Example: Germany's grid operators must manage days when wind and solar provide over 80% of electricity followed by periods where they contribute less than 10%, requiring backup generation or storage.
A metric that calculates the average net present cost of electricity generation over the lifetime of a generating plant, including capital costs, fuel costs, operations, maintenance, and decommissioning, divided by total energy output.
Example: The LCOE of utility-scale solar dropped from over $350 per megawatt-hour in 2009 to under $50 by the early 2020s, making it one of the cheapest sources of new electricity generation.
Electricity generated by harnessing the gravitational force of falling or flowing water. Conventional hydropower uses dams to create reservoirs, while run-of-river systems divert a portion of a river's flow through turbines without large-scale impoundment.
Example: The Three Gorges Dam in China is the world's largest hydroelectric power station, with an installed capacity of 22,500 MW, producing enough electricity to power tens of millions of homes.
Energy extracted from heat stored beneath the Earth's surface. Geothermal power plants use steam or hot water from underground reservoirs to drive turbines, while geothermal heat pumps exploit shallow ground temperatures for building heating and cooling.
Example: Iceland generates roughly 25% of its electricity and heats 90% of its homes using geothermal energy, tapping into volcanic activity beneath the island.
More terms are available in the glossary.
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