Renewable Energy Sources

New Renewable Energy Sources

  • Definition of New Renewables: New renewable energy sources (energy from the sun, wind, geothermal heat, and ocean water) differ from conventional alternatives like hydropower and biomass in that:

    • They are just beginning to be used on a wide scale.

    • They harness energy using technologies that are rapidly developing.

    • They are expected to play significantly larger roles in future energy landscapes.

Growth of New Renewables

  • New renewable energy sources currently contribute a small proportion of our energy budget but are experiencing rapid growth.

  • Historical Growth Rates:

    • Wind energy has expanded at nearly 50% annually since the 1970s.

    • Recently, solar power has outpaced wind in growth rate.

  • Benefits of New Renewables:

    • Reduction in air pollution.

    • Decrease in greenhouse gas emissions that contribute to global climate change.

    • Diversification of energy mix helps stabilize economies.

    • Creation of green-collar jobs in design, installation, and maintenance of renewable energy systems.

Policy Acceleration of Renewable Energy

  • Many renewable energy sources remain more expensive than fossil fuels despite falling prices.

  • Strategies to accelerate transition include:

    • Feed-in Tariffs: Policies like those in Germany incentivize renewable energy production.

    • Government Mandates: Requirements for a minimum percentage of power to come from renewable sources.

    • Research Investment: Government funding for renewable energy R&D.

    • Lending Programs: Support for startups in the renewable energy sector.

    • Tax Incentives: Credits and rebates for renewable energy producers and consumers.

Solar Energy

  • Definition: Energy derived from the sun.

  • The Earth receives sufficient solar energy daily to power human activity for 25 years.

Methods of Collecting Solar Energy

  1. Passive Solar Energy Collection:

    • Designing buildings to maximize sunlight absorption in winter and maintain coolness in summer.

    • Techniques including strategic placement of vegetation and using thermal mass materials.

  2. Active Solar Energy Collection:

    • Involves devices to focus, move, or store solar energy.

    • Example: Flat plate solar collectors heating water using sunlight.

  3. Concentrating Solar Power (CSP):

    • Gathers solar energy from wide areas focusing it on singular points:

    • Examples:

      • Solar cookers using reflectors.

      • Parabolic trough systems heating synthetic oil, converting it to steam for turbine operation.

      • Power towers utilizing mirrors to direct sunlight to steam-driven generators.

  4. Photovoltaic Cells:

    • Convert sunlight directly into electricity through the transfer of electrons in silicon plates.

Benefits of Solar Energy

  • Inexhaustible energy source.

  • Requires no fuel input and minimal maintenance due to lack of moving parts.

  • Potential for job creation in the green sector.

  • Produces zero greenhouse gas emissions or pollutants during use.

Drawbacks of Solar Energy

  • Variability in sunlight between regions makes it an intermittent energy resource.

  • Storage capacity is necessary for consistent energy supply.

Wind Power

  • Definition: Energy generated from air movement due to heated air masses.

  • Wind turbines convert mechanical energy of wind into electrical energy:

    • Wind turns a rotor's blades, which drives machinery in a nacelle.

    • Turbines are designed to yaw into changing wind directions.

    • Wind speed directly affects power generation.

    • Doubling wind velocity increases power output by eight times.

    • Wind farms consist of multiple turbines to harness collective wind energy.

Growth and Capacity of Wind Power

  • Capacity is doubling approximately every three years.

  • Leading countries in wind energy capacity: China, United States, Germany.

  • Smaller countries with a high percentage of electricity from wind: Denmark, Ireland, Portugal.

Offshore Wind Farms

  • Higher promise for offshore sites due to greater wind speeds and less turbulence.

  • Initial costs are higher, but long-term energy potential is greater.

Benefits of Wind Power

  • A single 1-megawatt turbine can prevent releasing:

    • 1500 tons of carbon dioxide.

    • 6.5 tons of sulfur dioxide.

    • 3.2 tons of nitrogen oxides.

    • 60 pounds of mercury.

  • High Energy Return on Investment (EROI): Wind turbines generate 20 times more energy than they consume.

  • Scalability by adding more turbines in an area.

Limitations of Wind Power

  • Intermittent energy source, similar to solar energy.

  • Geography influences available wind power, with the Great Plains and mountainous regions of the U.S. being more favorable.

  • Residents often oppose wind farm developments near population centers (NIMBY syndrome).

  • Wind turbines pose risks to avian populations, including birds and bats.

Geothermal Energy

  • Definition: Thermal energy from beneath Earth's surface.

  • Geothermal energy can manifest at the surface in specific areas through:

    • Wells drilled to heated groundwater for direct heating or electricity generation.

    • Geothermal power plants generating electricity using heated water and steam.

Global Usage

  • Iceland has the highest utilization of geothermal energy worldwide, exemplified at Nesjavellir power station which heats water for community use and electricity generation.

  • Ground-source heat pumps utilize stable underground temperatures for home heating and cooling.

Benefits and Limitations of Geothermal Power

  • Benefits:

    • Emits smaller amounts of dissolved gases compared to fossil fuels.

    • Renewable but can be depleted if not managed correctly.

  • Limitations:

    • Hot groundwater may not be sustainable over time as Earth's crust shifts.

    • Enhanced geothermal systems (EGS) that use cold water to generate energy can trigger minor earthquakes.

Hydrogen and Fuel Cells

  • Challenge: The major obstacle for renewables is large-scale energy storage.

  • Hydrogen serves as a stored power source in fuel cells:

    • When hydrogen combines with oxygen, it produces water, releasing energy without pollution.

    • Transitioning from gasoline to hydrogen could help reduce emissions and reliance on foreign fuels, adopted in some city bus fleets.

Hydrogen Production Methods

  • Coming from water through electrolysis (2H2O → 2H2 + O2).

  • The cleanliness of hydrogen production depends on the energy source used for electrolysis.

  • Hydrogen can also be extracted from methane (CH4), which, while cheaper, has higher pollution outputs.

Electricity Production from Hydrogen

  • The reverse reaction of hydrolysis occurs in fuel cells (2H2 + O2 → 2H2O).

  • Movement of electrons from hydrogen across electrodes generates electricity.

Costs and Benefits of Hydrogen Fuel Cells

  • Transitioning to hydrogen fuel infrastructure involves significant expense for transport, storage, and distribution facilities.

  • Potential environmental risks include hydrogen leaking into the stratosphere which could harm ozone levels and contribute to methane's atmospheric lifespan.

  • Benefits:

    • Hydrogen is the most abundant element in the universe.

    • Producing electricity from hydrogen generates no air pollution.

    • High energy efficiency (35-70% of the reaction's energy can be utilized).