GLOSSARY

• Renewable Energy

Renewable Energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly or indirectly from the sun, or from heat generated deep within the earth. Included in the definition is energy generated from solar, wind, biomass, geothermal, hydropower and ocean resources, and biofuels and hydrogen derived from renewable resources.

• Technologies (Policy Targets)

  Biomass

  Biomass refers to a wide variety of organic material that can be used as fuel to generate heat and power and can be a solid, liquid or gas. This energy is released directly, for example by combustion (burning), or is converted into intermediate products which are then converted to release the stored energy (for example refining, to produce liquid transport fuels or anaerobic digestion to produce 'biogas').
  

  Solid biomass (for heat and/or power)
  Solid biomass refers to organic material used as fuel for heat production and electricity generation. It includes charcoal (solid residue of the distillation and pyrolysis of wood and other vegetal material), wood and wood waste. This includes purpose-grown energy crops (poplar, willow) or generated by an industrial process (wood/paper industry) or directly by forestry and agriculture (wood chips, chips, shavings, black liquor). Solid biomass also includes other vegetable or animal waste, such as straw, rice husks and poultry litter.
  Biomass is most often combusted in combined heat and power (CHP) systems, also known as cogeneration. CHP refers to any system that simultaneously or sequentially generates electric energy (the power) and uses thermal energy that is normally wasted (the heat).

  Biogas (for heat and/or power)
  Biogas is principally composed of methane (CH4) and carbon dioxide (CO2), produced by the anaerobic digestion of biomass, and is generally combusted to produce heat and/or power. It can be formed by digestion of biomass from landfills, sewage sludge, and other waste sources in agro-food industries (such as abattoirs, breweries, agricultural processes).

  Liquid biofuels (for transport)
  Liquid fuels deriving from biomass transformation, these are often separated into biodiesel and biogasoline and further qualified as first or second generation.
  Biodiesel is a biofuel for diesel-powered vehicles generally produced from oilseed crops or other vegetable oil sources. This includes FAME (Fatty Acid Methyl Ester), FAEE (Fatty Acid Ethyl Ester), Fischer Tropsh, cold pressed biooil, and all other liquid biofuels which are added to, blended with or usedstraight as transport diesel.
  Biogasoline is a fuel made from biomass (for example corn, sugar cane) that can replace gasoline in small percentages or be used in pure form in specially modified vehicles. It includes bioethanol, biomethanol, bioETBE (produced on the basis of bioethanol; the percentage by volume of bioETBE that is calculated as biofuel is 47%) and bioMTBE (produced on the basis of biomethanol; the percentage by volume of bioETBE that is calculated as biofuel is 36%).

  • First generation biofuels
    Generally refers to biofuels produced from edible crops that are either high in sugar (sugar cane, sugar beet, corn) and
    used to produce bioethanol, or high in oil (rapeseeds, oil palm, soybean) and used to produce biodiesel.

  • Second generation biofuels
    Generally refers to biofuels produced from non-food components of plants (stems, leaves and husks), non-food crops
    (switch grass, jatropha), or industry and agricultural waste (wood chips, skins, pulp). It can also include biomass-to-liquids
    (BTS), such as biodiesel created using the Fischer Tropsch process.  These extractions are technically more difficult.  

  Geothermal Energy

  Energy available as heat emitted from within the earth’s crust, usually in the form of hot water or steam. It is exploited at suitable sites for electricity generation after transformation, or directly as heat for district heating, agriculture, etc. Geothermal energy can be used to generate electricity using deep wells in hot rocks, to heat a liquid used to generate power. Geothermal steam can be used directly to power turbines, or high-pressure hot water can be pulled into lower-pressure tanks and the resulting flashed steam used to drive turbines.
  A typical geothermal system consists of pipes buried in the shallow ground near the building, a heat exchanger, and ductwork into the building. In winter, heat from the relatively warmer ground goes through the heat exchanger into the house. Heat pumps can also use geothermal energy.

   

  Hydropower

  Potential and kinetic energy of water converted into electricity in hydroelectric plants. It includes large as well as small hydro, regardless of the size of the plants.

   

  Ocean energy

  Ocean renewable energy sources can be placed into five broad categories: tides, tidal currents, waves, temperature gradients and salinity gradients. Tidal energy refers to using the difference in water levels due to tides, causing water to flow into and out of gates and turbines to generate power.  Turbines can also be placed in the water to harness the kinetic energy from tidal currents, as well as the potential and kinetic energy created by ocean waves. Ocean thermal energy conversion (OTEC) is a method for generating electricity which uses the temperature gradients that exists between deep and shallow waters to run a heat engine. Finally, the entropy of mixing water with different salt concentrations (salinity gradients) can be used to create osmotic power.

   

  Solar energy

  Solar radiation exploited for hot water production and electricity generation. As used here the term does not account for passive solar energy for direct heating, cooling and lighting of dwellings or other.

  • Solar photovoltaic (PV)
    Solar photovoltaic (PV) refers to the use of solar cells interconnected in the form of a panel or module, usually made of semi-conducting material, that when exposed to light convert sunlight directly into electricity.
    
    

  • Solar thermal
    Solar thermal panels or collectors are mostly used to heat water or another fluid, for space heating and cooling, hot water production or process heat.
    Concentrating solar thermal technologies use equipment that collect the solar energy and convert it to heat, then electricity or (potentially) other energy carriers.

   

  Wind power

  Refers to the kinetic energy of wind captured by the rotors of wind turbines; these may be located individually, or in large configurations known usually as wind farms, onshore and offshore.

• Policy Instrument Types

  
  

  Feed-in tariff

  Refers to a fixed guaranteed price at which power producers can sell renewable power into the electric power network.

   

  Feed-in premium

  Refers to a fixed premium is provided on top of the market price. These are also called premium feed-in tariffs, and generally make up the shortfall between the market electricity price and the generally higher cost of producing electricity from renewable sources.

   

  Renewable energy tax credits

  These generally take the form of a production or investment tax credit. A production tax credit provides the investor or owner of a qualifying renewable energy production facility with an annual tax credit based on the amount of electricity generated. An investment tax credit allows investments in renewable energy to be fully or partially deducted from income or other tax obligations.

   

  Tradable permits: Green certificates

  Green certificates refer to renewable energy certificates. Each certificate represents the certified generation of one unit of renewable energy, generally one megawatt-hour (MWh). Certificates can be traded and used to meet renewable energy obligations among consumers and/or producers, and can also be used for voluntary renewable energy power purchases.

   

  Quota policies

  Quota policies can be known as renewable energy obligations or renewable portfolio standards. These require a minimum percentage of electricity sold or generation capacity installed to be provided by renewable energy, which utilities must meet. They can also set obligations that a minimum percentage of electricity purchased comes from renewable energy sources.

  
  For additional information, please contact: pamsdb@iea.org.