Glossary beginning with G

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  • geothermal energy

    (Geothermie / Erdwärme) The Earth generates heat from primordial energy and from radioactive decay in its interior. In layers close to the surface, the Earth also saves heat from the Sun. This energy can be harnessed, for example, by installing underground pipe systems to heat up (or cool down) fluids, which can then be used on the surface in geothermal heat pumps. Another method is to drill deep wells where hot water – e.g. from thermal springs – can be used to generate electricity in thermal power plants. In Germany, most geothermal energy is tapped close to the Earth’s surface (from a depth of 400 metres). The bulk of this energy is used for heating (these facilities currently have an installed capacity of about 4,400 MW), and only a few facilities generate power (36.9 MW installed capacity). Geothermal energy accounts for around 0.4 percent of Germany’s primary energy consumption.

  • GHG

    See → greenhouse gas

  • greenfield status

    (“Grüne Wiese”) Once a power plant has been decommissioned, the site must be restored to its original condition (also known as greenfield status). This is a particular challenge for contaminated nuclear sites. See also → recultivation.

  • greenhouse gas

    (Treibhausgase) Gases that trap heat in the Earth’s atmosphere are called greenhouse gases (GHGs). Carbon dioxide (CO2) is the dominant anthropogenic (man-made) GHG, but other gases, such as methane (CH4), nitrous oxide, and fluorinated gases, have an even greater global warming potential (GWP). GHG emissions are often quantified as CO2 equivalent emissions, but no single metric can accurately compare all consequences of different emissions, and all choices of metric entail limitations and uncertainties. According to the 5th IPCC report, methane has 28-34 times the GWP of carbon dioxide over 100 years, and the release of one tonne of methane is equivalent to the release of 28-34 tonnes of CO2 over 100 years.

  • grid fees

    (Netzentgelte) Power suppliers must pay grid operators a ’grid fee‘ for the use of their network. This fee is ultimately passed on to the consumer. The fee covers infrastructure costs, invoicing, and metering, and includes various surcharges. Grid fee also covers the costs of operating the grid (see → grid service). Partly due to rising volumes of fluctuating renewable power being fed into the grid, these costs have risen, and grid fees have become the largest component of household consumer electricity bills (see → industry exemptions). This increase has not been uniform across Germany, as the country’s grid is split into four zones managed by different grid operators (see → transmission grid operators, TSO). The regions with a higher share of renewables and/or fewer power consumers shoulder greater costs. A 2017 reform planned to harmonise grid fees across the country, but the idea was omitted from the recent federal government cabinet decision. As of June 2017, it is still debated in the federal parliament.

  • grid services

    (Netzdienstleistungen) Grid operators (see → Transmission grid operators, TSO) contract out ancillary services, such as frequency and voltage control, which are required to keep the grid stable and ensure security of supply. These services can be provided by traditional electricity generators, but have also opened up market opportunities for new technologies, such as battery storage plants (see → storage) or  → virtual power plants.

  • growth corridor

    (Ausbaupfade) See → deployment corridor

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