• decarbonisation

    (Dekarbonisierung) Decarbonisation of a sector, industry, or economy refers to the process of reducing – and ultimately eliminating – its carbon dioxide emissions.

  • decentralised energy

    (Dezentrale Energiesysteme) Sourcing energy from renewables rather than fossil fuels implies a differently structured energy system. Rather than generating power in a few, large plants, a multitude of distributed installations – from high-capacity offshore wind farms to farm-owned biogas plants and small rooftop PV installations – contribute to the power supply. This requires changes to grid infrastructure and raises questions about the design of energy markets.

  • defeat device

    (Abschalteinrichtung) Defeat device software has been at the centre of the → dieselgate scandal. The device is activated to prevent an engine’s emissions control system from working properly under real world conditions. As a result, the actual emission levels are higher than in a test situation, where the defeat device is inactive.

  • demand-side management

    (Nachfragesteuerung) Demand-side management is the targeted control of power consumption. As affordable power storage is not yet available on a large scale, the amount of electricity produced must roughly equal the amount of electricity consumed at any moment. Traditionally, the power system is balanced out by adjusting supply (electricity generation). Yet, power consumers – from large industrial operations to private households – can help balance out the grid by consuming more electricity when it is abundant and less when it is scarce. This can be more efficient and less costly than ramping power plants up or powering them down, and it can help companies save energy costs. Contracts that remunerate energy-intensive companies for reducing consumption during peak demand periods have existed for quite some time, but a regulation on interruptible loads aimed at standardising the practice was introduced in 2012 only. Since the production of wind and solar power fluctuates with environmental conditions, the electricity system needs to become more flexible, which makes the role of the targeted control of power consumption more important. Possibilities for demand-side management include powering down cooling units for some time; treating drinking water at a later/earlier moment in time; or charging e-car batteries during times of low demand. Modern intelligent information and control technology (see → smart grids) is needed for effective demand-side management.

  • deployment corridor

    (Ausbaupfade) In its 2013 coalition agreement, the German federal government specified deployment corridors for renewables development. By 2025, 40-45 percent of Germany’s gross power consumption should be covered by renewable sources, and by 2035, the respective figure should increase to 55-60 percent (80 percent by 2050). In accordance with the coalition agreement, lawmakers in 2016 reformed the Renewable Energy Act to increase the market exposure of the sector, and to keep renewable power development more closely in step with grid development. This reform confirmed the coalition agreement’s measures on the deployment corridors, and included the setting of annual auction volumes for new renewable capacity to stay within the deployment corridors. Each year, 2.5 GW of photovoltaic capacity is to be installed, of which 600 megawatts (MW) will be auctioned. Onshore wind installations will be set at 2.8 GW per year between 2017 and 2019, and at 2.9 GW from 2020 onward. The country’s total offshore wind capacity is to reach 6.5 GW by 2020, and 15 GW by 2030, by auctioning 730 MW per year from 2019 (in 2017 and 2018, a total of 3.1 GW is auctioned among already approved projects). Biomass capacity is to be expanded by 150 megawatts (MW) annually over the next three years, and by 200 MW in the following three years.

  • dieselgate

    In September 2015, the US Environmental Protection Agency issued a notice of violation of the Clean Air Act to Volkswagen, accusing the company of deliberately cheating on vehicle emissions tests. The German carmaker used software (see → defeat device) to keep nitrogen oxide emissions from diesel engines within legal limits only during tests, while on-the-road emissions were in fact 40 times higher. Other carmakers have since been found to have employed similar tactics. In December 2015, the European Commission announced its intention to take legal action against Germany and other member states for failure to comply with EU emissions laws.

  • distributed energy

  • distribution grid

    (Verteilnetz or Verteilernetz) The distribution grid brings power directly to consumers. It is operated by a variety of regional and municipal operators (unlike the maximum voltage transmission grid; see → transmission grid operators). It operates at three different levels of voltage: primary distribution; transformer substations; and private households. With local producers now feeding electricity into the grid (see →  decentralised energy, and → prosumers), power does not just flow from the higher voltage grids to the lower voltage local networks, but also back the other way, requiring upgrades to the system (see → smart grids).

  • district heating

    (Fernwärme) District heating supplies buildings with heat via a network of pipes. Heat is often generated by → CHP plants and carried as hot water.