Energy Glossary

Decentralized & Renewable Energy

2Degrees – Glossary for decentralized & renewable Energy

What is the 2°-Target?
Here you will find the most important terms from the fields of technology, economy and law of decentralized energy, the energy transition and renewable energies.

(Smartmeter-) Gateway

The Smartmeter Gateway, as an extension of the Smart Meter as a pure measuring device, enables storage and reconciliation of consumption and generation data. The gateway enables the coordinated behavior of generation, storage and consumption components. It is the basis for innovative energy offers.


Paris 2015, 195 countries, ratified by China, USA, India and EU. Objective: to minimize emissions of climate-damaging CO2 in the long term and to permanently avoid them. Thus, global warming should be limited to a maximum of 2 ° C.


Period in which an investment pays back through positive cash returns. Formula: investment amount / cash return per unit of time

Self-Sufficiency rate

The term self-consumption / total consumption gives the degree of self-sufficiency, that is to say: the proportion of your electricity consumption that does not have to be taken from the grid, but is generated by our own system.


The (sun) azimuth indicates the deviation from the 0 ° south, where -90 ° means a direct orientation to the east, + 90 ° a direct orientation to the west and +/- 180 ° a northern orientation.


Federal Office of Economics and Export Control. The BAFA regulates among others the subsidy applications for heat pumps and CHPs.


Combined heat and power plant: Electrical system for the simultaneous provision of electricity (power) and heat. CHPs come in various sizes and shapes, from single-digit kilowatts (kW) to several megawatts (MW).


Gas obtained by the anaerobic digestion of biomass. (according to the EEG).


Biogas or other gaseous biomass, which has been fed into the natural gas network (s). (according to EEG).


Also hot water heat pump, is a special form of the air / water heat pump. It extracts heat directly from the place of installation for the treatment of service water.


Fuel Cell

Fuel cell heatings generate electricity and heat with natural gas. Normally, so-called combined heat and power plants (CHP) work with an internal combustion engine. The fuel cell generates electrical energy from the chemical reaction energy according to the principle of „cold combustion“, which results in the connection of hydrogen and oxygen to water.


In contracting, IDR takes over an energy provider (EVU) to invest and maintain an electrical system, often a CHP. Over a fixed term, the Evu receives the supplied electricity and/or heat from the customer. Price increases are possible, but are regulated by the general conditions for the supply of district heating (AVBFernwärmeV)


The Frenchman Georges Darrieus invented the rotor named after him: a vertical wind turbine.

Decentralized Energy

In the decentralized energy system, electricity is generated on site and the highest possible proportion is directly consumed, stored or distributed locally. Decentralized energy systems range from large wind or solar parks to domestic systems. By combining photovoltaics, small wind, CHP and heat pumps with energy storage, electromobility, smart grid and smart markets, the decentralized energy system enables a multitude of innovations and design possibilities compared to a central energy sector based on fossil power generation.


In the context of the energy transition, digitization is above all the introduction of intelligent measuring systems: smart meters and smart meter gateways together form the backbone of the smart grid and the smart market.


Thin-film modules have a low material requirement and are generally less expensive than crystalline solar modules. As direct semiconductors, they are characterized by significantly lower efficiencies. With high absorption strength, however, they have higher shading and temperature tolerances and are therefore suitable i.a. in partially shaded locations. Its thin structure allows use in almost transparent modules


Law for the Development of Renewable Energies (Renewable Energy Sources Act – EEG 2014): This law provides i.a. Feed-in tariffs and expansion targets for renewable energies.


Law for the Promotion of Renewable Energies in the Heating Sector: This Act foresees i.a. the share of renewable energies in new buildings.


European Energy Exchange, energy exchange based in Leipzig. For operators of a CHP, the daily determined price (settlement price) is important: according to this index, the so-called „typical price“, the remuneration for the electricity fed into the grid is paid quarterly in addition to the supplements according to the KWKG or EEG (at Fuels from biomass) and the avoided grid usage charges.


Decentralized energy systems convert energy locally into another, usable form. Usually these are electricity and / or heat. The more you consume of this energy – directly or through storage – the higher your own-consumption. The current prices for electricity, as well as reduced costs for decentralized generation and storage components, mean achieving the highest possible own-consumption often makes economical sense.

Own-consumption share

The part of your self-generated electricity that is not fed into the grid, but that you consume directly. This includes the power for your battery, the electric car or a heat pump.

Electric mobility

First and foremost in electric mobility are electric passenger cars, but also e-bikes, electric scooters and trucks. In Germany at present, only electric cars are subsidized by the state (exceptions can exist at the municipal level).

Energiewende ( Energy Transition )

The Energiewende or energy transition is the initiative of the German Federal Government to enter the age of renewable energies. Herein are justified among others the EEG (Law on Renewable Energy ), the reorganization of the electricity market, the network expansion and the National Energy Efficiency Action Plan. In addition to the nuclear phase-out, another long-term goal is to permanently reduce climate-damaging emissions.

Renewable Energies

According to the EEG, hydropower (including wave, tidal, salt gradient and flow energy), wind energy, solar radiant energy, geothermal energy and energy from biomass (biogas, biomethane, landfill gas and sewage gas as well as from biodegradable fractions of waste) belong to the renewable energies

Flexible Tariffs

Offers that compensate for the provision or reception of energy at different rates.

Fossile Electricity Generation

Brown coal (lignite), hard coal, gas, oil, when burned in a thermodynamic process to generate electricity

Green Electricity or Green Power

Electricity derived exclusively from renewable energies.

Intelligent measuring point system

By combining a smart meter with a smart meter gateway, the intelligent measuring system is created.

Small Wind Power

Wind turbines in Germany count as small plants with a tower height of up to 50m and an installed capacity of up to 100kW.


KWEA (Kleinwindenergieanlage) stands for small wind energy plant. Wind turbines in Germany count as small plants with a tower height of up to 50m and an installed capacity of up to 100kW.


Combined Heat and Power or Cogeneration stands for the simultaneous generation of electricity (power) and heat. Their size ranges from a combined heat and power plant with several megawatts (MW) over combined heat and power plants to electricity generating heating in the range <1 kilowatt (kW).


Combined Heat and Power (Cogeneration) stands for the simultaneous generation of electricity (power) and heat. Their size ranges from a combined heat and power plant with several megawatts (MW) over combined heat and power plants to electricity generating heating in the range <1 kilowatt (kW).

Lee runner

Wind turbine with rotor in wind direction behind the mast.


Wind turbine with rotor in wind direction in front of the mast.


Solar cells consist of a single silicon crystal. Their surface is pyramid-shaped textured, which absorbs the incoming light better. Monocrystalline solar cells are characterized by high efficiency.


The aim of your inverter is to keep your PV system in the maximum power point (MPP), the point of maximum generation. This changes depending on the year and time of day due to the different position of the sun and the resulting degree of shading.

Tilt angle

Angle between module surface and plane. In Germany there is an optimal inclination angle between 35 ° – 45 °.


In short PV, stands for the generation of electricity from solar energy. The photoelectric, especially: the internal photoelectric effect in semiconductors (such as silicon), enables its application. Photovoltaics is a relatively easy way to generate your own electricity.



In the manufacture of these solar cells, many crystals form in different orientations. Due to the simpler production process, these solar cells are cheaper, but are also characterized by a lower efficiency.


For wind calculations, the Rayleigh distribution is used when assuming a Weibull form factor of 2. Based on the mean wind speed their frequency distribution is then derived.


Named after its inventor, Sigurd Savonius, this vertical runner is a wind turbine with two or more blade-shaped, overlapping wings mounted along the axis of rotation stretched between circular end disks.


The Smart Grid Ready function for heat pumps opens up the possibility to specify and control operating strategies according to your priorities.


A power grid must maintain the same voltage at all times with only marginal deviations. Too large deviations due to supply failures or a high additional consumption endanger the security of supply. This balance is automatically regulated by a digital energy network, the Smartgrid. In addition, it offers the possibility to include flexible consumers such as heat pumps, batteries or electric cars as needed in this system.

Smart Market

Decentralized energy systems in combination with flexible consumers who can provide or receive energy spontaneously and are connected via the Smartgrid are the infrastructure that enables a Smart Market. In theory, smart metering systems enable each of their owners to participate in the Smart Market, in flexible tariffs, and in innovative business models.

Smart Meter

A digital measuring system for recording energy consumption. The Smartmeter allows timely recording and billing. It is the foundation of the smart grid and the smart market. The bi-directional version allows not only consumption but also generation detection, for example a PV system.


Solar Collector

A solar collector is used to generate heat from solar radiation.

Solar Module

Individual solar cells are combined to form a module, which is then used to generate electricity.


Solar Thermal

In contrast to photovoltaics, the solar thermal system uses solar radiation to produce not electricity but warm water or heat.

Solar Cell

The solar or photovoltaic cell converts energy contained in solar radiation into electrical energy (see Photovoltaics).

Electricity Storage

The best known is the electro-chemical energy storage, the battery. In combination with PV systems, these are subsidized by the state. Other power storage devices include: Reservoirs, compressed air caverns, flywheels, but also electrical network components such as coils and capacitors. An electric vehicle has a battery and can thus act as a power storage. In the context of decentralized energy systems, especially in private households, more and more lithium-ion battery storage systems are being used.



Your PV system converts solar energy into DC voltage. Since the public grid works with AC voltage, an inverter is needed. It is important to have the highest possible efficiency, both at full and at partial load (cloudy sky, shading). The inverter, including the inverter, also ensures maximum power output by adjusting the voltage. This is called MPP tracking (Maximum Power Point).


Named after the Swedish engineer and mathematician Waloddi Weibull, the Weibull distribution gives a steady probability distribution over the set of positive real numbers. It often gives a good approximation of the wind speed distribution. 2 parameters are critical: 1. the Weibull scaling factor (a-value) in m / s, a measure of the wind speed characterizing the time series. The scaling factor (k value) is proportional to the mean value of the wind speed. 2. The Weibull form factor, which indicates the shape of the distribution and usually assumes a value between 1 and 3. The smaller the scaling factor, the more variable the wind..

Weibull Formfactor

The Weibull form factor parameter in Northern Europe is approximately 2, but may vary depending on the situation. The distribution of a mean wind speed can be described by this parameter: uneven wind conditions have a lower, even conditions a higher value.

Heat Pump

Heat pumps are available in different forms: air / water, water / water, brine / water, earth / water, air / air. The donating medium is first mentioned, the receiving medium is in second place. By adding energy, a thermodynamic process takes place in which temperature differences between the respective media cause more energy to be utilized than are introduced. This ratio is commonly called COP (Coefficient of Performance).


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