CER’s dictionary

Basic Concepts

Energy Cooperatives are Urban Cooperatives that are active in the field of energy (N.4513 / 2018). You can find more information here.

Energy Cooperatives can offer excellent economic empowerment opportunities. They are based on cooperative logic which works very well especially in times of crisis and lack of liquidity. The members of the energy community share the cost and risk of the investment they wish to make. They also have the opportunity to be a member of an entity that contributes to the local economy by creating investment moves and new jobs. The energy transition is a big change that concerns all the big players in the energy sector as the transition to a less energy economy will happen sooner or later. Apart from the environmental ones, three are also geopolitical reasons that lead, at least in Europe, to this direction. We want to facilitate the central role, which, for reasons of economics of scale and efficiency, they should have in the energy transition, for the benefit not only of the current generation through reducing unemployment but also of the coming, ensuring more clean energy and a fairer way of production and distribution energy.

A photovoltaic (PV / PV) system converts solar energy, specifically the energy of solar radiation into electricity, by utilizing the photovoltaic effect.

The key building block of a photovoltaic system is an electronic device called a solar cell or photovoltaic cell. The photovoltaic cell with its exposure to sunlight, due to the photovoltaic phenomenon, produces electricity.

The main purpose of building a photovoltaic park is to connect to the network or autonomously operate various loads that are otherwise supplied by the network. The electricity and specifically the electrical voltage of a photovoltaic cell is low enough to connect and power such loads and devices directly. For this reason, an increase in scale is made and the photovoltaic cells are connected in series and form an indivisible structure, the photovoltaic panels or otherwise the photovoltaic collectors. In the market, the basic structural unit of a photovoltaic generator is the photovoltaic frame.

The price of electricity and voltage of a photovoltaic panel still remain relatively small. Photovoltaic panels are electrically connected, with combinations of parallel and serial connection, and form photovoltaic panels and then photovoltaic arrays. All the photovoltaic panels of a park are the photovoltaic generator.

The photovoltaic system consists of the photovoltaic generator, which produces direct current and voltage, and the necessary devices and devices for the conversion of electricity into the desired form or for its storage.


Energy is a high-level abstract concept in which a single unambiguous definition can hardly be attributed. The concept of energy exists in many scientific fields, it is widely used in everyday life and as a result multiple meanings are attributed to it. Here we will focus on the concept of energy as a measurable physical quantity, as defined as a purely scientific concept in Physics.

The energy is not immediately noticeable, but is perceived and detected whenever there is a change in the properties of a body / system. The energy of a body / system is defined as its ability to produce work. The energy does not appear from nothing nor does it disappear, but it constantly changes form and moves constantly. The energy is stored in some form, converted from one form to another and is constantly moving. All forms of energy can be categorized into two primary categories –  kinetic energy and dynamic energy.

Kinetic energy is the energy that a body / system has due to its speed.

Dynamic energy is the energy that a body / system has due to its position or state in a field of forces.

The sum of these two forms of energy (kinetic + dynamic) is the mechanical energy of a body / system. These two forms of energy are sufficient to describe all types of energy, but for convenience it has been established that we refer to specific combinations of kinetic and dynamic energy as separate forms or as separate types of energy.

The energy we consume is classified into categories depending on its origin, ie the primary source of energy (natural resources) from which it comes. Primary energy sources are energy sources that are in nature and have not been converted by human intervention. A first categorization is Renewable Energy Sources and Non-Renewable or Contractual Energy Sources.

Renewable Energy Sources (RES) are energy sources that are rapidly renewing or can be considered virtually inexhaustible.

Non-Renewable or Conventional Energy Sources are energy sources that are depleted at a rapid rate relative to their rate of renewal.

The main primary energy sources that are classified in renewable sources are:

  • Wind energy: the dynamic energy of the wind
  • Solar Energy: the energy from the sun’s radiation
  • Hydraulic Energy: the dynamic energy from a liquid located at a higher potential
  • Geothermal Energy: the thermal energy of the earth
  • Wave energy: energy from the sea mass (waves, tides)

Other sources of energy that are considered renewable but are not primary forms are:

  • Biomass: solid fuels derived from natural sources
  • Biogas: fuels in the form of gas from natural sources
  • Urban waste / waste: waste / waste use as fuel

The main primary energy sources that are categorized in Contractual Energy Sources are:

  • Coal / Carbon: fossil fuel
  • Oil: fossil fuels
  • Natural gas: fossil fuel
  • Nuclear Energy: energy stored in the core of radioactive elements, mainly uranium (mining is required for uranium)

Green Energy Sources is an “unofficial” subcategory of Renewable Energy Sources. They are the energy sources that allow the production of energy with the least environmental impact.

Electric Energy is one of the most well-known forms of energy. Specifically, electricity is the kinetic and dynamic energy of electric charges. Electricity is a more general term and includes all phenomena related to the presence and flow of electric charges. Electricity is widely used to operate various devices that convert it into other forms of energy. We also call this conversion electricity consumption. Electricity is supplied by a combination of electricity and electricity transmitted over a power grid. Once the electricity is converted to another form, it ceases to be electricity and the energy is in the form of final use and possible loss due to non-unit performance. For example, with the use of a lamp we have light (light energy) and with a radiator the electricity is converted into heat (thermal energy).

Modern society is based on electricity for the smooth running of most of its activities. Most of the devices that surround us operate on electricity. Electricity accounts for 40% of Greek household consumption with the largest percentage being used for lighting, use of electrical household appliances, water heating and cooking.

Electricity is produced in a number of ways. In Greece, the main production stations are the thermal production stations (combustion of lignite, oil and natural gas), the large hydroelectric power plants and the production stations from Renewable Energy Sources (RES).

The average consumer does not know the size of his electricity consumption. Household consumption accounts for 34.6% of total electricity consumption, with the average household consumption being 3758kWh / year and the average household consumer consuming 1520kWh / year (Statistics 2014). The sense of cost of electricity consumption is confused with the total amount of electricity bill, which includes municipal fees and public television. Energy costs in Greece consist of two parts, supply charges / competitive charges which vary depending on the provider / supplier and adjustable charges which are common to all consumers. In addition to some fixed charges, which usually depend on the Consumer Power Consumption and correspond to a small percentage of the account, the remaining charges are calculated based on the number of kilowatt hours consumed.

The main unit of measurement of electricity is the watt-hour (Wh). Depending on the size of the power generation or consumption, the kilowatt hour (kWh) units equal to 1000Wh and the megawatt hour (MWh) corresponding to 1000kWh are often used. The term electric power (P) is also quite common. Electric power is the rate of consumption or production of electricity and the unit of measurement is the watt (Watt / W). The description of most devices includes their electrical power, as the energy consumed depends on the operating hours of the device. Respectively, in the production stations there is the term Installed Power, as the amount of energy produced is a function of the duration and the operating conditions of the station. What is worth noting is that the contribution of a production station to the total energy production differs from the percentage of the station in the total installed capacity. RES production stations (excluding large hydroelectric power plants) account for 33.6% of the total installed capacity, but for their percentage in the monthly electricity production it reached only 23.9% (October 2019). On the other hand, gas units account for 27.2% of the installed capacity, but their share in electricity production for the same month reached 49.9%.

The energy with which our planet is powered comes almost entirely from the sun. A small percentage of the earth’s energy is geothermal energy, which is the thermal energy of the planet and cosmic radiation.

Solar energy is nuclear energy that comes from the fusion and fusion of hydrogen nuclei and the creation of the nuclei of the chemical element helium.

Many natural phenomena, such as wind and rain, are caused by sunlight. However, the term solar energy usually refers to the energy we receive from the sun directly through radiation. This includes heat, light energy and radiation of other frequencies.

To exploit solar energy, two types of basic systems are used: active and passive solar systems. Passive systems take advantage of the natural properties of solar radiation and design a building based on optimal orientation and the use of appropriate building materials. In active systems there is a collection of solar radiation which is transported either in the form of heat or in the form of electricity for final consumption, using specially designed devices. A subcategory of active solar systems is photovoltaic systems, which convert solar energy into electricity.

Energy Market

The biggest disadvantage of electricity is its difficult and almost impossible long-term storage. In order to be stored, electricity is first converted into other forms, such as chemical or dynamic. Each conversion of energy from one form to another involves losses, usually thermal. For this reason, the production of electricity must be synchronized with its consumption. This need for direct consumption of electricity combined with the distance between the points of production and consumption led to the construction of a network of electrical networks. The operation of the electricity market / distribution / transport is very complex and with the opening of the electricity market many new roles have been created. That is why there are supervisory authorities who regulate the energy market. This role in Greece is played by the Energy Regulatory Authority (RAE).