GETEC VPP: Integration of decentralised energy generation systems


Electricity market 2.0

GETEC digitalises and integrates your decentralised energy generation system. This boosts the profitability of your system and helps achieve the energy transition.

Constant power supply through renewable energies

In the past, flexible consumers played a minor role in the power supply system, because of excess capacities on the production side that were financed by the electricity consumers. The flexibility demand on the power system is changing in the context of the move toward renewable energies.

The price signal is the core element of the power supply market 2.0. The flexible use of producers and consumers is gaining increasing traction because of the continuing expansion of renewable energies.

In the future, power generation in Germany will rely on renewable energies at a constantly growing rate. Power plants with conventional energy sources will increasingly be replaced with renewable energies as a result of policy-defined goals. Power production is high in times of strong wind and sun irradiation and very low at night and/or during low-wind times. Still, a reliable power supply must be guaranteed throughout the day. Alternatives to conventional power plants must be set up in order to achieve a constant power supply with renewable energies.

Alternative supply by means of the virtual power plant

The virtual power plant (VPP) is one alternative. A VPP is a network consisting of

  • grid operators,
  • decentralised power generation systems,
  • the power supply market,
  • energy storage units and
  • the energy consumer.

  

A VPP can be operated with fossil fuels or with renewable energies. Photovoltaic systems, wind turbines or biogas CHP plants are integrated into units and controlled jointly. The virtual power plant is not situated in a central location, and the power supply is no longer dependent on a fixed power plant. A digital platform is used for the communication among the individual systems. This enables the power producers, grid operators and energy consumers to communicate with each other in real-time. The virtual power plant combines the power generation from the individual power generation systems and/or the power demand of the individual consumers, by feeding or removing power into or from the public power grid.

What appears to be a straight-forward and reproducible principle at first glance is highly complex and challenging in terms of its implementation. Like any large-scale power plant, a virtual power plant is a critical component for the systems of the European supply landscape. It is vital that the grid stability is guaranteed at all times.

  

Function and design of a virtual power plant

A complex and well-planned communication system capable of determining with the greatest possible degree of accuracy the amount of power that needs to be supplied or purchased at any given time is required for the connection of the individual systems. This type of monitoring requires a control station system that enables real-time monitoring and control. The precisely timed documentation of consumer data, its evaluation as well as the smart communication of participants among one another are important factors.

The remote control technology is based on a standardised data transfer platform as well as data formats that make it possible to switch, control and monitor processes. A reliable data transfer is extremely important, because of fluctuations not only in the daily power consumption, but also in the power generated by means of renewable energies (wind and solar). With this in mind, meteorological models must also be considered in order to improve the projected demands and generation.

Smart systems are required to offset fluctuations in the generation and demand and to prevent bottlenecks or overloading of the power grid. These intelligent systems are used for the smart integration of all components of a virtual power plant, such as

  • the energy sources,
  • power producers,
  • energy storage units,
  • consumers and
  • grid operating resources

(smart grid).

An integration point is required to connect the system to the virtual power plant. The data is transferred to the virtual power plant and at the same time controlled at one-minute intervals by way of this connection. A bidirectional connection to the decentralised unit exists for the data communication by way of a cable link or radio engineering.

Several requirements must be fulfilled for the integration of decentralised generation systems into the virtual power plant. The format VHPready (Virtual Heat and Power Ready) is a standard for the control via a control station. A better and smarter control to a virtual power plant can be achieved by means of this communication standard. Moreover, the interfaces to the processing system must be standardised and have a uniform software version. Aside from the communication within the virtual power plant, the increased safety requirements for the energy system as a whole are of particular significance for the protection against unauthorised access.


Producers and storage units

Engine-based cogeneration systems can be operated conventionally with natural gas or heating oil or with regenerative energy sources such as vegetable oil, biogas/biomethane or other renewable raw materials. By linking it with the virtual power plant, the CHP unit can additionally achieve profits by way of commercialising balancing energy. When “positive” and “negative balancing power” is retrieved, the power plant is adjusted upward or downward to prevent a collapse of the power grid caused by an imbalance between the generation and consumption.

Emergency power systems are provided in many places in case of an emergency, including in

  • computer centres,
  • medical facilities or
  • banks.

In case of an unexpected power outage during vital moments, they must be fully functional within several seconds. However, as they are not in use most of the time, their capacity is not optimally exploited. This is where virtual power plants offer a solution: The emergency power systems are integrated into a virtual power plant, thereby participating in the balancing energy market. If the power consumption is too high compared to the power production, additional power must be generated for the sake of grid stability. The emergency power system integrated in the balancing energy market produces it for the required time frame and stabilises the grid. Additional profits are generated with the power supply via balancing energy market. A control room permanently ensures that the system is fully operational and functional.

A fuel cell converts the chemical energy of a fuel (e.g. hydrogen or methanol) into electricity and warm water by way of an anode and cathode. This is a flameless kind of “incineration” (oxidation). Thus, the fuel cell is an ultra-efficient and environmentally friendly power generator. Since the chemical energy can be converted in large part into electrical energy, the electrical efficiency is higher than with conventional thermal processes. As a result, the fuel cell too is a promising component for the energy transition and for a virtual power plant. In spite of the high electrical efficiency, the absolute electrical power capacity of a fuel cell is fairly low. Therefore, fuel cells are used primarily as a “electricity-generating heater” in residential buildings.

Heat pumps are ideal for use in virtual power plants because they are capable of converting excess power into heat, which can be stored easier than power. In times when wind parks and photovoltaic systems produce excess power, it can be used in an intelligent way by a heat pump.


Demand response

Demand response means a flexible mode of operation by producers and consumers, driven by signals from the electricity market. The supply of power from renewable energies is subject to strong fluctuations, resulting in an increased demand for balancing power and balancing energy. Analogous to the expansion of renewable energies, the flexible use of producers and consumers is gaining increasing importance. By turning on and off producers, demand response automatically counteracts fluctuations in the grid. The power grid is stabilised and a high supply security safeguarded. The response to the power supply market occurs in real time and attractive added benefits can be generated.

Primary and secondary balancing power

The primary and secondary balancing powers are of vital importance for the stable maintenance of the power grid at 50.00 hertz. Primary balancing power must be available in its entirety within the first 30 seconds of the demand, and hence represents the first stage of the stability mechanism. The second stage is the secondary balancing power, which must be available after five minutes at the latest. The tertiary balancing power (also minute reserve) must be available after 15 minutes at the latest. Depending on the demands, the primary and secondary balancing powers are required to balance different degrees of fluctuation.

Economic viability: Risk-free energy sale

The virtual power plant offers a large variety of possible applications. In so doing, a smart process and control technology always represents the indispensable core element. The systems must be able to react instantaneously to the slightest of changes on the market. Two options exist for the flexible sale to third parties of power generated in accordance with the EEG [Renewable Energy Sources Act]:

  • direct marketing on one’s own responsibility (market premium model) or
  • the legally stipulated allowance from the grid operator obligated to purchase the power.

The market premium and the market premium model are intended to promote the direct marketing of power generated with renewable energies. With direct marketing, the produced power is sold directly to the client. The grid operator is excluded from the otherwise common marketing cycle, in which the power is normally transferred to the consumer. In so doing, the system operators are not compensated in accordance with the EEG, but by way of the market premium model. The purpose of these premiums is to encourage the system operator to feed in power based on the demand. The power is sold at the power exchange and the operators are compensated with the regular market price. This price is usually considerably lower than the feed-in allowance set forth in the EEG. The resulting difference at the expense of the system operator is compensated by the market premium. Furthermore, system operators can participate in the balancing energy market, enabling them to generate additional revenue.

 

If the power is sold to the grid operator via compulsory allowance in accordance with the Renewable Energies Act (EEG), the system operator receives a consistent amount of the allowance for the sold power. The “green power” is purchased and paid by the responsible grid operator. This allowance is significantly higher than the common market price. The difference between the market price and the price of the allowance is passed on to the end users by way of the cost allocation according to the EEG. The grid operators jointly agree on the amount of this EEG levy every year. The system operator can decide whether he would like to receive payment for the produced power in accordance with the EEG or market it directly. In the medium term, the legislator is aiming for a compulsory direct marketing or self-consumption for any power generated with renewable energy systems.

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