The energy flow in the ENERTRAG Verbundkraftwerk®

An ENERTRAG Verbundkraftwerk^® includes many onshore wind turbines and photovoltaic systems that produce electricity.  

Wind turbines utilize the power of the wind to drive rotating rotor blades. The mechanical energy generated in this way is converted into electrical energy. Electricity can be generated from wind energy day and night. 

Photovoltaic systems generate clean electrical energy from the sunlight entering the solar cells. 

The hybridization of wind energy and PV systems has advantages: Wind and sun complement each other perfectly. They only very rarely generate a high output at the same time. Due to the spatial expansion of the ENERTRAG Verbundkraftwerk^® and the large number of systems, the feed-in to the public grid is many times more stable than with individual systems or individual wind fields. 
A positive side effect is that the public grid is significantly better utilized, as the fluctuations in generation do not reach the grid in the first place. 

The electricity from the ENERTRAG Verbundkraftwerk®’s many wind and photovoltaic systems is bundled into local collection centers and substations. The electricity is collected and fed into the transmission grid via a single large substation. 

The collection grids are pure power plant grids. They connect the systems of the interconnected power plant with each other and are not part of the public grid. This ensures considerably lower grid costs and highly simplified control. Due to the large-scale and decentralized feed-in, the power plant grid remains very stable. 

Substations collect electricity from various generation plants and transmit it to the power plant grid. The hybridization of wind and solar energy with hydrogen production has the advantage that the substations are optimally utilized.

In future, the hydrogen produced will be fed into the gas grids. They can transport large quantities of energy generated from wind power in the form of hydrogen.

All energy systems in the ENERTRAG Verbundkraftwerk®, from generation, conversion and transportation to the grid feed-in points, are reliably controlled by our proprietary control system. This ensures that energy is generated in a stable manner and fed into the grid as required.

Electricity that is not needed in the transmission grid is converted by the ENERTRAG Verbundkraftwerk^® or stored - for example, in a battery.  

 The battery storage units at the ENERTRAG Verbundkraftwerk^® balance out fluctuations in the electricity grid and provide additional power when little primary energy is available. They can also be black-started. This means that they can restore the power grid independently in the event of a blackout. 

The energy from mixed parks and EEG plants contributes to the stability of the electricity grid.  

A significant proportion of the surplus electricity is converted into green hydrogen at the ENERTRAG Verbundkraftwerk®. This is because the gas is easy to store and transport. An electrolyzer splits water into hydrogen and oxygen using electricity. The hydrogen flows mainly into the local hydrogen network. 

A portion is temporarily stored on site and is available to the electricity sector on the few days of the year when there is a dark doldrums. The hydrogen is then converted back into electricity in the connected hydrogen reconversion plant.  

Most of the fluctuations in generation are therefore already balanced out within the ENERTRAG Verbundkraftwerk® or absorbed by hydrogen and heat storage systems. In this way, the energy generated is utilized to its full extent. The plants do not have to be curtailed. When there is little wind and sun, the energy comes from the storage facilities. 

Good to know: ENERTRAG Verbundkraftwerk® only produces green hydrogen, as the electrolysis is fuelled by renewable energy. 

On a few days a year, wind energy and photovoltaic systems produce an above-average amount of energy. However, the electricity sector, battery storage and hydrogen production are fully supplied at some point. In the ENERTRAG Verbundkraftwerk®, the systems do not have to be curtailed even then: The surplus energy is decoupled locally as heat, with the help of a wind heat storage system and as waste heat from hydrogen production. 

A wind heat storage system converts electrical energy into thermal energy by heating water using a heating rod. The extracted heat supplies households in the region via the district heating network. 

All systems are connected directly to the control center, the central monitoring and control unit, via control lines. From there, a team continuously monitors the operation of the entire ENERTRAG Verbundkraftwerk® and its components. This includes energy generation, conversion, distribution and grid connection. 

ENERTRAG has developed the Powersystem software in-house for control purposes. The control room team optimizes plant performance as required and can initiate and monitor technical services. 

An ENERTRAG Verbundkraftwerk® should be controlled via its own fiber optic network, which is not connected to the Internet. This provides security against hacker attacks. 

The electricity from wind and solar power plants is fed into the national transmission grid. 
 

Good to know: Separate grid connections for wind and PV are not required. One to two tenths of the installed generation capacity is sufficient for the grid connection. This is due to the complementary generation patterns of wind and solar, but above all due to the fact that the integrated consumers (electrolysers, heat generators) absorb the entire output, which is not matched by simultaneous electricity demand in the grid. For example, a grid connection capacity of only 100-200 megawatts is sufficient for 1 gigawatt of wind power and 1 gigawatt of photovoltaics.   

Green hydrogen from electrolysis is transferred to the hydrogen grid. 

Heat from the wind heat storage and electrolysis flows into the local district heating network and supplies people in the region.