A local power system consists of a number of components, each unique system can be interchangeable with what suits the local conditions. Any form of production and consumption are required by default. This is complemented with storage to keep balance and a good electricity quality. These interchangeable units are controlled by a central control system that ensures that the objectives set by the local energy system are met. For example, the objective might be to maximize self-consumption of renewable production, clear island-grid operation or minimize costs.
In the pilot project, located in the small village Simris, the local energy system consists of a wind turbine, solar cells and a backup power generator. Storage is a battery.
Renewable electricity production
Electricity production in the Local Energy System will be one hundred percent renewable and come from three different types of production sources – wind, solar cells and a backup power generator powered on renewable fuel.
A wind turbine is usually the largest part of the production of electricity in a local energy system. A wind turbine with a nominal power of 660 kW can annually produce between 1.1 and 1.5 GW.
E.ON is convinced that photovoltaic cells have an important role in the future energy system and that, therefore, is a natural part of the Local Energy System. Micro production of solar cells on the roof becomes all the more relevant and to create a system as real as possible, it is hoped that more customers will want to install solar panels on their roofs.
Backup power generator
Because both sun and wind are intermittent* energy sources they will need support in the form of regulating electricity production. A backup power generator is installed to provide this on the occasions when the energy system is active in island mode. When the local energy system is not in operation, the central grid will account for the supply of electricity which is not produced locally. Backup power generator will operate on a renewable fuel.
* Intermittent = something that only occurs once in a while and which at times is interrupted
Battery as energy storage
Energy storage in the form of a battery can be seen as the heart of the energy system. Together with an advanced control system, the battery will be the one that makes sure that the correct voltage and frequency are kept in the local network. It will take or give effect to constantly keep the system in balance.
For the components that are connected to the local grid to function, the frequency needs to be kept at 50 Hz at all times, with a deviation of up to 0.5 Hz upwards or downwards. For the battery to be able to keep this balance, it is important that it is never fully loaded or empty, the control system will ensure this. Battery and control system will also ensure that connection and disconnection from the central grid works. At check-in and cut-out the grids must be synchronized and the battery will help to regulate the voltage, frequency and phase angle so that the transition runs smoothly.
For a local electricity grid with renewable and intermittent energy sources, the battery system plays a very important role. Balance in the grid is a prerequisite for a good power quality at all hours.
The control system is the brain of the system
A sophisticated control system is the brain of the Local Energy System. It will ensure that all production units can communicate with each other so that it delivers electricity of good quality the whole time. Control and regulation equipment controls the frequency of the local network so that it always keeps the required 50 Hz. It also makes sure that the correct voltage and phase angle is maintained. Everything is carried out in close collaboration with the battery system which is called a "grid-forming unit". This means that the battery is the source for instant regulation if consumption increases or decreases.
Control equipment will help with information about the instantaneous production from every unit in the Local Energy System, which means that you can always see exactly where the electricity is produced. This is information that those who work with the system will greatly benefit from at analysis, but the information can also be served to customers who are interested in following the local production of electricity.
Customers’ electricity use
Generally, it is a big challenge for the micro grid to meet maximum output on the local grid that occur only on rare occasions. The production units must be able to meet these peaks in order for customers to get electricity into their homes at all times. But there is also another solution which is to try to reduce these peaks and create a smoother load curve.
This can be done by steeringdown loads when the system indicates that there is a lot of consumption and the production is not sufficient. It is usually a more economical way to manage a lack in capacity. In the first phase of the project Local Energy Systems no load management is included, the battery will solve these scenarios instead. When the power top is at its worst, the central grid helps.