Microgrids are smaller and independent grid structures as opposed to supra-regional distribution grids. They are based on the idea to generate energy in a decentralised and self-sufficient manner where possible. In the case of surplus energy in the individual microgrid, they are virtually connected to the public grid to balance the load. The components within a microgrid itself also help to balance the load. The bulk battery, as well as bidirectional EV batteries, act as central interconnectors of temporally fluctuating energy flows between the generators (PV and CHP) and consumers (tenants and e-mobility). Surplus energy is stored, balancing the load, and can later be reintroduced into the microgrid for consumption when supply is low and demand high.
At the Baumwollspinnerei, CENERO, in conjunction with the EU project, SPARCS, is implementing a microgrid concept with various components, interconnected through the digital load and energy management, to ensure maximal efficiency. These components include a photovoltaic plant (PV), a CHP system, bulk batteries, and bidirectional charging points. The PV plant on the roof of one of the buildings, feeds renewable energy into the microgrid where it can either be directly utilised by the tenants, stored, or fed into the greater public grid. The CHP unit can be used as a backup when the PV supply is insufficient, and the storage is empty. The bidirectional charging of EVs assumes a prosumer nature. Acting as a consumer, the bidirectional EV offers sustainable mobility by consuming the renewable power (from the PV plant), which is temporarily stored in its battery, while acting as producer or generator, it can supply the grid with stored energy in times when the demand is excessive.
A further component included in the efficient use of energy in the grid is the intelligent steering of heat supply in response to demand. Smart thermostats are installed which communicate information about the heating demand of selected rental areas. They are also able to intelligently learn about their surrounding conditions and to integrate these into the heating process. Therefore, the heat-buffering potential of the historical walls form part of the heating process. If no there is no longer a demand for heat, the hardware communicates this to the corresponding steering valve and the pump system, which distributes the heat is switched off.
The digital interconnection between all these generators, consumers, storage systems and the subsequent public grid is where the challenge lies. This is neither sufficiently standardised nor adequately tested from a technical point of view. A load management concept for the efficient interconnection of self-generation and consumption is required in the area network, and a digital interface for the coordination of the energy transfer from the distribution network and vice versa must be implemented.
The power grid load is constantly increasing due to the ever-greater fluctuations in the input and output of energy. Since the frequency band of a stable power grid is very narrow, the amount of energy in the grid should be as constant as possible. The regulation of a feed-in or the additional consumption of energy can make this possible. To ensure that this is done in real time and in a way that is compatible with the system, digital load management is a central component of future-proof electricity grids. At the interface between area grids and large distribution grids, energy quantities can be exchanged on a larger scale, which promotes regional microgrid stability.
The possibility of avoiding expensive load peaks and electricity purchases through optimised own power generation plays a major role in the economic feasibility of load management. The integration of load management for grid stability also improves the efficiency potential of the network by identifying different types of demands and directing energy flow to specific areas, so as to avoid waste within the microgrid as a whole. For instance, by monitoring the generation, allocation and demand, the high capacity of PV power generated at midday can be directed to be used for the operation of an air conditioning system (which is in high demand at midday). In many cases, energy that is normally considered waste, can be used proactively elsewhere within the system, as often the case with thermal energy- the CHP system is a good example of sufficiency use of thermal energy as a biproduct.
For the required connectivity between individual producers and consumers with each other and the public grid interface, remotely readable smart sensors and meters are installed on site. The digital communication protocol used, is the innovative LoRaWAN wireless radio system. It is highly effective for the digital coverage of large building estates due to the long range and low energy consumption of the individual transmitters and receivers. This sensor technology is coupled with cenero.one, the company's own energy management system, and a load management system, using a central software platform. Using a combination of software and hardware, specifically calculated together with Stadtwerke Leipzig, the microgrid is coupled to the upstream public grid.
Cenero.one gives you a graphic, easy to analyse, view of the production and consumption of all your energy sources on one platform, allowing you to make direct comparisons and to manage the balancing of the network effortlessly. Automated alerting systems, linked to a notification feature can be activated to inform you if there are any unusual loads produced or consumed. The software’s learning potential allows it to forecast fairly accurate patterns for future usage, allowing you to strategize the energy flows in advance. The platform also makes the detection and locating of loses simple. A further advantage is the accuracy and transparency of the available data needed for billing of tenant consumption, which is a vital point to consider within a microgrid.