Small engine-based cogeneration plants and fuel cells can be combined together and operated as a network. Such a regional virtual power plant (RVPP) is currently being tested by researchers at the TU Dresden and EWE AG in the Oldenburg area. They are developing control and regulation concepts for operating in networked systems until the end of 2017.

The energy supply in Germany will be significantly decentralised in future. To achieve this, however, the potential flexibility provided by the regions must be utilised and there needs to be a greater interconnection of the electricity, gas and heating supply by using communication technology. Regional virtual power plants offer suitable solutions for this. They link the electricity and heating market, accelerate the integration of renewable energy and help reduce the need to expand the electricity grid. As the conversion technology with the currently highest efficiency, combined heat and power (CHP) complements this strategy perfectly: in particular micro-cogeneration (micro-CHP) units are suitable for this. They are aimed at the market offered by the 15 million single- and two-family homes in Germany – with correspondingly high efficiency gains.

Since 2011, scientists at the TU Dresden have been investigating the interaction between co-generation plants and electrical loads in buildings. In addition to measuring mini- and micro-CHP units in the laboratory and analysing different operating conditions, they researched superordinate control and optimisation strategies in the system network. They also developed a low-voltage emulator for depicting the local power grid. What had been lacking until now, however, was the large-scale testing of a virtual plant network. In particular, municipal utility companies and regional energy providers are showing considerable interest in this concept, since virtual power plants provide an important technological basis for future energy services in a changing market.

Field test intended to show benefits of the plant network

How can the energy production and demand be balanced regionally? This question provides the background to the field test with 15 micro-cogeneration units and two fuel cells in the Oldenburg area. The systems are connected to a control and marketing software and act together as a virtual power plant. This makes it possible to generate electricity and heat in accordance with demand and stabilise the local electricity supply grid. Researchers can therefore influence the operating mode of the systems or utilise, for example, hot water storage tanks. In addition, the surplus electricity increasingly common with the growth of renewable energy can be converted into usable heat with heating blades found in local storage systems.

Concept is technologically neutral

Virtual power plants currently generally consist of a few large plants, but smaller units are also suitable in principle. The regional virtual power plant is technologically neutral, which means, for example, that photovoltaic modules and battery storage systems can also be connected. The RVPP research project being conducted by the TU Dresden and EWE AG is focussing on CHP plants and fuel cells, and is investigating by way of example a number of fundamental questions: Are the plants installed by the users controllable and do the users accept the remote controlled operation of their plants? What are the options for universal interfaces? How stable are these plants, systems and communication links in remote operation? In addition, the focus is also on economic aspects and future marketing options. Based on the findings from the research, it is later intended that small generators and loads can also be linked flexibly in a virtual power plant using the RVPP gateway. After all, such a concept can be applied to many German cities and regions.

One year of continuous operation shall begin in October 2016, after which the data provided will be comprehensively analysed. Other properties will then be included to gradually enlarge the capacity of the RVPP system.

Further details and documents regarding the project, which is entitled "Field testing of the regional virtual power plant based on micro-CHP technology", are included in the project summary in the eneff-waerme.info web portal.

(fr)