# More Sustainability in Industry through Industrial Internet of Things?
## State of the Art
### Sustainable Energy  
The IIoT also offers opportunities to strengthen the role of sustainable energy in industrial production. In this paper, the term sustainable energy subsumes both improvements with regards to energy efficiency as well as the enhancement of renewable energy. The following paragraphs will present approaches of how IIoT technologies can be used to save energy and to combine digitized and interconnected factories with renewable energy systems. Energy can be saved, e.g., by optimizing or replacing specific (non-)digital technologies with digital more energy efficient alternatives, by applying new software solutions that offer energy optimization functionality, or by improving business processes based on the additional data generatedin digitized factories. Thirty percent of the total energy consumption by machine tools is consumed while they are in stand-by mode [26]. [PERSON] et al. have taken up this challenge and developed a generalized approach to manufacturing energy efficiency based on a machine-level study [27], while [PERSON] et al. present a case study on the remote monitoring of robot energy consumption, demonstrating the capability of intelligent applications for managing manufacturing processes [28]. An impressive example for more energy efficiency based on process optimization is presented in [29; 30], where an algorithm is introduced that allows reducing energy consumption for industrial robots up to 30% by adapting acceleration and deceleration behavior, without substituting hardware or negative consequences on the production rate. A more IT-based concept is the energy simulation of manufacturing systems. [PERSON] et al. argue that environmentally related aspects are currently not sufficiently considered as standard functions in manufacturing system simulation tools [31]. One potential solution approach is presented by [PERSON] et al. where a flexible energy flow-oriented manufacturing system was simulated [32]. Similarly, [PERSON] et al. analyze the sustainability impact of manufacturing by introducing a new information model for product lifecycle management that integrates an energy simulation framework [33]. A more general approach also aiming at energy efficiency in manufacturing is the methodology for planning and operating energy-efficient production systems [34]. Likewise, [PERSON] et al. propose a multi-purpose digital simulation approach dealing with sustainable manufacturing systems design through Discrete Event Simulation and 3D digital human modeling. This allowed in a demonstration case from the aerospace industry for a very significant reduction of energy consumption as well as an increase in energy efficiency [35]. A review by [PERSON] et al. details modeling approaches and discusses the simulation tools that allow for combining Building Energy Modeling and Manufacturing Process Simulation into a holistic approach [36]. IIoT technologies also contain the potential to increase the share of renewable energy consumed in industrial production. At the same time, they can help to reduce the volatility of renewable energy systems either: (a) by flexibly adapting their energy consumption; or (b) by storing or releasing energy (with the help of Power-to-X procedures) depending on the current availability of renewable energy in the market. A prerequisite for all these approaches is to integrate digitized factories as active players into the energy system to immediately detect and communicate the availability of energy in the system and to select and steer the flexible industrial loads. One way of achieving this integration is making use of so called Virtual Power Plants. Virtual Power Plants are heterogeneous coalitions of distributed energy resources, generally composed of intermittent renewable sources, storage systems, flexible loads, and small conventional power plants that need to negotiate some bilateral contracts in advance prior to participating in the day-ahead market [37].