Cross-Energy Management (CEM)

The optimization of multiple heterogeneous energy resources and consumers within a closed system is sometimes referred to as Cross-Energy Management (CEM). The CEM concept goes even further than the microgrid concept discussed previously, as it does not necessarily rely solely on electricity for energy storage and transfer. In many cases, however, electricity still plays an important role in CEM. In the following section, we will examine two examples of CEM.

CEM in Farms

Farms are an interesting area for Cross-Energy Management due to the many different forms of energy they produce and consume. Examples include:

  • Electric power: Wind power, photovoltaic systems, power plants
  • Thermo-chemical resources: Solid fuels and materials (wood, pellets, plant residues), liquid fuels (pure plant oil, biodiesel, etc.), and gaseous fuels (biomethane)
  • Thermal resources: Solar thermal systems, geothermal systems

Energy use on a farm can take multiple forms, including the following:

  • Power: Electric and mechanical power for stationary and mobile machinery and equipment
  • Heat: Required for heating stables, greenhouses, and farm buildings, as well as for drying goods and products
  • Cooling: Required for storing products like milk

Managing supply and demand as well as the transfer of energy between these different energy forms is both a challenge and an opportunity. Energy transfer will not always have such a reliance on electric energy; for example, pellets might be burned directly for heating purposes. However, electricity does have the potential to play an important role in several areas related to farm operations. Naturally, this is a domain in which farm equipment manufacturers like John Deere take a keen interest. Prof. Peter Pickel, Deputy Director at the John Deere European Technology Innovation Center, says: “Electricity plays a key role in agriculture, helping to bridge the gap between stationary energy creation and mobile energy consumption. No other industry is so well positioned to optimize interaction between the stationary network and the mobile machinery and equipment. A key factor here is that after work is completed, vehicles usually return to their home base, where they have access to necessary infrastructure such as charging stations. In addition, farm equipment can easily cope with the exchanging of heavy batteries, as they have lifting devices built in.”

Vision: Sustainable Energy Supply for Agricultural Machinery (Source: John Deere)

Vision: Sustainable energy supply for agricultural machinery (Source: JD1)

Renewable energies play a major role in this area. As Prof. Pickel explains: “Farms have large roofs and open spaces that can be used to generate photovoltaic and wind energy. Other important energy sources include biomass from farming and liquid manure. These energy sources are already widely used today. Where we see the biggest potential for improvement is in the flexible management of power flows across multiple energy sources and consumers, a concept we call Cross-Energy Management or CEM. Our goal is to create semi-autonomous energy networks that help to cut energy costs and even have the potential to generate additional revenue through the sale of excess energy. Furthermore, these networks will be flexible and will support the national grid by increasing network stability.”

As we mentioned at the beginning of this section, CEM does not rely exclusively on electric energy. Biodiesel, pure plant oil, and methane can also be used to power farm vehicles. Another interesting approach is the use of excess energy to create mineral fertilizer. Nonetheless, the use of electric energy to power mobile machinery and farm vehicles is still an attractive option. This would require an efficient infrastructure for managing electric farm vehicles.

Grid Management and Plug-In Infrastructure

The first challenge to be addressed in using electric farm machinery in a CEM environment is to actually make this equipment available and to provide a plug-in infrastructure that facilitates easy operation and integration. John Deere has developed an interface technology in the form of a hybrid interface that enables both communication and power transfer. The concept was developed by John Deere and adapted by the AEF (Agricultural Industries Electronics Foundation). This AEF high-voltage electrical interface was used in John Deere’s Battery Boost tractor, a “grid plug-in hybrid system” that combines an electrically powered tractor with a large lithium-ion battery. This system will be presented for the first time at the 2015 SIMA agri-business show in Paris. The figure below shows both the tractor and the AEF interface.

John Deere BatteryBoost Tractor with AEF Power Interface [JD1]

John Deere’s Battery Boost tractor with AEF power interface [JD1]

The ability of the grid plug-in hybrid system to support both power transmission and communication between the different components is a key prerequisite for the next step, which involves the implementation of a VPP/MMS system to optimize a farm’s energy supply and demand. As seen in the Smart City Rheintal case study discussed previously, VPP/MMS features such as the forecasting, scheduling, and real-time optimization of energy supply and demand will be instrumental in implementing the vision of efficient Cross-Energy Management in farms.

CEM in Steel Production

Steel production is an industry involving very long-term planning and massive economies of scale. For example, in 2012/2013, ThyssenKrupp Steel Europe produced more than 11 million tons of crude steel at its state-of-the-art integrated steel mill in Duisburg, Germany [TK14.1]. This steel mill is the size of a small city, with its own harbor and hundreds of kilometers of roads and railway tracks. It consumes more energy than the private households in the city of Berlin combined.

Liquid crude steel is produced in a two-stage process. First, iron ore is reduced with coke and auxiliary reducing agents like pulverized coal in a blast furnace, producing liquid hot metal. This is carried to the next stage in its liquid form. In the second stage (the “steelmaking” phase), impurities are removed and alloying elements are added to produce the required steel quality. These processes require massive amounts of raw materials such as coal, iron ore, fluxes, alloys, and refractory materials. The key systems involved are coke plants (which carbonizes coal into coke), blast furnaces (which create liquid hot metal from coke, coal, iron ore, and fluxes), and converters in the BOF shop (which convert liquid hot metal into steel). Investment volumes for these systems can reach billions of dollars; investment horizons typically stretch over multiple decades.

A modern steel mill achieves very high levels of system integration, in which coke plants, blast furnaces, and steel converters as well as hot and cold rolling mills represent a highly sophisticated network of material and energy flow. In coke plants, blast furnaces, and steel converters, large amounts of high-energy gases are generated, which are then used in local electrical power plants or as a heat source. A by-product of current carbon-based metallurgy processes is very high carbon dioxide (CO₂) output, which is widely regarded as the primary driving force behind global warming. In order to address this issue, ThyssenKrupp AG has initiated a cross-sector technology transfer project focusing on converting process gases from steel production into valuable chemicals [TK14.2]. The electricity for this initiative is to come from renewable sources. Dr. Reinhold Achatz, Head of Corporate Function Technology, Innovation, and Sustainability at ThyssenKrupp AG, says: “The philosophy behind the project is a broad-based, cross-industry approach. This type of cross-system solution will deliver better results than today’s sector-specific solutions, which have already been optimized as far as possible. The collaboration between the steel and chemical industries aims to enable cost-effective carbon recycling in order to produce chemical products like fertilizers or fuel. The project thus has the potential to significantly reduce CO₂ emissions from steel mills by 2030.”


Towards a CEM in the Steel Industry

Towards CEM in the steel industry

The basic chemical processes and technologies required are available today. However, thus far, no major steel manufacturer has been prepared to make the massive investment needed to implement this type of approach. The project is a first step towards making this vision a reality, says Dr. Achatz: “The goal of the project is to resolve important practical issues such as the durability of catalysts, the purification of gas streams, and efficient process control. Converting process gases from steel mills into ammonia for use in fertilizer production is already technically feasible, though not yet commercially viable. This process would recycle part of the CO₂ contained in steel mill gases. Another possibility would be to produce methanol from steel mill gases, a process in which the CO₂ content could be almost entirely re-used.”

The use of renewable energies for chemical conversion requires catalysts and technologies that can cope with fluctuating operation conditions. Another challenge relates to the fact that converting all of the CO₂ contained in steel mill gases requires large amounts of additional hydrogen. This calls for new, cost-efficient technologies for producing hydrogen that can operate even with a sharply fluctuating energy supply.

As we can see, the electric microgrid concepts discussed earlier on in this chapter only play a subordinate role in a CEM scenario. The main focus here is on aligning the processes in an integrated steel mill with those in a chemical plant. The term “Energy” in “Cross-Energy Management” primarily refers to the energy stored in the gases emitted by the steel mill. Nevertheless, energy from renewable sources will be required for many of the chemical processes used to create methanol or fuel from the top gases produced in the steel mill. For example, top gases can be enriched with hydrogen (H₂) generated by the electrolysis of water. The electrolyzer can be powered by solar and wind electricity.

As a consequence, a CEM system must be created that manages the dynamic processes between the electricity supply grid, steel mill, and chemical plant. This CEM system will have to balance out current electricity prices to support the chemical processes on the one hand, and the overall status of the individual subsystems that make up the overall steel mill on the other, including maintenance programs, production profiles, etc.

Vertical Integration

Different levels of vertical integration for CEM in a cross-industry plant network

Dr. Markus Oles, Head of Innovation Strategy and Projects at ThyssenKrupp, says: “We are effectively looking at a cross-industry plant network. This will require new levels of vertical and horizontal integration for CEM. We will have to leverage the Internet of Things and concepts from Industry 4.0 to ensure both full vertical integration from the top-level system down to the individual production units as well as horizontal integration of plant units, such as large individual high-power drives in rolling mills. New quality sensors will have to be added to the production units to support the top-level process. Performing an efficient analysis of the big data obtained from these sensors will be paramount.”

According to Dr. Oles, this data will include input from multiple areas:

  • Technical processes: Fuel-mix preparation, energy efficiency, energy transformation, resource transformation, resource transportation and storage, additional internal and external logistics processes
  • Economic data: Raw material prices, product prices, energy prices, production and operational costs
  • Sustainability: Life cycle analysis, energy usage, CO₂ footprint of products and processes

Controlling the top-level system based on this data will be an enormous challenge. One particular challenge will be to match input data and events with different time intervals, as shown in the figure above. These time intervals can range from seconds to weeks.

The complexity of this undertaking goes beyond what we have discussed so far in the context of Enterprise IoT. Our main focus – for example, in the Asset Integration Architecture – has been on the integration of individual systems. This example, however, calls for integration on a system-of-systems level (or even above). The proposed CEM solution comes pretty close to what we define as a “Subnet of Things” (SoT) in the introduction.

Given the long investment horizons in the steel industry, success will not come overnight. However, this initiative has the potential to make a very significant and positive contribution towards reducing the global CO₂ footprint. For this reason, it is a good example of the benefits that innovative integration solutions can offer.