energies Article Power-to-Steel: Reducing CO2 through the Integration of Renewable Energy and Hydrogen into the German Steel Industry Alexander Otto 1,2, Martin Robinius 1,2,*, Thomas Grube 1,2, Sebastian Schiebahn 1,2, Aaron Praktiknjo 3,4 and Detlef Stolten 1,2,5 1 JARA-ENERGY, 52425 Jülich, Germany; [email protected] (A.O.); [email protected] (T.G.); [email protected] (S.S.); [email protected] (D.S.) 2 Institute of Energy and Climate Research: Electrochemical Process Engineering IEK-3, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany 3 JARA-ENERGY, 52074 Aachen, Germany; [email protected] 4 Institute for Future Energy Consumer Needs and Behavior (FCN), RWTH Aachen University, Mathieustr. 10, D-52074 Aachen, Germany 5 Chair of Fuel Cells, RWTH Aachen University, c/o Institute of Electrochemical Process Engineering (IEK-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., D-52428 Jülich, Germany * Correspondence: [email protected]; Tel.: +49-2461-61-3077 Academic Editor: Bin Chen Received: 13 February 2017; Accepted: 17 March 2017; Published: 1 April 2017 Abstract: This paper analyses some possible means by which renewable power could be integrated into the steel manufacturing process, with techniques such as blast furnace gas recirculation (BF-GR), furnaces that utilize carbon capture, a higher share of electrical arc furnaces (EAFs) and the use of direct reduced iron with hydrogen as reduction agent (H-DR). It is demonstrated that these processes could lead to less dependence on—and ultimately complete independence from—coal. This opens the possibility of providing the steel industry with power and heat by coupling to renewable power generation (sector coupling). In this context, it is shown using the example of Germany that with these technologies, reductions of 47–95% of CO2 emissions against 1990 levels and 27–95% of primary energy demand against 2008 can be achieved through the integration of 12–274 TWh of renewable electrical power into the steel industry. Thereby, a substantial contribution to reducing CO2 emissions and fuel demand could be made (although it would fall short of realizing the German government’s target of a 50% reduction in power consumption by 2050). Keywords: power-to-steel; CO2 reduction in steel industry; sector coupling; renewable energy for steelmaking; alternative steelmaking processes 1. Introduction The growth of the global economy and population is strongly associated with a continuous increase in primary energy demand. In 2012, 81% of energy was generated by fossil fuels, which emitted around 30.2 billion tons of CO2 [1]. In its World Energy Outlook 2012 [1], the International Energy Agency (IEA) outlines in the “450 Scenario” that the average increase of global temperature ◦ could be limited to 2 C if CO2 emissions could be reduced to 22 billion tons a year by 2035. This would mean that annual global CO2 emissions must be reduced by approximately 30% from the year 2012 until 2035. As a worldwide leader in climate protection-focused policy, the targets of the German government are more ambitious. In its energy concept 2010/2011, it set out the goal of reducing greenhouse gas emissions in Germany by 80–95% by 2050 against 1990 levels, with a simultaneous reduction of electrical power demand by 25% and primary energy demand by 50% by 2050 against Energies 2017, 10, 451; doi:10.3390/en10040451 www.mdpi.com/journal/energies Energies 2017, 10, 451 2 of 21 2008Energies levels. 2017 The, 10, primary 451 means foreseen for achieving this is the expansion of renewable2 energies,of 21 which are intended to provide 60% of final energy consumption and 80% of power production by 20502008 [2]. Therefore,levels. The theprimary German means landscape foreseen for has achiev seening a continuous this is the expansion expansion of of renewable wind turbines energies, during 2003which to 2015 are from intended 14 to to 45 provide GW and 60% photovoltaic of final energy installations consumption in theand same 80% of time power from production 0.5 to 39 GWby for 2050 [2]. Therefore, the German landscape has seen a continuous expansion of wind turbines during power production [3]. 2003 to 2015 from 14 to 45 GW and photovoltaic installations in the same time from 0.5 to 39 GW for However, both technologies are characterized by fluctuating electrical power provision due to the power production [3]. volatile natureHowever, of wind both andtechnologies solar radiation, are characterized so that thereby fluctuating are times electrical when supply power ofprovision electricity due isto scare and timesthe volatile when nature it is abundant. of wind and To integratesolar radiation, a high so proportion that there are of windtimes andwhen solar supply power of electricity into the energyis system,scare a large-scaleand times when storage it is abundant. solution is To required integrate to a high compensate proportion for of the wind temporal and solar imbalances power into betweenthe productionenergy system, and demand. a large-scale For thisstorage task, solution power-to-gas is required technologies to compensate that for convertthe temporal surplus imbalances power into otherbetween forms of production final energy and such demand. as thermal For this or task, chemical power-to-gas energy (e.g.,technologies hydrogen that or convert synthetic surplus methane) are suitable,power into even other though forms of electrical final energy power such has as ther themal highest or chemical degree energy in energy (e.g., hydrogen [4–6]. The or production synthetic of gasesmethane) using excess are suitable, electrical even power though at electrical times when power more has electricitythe highest than degree needed in energy is produced [4–6]. The offers production of gases using excess electrical power at times when more electricity than needed is different opportunities. On the one hand, the gas can be reconverted into electrical power with gas produced offers different opportunities. On the one hand, the gas can be reconverted into electrical turbinespower or with fuel gas cells turbines during or periodsfuel cells whenduring demandperiods when for electricaldemand for power electrical is higherpower is than higher production. than On theproduction. other hand, On conventionalthe other hand, gas co powernventional plants gas can power be usedplants for can backup be used power for backup to compensate power to gaps in electricitycompensate production, gaps in electricity with the production, gases produced with the beinggases produced used in otherbeing applications,used in other applications, such as fuel for transportationsuch as fuel or for for transportation heating in several or for heating sectors in [ 5several,7,8]. The sectors direct [5,7,8]. or indirectThe direct use or ofindirect electrical use of power fromelectrical renewable power energies from renewable to provide energies heat, cold to provi andde operating heat, cold power and operating across allpower sectors across is alsoall sectors known as sectoris couplingalso known [9], as which sector is coupling shown in[9], simplified which is shown form inin Figuresimplified1. Furthermore, form in Figure synthetic 1. Furthermore, methane or hydrogensynthetic can methane be used directlyor hydrogen as a can feedstock be used in directly the chemical as a feedstock industry in the [10 ].chemical The integration industry [10]. of renewable The integration of renewable energies into different shapes, applications and sectors can lead to a energies into different shapes, applications and sectors can lead to a reduction in CO2 emissions beyond reduction in CO2 emissions beyond the power sector [6,11,12]. Although the step of converting the power sector [6,11,12]. Although the step of converting hydrogen to methane incurs additional hydrogen to methane incurs additional energy (η = 80%) [4,5], an advantage of synthetic methane is η energythat ( it= can 80%) be fed [4,5 directly], an advantage into the natural of synthetic gas grid methane so that existing is that infrastructure it can be fed and directly technologies into the for natural gas gridheat so generation that existing can be infrastructure used. and technologies for heat generation can be used. Figure 1. Principle of sector coupling, description from [9]. Figure 1. Principle of sector coupling, description from [9]. However, renewable power is not always directly convertible, especially in certain industrial However,processes. This renewable is exemplified power by is the not steel always industry, directly which convertible, is mainly dependent especially on incoal certain or coke, industrial not processes.only as This an energy is exemplified source but by also the for steel necessary industry, process which engineering is mainly dependent[13]. In a conventional on coal or blast coke, not onlyfurnace, as an energy coal or sourcecoke serves but as also a reducing for necessary agent, heat process provider engineering and ensures [13 the]. Inmechanical a conventional stability blast furnace,of the coal different or coke layers serves of ascoke a reducingand iron ore agent, inside heat the provider furnace (see and also ensures Section the 4.1). mechanical For the need stability to of reduce CO2 emissions is particularly acute in steelmaking, as it constitutes one of the most energy- the different layers of coke and iron ore inside the furnace (see also Section 4.1). For the need to reduce and carbon dioxide-intensive industrial processes worldwide; Germany, serving as a case study in CO2 emissions is particularly acute in steelmaking, as it constitutes one of the most energy- and carbon dioxide-intensive industrial processes worldwide; Germany, serving as a case study in this paper, is no Energies 2017, 10, 451 3 of 21 exception (see Section3)[ 14]. The literature contains many studies that deal with the overall potential of CO2 reduction in the steel industry in terms of increasing efficiency [15–18]. Fujii and Managi (2015) [19] for example proposed and measured optimal production resource reallocation using data envelopment analysis.