Available online at www.sciencedirect.com ScienceDirect Energy Procedia 99 (2016) 392 – 400 10th International Renewable Energy Storage Conference, IRES 2016, 15-17 March 2016, Düsseldorf, Germany Necessity and impact of power-to-gas on energy transition in Germany Martin Themaa*, Michael Sternera, Thorsten Lenckb, Philipp Götzb a Technical University of Applied Sciences Regensburg, Research Center on Energy Transmission and Energy Storage (FENES), Seybothstraße 2, D-93059 Regensburg, Germany b Energy Brainpool GmbH & Co KG, Brandenburgische Straße 86/87, D-10713 Berlin Abstract The present paper gives an outlook on a bandwidth of required installed power-to-gas capacity in the German power sector fed by 100 % renewable generation until 2050 Two scenarios were simulated to quantify cost effects of power-to-gas on the electricity system: once with, once without additional short-term flexibility options to a system using fossil natural gas as sole flexibility option instead As a result, at latest in 2035, power-to-gas capacity expansion has to take place to reach required installed capacities of up to 89-134 GW in 2050 Application of power-to-gas as long-term flexibility leads to cost savings of up to 11,7-19 bn Euro enabling a fully renewable system in 2050 © 2016 by by Elsevier Ltd.Ltd This is an open access article under the CC BY-NC-ND license © 2016The TheAuthors Authors.Published Published Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of EUROSOLAR - The European Association for Renewable Energy Peer-review under responsibility of EUROSOLAR - The European Association for Renewable Energy Keywords: power-to-gas; energy storage; renewable energy; system costs; surplus energy; supply security; energy transition; decarbonization Introduction Facing climate change, the German federal government made a commitment to own energy policy objectives within their coalition agreement and energy concept in 2010: greenhouse gas emissions in Germany shall be reduced by 40 % * Corresponding author: Martin Thema Tel.: +49-941-943-9200; fax: +49-941-943-1424 E-mail address: martin.thema@oth-regensburg.de 1876-6102 © 2016 The Authors Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of EUROSOLAR - The European Association for Renewable Energy doi:10.1016/j.egypro.2016.10.129 393 Martin Thema et al / Energy Procedia 99 (2016) 392 – 400 until 2020 and by 80-95 % until 2050 compared to the amount of 1990 Power consumption is supposed to decline by one quarter in the same period of time (10 % until 2020, 25 % until 2050) while shares of renewable energy generation ought to rise up to 80 % in 2050 (40-45 % in 2025, 55-60 % in 2035) Furthermore, the aim is to reduce the final energy consumption in the heat sector by -80 %, the one in the transport sector -40 % until 2050 To avert dangerous consequences of climate change, these aims are not sufficient A fully renewable power supply in the year 2050 is required and feasible [1] Because of highest potentials and lowest costs, the main supporting columns of energy transition in Germany will be wind and solar power (photovoltaics) Therefore, one of the major tasks will be balancing the fluctuating, weather-dependent generation of wind and solar power at contemporary highlevel security of supply For this, amongst different flexibility options, energy storage becomes increasingly important In the following, necessity and impact of power-to-gas (PtG) for energy transition in Germany [2-4] will be introduced Methodology The need for renewable energy storage options is depending on a variety of aspects such as upcoming extensions in renewable power plant capacity, national and international grid expansion or demand side integration Today, there are no final and reliable answers to tell how exactly the future energy system will look like For this reason, evidence at which point of time power-to-gas is needed, only can be given throughout a range of time 2.1 Assumptions To determine the role of power-to-gas as energy storage option, a simplified approach is introduced: the German power supply at 100 % renewable generation in 2050 outgoing from a trend-scenario set up by the environmental organization Greenpeace e.V (Table 1) To turn out the effect of power-to-gas on the system, its costs are calculated once with and once without power-to-gas as a flexibility and storage option while alternative flexibility options are not considered At assumed CO2-costs of 100 €/t CO2 [5], coal is not profitable anymore For this, maximum balancing costs for fluctuations in power generation (with the use of power-to-gas) become clear as a ‘worst-case-scenario’ [2] and can be compared to a system whose supply security is assured only by fossil natural gas In reality, a renewable power system gets cheaper because of other flexibility options get into market which are at lower price for specific situations This is the reason why in an extended analysis of Götz et al [3], the effect of short-term storage respectively flexibility options were examined There, fluctuations below two days get balanced through short-term options, for cycles above this benchmark, power-to-gas gets into action Table Trend-scenario for a 100 % renewable power supply system in Germany on specifications of the environmental organization Greenpeace e.V Assumptions made for generation capacity to be installed in GW, gross electricity production in TWh and full load hours (VLH) of different renewable generation capacities As a basis of this expansion phase, the real German generation situation in 2013 is taken from AG Energiebilanzen1) [6] and German Ministry for Economic Affairs and Energy2) [7] * Including not-appearing other sources e.g domestic waste (difference: 5,2 TWh) Installed Capacity GW Trend-Scenario (2013) 100 % 131 33,662) 30 0,522) 135 35,92) 5,6 5,62) 8,1 8,12) 0,0312) Wind Onshore Wind Offshore Photovoltaics Hydro power Biomass Geothermal Sum renewable energy generation Shares of renewable energy on gross electricity consumption in Germany Gross electricity consumption/demand Gross electricity production in TWh Trend-Scenario (2013) 100 % 262 49,81) 120 135 28,31) 22,4 21,21) 48,5 42,61) 18 0,042) 606 TWh 147,11)* 100 % 23,4 % 1) 569 TWh 629 TWh 1) Full load hours Trend-Scenario 100 % 2000 4000 1000 4000 6000 6000 394 Martin Thema et al / Energy Procedia 99 (2016) 392 – 400 The trend scenario (Table 1) particularly passes forward the expansion of wind and photovoltaic generation For ecological reasons, biomass and hydropower generation is not and geothermal generation is build up only limited It is valid that throughout Germany, grid expansion entirely follows network development plans Additionally, energy exchange at cross-border interconnections is permitted for balanced imports and exports in an annual average Further substantially assumptions for the simulations are summarized in Table Table Additional assumptions for the simulation of the German energy system Indication Costs natural gas Costs emission certificates Efficiency gas-fired power plants and their emission factor Assumed value 30 €/MWh 100 €/tCO2 60 % 0,2 tCO2/MWh thermal energy 2015: 49-54 % 2020: 58-70 % Efficiency power-to-gas [10] 2030: 68-75 % 2050: 77-84 % 2015: 1000-4000 €/kW, 0,1-0,6 €/kWh 2023: 800-1300 €/kW, 0,1-0,5 €/kWh Costs power-to-gas 2033: 400-900 €/kW, 0,05-0,4 €/kWh 2050: 250-700 €/kW, 0,05-0,3 €/kWh Power purchase for power-to-gas plants 0-35 €/MWh All surpluses get stored in, only differing costs are considered in the comparison of the two systems with and without power-to-gas (for more information, see Fig 5) 2.2 Simulation model: Power2Sim The hourly coverage of power consumption throughout the years and electricity prices were simulated with the fundamental model Power2Sim by Energy Brainpool The model falls back to established and, if possible, public and independent data sources like Eurostat, ENTSO-E or highly respected surveys such as Capros et al [5] It consists out of a number of modules in which different component models are implemented, simulating various components of the energy market such as electricity demand, particular controllable loads, fossil and renewable power generation or import- and exportation of electricity An overview of the different modules of Power2Sim is given in Fig Fig Functional diagram and structure of the different modules of the fundamental model Power2Sim (Energy Brainpool GmbH) 395 Martin Thema et al / Energy Procedia 99 (2016) 392 – 400 2.3 Storage capacity With 88 %, the main part of the German demand for natural gas is imported from which 40 % comes from Russia, the rest mainly from European countries like Norway and the Netherlands Supply security in the gas sector is guaranteed by big underground storage facilities which can theoretically cover the demand for 37 days [8] and compensate over- and undersupply Originating from this underground storage capacity, estimations for power-to-gas storage capacity are based in this survey The maximal feasible receptivity of the caverns and aquifers is determined for hydrogen and methane production Results 3.1 Surplus energy and demand for power-to-gas capacity at rising shares of renewable energy It was calculated, that energy surpluses of 154 TWh with power peaks up to 134 GW are to be expected until 2050 This corresponds to about 20 % of the German gross electricity production in 2012 Other studies as well predict energy surpluses of 80-100 TWh per year and more at high shares of renewable power generation (Fig 2) To take up every surplus production peak (Table 2) and transform it into renewable gas, resulting from the simulations, an installed power-to-gas-capacity of 89-134 GW (Fig 3) is required until 2050 The worst-case scenario (high demand for power-to-gas, no alternative flexibility) calculated, sets the upper benchmark [2], the lower one is set by Götz et al [3] where at latest in 2035 expansion of power-to-gas capacity in a gigawatt-scale has to occur to reach the needed level of at least 89 GW in 2050 Surplus electricity (mean value from literature) in TWh/a Share of renewable energy (RE) in the trend-scenario in % Share of RE (simulation results in a system with power-to-gas) in % Share of RE (simulation results in a system without power-to-gas) in % Share of RE on power generation (goals of German federal government) in % Surplus electricity (simulation results) in TWh/a 100 90 140 80 120 100 60 50 80 40 60 30 40 20 20 10 2013/15 2020 2025 2030 2035 2040 2045 Year Fig Surplus electricity at increasing shares of fluctuating renewable power generation until 2050 [1, 9-20] 2050 TWh/a Percent 70 396 Martin Thema et al / Energy Procedia 99 (2016) 392 – 400 300 600 250 500 200 400 150 300 100 200 50 100 TWh/a GW Range for needed power-to-gas capacity in GW Installed power-to-gas capacity in GW without short-therm flexibility Installed power-to-gas capacity in GW incl 48-h-short-term flexibility Installed renewable generation capacity in GW Power generation from renewable energy in TWh/a 2013/15 2020 2025 2030 2035 2040 2045 2050 Year Fig Required power-to-gas capacity for uptaking of renewable surpluses compared to cumulated built up capacity of fluctuating renewable generation (wind and photovoltaics) 3.2 German storage capacity for power-to-gas Based on the long-term-available storage capacity of about 30,6 billion m³(Vn) [8] for natural gas in German storage facilities, a storage potential for hydrogen of 612 million m³(Vn) results from volumetric feed-in limits of at maximum Vol.-% hydrogen (H2) in natural gas This is equal to a stored energy of about 2,2 TWh (Table 3) At a rise of the feed-in limitation to 10 Vol.-% H2, 3,06 billion m³(Vn) or about 11 TWh of hydrogen could be stored in the German gas storage infrastructure Table 3: Long-term-available power-to-gas storage capacity in German aquifers (pore storage) and caverns (without gas grid) Calculations based on gross calorific values of hydrogen 3,55 kWh/m³(Vn) and methane 11,0 kWh/m³(Vn) [8] Containing Storage technology Pore storage/aquifers Caverns Sum Gas storage total Vol.-%-hydrogen Gas storage total 10 Vol.-%-hydrogen Storeable volume (long-term) 10,8 bn m³(Vn) 19,8 bn m³(Vn) 30,6 bn m³(Vn) Storage capacity for hydrogen in TWh -70,3 612 m m³(Vn) 2,17 3,06 bn m³(Vn) 10,9 Storage capacity for methane in TWh 119 218 337 A distinction has to be made between power-to-gas producing either hydrogen or methane: caverns, in general can be charged with both renewable gases – hydrogen and methane But aquifers, to present knowledge, only can uptake methane at very low shares of hydrogen Martin Thema et al / Energy Procedia 99 (2016) 392 – 400 If renewable hydrogen is further converted into methane, because of the higher volumetric energy density of methane and more ascertainable storage potential (no feed-in limits), 337 TWh could get stored in 3.3 Cost development of the power-to-gas-technology At present, investment costs of power-to-gas are so high, that viable operation only is possible in niches [2, 21] Investment costs for power-to-gas will basically fall with scale and amount of built up facilities Upcoming cost development will mainly base on learning effects, improvement in efficiency and new, cost-cutting progress due to research and development for market introduction Based on present investment costs (see Table for costdevelopment) of 1000-3000 €/kW for power-to-gas with hydrogen production and 2000-4000 €/kW with methane production, with a realistic decreasing trend in costs of 13 % per doubling of the installed power-to-gas capacity [22], investment costs for both technologies will even out at around 500 €/kW (Fig 4) Fig Learning curve Comparison of cost development for power-to-gas producing hydrogen (H2) and methane (CH4) at decreasing trend in costs of 13 % per doubling of the installed power-to-gas capacity 3.4 Impact of power-to-gas on energy system costs in Germany In evidence, the effect of power-to-gas on the German electricity system simulated with Power2Sim in this survey is cost-cutting in comparison to a system without power-to-gas: Initially, system costs will decrease in both scenarios (with and without power-to-gas) because of rising renewable generation replacing expensive production from gas fired power plants Between 2020 and 2035, expansion of power-to-gas storage infrastructure causes higher costs in relation to the system without power-to-gas (Fig 5) From 2035 on, the variant without power-to-gas starts to cost-increase due to significantly rising expenditures for remunerated curtailment In addition, residual gaps have to be filled with costly gas power to guarantee supply security Meanwhile, in the system with power-to-gas, investment costs get overcompensated by the use of surpluses In 2040, annual savings sum up to 2-6 billion € and rise up to 18 billion € in 2050 The considerably lower-priced system with power-to-gas is able to reach full renewable supply in 2050 while only 86 % are reached without power-to-gas 397 398 Martin Thema et al / Energy Procedia 99 (2016) 392 – 400 Fig Surplus assimilation cost development for a German power supply system levelling fluctuating renewable feed-in at power purchase for power-to-gas plants between zero and 35 €/MWh The figure shows costs for a system once using power-to-gas with, once without additional short-term flexibility and the other using conventional gas-fired power plants for production balance The spread between both variants is shown as well as shares of renewable generation achievable In the comparison, only differing costs are considered These are electricity costs for gas power plants and curtailment of wind and pv generation in the system without power-to-gas In the system with power-to-gas, costs for invest and operation of power-to-gas accrue Prices for alternative short-term flexibility are not included to emphasize the effect of power-to-gas [2, 3] Discussion 4.1 The need for power-to-gas capacity The large range of power-to-gas demand examined (Fig 3) is to be understood as guideline The upper benchmark stands for the unlikely case that no alternative flexibility options than power-to-gas get carried out Nonetheless, the calculations show that even with assumed short-term options and scheduled grid expansion, there is a need for at least 89 GW of power-to-gas until 2050 by only considering the power sector Throughout the decarbonization, even if this high power-to-gas capacity is not necessary for the conventional electricity sector alone, the other energy sectors mobility, chemistry and heat will have considerably a high demand on renewable gas for which building up power-to-gas capacities seems to be meaningful in any case 4.2 Storage capacity, allocation and use Most of the existing gas storages are former crude oil and natural gas reservoirs Since the commissioning of the German gas grid in 1955, their working gas volume is steadily increasing until today to one of the biggest in the world Most of the more flexible and latter built facilities are, for geological reasons, located in the northern half of the country in favourable proximity to prior wind sites [23] There, they can directly collect surpluses at the origin of bottlenecks and minimize losses At determined storage capacities of 2,2-11 TWh for renewable hydrogen and up to 337 TWh for renewable methane, after reconversion into electricity in a combined-cycle gas turbine power plant with an efficiency of 60 % results an electricity-to-electricity storage capacity of 1,3-6,6 TWh (hydrogen) and 202 TWh (methane) Thereby, a complete renewable supply with a backup capacity of 66 GW gas power plants run by the renewable gas could be Martin Thema et al / Energy Procedia 99 (2016) 392 – 400 guaranteed for a duration of over three months Present existing pumped hydro storage in Germany only can render about a tenth of this service for an average of six hours The gas storage disposes the 33-5.000-fold of the storage capacity of all German pumped hydro storage 4.3 Cost development and cost benefits of power-to-gas and its impact on system costs If costs for storage capacity will fall mainly because of learning effects like explained in Fig and prices for emissions certificates, and with it for fossil fuels, will rise as assumed in [24], power-to-gas can exist at procurement costs for electricity between 4-7 ct/kWh at rising full load hours With power-to-gas, electricity surpluses which get lost in the comparative simulation without power-to-gas, can be used to fill the gaps in supply As shown in this examinations, power-to-gas will achieve system relevance as storage and flexibility option at shares of about 70 % renewable power generation in about 2035 From then on, a system with power-to-gas gets more cost effective as a comparative system using only natural gas as flexibility option and saves several billions of Euros every year (Fig 5) If consequently thought to the end, even under adverse conditions, power-to-gas effects costcutting on a supply system with high shares of renewable energy generation If necessary grid expansion ought to be retarded, massive bottlenecks and surpluses are predicted already from 2020 onwards In this case and at constant building up of renewable generation capacity, energy storage capacity is needed on an earlier occasion For optional implemented methanation, CO2-sources are adequate Especially if the CO is taken from the atmosphere, it is not relevant for the climate footprint of power-to-gas technology As for every other flexibility option in energy transition, it is important for power-to-gas to take stored-in electricity only from renewable generation Benndorf et al [25] assume fuels made from power-to-gas with an energy content of 360 TWh/a in 2050 only for the mobility sector Moreover it is postulated that the chemical industry needs to substitute feedstocks with an energy equivalent of about 293 TWh/a This indicates, that a decarbonization beyond the electricity sector without renewable gas as raw material for present mineral oil and chemical industry is barely not possible Electricity as high-quality primary energy is today still often regarded separated from the other energy sectors But as an intersectoral connecting element, power-to-gas will play a key-role in energy transition – not only in Germany Conclusion To sum up, power-to-gas on the long run effects cost-efficient on energy transition in the electricity system It allows higher shares of renewable electricity generation in the power system and is the only present storage option with significant large long-term capacities At least, power-to-gas and its derivates power-to-liquid and power-tochemicals enable a comprehensive decarbonization of mobility and chemistry sectors as well There is a dilemma which needs to be resolved: from an economical point of view, power-to-gas is a prospective required technology which is not worthwhile to operate today mainly because of an unsuitable framework To reach the technically required power-to-gas capacity at the right point of time, we have to start building up the necessary infrastructure now Acknowledgements Hereby, we express our appreciation to all colleagues involved during the process leading to this paper: Fabian Eckert from FENES in Regensburg, Fabian Huneke and Carlos Linkenheil from Energy Brainpool in Berlin and last but not least to Marcel Keiffenheim and Michael Friedrich from Greenpeace Energy who initiated the work done on this topic 399 400 Martin Thema et al / Energy Procedia 99 (2016) 392 – 400 References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] Klaus 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For this, amongst different flexibility options, energy storage becomes increasingly important In the following, necessity and impact of power- to- gas (PtG) for energy transition in Germany [2-4]... (simulation results in a system with power- to- gas) in % Share of RE (simulation results in a system without power- to- gas) in % Share of RE on power generation (goals of German federal government) in. .. Comparison of cost development for power- to- gas producing hydrogen (H2) and methane (CH4) at decreasing trend in costs of 13 % per doubling of the installed power- to- gas capacity 3.4 Impact of power- to- gas