Power-to-X

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Transformation in joining up sectors Transformation in joining up sectors.jpg
Transformation in joining up sectors

Power-to-X (also P2X and P2Y) are electricity conversion, energy storage, and reconversion pathways from surplus renewable energy. [1] [2] Power-to-X conversion technologies allow for the decoupling of power from the electricity sector for use in other sectors (such as transport or chemicals), possibly using power that has been provided by additional investments in generation. [1] The term is widely used in Germany and may have originated there.

Contents

The X in the terminology can refer to one of the following: power-to-ammonia, power-to-chemicals, power-to-fuel, [3] power-to-gas (power-to-hydrogen, power-to-methane) power-to-liquid (synthetic fuel), power to food, [4] power-to-heat. Electric vehicle charging, space heating and cooling, and water heating can be shifted in time to match generation, forms of demand response that can be called power-to-mobility and power-to-heat.

Collectively power-to-X schemes which use surplus power fall under the heading of flexibility measures and are particularly useful in energy systems with high shares of renewable generation and/or with strong decarbonization targets. [1] [2] A large number of pathways and technologies are encompassed by the term. In 2016 the German government funded a €30 million first-phase research project into power-to-X options. [5]

Power-to-fuel

Surplus electric power can be converted to gas fuel energy for storage and reconversion. [6] [7] [8] [9] Direct current electrolysis of water (efficiency 80–85% at best) can be used to produce hydrogen which can, in turn, be converted to methane (CH4) via methanation. [6] [10] Another possibility is converting the hydrogen, along with CO2 to methanol. [11] Both these fuels can be stored and used to produce electricity again, hours to months later.

Storage and reconversion of power-to-fuel

Hydrogen and methane can be used as downstream fuels, fed into the natural gas grid, or used to make synthetic fuel. [12] [13] Alternatively they can be used as a chemical feedstock, as can ammonia (NH3).

Reconversion technologies include gas turbines, combined cycle plants, reciprocating engines and fuel cells. Power-to-power refers to the round-trip reconversion efficiency. [6] For hydrogen storage, the round-trip efficiency remains limited at 35–50%. [2] Electrolysis is expensive and power-to-gas processes need substantial full-load hours to be economic. [1] However, while round-trip conversion efficiency of power-to-power is lower than with batteries and electrolysis can be expensive, storage of the fuels themselves is quite inexpensive.[ citation needed ] This means that large amounts of energy can be stored for long periods of time with power-to-power, which is ideal for seasonal storage. This could be particularly useful for systems with high variable renewable energy penetration, since many areas have significant seasonal variability of solar, wind, and run-of-the-river-hydroelectric generation.

Batteries

Despite it also being based fundamentally on electrolytic chemical reactions, battery storage is not normally considered a power-to-fuel concept.

Power-to-heat

The purpose of power-to-heat systems is to utilize excess electricity generated by renewable energy sources which would otherwise be wasted. Depending on the context, the power-to-heat can either be stored as heat, or delivered as heat to meet a need. [14]

Heating systems

In contrast to simple electric heating systems such as night storage heating which covers the complete heating requirements, power-to-heat systems are hybrid systems, which additionally have traditional heating systems using chemical fuels like wood or natural gas. [15] : 124  When there are excess energy the heat production can result from electric energy otherwise the traditional heating system will be used. In order to increase flexibility power-to-heat systems are often coupled with heat accumulators. The power supply occurs for the most part in the local and district heating networks. Power-to-heat systems are also able to supply buildings or industrial systems with heat. [16]

Power-to-heat involves contributing to the heat sector, either by resistance heating or via a heat pump. Resistance heaters have unity efficiency, and the corresponding coefficient of performance (COP) of heat pumps is 2–5. [6] Back-up immersion heating of both domestic hot water and district heating offers a cheap way of using surplus renewable energy and will often displace carbon-intensive fossil fuels for the task. [1] Large-scale heat pumps in district heating systems with thermal energy storage are an especially attractive option for power-to-heat: they offer exceptionally high efficiency for balancing excess wind and solar power, and they can be profitable investments. [17] [18]

Heat storage systems

Other forms of power-to-X

Power-to-mobility refers to the charging of battery electric vehicles (BEV). Given the expected uptake of EVs, dedicated dispatch will be required. As vehicles are idle for most of the time, shifting the charging time can offer considerable flexibility: the charging window is a relatively long 8–12 hours, whereas the charging duration is around 90 minutes. [2] The EV batteries can also be discharged to the grid to make them work as electricity storage devices, but this causes additional wear to the battery. [2]

Impact

According to the German concept of sector coupling interconnecting all the energy-using sectors will require the digitalisation and automation of numerous processes to synchronise supply and demand. [19]

A 2023 study examined to role that power‑to‑X could play in a highly‑renewable future energy system for Japan. The P2X technologies considered include water electrolysis, methanation, Fischer–Tropsch synthesis, and Haber–Bosch synthesis and the study used linear programming to determine least‑cost system structure and operation. Results indicate that these various P2X technologies can effectively shift electricity loads and reduce curtailment by 80% or more. [20]

See also

Related Research Articles

<span class="mw-page-title-main">Fuel cell</span> Device that converts the chemical energy from a fuel into electricity

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel and an oxidizing agent into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.

<span class="mw-page-title-main">Energy storage</span> Captured energy for later usage

Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an accumulator or battery. Energy comes in multiple forms including radiation, chemical, gravitational potential, electrical potential, electricity, elevated temperature, latent heat and kinetic. Energy storage involves converting energy from forms that are difficult to store to more conveniently or economically storable forms.

Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol. Syngas is combustible and can be used as a fuel. Historically, it has been used as a replacement for gasoline, when gasoline supply has been limited; for example, wood gas was used to power cars in Europe during WWII.

<span class="mw-page-title-main">Combined cycle power plant</span> Assembly of heat engines that work in tandem from the same source of heat

A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turbine (CCGT) plant, which is a kind of gas-fired power plant. The same principle is also used for marine propulsion, where it is called a combined gas and steam (COGAS) plant. Combining two or more thermodynamic cycles improves overall efficiency, which reduces fuel costs.

<span class="mw-page-title-main">Alternative fuel</span> Fuels from sources other than fossil fuels

Alternative fuels, also known as non-conventional and advanced fuels, are fuels derived from sources other than petroleum. Alternative fuels include gaseous fossil fuels like propane, natural gas, methane, and ammonia; biofuels like biodiesel, bioalcohol, and refuse-derived fuel; and other renewable fuels like hydrogen and electricity.

<span class="mw-page-title-main">Hydrogen economy</span> Using hydrogen to decarbonize more sectors

The hydrogen economy is an umbrella term for the roles hydrogen can play alongside low-carbon electricity to reduce emissions of greenhouse gases. The aim is to reduce emissions where cheaper and more energy-efficient clean solutions are not available. In this context, hydrogen economy encompasses the production of hydrogen and the use of hydrogen in ways that contribute to phasing-out fossil fuels and limiting climate change.

<span class="mw-page-title-main">Sabatier reaction</span> Methanation process of carbon dioxide with hydrogen

The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures and pressures in the presence of a nickel catalyst. It was discovered by the French chemists Paul Sabatier and Jean-Baptiste Senderens in 1897. Optionally, ruthenium on alumina makes a more efficient catalyst. It is described by the following exothermic reaction:

<span class="mw-page-title-main">Grid energy storage</span> Large scale electricity supply management

Grid energy storage, also known as large-scale energy storage, are technologies connected to the electrical power grid that store energy for later use. These systems help balance supply and demand by storing excess electricity from variable renewables such as solar and inflexible sources like nuclear power, releasing it when needed. They further provide essential grid services, such as helping to restart the grid after a power outage.

<span class="mw-page-title-main">Methanol economy</span> Economic theory

The methanol economy is a suggested future economy in which methanol and dimethyl ether replace fossil fuels as a means of energy storage, ground transportation fuel, and raw material for synthetic hydrocarbons and their products. It offers an alternative to the proposed hydrogen economy or ethanol economy, although these concepts are not exclusive. Methanol can be produced from a variety of sources including fossil fuels as well as agricultural products and municipal waste, wood and varied biomass. It can also be made from chemical recycling of carbon dioxide.

<span class="mw-page-title-main">Electrolysis of water</span> Electricity-induced chemical reaction

Electrolysis of water is using electricity to split water into oxygen and hydrogen gas by electrolysis. Hydrogen gas released in this way can be used as hydrogen fuel, but must be kept apart from the oxygen as the mixture would be extremely explosive. Separately pressurised into convenient 'tanks' or 'gas bottles', hydrogen can be used for oxyhydrogen welding and other applications, as the hydrogen / oxygen flame can reach approximately 2,800°C.

Hydrogen gas is produced by several industrial methods. Nearly all of the world's current supply of hydrogen is created from fossil fuels. Most hydrogen is gray hydrogen made through steam methane reforming. In this process, hydrogen is produced from a chemical reaction between steam and methane, the main component of natural gas. Producing one tonne of hydrogen through this process emits 6.6–9.3 tonnes of carbon dioxide. When carbon capture and storage is used to remove a large fraction of these emissions, the product is known as blue hydrogen.

<span class="mw-page-title-main">Energy conversion efficiency</span> Ratio between the useful output and the input of a machine

Energy conversion efficiency (η) is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radiation), or heat. The resulting value, η (eta), ranges between 0 and 1.

<span class="mw-page-title-main">Gas-fired power plant</span> One or more generators which convert natural gas into electricity

A gas-fired power plant, sometimes referred to as gas-fired power station, natural gas power plant, or methane gas power plant, is a thermal power station that burns natural gas to generate electricity. Gas-fired power plants generate almost a quarter of world electricity and are significant sources of greenhouse gas emissions. However, they can provide seasonal, dispatchable energy generation to compensate for variable renewable energy deficits, where hydropower or interconnectors are not available. In the early 2020s batteries became competitive with gas peaker plants.

Electromethanogenesis is a form of electrofuel production where methane is produced by direct biological conversion of electrical current and carbon dioxide.

<span class="mw-page-title-main">Microbial electrolysis cell</span>

A microbial electrolysis cell (MEC) is a technology related to Microbial fuel cells (MFC). Whilst MFCs produce an electric current from the microbial decomposition of organic compounds, MECs partially reverse the process to generate hydrogen or methane from organic material by applying an electric current. The electric current would ideally be produced by a renewable source of power. The hydrogen or methane produced can be used to produce electricity by means of an additional PEM fuel cell or internal combustion engine.

<span class="mw-page-title-main">Electrofuel</span> Carbon-neutral drop-in replacement fuel

Electrofuels, also known as e-fuels, are a class of synthetic fuels which function as drop-in replacement fuels for internal combustion engines. They are manufactured using captured carbon dioxide or carbon monoxide, together with hydrogen obtained from water split. Electrolysis is possible with both traditional fossil fuel energy sources, as well as low-carbon electricity sources such as wind, solar and nuclear power.

A solar fuel is a synthetic fuel produced using solar energy, through photochemical, photobiological, electrochemical, or thermochemical methods. Sunlight is the primary energy source, with its radiant energy being transduced to chemical energy stored in bonds, typically by reducing protons to hydrogen, or carbon dioxide to organic compounds.

Power-to-gas is a technology that uses electric power to produce a gaseous fuel.

<span class="mw-page-title-main">Proton exchange membrane electrolysis</span> Technology for splitting water molecules

Proton exchange membrane(PEM) electrolysis is the electrolysis of water in a cell equipped with a solid polymer electrolyte (SPE) that is responsible for the conduction of protons, separation of product gases, and electrical insulation of the electrodes. The PEM electrolyzer was introduced to overcome the issues of partial load, low current density, and low pressure operation currently plaguing the alkaline electrolyzer. It involves a proton-exchange membrane.

<span class="mw-page-title-main">Reversible solid oxide cell</span>

A reversible solid oxide cell (rSOC) is a solid-state electrochemical device that is operated alternatively as a solid oxide fuel cell (SOFC) and a solid oxide electrolysis cell (SOEC). Similarly to SOFCs, rSOCs are made of a dense electrolyte sandwiched between two porous electrodes. Their operating temperature ranges from 600°C to 900°C, hence they benefit from enhanced kinetics of the reactions and increased efficiency with respect to low-temperature electrochemical technologies.

References

  1. 1 2 3 4 5 acatech; Lepoldina; Akademienunion, eds. (2016). Flexibility concepts for the German power supply in 2050 : ensuring stability in the age of renewable energies (PDF). Berlin, Germany: acatech — National Academy of Science and Engineering. ISBN   978-3-8047-3549-1. Archived from the original (PDF) on 6 October 2016. Retrieved 10 June 2016.
  2. 1 2 3 4 5 Lund, Peter D; Lindgren, Juuso; Mikkola, Jani; Salpakari, Jyri (2015). "Review of energy system flexibility measures to enable high levels of variable renewable electricity" (PDF). Renewable and Sustainable Energy Reviews . 45: 785–807. Bibcode:2015RSERv..45..785L. doi:10.1016/j.rser.2015.01.057.
  3. ↑ Trakimavicius, Lukas (December 2023). "Mission Net-Zero: Charting the Path for E-fuels in the Military". NATO Energy Security Centre of Excellence.
  4. ↑ Sillman, J.; Uusitalo, V.; Ruuskanen, V.; Ojala, L.; Kahiluoto, H.; Soukka, R.; Ahola, J. (1 November 2020). "A life cycle environmental sustainability analysis of microbial protein production via power-to-food approaches". The International Journal of Life Cycle Assessment. 25 (11): 2190–2203. Bibcode:2020IJLCA..25.2190S. doi: 10.1007/s11367-020-01771-3 . ISSN   1614-7502.
  5. ↑ "Power-to-X: entering the energy transition with Kopernikus" (Press release). Aachen, Germany: RWTH Aachen. 5 April 2016. Retrieved 9 June 2016.
  6. 1 2 3 4 Sternberg, André; Bardow, André (2015). "Power-to-What? — Environmental assessment of energy storage systems". Energy and Environmental Science . 8 (2): 389–400. doi:10.1039/c4ee03051f.
  7. ↑ Agora Energiewende (2014). Electricity storage in the German energy transition : analysis of the storage required in the power market, ancillary services market and the distribution grid (PDF). Berlin, Germany: Agora Energiewende . Retrieved 30 December 2018.
  8. ↑ Sterner, Michael; Eckert, Fabian; Thema, Martin; et al. (2014). Langzeitspeicher in der Energiewende — Präsentation [Long-term storage in the Energiewende — Presentation]. Regensburg, Germany: Forschungsstelle für Energienetze und Energiespeicher (FENES), OTH Regensburg. Retrieved 9 May 2016.
  9. ↑ Ausfelder, Florian; Beilmann, Christian; Bräuninger, Sigmar; Elsen, Reinhold; Hauptmeier, Erik; Heinzel, Angelika; Hoer, Renate; Koch, Wolfram; Mahlendorf, Falko; Metzelthin, Anja; Reuter, Martin; Schiebahn, Sebastian; Schwab, Ekkehard; Schüth, Ferdi; Stolten, Detlef; Teßmer, Gisa; Wagemann, Kurt; Ziegahn, Karl-Friedrich (May 2016). Energy storage systems: the contribution of chemistry — Position paper (PDF). Germany: Koordinierungskreis Chemische Energieforschung (Joint Working Group on Chemical Energy Research). ISBN   978-3-89746-183-3 . Retrieved 9 June 2016.
  10. ↑ Pagliaro, Mario; Konstandopoulos, Athanasios G (15 June 2012). Solar Hydrogen: Fuel of the Future. Cambridge, United Kingdom: RSC Publishing. doi:10.1039/9781849733175. ISBN   978-1-84973-195-9. S2CID   241910312.
  11. ↑ George Olah's renewable methanol plant
  12. ↑ König, Daniel Helmut; Baucks, Nadine; Kraaij, Gerard; Wörner, Antje (18–19 February 2014). "Entwicklung und Bewertung von Verfahrenskonzepten zur Speicherung von fluktuierenden erneuerbaren Energien in flüssigen Kohlenwasserstoffen" [Development and evaluation of process concepts for storing fluctuating renewable energy in liquid hydrocarbons]. Jahrestreffen der ProcessNet-Fachgruppe Energieverfahrenstechnik. Karlsruhe, Germany. Retrieved 9 May 2016.
  13. ↑ Foit, Severin; Eichel, Rüdiger-A; Vinke, Izaak C; de Haart, Lambertus GJ (1 October 2016). "Power-to-Syngas – an enabling technology for the transition of the energy system? Production of tailored synfuels and chemicals using renewably generated electricity". Angewandte Chemie International Edition. 56 (20): 5402–5411. doi:10.1002/anie.201607552. ISSN   1521-3773. PMID   27714905.
  14. ↑ Bloess, Andreas; Schill, Wolf-Peter; Zerrahn, Alexander (15 February 2018). "Power-to-heat for renewable energy integration: a review of technologies, modeling approaches, and flexibility potentials". Applied Energy. 212: 1611–1626. Bibcode:2018ApEn..212.1611B. doi: 10.1016/j.apenergy.2017.12.073 . hdl: 10419/200120 . ISSN   0306-2619. Open Access logo PLoS transparent.svg
  15. ↑ Sterner, Stadler, Michael, Ingo (2014). Energiespeicher – Bedarf, Technologien, Integration. Berlin and Heidelberg.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: multiple names: authors list (link)
  16. ↑ Schweiger, Gerald (2017). "The potential of power-to-heat in Swedish district heating systems". Energy. 137: 661–669. Bibcode:2017Ene...137..661S. doi:10.1016/j.energy.2017.02.075.
  17. ↑ Zakeri, Behnam; Rinne, Samuli; Syri, Sanna (31 March 2015). "Wind integration into energy systems with a high share of nuclear power – what are the compromises?". Energies. 8 (4): 2493–2527. doi: 10.3390/en8042493 . ISSN   1996-1073.
  18. ↑ Salpakari, Jyri; Mikkola, Jani; Lund, Peter D (2016). "Improved flexibility with large-scale variable renewable power in cities through optimal demand side management and power-to-heat conversion". Energy Conversion and Management. 126: 649–661. Bibcode:2016ECM...126..649S. doi:10.1016/j.enconman.2016.08.041. ISSN   0196-8904.
  19. ↑ "Sector coupling – Shaping an integrated renewable energy system". Clean Energy Wire. 18 April 2018. Retrieved 6 March 2019.
  20. ↑ Onodera, Hiroaki; Delage, Rémi; Nakata, Toshihiko (1 October 2023). "Systematic effects of flexible power-to-X operation in a renewable energy system: a case study from Japan". Energy Conversion and Management: X. 20: 100416. Bibcode:2023ECMX...2000416O. doi: 10.1016/j.ecmx.2023.100416 . ISSN   2590-1745 . Retrieved 1 September 2023. Open Access logo PLoS transparent.svg
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