Power-to-X (aka P2X or PtX) is a generic term for energy conversion technologies that turn (renewable) electricity into carbon-neutral synthetic fuels. These can be Hydrogen (H2), Methane (CH4), Sustainable Aviation Fuels (SAF), or chemicals. PtX is an important tool in enabling the green transition.
These synthetic fuels are used in applications and sectors that are hard to decarbonize and can be stored for later use.
Advantages of Power-to-X
The main advantages of PtX are:
Power-to-X is essential in achieving a carbon-neutral economy that meets the increasing demand for energy. Through electrolysis and CO2 reutilization, Power-to-X can unlock carbon-neutral solutions that mitigate unavoidable emissions from industry, by capturing concentrated CO2 streams from biomass-fired power plants or anaerobic digestion. It also offers a competitive option for energy storage.
- Reduce fossil CO2 emissions
- Potential to replace fossil fuels with limited changes in applications/consumers.
- Long-term energy storage of renewable energy
New technologies are now being deployed at scale across sectors to decarbonize society and fight climate change. Fossil fuels are being replaced by renewable energy such as wind, solar, and hydropower. Also, direct electrification of household heating and passenger transport in cars is on the rise.
However, some sectors cannot easily be electrified. Where high amounts of energy are required, batteries will not be sufficient to store and transport energy. Heavy-duty transport, shipping, and aviation all require fuel in a liquid or gaseous form, as the weight of batteries makes them unsuitable for these applications.
Although direct electrification is an important means of decarbonization, we expect green hydrogen and e-fuels to be the main solutions for sectors that are hard to electrify from 2030 onwards. Countries and private companies are increasingly developing and promoting strategies with hydrogen as a key energy carrier on the path to net zero emissions.
How does it work
Power-to-X covers multiple processes for converting electric renewable energy (“Power”) to a fuel or energy carrier (“X”). This can be in a gaseous form such as hydrogen or methane (synthetic natural gas, Power-to-Gas), or liquid synthetic fuels such as methanol, ammonia, synthetic diesel, or kerosene (Power-to-Liquid). Liquid fuels from Power-to-X are also often called to as electrofuels or merely e-fuels.
Multiple technologies are part of the PtX family, with different technical and commercial development and therefore installed capacity worldwide. Below are some of the most common:
Electrolysis – H2
Electrolysis of water splits the water molecules (H2O) into hydrogen (H2) and oxygen (O2) molecules according to the equation below. The reaction requires energy, either heat or electrical energy (or a combination of both. Therefore renewable electricity or heat is needed together with water to enable the reaction.
2H2O → 2H2 + O2
There are different electrolysis technologies: alkaline electrolysis, PEM electrolysis, and solid oxide electrolysis. Each with its advantages and Technology readiness level (TRL). According to the EIA, in 2021 the capacity reached 0.5GW. Capacity is expected to grow to over 1GW by the end of 2022.
Methane – CH4
Steam methane reforming (SMR) is a chemical reaction consisting in extracting hydrogen from methane (CH4) using steam at high temperatures (800-1000°C) at moderate pressures (15-30 bar). It is therefore a highly energy-intensive process.
CH4+2H2O= CO2+4H2
Ammonia – NH3
Ammonia (NH3) is key for food production to feed a growing global population. But it can also be used to produce electricity with air and water as the only emissions or used as a storage medium for energy generated from renewable sources. In 2021, 80% of the annual global production of over 170 million metric tons was used to produce fertilizers. This figure will increase. Green ammonia synthesis processes are based on the Haber–Bosch process. Where hydrogen and nitrogen react together at high temperatures and pressures and catalysts. Currently, the hydrogen used in the industry is not green.
Methanol (CH3OH or MeOH) is produced through the hydrogenation of carbon monoxide (CO) and hydrogen over a catalyst. This occurs after the conversion of CO into CO2. Methanol can be an excellent replacement for gasoline and is used in mixed fuels to decarbonize heavy industry. The international shipping giant Maersk has purchased 8 methanol-powered ships.The chemical industry uses widely methanol technology and infrastructure.
CO+2H2= CH3OH
CO2+3H2= CH3OH+4H2O
Power-to-X enables energy security and storage of renewable energy, providing new paths for decarbonization. As installed capacity increases and research develops, these technologies will play a part in the green transition together with the rising of wind and solar. Some allow tapping into existing infrastructure to store intermittent renewable energy.
Under development
As per a recent study by European Patent Office (EPO) and the International Renewable Energy Agency (IRENA), from 2005 to 2020, 10 894 patent families related to water electrolysis were published. This represents an average annual increase of 18%.
Offshore wind, Solar PV, and other renewable power-to-X will play a crucial role in decarbonizing the World. Furthermore, it will support energy security. However, several obstacles are holding back its full potential. Investment is needed, and costs need to be reduced to become competitive without a carbon tax.
