Clean Energy Technology

Electrolysis uses electricity to split water into its basic components (H2 and O2). Polymer electrolyte membrane (PEM) electrolysers use a proton conducting solid polymer electrolyte (SPE) for the assembly of the electrolysis cell and separation of H2 and O2 evolution reactions separately on cathode and anode sides. While it is currently one of the two commercially matured technology together with alkaline electrolysers, its cost-reduction potential is considerably larger while presenting other advantages such as higher flexibility, higher operating pressure (lower need for compression), smaller footprint (relevant for coupling with offshore wind), faster response and lower degradation rate with load changes. PEM electrolysers need, however, expensive electrode catalysts (platinum, iridium) and membrane materials. Currently, the lifetime of PEM and Alkaline is similar. There is a lot of research done in the direction of new acid stable electrolysers, that could enable the development into usable technologies in the near future, further reducing PEM electrolyser costs, and increasing lifetimes.

Electrolysis uses electricity to split water into its basic components (H2 and O2). Wastewater as novel feedstock for hydrogen production by electrolysis can be classified according to its physicochemical properties and composition before entering the electrolysis cell: - Pre-treated wastewater (that is, purified and demineralized) to achieve the required properties, for example, ionic conductivity

Methane splitting/pyrolysis/cracking is a thermochemical process in which methane is decomposed at high temperatures in H2 and solid carbon in the presence of a catalyst, thus generating CO2-free H2 since the carbon present in the methane is separated as a solid carbon that can be used in different applications. The plasma torch generates temperatures in excess of 2000°C, which is sufficient to break down the molecular bonds of methane, resulting in the formation of carbon (C) and hydrogen (H2). However, there are some challenges associated with thermal plasma methane pyrolysis. The process requires a significant amount of energy to maintain the plasma discharge, which can be expensive. The electric energy ignites the plasma (an ionised gas), which reaches temperatures in the range of 1 000-2 000°C and splits CH4 into its elements. Although this technology is based on plasma-arc reactors driven by electricity, there are other concepts based on the use of microwaves to heat the gas.

The combination of autothermal reforming (ATR) with a Gas Heated Reformer (GHR) is an improved design of ATR that allows for achievement of higher efficiencies, lower CO2 production and lower oxygen consumption. The ATR and GHR are in series and the GHR acts both as a pre-heater and cooler of the inlet/outlet of the ATR. The GHR benefit is that it pre-reforms the gas going to ATR using the heat from the exhaust gases of the ATR and performs part of the reforming that would otherwise take place in the ATR. The main technical challenge for GHR is carbon deposition (metal dusting) on the shell side (high temperature from the ATR outlet at around 1 100 °C to 600-800 °C). This can be solved by either material selection that can withstand the conditions and thermal cycling (cost) or by either decreasing the operating pressure or adding more steam, both of which come with penalty in process efficiency.

Electrolysis uses electricity to split water into its basic components (H2 and O2). Solid oxide electrolysers (SOEC) are electrochemical systems operating at high operating temperatures (600-900C), allowing the splitting of steam into hydrogen (H2) and oxygen (O2), by use of a ceramic solid oxide membrane across which O2- ions formed in the cathode (fuel electrode) along with H2, are transported towards the anode (air electrode) to complete the electrolytic process. This is the most efficient way to produce hydrogen as the HT-process is using direct steam conversion but has not yet reached commercial scale yet. They are also less flexible than PEM electrolysers regarding start/stop system conditions. SOEC technology can load follow very well and with a very rapid response however, they need to operate in a "hot idle" mode when at 0% load. The SOEC operating conditions requiring an initial source of heat (such as waste heat, bioenergy or nuclear energy), means they may be well attractive for co-location and integration with other industrial or chemical processes. Lower temperature SOEC (i.e. 500 to 600C) has the advantage of using metal-supported cells leading to lower costs and higher robustness.

Methane splitting/pyrolysis/cracking is a thermochemical process in which methane is decomposed at high temperatures in H2 and solid carbon, thus generating CO2-free H2 since the carbon present in the methane is separated as a solid carbon that can be used in different applications. In catalytic pyrolysis, methane breaks down into hydrogen and carbon over a metal catalyst, which is typically nickel- or iron-based, at temperatures typically under 1 000°C. The use of a catalyst in methane pyrolysis offers several advantages over the non-catalytic thermal decomposition process. The catalyst reduces the energy required for the process by providing an alternate reaction pathway with lower activation energy, which makes the process more energy-efficient. The catalyst can also improve the selectivity and yield of the reaction, allowing for more efficient conversion of methane to hydrogen. Catalytic methane pyrolysis is still in the research and development stage, and several types of catalysts have been investigated, including metal catalysts, metal oxide catalysts, and carbon-based catalysts. The performance of the catalyst depends on several factors, such as its composition, structure, and activity, as well as the process conditions, such as temperature, pressure, and gas composition.

Methane splitting/pyrolysis/cracking is a thermochemical process in which methane is decomposed at high temperatures in H2 and solid carbon, thus generating CO2-free H2 since the carbon present in the methane is separated as a solid carbon that can be used in different applications. Methane cracks to H2 and C at temperatures of > ~ 400 °C, while temperatures of > 1000 °C are required to achieve a high conversion. Nonetheless, a reactor operating temperature of > 1000 °C, can lead to significant technical challenges e.g. material compatibility and corrosion. To address this challenge, three patent-pending process configurations have been proposed to lower the temperature of the methane pyrolysis reactor to less than 1000 °C, which enables the use of commercially available stainless steels and offers potential to mitigate costs. The high temperatures required for the process can make it energy-intensive, requiring a significant amount of energy to be supplied to maintain the high temperatures. Additionally, the solid carbon produced during the process can cause fouling and clogging of equipment, leading to operational challenges. There could be either with or without catalyst. reaction may be produced in liquid media, as a molten metal or a molten salt, by bubbling reactor. Depending on the composition of the molten media, temperatures are reduced to take into account the effect of the catalyst.

In electric-powered steam reformers, the use of natural gas for providing the heat needs of the process is replaced by direct electrification, thus improving the overall efficiency of the whole process and decreasing process emissions by avoiding exhaust gases

Electrolysis uses electricity to split water into its basic components (H2 and O2). The use of seawater as the electrolyte is still at early stages of development, due to its high fouling/scaling potentials to both the membrane and electrodes. Furthermore, the low conductivity of the seawater also leads to the low process efficiency, since more electricity from the solar panels converts to heat rather than for hydrogen production, in comparison to the conventional electrolyte (30 wt% KOH solution). It can involve a two-stage process of desalinisation followed by electrolysis, with technologies that are already developed but by also increasing CAPEX needs and efficiency losses. The quality of water from seawater reverse osmosis is not sufficient, residual trace ions can poison active Pt- and Ir catalysts. Or it can be done in a one-stage process using water directly in the electrolyser, operating at low power densities and electrolysing only part of the water put in contact with the electrodes, although this technology is still at lab-scale. Seawater electrolysis can be an enabler for electrolysis in geographical regions that present high water-stress.

Methane splitting/pyrolysis/cracking is a thermochemical process in which methane is decomposed at high temperatures in H2 and solid carbon in the presence of a catalyst, thus generating CO2-free H2 since the carbon present in the methane is separated as a solid carbon that can be used in different applications. The non-thermal plasma process has several advantages over the thermal decomposition process. It operates at lower temperatures, which reduces the energy required for the process, making it more energy efficient. Additionally, the non-thermal plasma process can operate at atmospheric pressure, which reduces the complexity and cost of the equipment needed for the process. One technology option for the non-thermal plasma process is based on shockwaves. Shockwave pyrolysis utilizes shockwaves to pyrolyze methane into carbon black and hydrogen gas. Shockwaves are produced by a high-pressure gas stream into a tube with a closed end, to create a compression wave that decompose the methane molecules.

Autothermal reformation is a variation of SMR in which the methane reacts in an O2-deficit atmosphere instead of using high temperature steam, avoiding the need for an external input of heat and, therefore, avoiding the production of a diluted CO2 stream. The process takes place at 800-1150°C.Once the syngas is produced, the rest of the process is like SMR with the difference that the H2/CO ratios are different and the operating and designing conditions of downstream processes must be adapted. CO2 capture above 90% can be achieved by applying capture only to the concentrated process stream.

Sorption Enhanced Steam Reforming (SESR) is a pre-combustion CO2 capture process in which natural gas is reacted with steam in the presence of a CO2 sorbent and reforming catalyst. The CO2 is absorbed continuously over the absorbent, and thus removed from the reaction, which allows for shifting the reaction equilibrium towards the products, increasing conversions. It allows the production of decarbonised H2 and a concentrated CO2 stream suitable for transport and geological storage (or reuse).