Reformed Methanol Fuel Cell (RMFC) or Indirect Methanol Fuel Cell (IMFC) systems are a subcategory of proton-exchange fuel cells where, the fuel,

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

(CH₃OH), is reformed, before being fed into the

fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requ ...

. RMFC systems offer advantages over

direct methanol fuel cell Direct-methanol fuel cells or DMFCs are a subcategory of proton-exchange fuel cells in which methanol is used as the fuel. Their main advantage is the ease of transport of methanol, an energy-dense yet reasonably stable liquid at all environmental ...

(DMFC) systems including higher efficiency, smaller cell stacks, less requirement on methanol purity, no water management, better operation at low temperatures, and storage at sub-zero temperatures because methanol is a liquid from -97.0 °C to 64.7 °C (-142.6 °F to 148.5 °F) and as there is no liquid methanol-water mixture in the cells which can destroy the membrane of DMFC in case of frost. The reason for the high efficiency of RMFC in contrast to DMFC is that hydrogen containing gas is fed to the fuel cell stack instead of methanol and overpotential (power loss for catalytic conversion) on anode is much lower for hydrogen than for methanol. The tradeoff is that RMFC systems operate at hotter temperatures and therefore need more advanced heat management and insulation. The waste products with these types of fuel cells are

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

and water.

Methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

is used as a fuel because it is naturally hydrogen dense (a hydrogen carrier) and can be steam reformed into hydrogen at low temperatures compared to other

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

fuels. Additionally, methanol is naturally occurring,

biodegradable Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...

, and energy dense. RMFC systems consist of a fuel processing system (FPS), a

, a fuel cartridge, and the BOP (the balance of plant).

Storage and Fuel Costs

The fuel cartridge stores the

fuel. Depending on the system design either 100 % methanol (IMPCA industrial standard) or a mixture of methanol with up to 40 vol% water is usually used as fuel for the RMFC system. 100 % methanol results in lower fuel consumption than water-methanol mixture (Premix) but goes along with higher fuel cell system complexity for condensing of cathode moisture. Fuel Costs for RMFC typically are about 0.4-1.1 USD/kWh (conventional methanol) resp. 0.45-1.3 USD/kWh ( renewable methanol produced from municipal waste or renewable electricity). By comparison, for a hydrogen fueled Low Temperature-PEM fuel cell costs for conventional hydrogen (in bundle of bottles) are about 4.5-10 USD/kWh.

Fuel processing system (FPS) in

→

Partial oxidation Partial oxidation (POX) is a type of chemical reaction. It occurs when a substoichiometric fuel-air mixture is partially combusted in a reformer, creating a hydrogen-rich syngas which can then be put to further use, for example in a fuel cell. A d ...

(POX)/

Autothermal reforming Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly natural gas is the feedstock. The main purpose of this technology is hydrogen product ...

(ATR)→ Water gas shift reaction (WGS)→

preferential oxidation PROX is an acronym for PReferential OXidation, and refers to the preferential oxidation of a carbon monoxide in a gas mixture by a catalyst. It is intended to remove trace amounts of CO from H2/CO/CO2 mixtures produced by steam reforming and wate ...

(PROX) The

methanol reformer A methanol reformer is a device used in chemical engineering, especially in the area of fuel cell technology, which can produce pure hydrogen gas and carbon dioxide by reacting a methanol and water (steam) mixture. :\mathrm \Delta H_^0 = 49.2\ \ ...

converts methanol to H₂ and CO₂, a reaction that occurs at temperatures of 250 °C to 300 °C.

Fuel cell

→The membrane electrode assembly (MEA) fuel cell stack produces electricity in a reaction that combines H₂ (reformed from methanol in the fuel processor) and O₂ and produces water (H₂O) as a byproduct. Usually Low Temperature Proton-exchange membrane fuel cell (LT-PEMFC) or High Temperature Proton-exchange membrane fuel cell (HT-PEMFC) is used for RMFC.

Fuel processing system (FPS) out

→Tail gas combustor (TGC)

catalytic combustion afterburner Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

or (

catalytic combustion Catalytic combustion is a chemical process which uses a catalyst to speed desired oxidation reactions of fuel and so reduce the formation of undesired products, especially pollutant nitrogen oxide gases (NOx) far below what can be achieved without ...

) with a

platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Platinu ...

- alumina (Pt–Al2O3)

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

→ condenser

Balance of plant

The balance of plant (BOP) consists of any

fuel pump A fuel pump is a component in motor vehicles that transfers liquid from the fuel tank to the carburetor or fuel injector of the internal combustion engine. Carbureted engines often use low pressure mechanical pumps that are mounted outside the f ...

air compressors An air compressor is a pneumatic device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). By one of several methods, an air compressor forces ...

, and

fans Fan commonly refers to: * Fan (machine), a machine for producing airflow, often used for cooling ** Hand fan, an implement held and waved by hand to move air for cooling * Fan (person), short for fanatic; an enthusiast or supporter, especially wit ...

required to circulate the gas and liquid in the system. A control system is also often needed to operate and monitor the RMFC.

State of development and commercial products

RMFC systems have reached an advanced stage of development. For instance, a small system developed by Ultracell for the United States military

has me
environmental tolerance
and performance goals set by the

United States Army Communications-Electronics Research, Development and Engineering Center The Combat Capabilities Development Command (CCDC) C5ISR Center, formerly the Communications-Electronics RD&E Center (CERDEC), is the United States Army information technologies and integrated systems center. CCDC C5ISR Center is headquartered ...

, and is commercially available. Larger system
350W
to 8 MW are also available for multiple applications, such as power plant generation, backup power generation, emergency power supply, auxiliary power unit (APU) and battery range extension (electric vehicles, ships). In contrast to

diesel Diesel may refer to: * Diesel engine, an internal combustion engine where ignition is caused by compression * Diesel fuel, a liquid fuel used in diesel engines * Diesel locomotive, a railway locomotive in which the prime mover is a diesel engin ...

or gasoline generators maintenance interval of RMFC systems is usually significantly longer as no exchange of oil-filters and other engine service parts is needed. So the use of RMFC in

off-grid Off-the-grid or off-grid is a characteristic of buildings and a lifestyle designed in an independent manner without reliance on one or more public utilities. The term "off-the-grid" traditionally refers to not being connected to the electrical g ...

applications (e.g. highway maintenance) and remote areas (e.g. telecom, mountains) is often preferred over diesel gensets. Also other features as

biodegradability Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...

of methanol, the possibility to use renewable methanol, low fuel costs, no emission of particlulate matter/NOx, low noise and a low fuel consumption (long fuel supply interval) are seen advantageous. The electric vehicle sports car

Gumpert Nathalie The Gumpert Nathalie or RG Nathalie is a hydrogen-electric hybrid sports car running on Reformed methanol fuel cell, methanol to generate hydrogen that is scheduled to enter production in 2021. It is the first car produced by the new car manufact ...

contains RMFC technology. Danish company called Blue World Technologies is building the biggest plant in the world to produce indirect methanol fuel cell stacks for automotive applications

References

External links

Fuel Cells for Portable Computing and Communications: Extended Power Away from the Grid
{{Fuel cells Fuel cells Methanol