science & technology center
Fuel cells are energy-conversion devices, which produce electricity and heat by electrochemically combining fuel and oxidant without the Carnot limitation. High-temperature fuel cells, for example solid oxide fuel cells (SOFC), operate between 600°C and 1000°C and can utilize hydrogen, natural gas, or hydrocarbons.
The main components of SOFC: anode, electrolyte, cathode.
The porous electrodes (anode: fuel, cathode: oxidant) are separated by a gastight electrolyte. With the aid of electrons the oxygen in the oxidant (e.g. air, O2) will be reduced to oxygen ions O2- at the cathode side. The oxygen ions will be incorporated into the electrolyte material which is an oxygen ion conductor and therefore permits only the oxygen ions to pass through towards the anode side. There the oxygen ions combine with the fuel (e.g. H2, CH4, CO) in a combustion process to form water and, if carbon-containing fuels are involved, CO2. During this oxidation reaction electrons are released and lead via an external circuit to the cathode side where reduction of the oxygen proceeds. Thus, electrical power can be obtained from the cell.
The fuel cell can continuously produce electricity while it is fed fuel and air (oxygen). In order to obtain sufficient voltage for use, fuel cells are connected in a so-called stacks. Stacks of fuel cells connected in a system with fuel supply and outlet of electricity and heat, may have broad application.
DC which is produced by fuel cell can be used directly or converted to alternating current with a predetermined frequency using an inverter.
The generated heat can be partially used for preheating of fuel or completely be taken off for central heating and heating of water.
Fuel cell systems are the main unit of the system (generator), which also includes the units for the preparation of fuel, air (oxygen) and fuel control, heating and cooling control.
By types/areas of application:
scooters, passenger cars, buses, lorries, industrial vehicles, subway, railway transport, water transport.
laptops, mobile phones, video cameras, lighting, lawn mowers, battery chargers for electric tools, wheelchairs, instruments for military use, etc.
The principle of the fuel cells operation (direct conversion of chemical energy into electrical and thermal) implies the existence of a number of advantages for the fuel cell generators of heat and electricity in comparison with conventional types of generators.
The electrochemical process that occurs in the fuel cell can be done using a variety of materials in various forms and at different temperatures. As fuel could be used hydrogen, as well as products of processing of hydrocarbons.
For the preparation of hydrocarbon fuels for fuel cells, the system (generator) is equipped with unit for fuel reforming and its purification for contaminants (e.g., sulfur).
When reforming products (hydrogen and combustible hydrocarbon compounds) used as a fuel for fuel cell, carbon dioxide will release in addition to electricity, heat and water.
Fuel cells are classified by kind of the electrolyte and the operating temperature. The electrolyte could be a liquid (alkali carbonates, phosphoric acid) or solid (polymer and ceramics). The electrolyte material determines the design and operating temperature of the cell and also the choice of anode and cathode materials.
Operating temperature is a key factor in determining the scope of the use of fuel cell systems.
The fuel cell types
The most common classification of fuel cells:
Solid oxide fuel cell’s (SOFC) are a unique technology in many ways.
SOFC power generator is unparalleled in efficiency by any other type of power conversion technology, independent of scale, in a single cycle, and it is inherently modular.
High operating temperature of solid oxide fuel cells makes these systems flexible for operating on different fuel compositions. Due to clean, hot exhaust gas, SOFC systems are also ideal for combined heat and power generation omitting transmission and distribution losses of power and heat networks.
Fuel cells are electrochemical energy conversion devices and as a consequence, there are very few moving parts in a SOFC system. As a result, SOFC systems are low maintenance and long maintenance interval generators suited for continuous operation.
Extensive experience and focus on process architecture, integration and process control together with the unique features of SOFC technology open up interesting possibilities for distributed base load type power generation.
Zirconium-ceramic fuel cells (SOFC) and proton exchange membrane (PEM) are most suitable to meet the needs of a wide range of consumers due to the state of the current development of these technologies among the known types of fuel cells.
Solid oxide fuel cells are the most attractive for use at home, on transport, at plants, enterprises, where there is a need for relatively high power and high efficiency, while PEM generators are more suitable for low power portable devices (and production of PEM requires platinum). The table shows that the solid oxide fuel cells have higher efficiency compared with conventional heat and power generators and (at comparable power, data given for the 10 MW).
|Fuel||Generation mode||Power output rate for 1t equivalent fuel||Heat output rate for 1t equivalent fuel (for electricity generation mode)|
|Natural gas, coal, oil||Steam turbine||0,3||0,5|
|Natural gas, synthesis gas||Gasturbine||0,35||0,5|
|Natural gas, synthesis gas, hydrogen, acetylene, biogas||Solid oxide fuel cell (SOFC)||0,6||0,2|
For a customer
High efficiency, quiet operation, the ability to use stand-alone, high-quality electricity (slight deviation of frequency voltage fluctuations and other parameters), environmental friendly operation, fuel consumption in the process only to the extent required to produce consumed in a given period of electricity savings of expenses on electricity and heat, comfort.
The possibility of increasing and the efficiency of the use of alternative fuels (bio-ethanol, the synthesis gas produced from solid waste, carbon-containing industrial waste, coal gasification) and the efficiency of solar energy reducing dependence on imported gas volumes, the reduction of CO2 emissions.
А) Low cost local natural gas: Middle East, Africa, Asia. The reaction product including Н₂О: 400 l/h at 1 MW generated energy.
B) Synthesis gas (СО+Н₂) with are produced by the gasification organic fuel (coal, coal sludge, oil processing waste, municipal solid waste, medical waste, organic waste and other organic raw materials, biomass) – Europe.
To sale SOFC-CHP generators to industrial and commercial customers of B Group is necessary cooperation with manufacturing companies (gasifier of organic raw materials) which have innovative technological solutions (with no harmful emissions from the gasification process) of low budget cost.