Researchers from the town of Sarov (Research Institute of Experimental Physics (Russian Federal Nuclear Center)) have received a patent for a unique low-temperature hydrogen sensor. Eight sensor types were developed for use in diverse conditions. Alexander Gusev, editor-in-chief of the International Research Magazine "Alternative Power Engineering and Ecology", and scientific project manager, recounts about Project #1580 supported by the International Science and Technology Center (ISTC).

Sooner or later, mineral resources of the planet will be exhausted. In about 25 to 30 years, there will be no mineral oil available. Hydrogen energy is one of the most promising options for alternative power engineering. Hydrogen is a power-consuming, multi-purpose and economic energy source. It can replace conventional fuel for transport and for thermal and electric energy production. On the one hand, hydrogen can be burnt down, providing thermal energy and ordinary water as waste products. On the other hand, when obtaining electromotive force, hydrogen can be used as one of oxidizing agents in the electrochemical cell. In this case, chemical energy of the water oxidation reaction is directly converted into electric power without thermal phase. However, when developing hydrogen energy, its safety should be primarily focused on.

What would happen if liquid hydrogen suddenly spills out of the automobile fuel tank and a pool of one square meter is formed? "I have made the following calculations. An explosion will set off, its capacity being equal to forty kilograms of trotyl. This would make a small bomb", says Alexander Gusev. Certainly, everything is not that frightful, adds the researcher. To ensure safety, high-tensile air-cushion tanks are created to stand mechanical loading in case of wreck. A motor-car dropped from the ninth storey would fall apart, but the tank would jump safe and sound. Hydrogen can be kept in such tanks in a liquid or gaseous state. However, hydrogen sensors are required to know precisely what happens with hydrogen in the tanks. Rocket production, which passes on to pure hydrogen fuel, can not do without such sensors.

"Our effort intended to develop hydrogen sensors actually started back in 1994 in Baikonur, when we tested the "Energy-Buran" carrier rocket. We faced a dangerous situation during normal hydrogen filling, when burning jet propulsion. A camera-recorder helped to detect a leak of hydrogen, while standard piping is not designed for leakage detection and are not equipped with special sensors. Fortunately, the leaking pipe was in the premises where a gas-analyzer was installed, therefore we managed to prevent the accident. Otherwise, an explosion could have happened.

In case of leakage, hydrogen gets accumulated, and, having reached dangerous concentration of about 3.7 percent of volume, interacts with oxygen. The combustible mixture explodes. As pipelines pump over large quantity of liquid hydrogen, the explosion could have caused unpredictable consequences. The explosion calculated power both in Russian systems and American "shuttles" makes approximately thirty percent of the Hiroshima bomb explosion. It means that the severe damage area could have made fifteen kilometers, and partial damage area could have been twice as much", said Alexander Gusev. It was on that point that the researchers suggested that the device for best hydrogen leakage tracking should be developed.

The existing vacuum-sensing devices that check pipeline leakage or depressurization, do not fit for objective appraisal of hydrogen pipe damages. The pipeline for hydrogen consists of internal and external casing, frost protection layers being placed between them. First of all, it is important for us to know whether internal pipe depressurization occurred, but vacuum-sensing devices are not able to determine the source. Hydrogen sensors are needed specifically. However, these should be not ordinary sensors but low-temperature ones - explains the researcher. To localize the leakage most precisely, the hydrogen sensors may be placed as close to the cryogenic tunnel as possible. That means the sensors should operate at extremal low temperatures. The liquid hydrogen temperature, and hence that of the cryogenic tunnel is 20.2 degrees Kelvin (or minus 253 degrees centigrade), and the warm layer temperature is 273 degrees Kelvin (zero degrees centigrade).

"We were facing the task to develop a sensor that could approach the cryogenic tunnel as much as possible. That is, the sensor should be able to work at the temperature of 77 degrees Kelvin (minus 196 degrees centigrade). The sensor should at least stand the temperature of minus 70 degrees (such temperature can occur in the north of Russia). The task is extremely complicated. Numerous companies do not guarantee the sensor operations at temperatures below freezing point. There are no hydrogen sensors available in the worldwide practice, which could operate normally at the temperature below zero centigrade. That is why our project is a special one", emphasized Alexander Gusev.

Within the framework of the International Science and Technology Center (ISTC) project, the researchers obtained a patent for pioneering method for development of a unique low-temperature sensor to track hydrogen leakage and determine its bulk concentration.

After the initial phase n Baikonur, main effort was performed in Sarov (Research Institute of Experimental Physics (Russian Federal Nuclear Center)) in 2000. The researchers obtained funding via the ISTC form the US collaborators. The project has been supported by Vizir Ogly, Professor, University of Miami, President of the International Association for Hydrogen Energy, and Professor Michael Hampton, University of Central Florida.

During the project, researchers developed and exposed to competitive selection the sensors with different operating substances for various conditions. Those were an acoustical emission sensor, a thermochemical sensor, a piezoresonant sensor, a resistive sensor, a resistive sensor on carbonic nanostructure fractals and a sensor based on metals sprayed on ceramized base. The sensors were developed and tested by several research teams - from the Institute of Physical Chemistry (Russian Academy of Sciences) in Chernogolovka, St-Petersburg State University, Mozhaisky Military Space Academy, Voronezh State Technical University and Research Institute of Experimental Physics (Russian Federal Nuclear Center) in Sarov.

Researchers from Sarov are now actively testing a thermochemical sensor of a pea-size. The sensor consists of a penetrable case made of porous, superthin stainless steel. The case is equipped with thermochemical sensory substance based on palladinized manganese dioxide - technology of its production being a "know-how". This substance's interaction with hydrogen is accompanied by heat release, therefore, the sensor is called thermochemical. This sensor is one of the most efficient, it was certified by the Mozhaisky Military Space Academy and recommended for implementation for safe operation with hydrogen during lift-offs.

The resistive-type sensor consists of a ceramized base, where layers of various metal oxides are sprayed on, sometimes promoted by various catalysts. Special devices serve for recording electric response.

The next type of sensors is established on the basis of specially developed carbonic nanostructures as a sensory substance. They actively interact with hydrogen and along with that change their electroconductivity significantly.

Now the development of acoustical emission sensor based on principle of sonic speed changing in diverse gases is under way. The sonic speed in hydrogen is known to be four times higher than that in the air.

"Today, rocket production is facing struggle for pollution-free transport, says Alexander Gusev. At present, the researchers (including those in Russia) are developing carrier rockets, where hydrogen and oxygen is used as fuel for the upper-stage - the "Energy-Buran" rocket and space complex is known worldwide. How can safety be ensured in the course of transportation and refueling carrier rockets, and storing large quantities of hydrogen? This problem is everybody's concern".

Hydrogen is widely used not only in power engineering industry, but also in chemical and even confectionary industry. To ensure safe hydrogen storing, transportation and utilization of hydrogen can not do without sensors. All pipelines and reservoirs should be equipped with sensors. "It is very important that Russia could occupy its niche in this production", says A. Gusev.

The Sarov researchers' development is of interest for Khanty-Mansiysk, multiple oil companies and even regions recognize that oil-deposits are not everlasting, and they need to occupy their niche in the innovation sphere.

According to the scientists idea, the sensors of the future should include several different elements that would allow them to operate in diverse conditions, in a wide range of temperatures and pressures. They are also preparing a project for establishing a safe design of gas-hydrogen tank.

Olga Baklizkaja

Further information: A.L. Gusev, Head of research team, All-Russian Scientific Research Institute of Experimental Physics (Russian Federal Nuclear Center), editor-in-chief, International Research Magazine "Alternative Power Engineering and Ecology", Director General, Scientific and Technical Center <TATA>, Sarov,

gusev@hydrogen.ru