Renewable Energy: A Case For Hydrogen Energy

 

As the global demand for energy sours, scientists have stepped up their quest to find sustainable and practical solutions to the problem. Other factors such as climate change, high oil prices and demands for CO₂-neutral energy production have all lent credence to these calls, hence the renewed interest in renewable energy technologies.

 In spite these calls, one form of renewable energy is often left out of the energy equation – hydrogen. The element hydrogen is the most abundant chemical element and constitutes approximately 75% of the universe’s elemental mass. In spite of this, hydrogen in its elemental form (H) is rare on earth but the gaseous form (H₂ – hydrogen gas) is produced extensively (95%) from fossil fuels and used widely in the production of ammonia for fertilizers and in hydrocarbon processing processes such as cracking.

Though this leaves much to be desired in terms of carbon emissions, hydrogen is till heralded as a future energy source. The question is why? Why do hydrogen energy pundits and scientists continue to call the implementation of a hydrogen economy? Answers to this question will form the basis for a case for hydrogen energy and economy.

 

There exists a lot of research going on in the world of hydrogen energy; however a lot of questions remain unanswered about the future of the world’s energy supply that is expected to come from hydrogen. It is has however been established that hydrogen is in fact not a source of energy but an energy carrier. This term has been adopted because unlike solar, wind and biomass, hydrogen has to be produced from another source(s) of primary energy – fossil fuels – and the production, use, and storage of hydrogen requires additional energy. These revelations pose huge problems for the adoption and realization of a hydrogen economy but it must however be noted that this is not peculiar to hydrogen as a renewable energy alone.

 

So the question remains why hydrogen? Why do hydrogen energy pundits and scientists continue to call the implementation of a hydrogen economy in spite of the problems associated with its production, storage and use? First lets us explore the problems.

 

Hydrogen Production

Currently 95% of hydrogen used in the world is produced from fossil fuels, since it is the most economic route to effectively for production available. This statement assertion alone eliminates hydrogen as a potential solution to climate change debacle and calls for CO₂ reduction and reliance on fossil fuels. Past debates have proposed the use of electrolysis of water using sustainable nuclear energy; however, the controversy behind nuclear technologies and the cost of electricity pose additional problems.  Currently much of the hydrogen produce from fossil fuels is via the process of steam methane reforming a process that not only produces CO₂ but also requires a lot of energy to sustain.

 

Hydrogen Storage and Use

Storage of hydrogen is still a major issue in the adoption of a hydrogen economy. Presently hydrogen is stored physically in cryogenic tanks and as pure compressed hydrogen in hydrogen tanks. Research is focused on producing materials that are lightweight, compact and can store hydrogen for long periods of time without consuming large amount of energy in loading and unloading – which is the major problem with chemical storage methods.

These include storage of hydrogen in metal organic frame works (MOF), metal hydrides – compounds that combine hydrogen and a metal usually Magnesium since it has the highest capacity of approximately 8wt%. Other methods include storage in carbon nanotubes which most scientists have long debunked due it is low storage capacities.

 The storage in cryogenic tanks and hydrogen tanks remains the most widely used but these also pose problems of boil off and safety issues especially in mobile applications such as cars which the solution is sort to replace fossil fuels. Fuel cells are another alternative.

These convert hydrogen by the principle of reverse electrolysis into electricity which can be used by cars. However even this has its drawbacks which include poisoning of the fuel cell catalyst by sulfur of carbon monoxide even at low temperatures in low temperature fuel cells or the excessive heat in high temperature fuel cells such as solid oxide fuel cells.

 

Possible Solutions

Due to the antecedent problems posed by the use of hydrogen, it may appear that the solution may not be in hydrogen. Alas this is not the case, but it must be noted that the adoption of hydrogen like many other renewable energy sources is prone to a myriad of problems.

The benefit of adopting hydrogen in the opinion of scientists is that a hydrogen economy will reduce the dependence of mankind on fossil fuels, reduce CO2 emissions and global warming. This is true, however the practicality of the ideas remain a problem.

 Many studies have shown that the future of hydrogen as a possible source of renewable energy will not be in mobile applications like cars but the problems mentioned above. Therefore current research efforts are directed at the use of fuel cells combined with gas turbines – a hybrid system which uses the excess heat from high temperature fuel cells to generate electricity via various thermodynamic cycles.

Therefore the consensus is that hydrogen will be a major player in the renewable energy equation of the future, however this will be employed more in stationary electricity generation applications like hybrid systems, high temperature fuel cells like solid oxide fuel cells (SOFCs), hydrogen generators a technology already operational; rather than the much desired mobile applications such as cars due the higher efficiency of such systems.

More over the efficiency of fuel cell as against batteries is much lower and hence the use of hydrogen and fuel cells in the future remains a doubt. With the adoption of these and future improvements in present technologies hydrogen will one day provide the energy the world needs.