Adrian Tylim, All Energy Matters Incorporated, USA
The ‘hydrogen economy’ is the vision that in the near future hydrogen will be one of the primary fuels used in producing electricity and moving our economy.
In recent years, the US Department of Energy (DOE) has been investing large amounts of money in funding projects to validate and demonstrate hydrogen and fuel cell technologies in real-world conditions. It was evident during the 2009 National Hydrogen Association conference that a great deal of work is taking place and progress is being made by the collaboration between government, industry and academia.
Hydrogen has a high-energy content it has three times the energy density by mass compared to petrol (known as gasoline in the US) making it an appealing product to replace hydrocarbon-based fuels. When used for electric power, it emits only water and therefore produces no greenhouse gas emissions.
Although hydrogen is produced mostly from fossil fuel sources, truly ‘green hydrogen’ is possible, but at the moment it is a distant vision, which will be realized only when its production is carbon- free. Moving towards a green, renewable-based hydrogen economy will take many years of research and development, but important strides have been made in recent years relative to the applications and use of hydrogen.
Fuel cells have come a long way from the first space applications used decades ago. Today’s fuel cells are found in forklifts around the world and in commercial and emergency both portable and stationary applications. The Honda FCX, a zero-emission fuel cell car, has gained warm acceptance.
The important thing to consider is that hydrogen has become a very viable product to generate electricity, and demand is bound to increase significantly in the next few years. Many types of fuel cells need hydrogen to produce electricity.
How is hydrogen produced today?
With all the talk about hydrogen’s future, we usually concentrate on the emission attributes with the upshot that there is little discussion on how hydrogen is actually made.
Over 200 Air Liquide units worldwide produce hydrogen in gaseous form Source: Air Liquide
Today, hydrogen is produced and distributed primarily by large speciality gas and oil companies. For many years, hydrogen has been used and distributed in compressed or liquefied form for industrial use. Compressed hydrogen used in motive power is kept in tanks at 5000 and 10 000 psi.
Hydrogen is produced in a variety of ways, from different sources, and using diverse technologies. The majority of hydrogen generated today is based on fossil fuel processes. Hydrogen-containing compounds such as petroleum, natural gas, and coal are some of the most common sources for the production of hydrogen. Thermo-chemical processes are used to extract hydrogen from biomass and fossil fuels.
The large availability of coal indicates that it will remain one of the main hydrogen sources through processes of gasification, partial oxidation, and auto-thermal reforming. One of the most economical means to produce hydrogen today is through steam reforming a process which uses natural gas as a source.
It is common to see hydrogen production plants next to oil refineries. Often large specialty chemical companies own these hydrogen facilities. An increase in the construction of hydrogen plants is the result of a surge in the demand for hydrogen in two areas: refinery requirements to produce low sulphur petrol and from the merchant hydrogen business. But none of these processes are zero greenhouse gas emissions and carbon-free.
At present, no significant industrial green hydrogen production facility exists. The most common methods for producing green hydrogen apply wind, solar, or other renewable energy sources, to water electrolysis and electrochemical water splitting. However, with the intermittency of these energy sources, it would be important to find a means to store the hydrogen for later use. And, ideally, we need a storage method that does not spend additional energy to preserve the energy carrier.
The hydrogen storage issue has been dominant for some time. It is a largely unresolved issue that revolves around the development of infrastructure for use and distribution of hydrogen. Finding an economical way to store and distribute hydrogen is key to the development of the hydrogen economy. While we can envisage hydrogen produced and used locally in many geographies, how will it be made economically available in other areas remains unclear.
Long-term storage and transport of hydrogen
Hydrogen storage is a key element in the transition from a fossil to a hydrogen fuel economy. For the hydrogen economy to become a reality, we need to find a way to store, transport and distribute it in an economical and technically reasonable fashion. Today’s economy is based on petroleum shipped or sometimes pumped via a pipeline from source to distilleries and then distributed and moved around by trucks to storage facilities or retail sales facilities.
Cost of hydrogen (delivered $/gallon gasoline equivalent, untaxed). The US DOE’s hydrogen programme is reducing the cost of producing and delivering hydrogen Source: DOE
A key reason is that petrol is a stable product that is easy to store and transport. Hydrogen can be stored as a compressed gas, liquid or as a metal or chemical hydride. Compressed hydrogen is usually distributed in cylinders to the final user. Liquid hydrogen is transported in cryogenic container trucks.
Chemical hydrides are chemical compounds usually made of a metallic element bonded with hydrogen in a chemical reaction. Metal hydrides are of particular interest because of their potential for reversible on-board hydrogen storage and release at low temperatures and pressures. Complex metal hydrides such as alanate (AlH4ˉ) materials are studied for their higher gravimetric hydrogen capacities. Ongoing research is focusing on hydrides that can be used in low-temperature ranges.
The advantage of a chemical hydride is its safety and stability. Neither gas nor liquid forms are viable for long-term storage of hydrogen as an energy carrier because they both require a continuous input of energy to preserve them in either state forever. Most hydrides however, have limitations in terms of temperature, storage conditions or generated by-products that need special handling. And still, not all of these processes necessarily use a carbon-free route.
The market will eventually select a material that is most favourable. And when this happens, any of these products will necessitate new infrastructure to be developed for distribution and supply to different applications including motive power. New business and logistics models will have to be developed. How hydrogen will be moved from production and storage to use is yet to be determined.
But, what if there was a way to store hydrogen and distribute it using a comparable model to the one used today for petrol? And the question remains: Is there a way to produce, store, distribute and use hydrogen in a manner that is 100 per cent carbon-free? Fortunately there is, and it is based on a method which seems surprisingly simple when compared to current available processes.
Scientists at the University of Frankfurt in Germany developed a process to store and produce hydrogen in a green manner using natural resources: sand, water, and sunlight. The R&D division of a German solar power plant company subsequently acquired the technology, and further developed and optimized this process a few years ago, during the shortage of silicon, in the search for a cheaper and better way to obtain photovoltaic grade silicon.
The green way to produce hydrogen
The researchers came up with a low temperature plasma process (below 199 °C) based on the transformation of sand and other reactants into a solid hydrogen carrier compound. This material is stable under ambient temperature and pressure. The product known as hydrogenated polysilane, or HPS, is made of stable silicon atoms linked together with hydrogen atoms attached.
Using patented plasma technology, sand or silicon dioxide is transformed into a long-chain silicon polymer with fluorine atoms attached. Subsequently, the fluorine is chemically replaced by hydrogen to form HPS, the stable hydrogen carrier. HPS is a solid powder and does not decompose at low temperatures. The challenge with some reversible hydrogen storage chemical hydrides is they need higher decomposition temperatures, which make them unsuitable for some applications.
HPS does not react when it comes in contact with water at room temperature so it does not rapidly decompose when exposed to air. It can be reacted at lower temperatures with water and a catalyst to generate the hydrogen, which can in turn be supplied to fuel cells or other hydrogen-fueled power devices. This is a dream come true when we consider that, most notably, its by-products are hydrogen, water, and sand.
Silicon dioxide is reacted with hydrogen fluoride to produce silicon tetrafluoride (SiF4) in a conventional wet chemical process. Silicon tetrafluoride can also be found as a by-product of the fertilizer industry. The SiF4 is subsequently polymerized by partial reduction with hydrogen in the plasma process.
Relative to other comparable metal hydrides, HPS has a very high hydrogen release capacity of up to 20 per cent weight. What this means to the hydrogen economy is that we have found a way to store hydrogen in a stable manner and for long periods of time without the need to pressurize or liquefy. This reduces the cost of storing this fuel.
The sand can be converted to a solid hydrogen carrier compound using solar power or other renewable energy sources and then the hydrogen is extracted to generate clean electricity. Over 20 patents have been filed for this technology, including applications as a precursor for fuel cells. It offers a carbon-free route for the energy storage material. HPS supports a full, closed, zero-emissions cycle for the production and use of energy.
Sand is a very stable material, but it requires a lot of energy to break the silicon bond. However, the plasma technology has created a new form of polymer that until now was not possible. The compounds based on silicon atoms linked together are known as silanes.
Specifically the ones with no more than four atoms of silicon are known as dangerous products to work with. They explode upon contact with air or are at least are self-igniting. Molecules with up to four silicon atoms have been very hard to create. But the plasma technology has enabled researchers to create a long-chain silicon polymer that is both stable and safe to use. Ongoing research seeks to reduce cost and the amount of energy needed for the process, and the upside for this technology looks increasingly favourable to serve market needs.
A clean way to power the world’s economies
The unique combination of properties of the compound and the fact that HPS starts with an unlimited feedstock resource like sand makes it a very appealing energy storage solution. It is envisioned that, by using HPS, hydrogen could be produced virtually anywhere in the world. This process could become a catalyst for many countries to have access to an inexpensive source of clean energy. Perhaps the many nations, which subsidize the cost of energy will now be able to invest in improving their education and health programmes.
It could significantly improve the standard of living of the world’s population. With this new method for energy storage, many of the economically-challenged segments of the earth’s population will be able to develop without negatively impacting the environment.
There are many advocates for the use of photovoltaic solar power to produce hydrogen. But the issue of energy intermittency and the ability to store it still need to be addressed. The difference between producing hydrogen from water electrolysis using solar power and making HPS is that we can now store and transport the hydrogen to be used at will.
For its 2010 budget, the Obama administration requested that the hydrogen programe be cut in favour of other energy technologies by about 60 per cent or $100 million. This would be an important set-back in terms of Washington’s commitment to a programme initiated by President Bush and that has already funded more than $1.5 billion in research and development.
The US Congress is currently debating an energy bill which will re-establish funding to approximately the same levels as last year’s. Regardless of the outcome, it is evident that technologies for the production and utilization of hydrogen have evolved thanks to government support and to the visionary initiative of many private companies. Many of these companies are already in their second and third generation of products, and some are even turning a profit.
A report announcement by the market research firm Innovative Research and Products Incorporated estimates the current market for fuel cells, hydrogen energy and related nanotechnology at over $8 billion. More than 3500 organizations are involved with these technologies. With this in mind, it is clear that the growing contribution of the US government has enabled the industry to grow.
In addition, it is expected that the new energy bill will incorporate measures to start taxing or discouraging the use of carbon-based fuels. The carbon cap and trade, as it is known, will limit the ability of many companies to remain viable unless they become more innovative with their use of energy. When this happens, it is evident that technologies like solar, wind, geothermal and the production of green hydrogen will be in a much more competitive position.
As carbon emissions become more costly, industry will slowly start to realize that the only way to succeed will be by using cleaner energy. It may take many years for this to happen, but it is doubtful that we will continue to do business as usual. Green technologies and green hydrogen are here to stay.
Adrian Tylim is the CEO of All Energy Matters Incorporated, a technology consulting firm specializing in renewable energy. For more information visit www.allenergymatters.com.