July 08, 2006

PAKISTAN is paradoxically dependent on oil imports. The total annual oil import bill for the year 2004-05 was $4,604 million. Power, gas, petroleum and coal are the main components of the country’s energy mix and the share of locally supplied natural gas in primary energy supplies during 2004-05 also reached 50.4 per cent.

On Jan 1, 2006, the recoverable reserves of natural gas were estimated at 32.928 trillion cubic feet. However, with the present consumption rate of 3,826 million cubic feet per day, these resources will last only 20 years at the most. It is therefore a matter of economic security to develop alternative energy resources.

Worldwide, hydrogen is being considered as a fuel for the future. It is an environmentally benign replacement for gasoline, diesel, heating oil, natural gas, and other fuels in both the transportation and non-transportation sectors. Hydrogen is a versatile secondary energy carrier that can be produced from a variety of widely available primary energy sources, including coal and natural gas.

The US government has planned to develop hydrogen power to reduce demand for oil by over 11 million barrels per day by the year 2040. It plans to produce electricity and hydrogen through a process called fusion, which is the same kind of nuclear reaction that “powers” the Sun.

Hydrogen holds the potential to provide a clean, reliable, affordable and sustainable energy supply system that may enhance the economy as well as the environment. In future, it is anticipated that hydrogen will feature as an energy carrier as compared to today when electricity serves as one.

Electricity produced by the conversion of primary energy sources is easily transported and delivered in a usable form to end-users. Similarly, a hydrogen economy would rely on the gas as the primary fuel for transportation, power, heating, and other applications. In this regard, hydrogen produced from hydrogen-containing feedstock using primary energy sources is the first and most crucial step in the path towards a future hydrogen energy economy.

Hydrogen is the most abundant element in the universe. However, it is not a primary fuel. A fuel is any high energy substance that can be consumed to produce useful work. Also, primary energy sources are found or stored in nature.

These include biomass, coal, oil, natural gas, sunlight, wind, water, and nuclear power from radioactive substances, thermal power stored in the Earth’s interior and oceans, and potential energy from Earth’s gravity.

Secondary sources of energy are produced from primary ones, using appropriate technology. The secondary energy sources include the production of electricity by burning coal, using photovoltaic cells to harness solar energy, or the production of alcohol or methanol from corn and other crops. Secondary energy sources are also energy carriers. Therefore, hydrogen is an energy transfer medium rather than a primary source of energy.

Today, about half the world’s hydrogen supplies are produced through steam reforming of natural gas. The steam methane reformation of natural gas consists of two steps: reformation of methane with high temperature steam supplied by burning natural gas to obtain a synthesis gas; and, a water-gas shift reaction to form hydrogen and carbon dioxide from the carbon monoxide produced in the first step.

In refineries, hydrogen is produced as a by-product of naphtha reforming, while some chemical plants use coal gasification (that is, partial oxidation). In its simplest form, coal gasification works by first reacting coal with oxygen and steam under high pressures and temperatures to form a synthesis gas consisting primarily of carbon monoxide and hydrogen. This synthesis gas is stripped of its impurities and shifted to produce additional hydrogen. The clean gas is sent to a separation system to recover hydrogen.

To a lesser degree, hydrogen is produced electrochemically from water when high purity hydrogen is needed. The process by which hydrogen is produced from water is called electrolysis, where electricity is passed through water in an ionic transfer device to separate water into its hydrogen and oxygen parts.

These processes are well understood and time-tested, but are too expensive to produce hydrogen in the quantities necessary to serve the energy sector. The cost of hydrogen production is an important issue in its future development as a fuel. Hydrogen production requires all the energy we get from burning the gas and a bit more on account of inefficiencies.

Hydrogen produced by steam reformation costs approximately three times more that the natural gas per unit of energy produced. Also, producing hydrogen from electrolysis using electricity will cost slightly less than two times the cost of hydrogen from natural gas.

The cost analysis shows that if oil or natural gas is used to generate electricity, there is no advantage of hydrogen use over using the fossil fuels directly. Indeed, we still get all the CO2, and there is a considerable loss of energy. World over, efforts are being made to develop new technologies that can dramatically lower the cost of producing hydrogen from coal.

Coal gasification offers one of the most versatile and cleanest ways to convert coal into electricity, hydrogen, and other energy forms. The first few coal gasification electric power plants are now operating commercially in the US and in other developed nations, and many experts predict that coal gasification will be at the heart of future generation of clean coal technology plants for several decades to come.

Gasification, in fact, may be one of the best ways to produce clean-burning hydrogen for tomorrow’s automobile and power-generating fuel cells.

Coal gasification represents the most promising approach for the production of hydrogen from coal, as well as for the next generation of coal-based electricity generation. Rather than burn coal directly, coal gasification involves the interaction of coal with steam and carefully controlled amounts of air or oxygen under high temperatures and pressures. The heat and pressure break carbon bonds in the coal’s complex molecular structure and allow carbon atoms to react with steam to form a gaseous mixture containing hydrogen, carbon monoxide, and smaller amounts of gaseous impurities.

These impurities are separated from the gaseous steam, leaving behind a coal-derived gas (syngas) that competes against natural gas in environmental quality. In a water-gas shift reactor (WGS) that uses membrane systems, the syngas is converted into hydrogen, carbon monoxide and carbon dioxide, and hydrogen is then available for electric power generation, distributed power applications, or conversion to liquid fuel.

Gasification-based systems are capable of utilising all carbon-based feedstocks, including coal, petroleum coke, biomass, municipal and hazardous wastes, and is the only advanced power generation technology capable of co-producing a wide variety of products to meet future market requirements.

Gasification-based systems are the most efficient and environment-friendly technologies for the production of low-cost electricity and other products, and can be readily adapted for concentrating and sequestering.

In future, it is also anticipated that nuclear, wind and solar electricity will contribute significantly in the large-scale use of hydrogen. In both the nuclear and solar cases, there are possible but undeveloped technologies that do not use electricity as an intermediate form of energy. The use of hydrogen as an intermediate is justified only when there is some reason not to use the primary source directly. In the case of vehicles, both nuclear and solar power plants are too big to carry around, except that nuclear power is suitable for large ships.

As large-scale use of solar energy is likely to be generated far from where it is used and at a different time, hydrogen has been proposed as both a storage and transmission medium. Hydrogen can be transported by pipelines similar to the ones used to transport natural gas.

However, this can create some problems since hydrogen tends to leak more and can make some metals used for pipelines brittle. But having said that, the existence of a 208km hydrogen pipeline in Germany provides evidence that these difficulties can be overcome.

In fact, solar energy cannot be used directly in cars except as a stunt. The solar panel of a size that can be mounted on a car produces too little energy to give good performance, and even that is not useful at night or when it is very cloudy. Hydrogen has an advantage here because it can be used as a fuel directly in an internal combustion engine not much different from the engines used with gasoline.

The drawback is that while hydrogen supplies three times the energy per pound of gasoline, it has only one-tenth the density when it is in a liquid form, and very less when it is stored as a compressed gas. This means that hydrogen fuel tanks must be large.

The large-scale use of hydrogen for cars requires a very large investment in infrastructure. In this regard, the existing gas stations can have hydrogen tanks and hydrogen pumps added, just as many gasoline stations sell diesel fuel.

In Pakistan, hydrogen is largely produced in the fertiliser industry from natural gas, which is used for the production of anhydrous ammonia — the building block for nitrogen fertiliser. On an average, the fertiliser sector has consumed 22.5 per cent of our natural gas during the last 10 years.

In Pakistan, despite the estimated coal reserves of about 193 billion tonnes in the Thar coalfield, the share of coal in the country’s primary energy supply is about five per cent only. Therefore, it has now become imperative that new investments in energy sector should be directed at gasification-based systems, with an emphasis on co-production of multiple energy carriers, and chemicals as well, at the same site (polygeneration).

The development of hydrogen-based technology will not only lessen our dependence on imported fuel but also help us develop indigenous energy resources. Hydrogen technologies will enable a variety of renewable sources of electricity, such as wind energy and solar energy to be independent of the national grid because hydrogen made by electrolysing water can be stored and will also have added value as a vehicle fuel.

Fortunately, Pakistan has a well-developed infrastructure for a CNG system which can be used for hydrogen as well. As of May 2006, some 930 CNG stations were operating in the country while 200 were under construction. Cars that run on hydrogen fuel will produce only water and no other exhaust fumes.

Depending on how hydrogen is produced, this fuel could help improve fuel supply stability, while lowering or eliminating emissions of pollutants and greenhouse gases. Eliminating pollution from cars will obviously make our air healthier, helping the nation to take the lead when it comes to tackling environmental challenges.

The writer abdulwaheed27@ hotmail.com works as an assistant professor for the Dawood College of Engineering and Technology

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