Hydrogen Economy

UNITED NATIONS ENVIRONMENT PROGRAMME

Interest in hydrogen as a way of delivering energy services has been
growing in recent years in response to heightening concerns about the
environmental impact of energy use and worries about the security of
fossil-fuel supplies. Hydrogen, as an energy carrier, can in principle
replace all forms of final energy in use today and provide energy
services to all sectors of the economy. The fundamental attraction of
hydrogen is its potential environmental advantages over fossil fuels.
At the point of use, hydrogen can be burned in such a way as to
produce no harmful emissions. If hydrogen is produced without
emitting any carbon dioxide or other climate-destabilising greenhouse
gases, it could form the basis of a truly sustainable energy system – the
hydrogen economy.

What is Hydrogen?

Hydrogen is the simplest, lightest and most abundant element in the universe, making up 90% of all matter. It is made up of just one electron and one proton and is, therefore, the first element in the periodic table. In its normal gaseous state, hydrogen is odourless, tasteless, colourless and non-toxic. Hydrogen burns readily with oxygen, releasing considerable amounts of energy as heat and producing only water as exhaust:
2 H2 + 02 ➛ 2 H20
When hydrogen burns in air, which is made up mostly of nitrogen, some oxides of nitrogen – contributors to smog and acid rain – are formed. Hydrogen is highly flammable with a high flammability range, burning when it makes up 4% to 74% of air by volume. It has a high energy content by weight – nearly three times that of gasoline, for example. By contrast, hydrogen has a low energy density by volume at a standard temperature and atmospheric pressure. One gramme of hydrogen gas at room temperature occupies about 11 litres of space. Storing the gas under pressure or at temperatures below minus 253º C, at which point it turns into a liquid, raises its volumetric density.

Hydrogen is a carrier of energy, not a source (Box 1). It does not exist in a natural state on earth and must be manufactured using a hydrogen-rich compound as the raw material. Today, hydrogen is produced mainly through steam reforming of natural gas, but it can be extracted from other hydrocarbons by reforming or partial oxidation. A major shortcoming of the processing of hydrocarbons is the resulting emissions of carbon dioxide and airborne pollutants. Most other
production processes in use or under development involve the electrolysis of water by electricity. This method produces no emissions, but is typically more costly compared to hydrocarbon reforming or oxidation because it requires
more energy and because electricity is, in most cases, more expensive than fossil, fuels. Today, the commercial production of hydrogen worldwide amounts to about 40 million tonnes, corresponding to about 1% of the world’s primary energy needs. This output is primarily used as a chemical feedstock in the petrochemical, food, electronics and metallurgical processing industries.

Hydrogen holds the potential to provide energy services to all sectors of the economy: transportation, buildings and industry. It can complement or replace network-based electricity – the other main energy carrier – in final energy uses.
Hydrogen can provide storage options for intermittent renewables-based
electricity technologies such as solar and wind. And, used as an input to a device
known as a fuel cell, it can be converted back to electrical energy in an efficient way in stationary or mobile applications. For this reason, hydrogen-powered fuel
cells could eventually replace conventional oil-based fuels in cars and trucks.
Hydrogen may also be an attractive technology for remote communities which cannot economically be supplied with electricity via a grid. Because hydrogen can be produced from a variety of energy sources – fossil, nuclear or renewable– it can reduce dependence on imports and improve energy security.

Road transportation is an important and growing source of both air pollutants and climate-destabilising greenhouse gases. There is clear evidence of the harmful impact on human health of exposure to pollutants emitted by cars and
trucks. As a result, local air quality has become a major policy issue in almost all countries. Air pollution in many major cities and towns in the developing world has reached unprecedented proportions. Most rich, industrialised countries
have made substantial progress in reducing pollution caused by cars and trucks through improvements in fuel economy, fuel quality and the installation of emission-control equipment in vehicles. But rising road traffic has offset at least part of the improvements in emissions performance. Because of increasing pollution from road traffic, road vehicles have been the focus of efforts to develop fuel cells. Replacing internal combustion engines
fuelled by gasoline or diesel with hydrogen-powered fuel cells would, in principle, eliminate pollution from road vehicles. Fuel cells can also be used to provide electrical-energy services in industrial processes and buildings, replacing direct use of petroleum products, natural gas and coal.

Hydrogen could also contribute to reducing or eliminating emissions of carbon dioxide and other greenhouse gases. For this to happen, the process of manufacturing hydrogen would have to be carbon-free or at least less carbon-intensive than current energy systems based on fossil fuels. This could be achieved in one of three ways: through electrolysis using electricity derived solely from nuclear power or renewable energy sources; through steam reforming of fossil fuels combined with new carbon capture and storage technologies; or through thermochemical or biological techniques based on renewable biomass. Despite the potential local and global environmental benefits of switching to hydrogen, there are a number of uncertainties about other environmental consequences of a large-scale shift towards a hydrogen economy. These concern mainly the potential effects of significant amounts of hydrogen being released into the atmosphere. The widespread use of hydrogen would make such releases inevitable, but the effects are very uncertain because scientists still have a limited understanding of the hydrogen cycle. Any build-up of hydrogen concentrations in the atmosphere could have several effects, the most serious of which would be increased water vapour concentrations in the upper atmosphere and, indirectly, destruction of the ozone layer. Increased hydrogen releases could also lower the oxidising capacity of the atmosphere, and so increase the lifetime of air pollutants and greenhouse gases such as methane, hydro-chlorofluorocarbons(HCFCs) and hydro-fluorocarbons (HFCs). More research is needed to obtain a better understanding of hydrogen sources and sinks.
Safety is a critical issue.

Contrary to popular opinion, hydrogen is actually less flammable than light oil products, such as gasoline, and most other fossil fuels (Box 2). But the need to transport and store it under high pressure or at very low temperature brings other hazards. There is plenty of evidence that, with proper handling and controls, hydrogen can be as safe as the fuels in use today. Indeed, hydrogen has a long history of safe use in industry. But, for it to become widely accepted in other applications, it will become increasingly important to develop and implement internationally agreed rules, regulations, codes and standards
covering the construction, maintenance and operation of hydrogen facilities and equipment safely, along the entire fuel-supply chain. Uniformity of safety
requirements and their strict enforcement will be essential to establishing consumer confidence.

Hydrogen Exonerated as the Cause of the Hindenberg Disaster :-

Televised images of the spectacular destruction of the Hindenburg airship affect people’s perception of hydrogen
and their acceptance of the gas as a safe energy carrier. The Hindenburgburst into flame in full view of a crowd of reporters and newsreel cameras while landing in New Jersey, in the United States, on 6 May 1937. The flammability
of the hydrogen that fuelled the airship was blamed for the disaster, which effectively ended travel by airship. But a 1997 study by a retired National Aeronautics and Space Administration (NASA) engineer, Addison Bain, concludes that hydrogen played no part in starting the Hindenburg fire. According to the study, the paint used on the skin of
the airship, which contained the same component found in rocket fuel, was the primary cause of the fire. As the
Hindenburg docked, an electrical discharge ignited its skin, and a fire raced over the surface of the airship. Of the 37 people who died, 35 perished from jumping or falling to the ground. Only two of the victims died of burns, and these were caused by the burning coating and on-board diesel. The hydrogen burned quickly, upward and away from the people on board.

A Global Hydrogen Energy System

The transition to a hydrogen-energy system would represent the ultimate step on the path away from carbon-based fossil energy. The world’s energy system has
been becoming gradually less carbon-intensive as it has moved from coal to oil and then natural gas. The technology exists today to produce, store, transport and convert hydrogen to useable energy in end-use applications, such as fuel cells.
Technologies to capture carbon dioxide and other gases released during the process of producing hydrogen from fossil fuels and store them have also been demonstrated. Almost every big car manufacturer plans to begin commercial
production of fuel-cell cars within a few years, and small fuel cells to supply power to remote communities are already coming onto the market. Most of the major oil companies have active hydrogen and carbon capture and storage programmes. We can imagine today what the hydrogen economy might look like (Box 3).
Major technological and cost breakthroughs are needed before the hydrogen economy can become a reality. The cost of supplying hydrogen energy using
current technologies, which have been developed over many decades, is still very high compared to conventional energy technologies. And some major technical problems need to be resolved. The main areas in which progress is needed are fuel cells; hydrogen production from renewables; distribution and
storage infrastructure that meets environmental and safety criteria; and carbon capture and storage, without which hydrogen may never become a viable energy solution. Achieving this will require a lot more research and development. The pace of technological progress and its impact on lowering the costs of
hydrogen supply is inevitably extremely uncertain and hard to predict. Indeed, it is by no means certain that hydrogen will ever become cost-competitive. Rapid
advances in carbon capture and storage technologies might allow us to continue using fossil fuels to generate electricity in an environmentally acceptable manner and at an acceptable cost. The Earth’s resources of oil, natural gas and coal are
certainly large enough to meet our energy needs for many decades to come.
Improved electric batteries in cars and trucks or improved emissions performance
of technologies in use today could prove to be the preferred solution to urban pollution problems. Renewable energy sources or nuclear power may turn out to be a more cost-effective solution to the threat of global warming.

If hydrogen does emerge as a competitive energy carrier, it will not displace existing systems overnight because of the slow pace at which much of the capital stock that makes up the global energy system is replaced. And the widespread
deployment of carbon capture and storage technology – most likely a key
element of the hydrogen economy for as long as fossil fuels remain theworld’s main primary source of energy – will be a mammoth undertaking. The transition
to a hydrogen economy would, therefore, be gradual, possibly taking several decades. The construction of entirely new supply infrastructure for hydrogen distribution would undoubtedly be costly and risky, which might be a major barrier to switching to hydrogen. And consumers must be convinced that
hydrogen is economical, practical and safe. Strong government incentives will surely be needed to kick-start the transition process, in addition to continuing major investments in research, development and demonstration.

Box 3: – A Vision of the Hydrogen Economy What might a hydrogen economy look like? Jump forward in time – perhaps 100 years, but possibly much less.

The world has made the transition to a hydrogen economy. An efficient and competitive hydrogen production,
storage and transport system has been built. Hydrogen has become widely accepted as a clean, safe and
sustainable form of energy. Emissions are a fraction of what they once were, even though the world’s population
and economy are now much larger. Cities and towns are filled with highly efficient hydrogen-powered vehicles
conveying people and goods, emitting only water vapour and driving along with only a gentle hum. Many of these
vehicles refuel at public stations where hydrogen supplies are received by pipeline from centralised production facilities. Others fill their hydrogen tanks from home or at their workplace from either small-scale natural gas reformers or renewable energy powered electrolysis plants, some using photovoltaics.
In this future world, home owners have the choice of buying electricity from the grid or supplying their own energy needs with a dedicated fuel cell that provides electricity and thermal energy for heating and cooling. That fuel cell uses hydrogen produced by a small reformer, using natural gas supplied through the local pipeline distribution network. Electricity is produced in centralised power plants, using gasified coal or natural gas. The carbon emitted
is captured and piped to a storage site or converted to useful and safe solid products. Some of the hydrogen
produced is burnt in highly efficient gas turbines to provide electricity, and some is piped to customers for use in
vehicles and distributed generation plants. Renewable energy sources also contribute to both power and hydrogen production. Hydrogen is used to store the intermittent energy generated from wind turbines and photovoltaics.

POSTED BY :- DR. PRASHANT

(Medical practitioner)

Source :- UNEP

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