By Dr Zivayi Chiguvare
Green hydrogen has been internationally recognised as one fuel that could replace fossil fuels in the long run, because it can do most of what these fuels can.
Hydrogen can burn in oxygen, releasing a lot of heat (3 times more than that released by petrol, by mass), but exhausting only water. Hydrogen is the lightest element, so it has the smallest density, and a small mass will occupy a large volume. To store, or transport hydrogen economically, it must be compressed, or it must be combined with other elements like nitrogen to make ammonia, which is easier to transport as a liquid.
Ammonia, an energy carrier, also has many uses in the chemical industry, potentially providing new opportunities for countries like Namibia, in the production of fertilisers and detergents.
It is important to note that fossil fuels are nothing but hydrogen combined with carbon and a bit of oxygen. Ignition of fossil fuels supplies just sufficient energy to break the chemical bonds between these elements. Supply of oxygen allows the recombination of with hydrogen, and with carbon separately, releasing a lot of energy, but the exhaust includes carbon dioxide (CO2) and water. The CO2 that has been released by such combustion of fossil fuels since the beginning of the industrial revolution has increased to levels that plants and other natural processes are not able to absorb it to maintain equilibrium.
Unfortunately, CO2 remains and continues to increase in the atmosphere, and it absorbs heat from the sun then releases it into the atmosphere. Some of the heat is radiated away from the earth-atmosphere system, but some is retained, thus increasing the temperature – a phenomenon defined as global warming.
GLOBAL WARMING
Global warming threatens planet earth’s resilience to maintain the natural cycles as they have occurred over millennia. The carbon cycle, hydrogen cycle, oxygen cycle, and the water cycle are then severely affected, and unusual temperature gradients have been linked to global warming, causing climate change. The livelihood of mankind is affected differently in several regions of the earth, for instance the increased number and severity of wildfires, flooding, severe droughts that disturb the ecosystem have been attributed to extremely high temperatures.
Continuing with life-as-usual scenario is not a viable solution, but because humans are so used to the ease of doing their daily work through mechanisation, most of which uses fossil fuels for security of food availability and thermal comfort, the use of fossil fuels is bound to increase.
Green hydrogen, produced by harnessing solar and/or wind energy through energy conversion technologies like photovoltaic cells and wind turbines, respectively, to produce electricity that is then used to electrolyse water, could contribute towards reduction of fossil fuels use, especially in hard to abate sectors such as mobility. Electricity from renewable energy can be used to break the water molecule, H2O, into two atoms of hydrogen, and one of oxygen.
Since the Hydrogen ions are positively charged, they will be attracted by the negative electrode (cathode), while the negatively charged oxygen ions are attracted by the positive electrode (anode).
In Namibia, a water scarce country, the water will mostly be sourced from the Atlantic Ocean, and it must be desalinated and deionised before it can be used in electrolysis. Fortunately, Namibia has cloudless skies for more than 300 days in a year, with insolation surpassing 5kWh/m2 per day, and has vast tracts of open land that could be used for large photovoltaic fields.
BRINE OPPORTUNITIES
Copious amounts of brine from desalination of sea or ground water could become a huge resource for extraction of minerals, and the large amounts of oxygen from electrolysis, usually released into the atmosphere, can find use in the industry and in the health sector. These sectors can however not take-up all the oxygen, and it is not yet clear how increase of oxygen in the atmosphere due to large scale electrolysis of water worldwide, will affect the earth-atmosphere equilibrium.
The bold political decision by the Namibian Government to develop a Green Hydrogen Economy has generated a lot of interest locally and internationally. Sustainable and local, energy production and supply systems can catalyse the industrialisation of developing nations, such as Namibia.
The Green Hydrogen (GH2) Strategy of Namibia aims to produce 10 to 15 million tons of hydrogen annually by 2050. Such production requires massive infrastructure, financial and human resource capital, as well as favourable legislation that protects investments and secure long term offtake markets for the hydrogen.
The government is not venturing into green hydrogen blindly and the Green Hydrogen Research Institute (NGHRI), hosted at the University of Namibia, has been established to ensure that all steps taken are carefully researched and scientifically advised. Research by the NGHRI spans the whole value chain from renewable energy resource identification and quantification, hydrogen production processes, starting from desalination and deionising the water for electrolysis to storage and distribution of the hydrogen, and local and international usage of the hydrogen and its derivatives.
The NGHRI also researches on materials for electrodes used in electrolysers and fuel cells, as well as materials for distribution pipelines and storage tanks in terms of compatibility with hydrogen moving at high velocities and under pressure.
HYDROGEN USES
Uses of hydrogen include use as a fuel for heating, so homes in cold countries such as those in Europe could be warmed by burning hydrogen. It can be used in hybrid diesel combustion engines, as is already happening for heavy trucks, tractors, and ships.
If passed through a fuel cell, the recombination of hydrogen and oxygen can reproduce electricity, so hydrogen can be an energy storage medium, allowing baseload electricity to be supplied from intermittent generators like photovoltaics. By deliberately oversizing the photovoltaic field, more hydrogen can be produced during the day, and when the sun has set, electricity can be retrieved through fuel cells, allowing a continuous supply. A growing market of electric vehicles to abate the emission of carbon dioxide into the atmosphere, is good motivation for hydrogen use for mobility.
Namibia has taken the right decision at the right moment in development, and it stands to boost its economy through large scale production of green hydrogen – an environmentally friendly fuel.
The government is not venturing into green hydrogen blindly and the Green Hydrogen Research Institute (NGHRI), hosted at the University of Namibia
