Electricity won’t get caught
To reach the decarbonization goals set in the Paris Agreement, we need a true energy transition. That will mean rapid development of renewable energy sources and rapid rejection of fossil fuels, starting with coal. In particular we will need to make a decisive step towards gradually making cars, engines and plants electric. However, electricity must not come from thermal power plants that burn fossil fuels. That wouldn’t solve the problem. It must come from renewable sources, most of all sun and wind.
But things aren’t that simple. The International Renewable Energy Agency estimates that by 2050 more than half of the things we consume will come from sectors that can’t go electric.
Another unsolved problem is that renewable sources are intermittent and not in line with changing demand for energy. Solar panels don’t work at night and neither do turbines when there’s no wind. Unlike fuel, electricity can’t be stored. You have to use it right when you generate it, or it’s lost for ever.
Batteries that collect the energy produced
One solution for gathering green energy when it’s available, then using it when it’s needed, is batteries. Inside these, a reaction turns electricity into chemical energy, storing it in the links between the molecules and metals. The inverse reaction turns the chemical electricity into electricity when you need it. But batteries have quite a few downsides. They often use rare metals that are costly and hard to repair. Producing and disposing of them causes pollution. They are heavy and only fit in certain kinds of mobile devices.
They can also be useful when it comes to compensating for daily fluctuations in supply and demand, as with the day and night cycle of solar panels. Wind plants, however, have far longer, often seasonal cycles. Harsh winter winds can give way to summers without even a breeze. To compensate for these seasonal cycles, you need big packs of batteries that can store energy for months, to avoid the problem of them naturally draining over time.
Hydrogen and its utilization
Hydrogen (H2) could be just the molecule we need in all these challenges.
The most abundant element in the universe – three quarters of the sun and the Milky Way is hydrogen – is a great energy vector in gas form. Just 1 kg of H2 is enough to develop 12 MJ of energy. It takes 56 kg of natural gas, 45–46 kg of petrol, diesel or kerosene, 30–32 kg of coal, and 16 kg of wood to do the same. It can be easily transported in gas pipes, and best of all, it emits no CO2 or other pollutants!
So why is hydrogen still not in common use around the world?
First of all, because there’s a big problem with getting hold of it here on earth. You can find whole oceans of it, in an oxidised form known to experts as... water.
To use it for energy, first you have to extract it from the water molecules and store it. That’s why, until we can get hold of it directly from the sun – where it exists in an unoxidised form – hydrogen is seen as an energy courier and warehouse rather than an energy source.
The main way of producing it from renewable sources is using an electrolyser. With this device, water is fed with electricity to break down the H2O molecules into their components, hydrogen and oxygen, turning electricity into chemical energy. But used the other way round, the electrolyser can become a fuel cell transforming chemical energy back into electricity, using the H2 and O2 molecules to produce H2O molecules.
A fuel cell
This is how you store the excess energy produced by renewables instead of wasting it. When you produce more energy than there is demand for, for example at a plant with solar panels or a wind farm, you can direct the excess electricity towards an electrolyser powered by water, and use or release the oxygen into the atmosphere and store the hydrogen in canisters. When, however, the demand for energy overtakes the production capacity from renewables, you can make the electrolyser work the other way round and turn the chemical energy back into electricity.
Besides stabilising the electricity grid, hydrogen gets used as fuel in cars, lorries and even whole ships, and to power industrial processes that need big quantities of energy, like steelworks or silicon production, thereby making them more eco-friendly.
Research, in between costs and efficiency
Another advantage of hydrogen is its conversion efficiency. One fuel cell (which can turn chemical energy into electricity) will reach efficiency of 60% in a vehicle running on H2, while a petrol engine will achieve a measly 20%. A modern coal-powered thermoelectric plant will reach 45%, but 10% is lost in the electric current before it reaches the end users.
There’s just one downside. Currently the cost of hydrogen is too much higher than that of traditional technologies. But we’re heading in the right direction. In 2000, producing energy by burning petrol cost 40 times less than getting it out of hydrogen from renewable sources. In 2010 that factor fell to 10, and now energy from green H2 costs just double that from fossils.
The International Energy Agency forecasts that in 2030 the price of H2 will have fallen by another 30%, thanks to a rise in production and above all improved renewable and hydrogen-generating technologies.
Research and development do not rest. We do not give up the idea of keeping in a jar a small piece of the Sun to be used just in case.
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