Victor Luca, 2-Jul-20.
The Beacon 8-Jul-20
Hydrogen is a clean energy carrier and has been under study for many decades.
Science has been telling us for decades that a new energy revolution is essential if humanity is to avoid becoming a victim of its own success. Our addiction to hydrocarbons and petrochemicals has simply got to stop. Decarbonizing the energy system is a very achievable first step with the technology we have today and would be followed by decarbonization of transport, food production and other sectors. None of this of course works unless we embrace equilibrium rather than growth, and especially exponential growth. Yes, it is all very complex, so where do we start?
In many parts of the world the following expression is used; “How do you eat an elephant?”, to which the answer is “one mouthful at a time”. So let’s concentrate on energy and transport.
By now we are all starting to become familiar with battery electric vehicles (BEV) which we are seeing in increasing numbers on our roads and I am guessing are set to become the future of motorized transport as costs of production decrease, range is extend and charging times are shortened. None of this development happened overnight. Electric vehicles began to be manufactured commercially more than a century ago. This initial technological development eventually stalled and was overtaken by the internal combustion engine (ICE) which has become an indispensable part of our daily lives. The victory of the ICE vehicle over the BEV was propelled by virtually free petrol and the rapid roll-out of refueling infrastructure and the convenience that this brought us.
However, the BEV is now back with a vengeance, and in time, I am certain that this superior tech will eventually displace ICE vehicles. The resurgence of the BEV was due not just to the recognition of the need to reduce greenhouse gas emissions during use, but also advances in batteries, electric motors and other technology. As long as the electricity used for BEVs comes from renewable sources, then the life-cycle emissions (LCE) of such vehicles can be as much as half those of ICE cars. By LCE we mean the sum total of emissions generated during the vehicle’s production phase and operational lifetime. A saving of 50% on emissions is nothing to be sneezed at, although it would be much better if we could reduce these LCE values closer to zero.
In NZ we are very fortunate to have a relatively clean electricity generation system due to the fact that it is dominated by hydro and geothermal power stations that are considered to emit relatively few greenhouse gas emissions. The Matahina generating station is an example of the former and Wairaki power station of the latter. These renewable methods of electricity generation account for about 85% of our electricity. The remaining 15% of electricity generation in NZ essentially comes from burning coal and gas - mainly at the Huntly power station - and we should stop this. Although we are blessed in having a relatively low-emission electricity generation system, we burn a lot of gasoline in our cars and trucks and generate considerable methane emissions through farming. Therefore, as a country we produce significant per capita emissions. Whilst we are a small country, we punch well above our weight in car ownership with almost every single New Zealander owning one vehicle.
BEV development started more than a century ago but it is not the only green tech that got an early start. Unbeknown to many, the development of an electrochemical device known as a fuel cell (FC) also commenced more than a century ago. A FC converts fuels such as hydrogen to electricity and they are now very refined devices. Fuel cell cars can use these electrochemical devices to convert hydrogen to electricity which can then be used to power electric motors to propel the car. In other words they are called hydrogen cars but in reality the hydrogen is used to make electricity that drives the electric motor just as in a conventional BEV. The beauty of this tech is that the only thing that comes out of the tailpipe is water. Water is the only thing produced whether you use hydrogen in a fuel cell to generate electricity or burn it directly. The chemical reaction for burning hydrogen is as follows:
2H2 + O2 = 2H2O
Notice that the only product that is formed is water.
There are currently many hydrogen/fuel cell cars in commercial development by both traditional makers including Toyota (Mirai), Honda (Clarity), Mercedes (LGC F-cell) and Hyundai (Nexo) and others and non-traditional makers such Nikola (Badger).
Notice that the only product that is formed is water.
There are currently many hydrogen/fuel cell cars in commercial development by both traditional makers including Toyota (Mirai), Honda (Clarity), Mercedes (LGC F-cell) and Hyundai (Nexo) and others and non-traditional makers such Nikola (Badger).
The beauty of hydrogen as a transport fuel is that you can refuel in much the same way as you refuel a conventional ICE car. Unlike a BEV, this operation takes only a few minutes and the range is typically better than that of the average full BEV. According to Toyota, the 2021 Toyota Mirai will be able to travel 640 Kms before refueling, enabling one to get from Whakatāne to Wellington comfortably without stopping for gas. The Nikola Badger pickup truck also has impressive specs with a total range of 965 Km and a 0-100 Km time of 2.9 seconds. It all sounds quite compelling doesn’t it? You would have to conclude that there are some significant advantages of this futuristic tech.
The good news for a hydrogen energy system is not just in the transport area. Hydrogen gas is easy to generate by using the electricity from renewable sources such as solar and wind to electrolyze water. The hydrogen generated from electrolysis of water can then be readily compressed and stored in high pressure tanks to be used later as required. Our district has among the highest sunshine hours in the country and we should make greater use of this free energy.
Hydrogen can be used directly as a transportation fuel in the FC vehicles I have just described or it can be used to generate electricity for domestic, industrial and other uses in much the same way as natural gas is used domestically and in a generating station such as Huntly. The beauty of this form of storing energy as compressed hydrogen is that it couples well to the generation of electricity using renewable sources and is useful for flattening out the electricity load when the renewable sources are not generating. Remember that renewable electricity sources such as wind and solar only generation when the Sun shines and the wind blows. One potential scheme for how the system might work in the case of solar energy is shown in the figure below.
The Sun, which is essentially a nuclear fusion reactor, shines its energy on photovoltaic panels that generate electricity at essentially no cost. This electricity can be used directly during the day and any excess then used to produce hydrogen through water electrolysis and the gas stored. In the early evenings when demand is highest and the Sun goes down, the stored hydrogen gas is then converted back into electricity using a generator similar to those that can be purchased at the hardware store for a few hundred bucks.
These solar hydrogen generating stations are not just figments of my imagination, they are becoming a reality. The figure shows an actual 10 MW hydrogen plant in Fukushima, Japan that uses solar energy (note the PV panel arrays) to produce hydrogen that is stored in the large vertical tanks. Of course in the process of converting solar electricity to hydrogen and then back to electricity losses will be incurred. But since the electricity was generated for nothing in the first place, who cares?
This sort of scheme has been implemented in nuclear powered submarines for decades. In this case the fission nuclear reactor generates unlimited electricity which is then used to electrolyze water to produce hydrogen and oxygen. The oxygen produced is what the crew breathe. This enables these submarines to stay submerged indefinitely only needing to surface to take on board food.
There are in fact many ways of storing renewable energy that I have not address here since we are concentrating on hydrogen and what is called the hydrogen economy. They include pumped hydro, fly wheels (mechanical), compressed air energy storage, batteries (and there are many types) and so forth.
All of this may seem fanciful, but so was every technological development that has ever revolutionized our lives.
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