Scheme of operation of the fuel cell stack of solid oxide or SOFC
When we talk about biofuels, we tend to think of bioethanol (E-85 or E-100) or biodiesel, which are used in conventional engines of the gasoline or diesel with a few small adaptations. On the other hand, when we think of hydrogen fuel cells, we think of a fuel that is not as easy or as inexpensive to obtain, and it is complex to manipulate (as we saw previously).
But Nissan is working on a system that could be revolutionary, by combining the best of both systems. Broadly, they are electric cars that can refuel immediately with liquid biofuel, without waiting to long recharges their batteries, and with some emissions are virtually harmless. It is an application of the technology stacks of solid-oxide fuel (SOFC).
In a presentation to the press, the manufacturer has explained that has a vision for the future of zero accidents and zero emissions. To get that last working on methods of alternative propulsion that either do not produce emissions, or do not produce net emissions, which almost means the same thing. We will explain each concept separately…
electric Car, hybrid electric/petrol and stack SOFC
Differences between different types of electric cars
The first thing that comes to mind speaking of electric cars are batteries and electrical outlets. It is the simpler system that exists, that the vehicle is stored in batteries, electrochemical energy that you need, and is recharged through a plug, through the electric network outside. The recharge is slow, and the battery energy is big, bulky, and expensive, and does not have a lot of autonomy compared to a normal car.
on the other hand, we can feed an electric motor by a fuel cell, that is to say, a system that transforms a fuel of a different nature, in electricity, is generated on-board, not brought from outside. The tanks can store more energy to have greater energy density, or in other words, you can have more autonomous with a lower weight and volume, and the recharge is much faster. The overall performance is lower, but it can be more comfortable and convenient.
Many components are common to existing designs, there is a solution too expensive
The fuel cells extract the hydrogen, they combine with hydrogen, and produce a chemical reaction that releases electricity and water. Ideally using pure hydrogen, but both refinement has a cost significant energy, not to mention the conditions that have to have the network of transport, refuelling system and storage until the vehicle’s tank.
If you are using a fuel that contains hydrogen and more things, those other things are disposed by the exhaust.
¿How it works?
The system proposed Nissan operates in the following way:
- Is introduced in the tank of the vehicle bioethanol, fuel of vegetable origin and renewable, as in a car totally normal. Unlike the bioethanol conventional, which is mixed with gasoline, you can go pure (E-100) or go mixed with water. In this last case, being of a lower purity, you will have lower energy content.
- In a first step, using heat and a catalyst to break down the complex molecules and molecules are released from hydrogen (H2) and carbon dioxide (CO2). In the case of the former, mixed with oxygen in a fuel cell solid oxide (SOFC), to generate electricity. In the case of CO2, it is discarded through the exhaust pipe.
- The oxygen of the common air mixed with the hydrogen, leading to electricity and water (in the gaseous state, steam) in the same way that is done in a hydrogen fuel cell. The hot exhaust gases is recycled to the previous step, since heat is also required.
- As exhaust products, we have, in total, water vapor and carbon dioxide, which has previously been absorbed by the plants through photosynthesis, net CO2 emissions to the atmosphere are very low, since the production of biofuels has secondary emissions are unavoidable (such as the use of tractors)
- The electricity obtained is used for an electric motor, exactly that in a car battery, a battery buffer capacity is low (such as in a hybrid), and to feed the secondary systems of the vehicle.
- When you exhaust the bioethanol of the deposit, the vehicle is stopped, as on any other vehicle.
advantages of the system are evident, especially in countries with an infrastructure of production and distribution of bioethanol, as it is the case of Brazil. Do not produce polluting gases: there are no particles, or nitrogen oxides, or carbon monoxide, or oxides of sulfur… Everything that comes out of the exhaust is as harmless as the common air. The filling is fast, does not require a special infrastructure, is already worth gas stations today serve as bioethanol, pure or mixed with water, it is mixed with gasoline and E-85 (15% oil fossil).
Nissan speaks of the autonomy of more than 600 km
disadvantages are inherent to all experimental technology, as well as by the wear and tear suffered by the fuel cell stack and its price. Nor is it clear the consumption of bioethanol, but discarding all the friction mechanics of an engine of spark ignition, we talk about a consumption lower than that of an internal combustion engine using bioethanol. This system has losses, of course, but much less; the yield is 60% of maximum. Also have the problem of what is the source of bioethanol, is not the same that comes from food crops, that of organic debris or discards.
Many are the questions that we do at the moment, but is a technology very promising and has decades of travel. Fuel cells have existed since long ago, it is another thing to use in cars. In a future in which no oil or very expensive, you will always be able to produce bioethanol in acceptable quantities, and be an alternative to the hydrogen and to the car battery. According to Nissan, the cost of use will be competitive to that of today’s electric cars.