By: Jose Luis Caceres
As we have seen in parts 1 & 2, hydrogen (H2) can be produced from a variety of sources, such as pure water (H2O) and waste-water / sludge in the form of hydrogen sulfide (H2S). The common requirement in both cases, for separating the components of either H2O or H2S is the use of energy. In the case of water -which is an abundant and reliable supply-, the most common approach to split H2O into hydrogen and oxygen is by using the method of electrolysis.
Electrolysis as its name implies, uses electricity. Electricity in turn is produced by a source of energy, whether it be fossil fuels or renewable (solar, wind, geothermal, hydropower, biomass). Considering the carbon emissions implications of using fossil fuels, the favoured option for the electrolysis process, is the use of clean – renewable energy.
Once hydrogen is obtained, it can be stored (and easily transported if needed) and/or used directly as a combustion fuel in engines, or for production of electricity in fuel cells.
This article explores the possibility of using hydrogen harvested from water using electrolysis produced with electricity generated by renewable energy -in a cost effective manner- and then used in fuel cells. An energy chain that could eventually become the future of transportation, the ultimate hydrogen – fuel cells opportunity: Fuel Cells Vehicles (FCV’s). Lastly, we will see that this possibility is not at all farfetched and that there are in existence vehicles based on the above premises, such as the Toyota Mirai.
Electrolysis and synergy with renewable energy
Electrolysis is a promising option for hydrogen production from renewable resources. According to the US department of energy in its website energy.gov, electrolysis is defined in the following manner: “Electrolysis is the process of using electricity to split water into hydrogen and oxygen. This reaction takes place in a unit called an electrolyzer. Electrolyzers consist of an anode and a cathode separated by an electrolyte.” The diagram below shows how this process works.
Fuel Cells. How do they work?
Fuel cells are energy conversion devices that can harness the power of hydrogen. Hydrogen in turn is a versatile fuel that can power almost everything.
The Canadian Hydrogen and Fuel Cell Association (CHFCA) in its website chfca.ca provides the following definitions on regards the way fuel cells work:
A fuel cell produces electricity through a chemical reaction, but without combustion. It converts hydrogen and oxygen into water, and in the process also creates electricity. It’s an electro-chemical energy conversion device that produces electricity, water, and heat.
Fuel cells operates much like a battery, except they don’t require electrical recharging. A battery stores all of its chemicals inside and coverts the chemicals into electricity. Once those chemicals run out, the battery dies. A fuel cell, on the other hand, receives the chemicals it uses from the outside; therefore, it won’t run out. Fuel cells can generate power almost indefinitely, as long as they have fuel to use.
The reactions that produce electricity happen at the electrodes. Every fuel cell has two electrodes, one positive, called the anode, and one negative, called the cathode. These are separated by an electrolyte barrier. Fuel goes to the anode side, while oxygen (or just air) goes to the cathode side. When both of these chemicals hit the electrolyte barrier, they react, split off their electrons, and create an electric current. A chemical catalyst speeds up the reactions here.
The following short video (from chfca.ca) provides illustrate how fuel cells works:
The perfect coupling of hydrogen produced with renewable energy and fuel cells is elegantly shown in the following video from Toyota – Global:
Here are some of the advantages and benefits of Fuel Cells (source: chfca.ca):
· Environmental Performance
Since hydrogen fuel cells don’t produce air pollutants or greenhouse gasses, they can significantly improve our environment.
· Health Benefits
Hydrogen fuel cells only produce heat and water – no toxins, particles, or greenhouse gasses, which means cleaner air for us to breathe.
· Energy Efficiency
Fuel cells are 2 to 3 times more efficient than combustion engines. For co-generation applications, where fuel cells generate both heat and electricity, efficiencies can be close to 80%.
· Fuel Flexibility
There are many types of fuel cells, and each can operate in a clean manner using different fuels including hydrogen, natural gas, methanol, ethanol, biogas.
· Versatile
Fuel cells are scalable, and provide everything from milliwatts to megawatts of power in a variety of uses – from cellphones, to cars, to entire neighborhoods.
· Complementary
Fuel cells can readily be combined with other energy technologies, such as batteries, wind turbines, solar panels, and super-capacitors.
Advancements in Fuel Cell Efficiency – Toyota Fuel Cells Vehicles: The Toyota Mirai
Through the chemical reaction between hydrogen and oxygen, fuel cell vehicles are capable to generate electricity to power a motor. Toyota is turning the fuel cell option into a real and attainable possibility. Their model Mirai is the perfect example of it. The below diagram shows how the electricity for powering the vehicle is generated in a fuel cell stack provided by the input of both hydrogen and oxygen.
Below are some features of the Toyota Mirai, as described in the Toyota-Global website:
“The Mirai features the Toyota Fuel Cell System, which combines fuel cell technology with hybrid technology.
The system is more energy efficient than internal combustion engines, and offers excellent environmental performance without emitting CO2 or other harmful substances during driving. At the same time, the system gives vehicles convenience on a par with conventional gasoline engine vehicles, thanks to a cruising range of roughly 650 km and a refueling time of about three minutes.
In addition, the Mirai can serve as a high capacity power supply during emergencies. It is capable of supplying roughly 60 kWh of electricity, with a maximum DC power output of 9 kW. When a separately-sold power supply unit is connected, the Mirai converts the DC power from the CHAdeMO power socket located inside the trunk to AC power and can power a vehicle-to-home system or a vehicle-to-load system. Consumer electronics can also be connected directly and used from the interior accessory socket (AC 100 V, 1,500 W).”
ToyotaMirai: FC Stack and Technical Information -Toyota Global
Insight and Conclusions:
An economy and an energy matrix in which hydrogen and fuel cells could represent a significant component is a real possibility and moreover, a real solution to the need for decarbonizing the economy in the face of climate change. The positive implications of using hydrogen generated with renewable energy coupled with the use of fuel cells would be greatly beneficial for the environment should it be done at a massive scale and in contraposition to the use of fossil fuels.
It is not the technical aspect but the economic viability of hydrogen production and fuel cells utilization that could ultimately determine the fate of the FCV’s and of the reliance on fossil fuels -oil in particular- for transportation. The possibility of a future of non-polluting vehicles is more than ever within reach, FCV’s represent a real option which in time will surely be joining (or competing) in parallel to the burgeoning EV’s (electric vehicles) revolution.
The use of clean – renewable hydrogen and fuel cells, epitomizes the definition of sustainable energy. Undoubtedly there are many reasons to believe that a promising outlook is in store for this option. Depending on how we embrace fuel cell vehicles and hydrogen as an energy source, the potential results could definitely change and shape the energy use at a global scale.
Special thanks to Bob Kellaway for proofreading this article.
Sources:
http://energy.gov/eere/fuelcells/hydrogen-production-electrolysis
http://www.chfca.ca/education-centre/what-is-a-fuel-cell/
http://www.toyota-global.com/innovation/environmental_technology/fuelcell_vehicle/
