In the past man was struggling to conquer the physical nature while today he must conquer his own nature. This will not be easy as past history is little more than a record of the sins of nations. To conquer the human disposition for greed, power and violence, to protect the common good, global institutions are needed. Yet the goals of the multi-national corporations and of the military-industrial complex are simply to make money. This is not new. What is new is that that this global jungle is now destroying our own environment and are exhausting our resources.
In 2010 the global energy consumption was about 0.5 ZJ (zettajoule = 1021 joules). 82% came from fossil, 6% nuclear, 7% hydraulic, 6% biomass, <1% renewable sources. By the end of the century, this consumption is expected to reach 1.0 ZJ. The total proved exhaustible energy deposits today amount to 40 ZJ (Coal ~ 20, Gas ~ 9, Oil ~ 8, Uranium ~ 3) and the rate at which energy consumption is rising already exceeds the rate at which new deposits are being discovered.
The yearly renewable energy available is about 5,600 ZJ/yr (Solar ~ 5,500, Wind ~ 80, Geo/ocean thermal ~ 32, River/tide/wave ~ 8, Biomass ~ 4). Therefore the continued dependence on the remaining exhaustible deposits (40 ZJ) is shortsighted and are likely to lead to energy wars. These wars will be more dangerous than past ones, because of the terrific forces at our disposal, which we are clever enough to release, but are not smart enough to limit their consequences or even to comprehend them.
New ideas always encountered intense opposition (Galilei: “and yet it moves!”, Einstein: “Only two things are infinite, the universe and human stupidity, and I’m not sure about the former”). The opposition that Galileo Galilei faced and those who want a nuclear free world or the conversion to renewable energy is not much different. Goals serving the common good (or in this case the survival of civilization) are usually opposed by people who claim that their endeavors are motivated by a concern for man and his fate, when in fact they are only interested in power and profits. These people make pronouncements to the effect that change is not urgent, that the new ideas will not work or that they are too expensive. These people always irritated me, but enough of my preaching and let me get to the specifics.
The mothers of life on Earth planet are the Sun and water. Therefore, in order to reach a clean and inexhaustible energy future, we should stop making energy by splitting uranium or oxidizing carbon and should obtain all our energy from the Sun, distribute it (wirelessly) in the form of hydrogen, and convert it back into energy at the users by oxidizing the hydrogen back into water.
In the previous articles of this series I described the technology to transport the solar energy from the Sahara or from the Mojave Desert in the form of hydrogen to run our industries, homes and transportation. I described the controls needed to operate energy free homes with roofs covered by solar shingles, the electric cars with battery swap capability and the hydrogen burning power plants.
In many parts of the world there is no electric grid or the electric companies do not allow the use of two-directional electric meters. Under these conditions self-supporting solar packages are needed. Therefore, in the next paragraphs I will describe the key component of a wireless and fully distributed solar-hydrogen system, the RFC.
The Reversible Fuel Cell (RFC)
One of the key components needed to convert to a renewable energy technology is the RFC. This device can be visualized as a two directional fuel cell. The RFC does not exist today, but in the wireless and fully distributed energy economy of the 22nd century is likely to be as common as are the PCs are today. One of the key requirements of developing a save, efficient and inexpensive RFC is good process control.
In a reversible fuel cell, the functions of the electrolyzer and of the fuel cell are combined into a single unit, which in one direction (when solar energy is in excess) can operate as an electrolyzer and in the other direction (when solar energy is insufficient or unavailable) as a fuel cell. Therefore at night or on cloudy days the RFC is automatically switched into its fuel cell mode to generate electricity from the stored hydrogen. The automation of this operation is described in detail in my book titled “Post-Oil Energy Technology”.
It takes the same amount of energy to split water into hydrogen and oxygen as the energy that is obtained when hydrogen is oxidized into water. The only difference is that electrolysis increases the entropy, and therefore, not all the energy needs to be supplied in the form of solar electricity because some of the energy is supplied as thermal energy by the environment. Inversely, when the RFC is operated in the fuel-cell mode, part of the energy in the hydrogen fuel is released as heat. This waste heat can be used to heat hot water, condition buildings, etc. Therefore, the electrolysis mode of operation requires heat, and the fuel cell mode releases heat.
For a sketch of the detailed design of the RFC refer to the web page Index on the right and click on “RFC”.
The RFC described here does not exist yet. It will take a major research and development effort before a miniaturized, safe, simple and inexpensive version can be developed and mass-produced. Yet, I believe that similarly to the PC which 70 years ago seemed to be a pipe dream, the RFCs could also be as common as the PCs are today, by the end of this century. If (when?) this occur it will help to make our energy technology inexhaustible, clean, wireless and fully distributed.
Controlling the RFC
Once the RFCs are ready for marketing they must be as simple to operate as are today’s thermostats. The control software of the RFC will integrate four software packages. One will control the system in the electrolyzer mode. The second sub-package will control the RFC in the fuel cell mode. The third sub-package will control the automated steps of conversion between the electrolyzer and the fuel cell modes. The fourth sub-package will interface with the users of electricity in the household, the insolation detectors and past demand data in order to optimize the total system.
The role of process control is critical to the safe operation of the RFC. The complexity of the control challenge can be appreciated by realizing that operating a 400-cell RFC stack is like operating 400 pumps in parallel. Similarly, the switching between operating modes is like automatically terminating the operation of one process, purging the equipment to get it ready for a serving the operation of a different process having flows in the opposite direction and starting that process. Fortunately, the switchover from one mode to the other does not need to be done quickly and is predictable.
The material and heat balance controls in both of these modes require accurate and high rangeability flow detectors and a massive quantity of other, highly sensitive sensors. Sensitivity and reliability are both required because the cell diaphragms for example must be protected from high pressure differentials and leaks must be immediately detected for safe and automatic shut down. All the sensors and control chips will have to be miniaturized, accurate and inexpensive, just like the ones used in today’s automobile industry where we have some 500 sensors in one car.
Conclusions
It is debatable how much fossil or nuclear resources are left. It is also debatable how much climate change we can live with or how long we can use our oceans, ground waters and atmosphere as garbage dumps. What is not debatable is that the conversion to a clean, free and inexhaustible energy economy is unavoidable and the sooner we start that conversion the smoother it will be. In other words, the only thing that is un-debatable is that the debate should stop.
This conversion should start with the design of prototype equipment and with operating fully automated pilot and demonstration plants to prove their feasibility, safety and affordability. I am sure that the process control profession will meet its share of the challenges involved in this transformation and will play not only a key role in this third industrial revolution, but will also gain the respect it deserves as one of the most important field of engineering.
