By Béla Lipták, Columnist
For several months now, I have been writing about process controls role in addressing the global energy crisis. In this article, I will lay out in some detail my approach to solving the problem through combining the technologies of the electrolyzer and the fuel cell to make solar energy available, both during the day and at night.
During the last century, the world population quadrupled. During the last 50 years, the global energy consumption has also quadrupled, and on top of that, during the last five years, the wholesale price of energy also quadrupled.
In addition to running out of fossil fuel deposits, the carbon dioxide concentration of the atmosphere has also reached the highest level in 650,000 years and is rising faster than ever. This will cause natural disasters, while half a billion people are already starving.
It is time to realize that the market forces cannot solve the energy crisis, because rising prices cannot increase the sum total of the size of the global deposits, they can only motivate the exploitation of more and more damaging sources. The energy crisis has no military solution either! More nuclear missiles will not reduce carbon emissions nor will they increase the remaining fossil or nuclear deposits. They will only waste our economic resources and consume the funds that are needed to solve the crisis.
Yet, solar energy is free, clean and plentiful. Therefore, we must accept that the solution is new technology. We should also realize that advanced process control will play a key role in this transition.
In the May issue (Green Energy Can Stop Recession] I mentioned that I am publishing a book (See Figure Here), describing this solution by providing and explaining the detailed design and controls of the worlds first, full size (1,000 mW) solar-hydrogen power plant. In the May issue I also referred to my invention of the reversible fuel cell (RFC), the Lipták cell. The reason why the RFC is so important is because it makes solar energy available night and day, continuously.
In the May issue I concentrated on the electrolyzer and just briefly mentioned that its operation can be reversed to operate as a fuel cell. I also described how process control can reduce the size, weight and, therefore, the cost of these reversible fuel cells (RFC) from todays price of about $3,000/kW to about $250/kW by the steps I will briefly describe below and in more detail in my book.
The traditional fuel cell generates electricity, heat and distilled water by reacting hydrogen with air (oxygen). In the space shuttle and in the space station, both electricity and water are generated as the stored hydrogen is oxidized in it. Fuel cells have been used not only in space exploration, but also in submarines (because they generate no noise or vibration). They have also been used to recover the energy from methane, which can be generated by wastewater and garbage dumps or from natural gas and more recently been also used in buses, automobiles and other vehicles as alternatives to the internal combustion engine.
The fuel cell consists of an electrolyte, which is sandwiched between two electrodes (See Figure). They come in many designs, including alkaline, DMFC (direct methanol fuel cell), MCFC (molten carbonate fuel cell), PAFC (phosphoric acid fuel cell), PCFC (protonic ceramic fuel cell), PEM (proton exchange membrane), RFC (reversible fuel cell), SOFC (solid oxide fuel xell) and ZAFC (zinc-air fuel cell), etc. The electrolytes can be acidic or alkaline and liquid, solid or solid-liquid composites.
PAFCs are the first generation of the mature designs. They are often used in larger vehicles and buses. These are medium temperature 200 °C (about 400 °F) units, generally available in the 60kW to 200 kW size range. They can be up to 85% efficient when used to generate both electricity and heat, but are only about 50% to 60% efficient when generating electricity only. They are large, heavy and cost about $4,000/kW.
The first fuel cell design used in the U.S. space program was that of the low-temperature alkaline fuel cell (AFC). Its disadvantages include that it is subject to carbon monoxide poisoning, is expensive and its operating life is short. The AFC electrodes are made of porous carbon plates laced with catalyst. The electrolyte is potassium hydroxide. At the cathode, oxygen forms hydroxide ions that are recycled back to the anode. At the anode, the hydrogen gas combines with hydroxide ions to produce water vapor and electrons that are forced out of the anode and produce the electric current.
Single cells are rarely able to produce enough power as is required by commercial applications. Therefore the cells are combined into stacks. Commercial stacks frequently have more than a hundred and sometimes as many as 400 cells. Todays fuel cells are expensive. In the 2 mW to 4 mW size range they cost from $3000/kW to $4,000/kW. According to the U.S. Department of Energy, this cost range compares to a diesel generator cost range of $800 to $1,500 per kilowatt, and a natural gas turbine, which can be purchase for $400 per kilowatt or even less. Therefore, reducing the fuel cell cost to $250/kW would make it competitive for virtually every type of power application.
This year, in Folsom, Calif., Altergy Systems started up the worlds first automated assembly line for the manufacturing fuel cells. The Department of Energy and the National Renewable Energy Laboratory estimated that if the production volume of proton electrolyte membrane (PEM) fuel cells reached 500,000 units per year, their unit cost could drop by an order of magnitude.