miles.maxwell.energy.water.spring.2010

In today’s society we are seen as wasteful people, not conserving what is slowly or maybe even quickly running out. Fossil fuels and freshwater two of the largest natural resources and two of the most consumed natural resources. Scientists say that we are consuming these at a rate grater the they can naturally be replenish and before long we will suck our sources dry and need for find alternatives to both fossil fuels and fresh water. In this paper we will discuss possible solutions to the drying up of fossil fuels, specifically fuels cells their issues and bio fuels. Even though most renewable energy sources especially these seem like common sense changing something as big as a fuel source takes time and money. Both Fuel cells are Bio fuels are a source of renewable energy but both are a new idea to most people, although both have been around and in use for years. One of the main issues with a fuel cell is the internal voltage regulation, to understand how voltage in a hydrogen fuel cell can be internally controlled one must first understand how a fuel cell works and to entirely understand how a fuel cell works you need to know the parts of a fuel cell. A fuel cell takes stored chemical energy, in our case hydrogen, to produce electrical energy. Through two electro chemical reactions the fuel cell converts the chemical energy into electrical energy. The electrolyte separates the reactants inside the fuel cell, on one side of the cell hydrogen, on the other oxygen. On each side of the electrolyte are electrodes, one positive and one negative, the anode and cathode. Each electrode houses the electrochemical reaction which produces the electricity. On the outside of each electrode is a bi-polar plate, the bipolar plate collects the current and builds voltage within the cell. Hydrogen enters the cell, from the tank through a series of lines, at the anode. In the anode the electrochemical reaction begins, the hydrogen is stripped of its electrons. After the electrons have been taken from the hydrogen they are considered ionized. The positively charged ions pass through the electrolyte membrane than combine with oxygen in the cathode, making water, completing the second electrochemical reaction. The negativity charged ions, electrons, than pass wires to the device needing power and finally into the cathode where they also join with the oxygen to become water. The oxygen can enter the fuel cell in two places depending on the cell, it can enter in the cathode where it combines with the hydrogen electrons and ions to create water, or it can enter in the anode, travel through the electrolyte and at last combine with the hydrogen electrons to produce water.

The partial fuel pressure method was developed by A. Gay. He proposed that by adding excess hydrogen to the anode and re circulating the exhaust until all of the hydrogen is used. This reduces the voltage and still permits the flow of undesired bi products to exit the cell. Another way of expanding on this method is by diluting the hydrogen with inert nitrogen this also can reduce the voltage and still sustain flow. Size regulation is a less than ideal method for voltage regulation. The size of the fuel cell maters little in the output voltage because even some of the smallest cells can handle very high flow rates of hydrogen, which is the determining factor for voltage output. To large of a cell is useless because the entire surface area of the cell would have to be saturated with hydrogen and with the same flow rate as a smaller cell you would still produce the same voltage. Increasing the size of the cell will make more power by increasing the amperage in the cell, but this is not cost effective. The fuel cells are progressively getting smaller as the technology allows them. Smaller fuel cells can generate just as much as power as larger earlier generation fuel cells. The difference in size from one generation of this car fuel cell is a testament to this.

“On the left side of the photo above is the fuel cell stack from the [|hydrogen-powered GM Equinox] (93kW of output) and on the right side you can see the new fifth generation GM fuel cell stack (93kW of output also). Even without looking at the technical specifications, it is pretty obvious that the next gen GM fuel cell is an improvement on the previous version, but size and weight is not all there is to it...”(GM Shrinks)
 * GM's Fifth Generation Hydrogen Fuel Cell**



Stacking cells seems to be the most common way to acquire the necessary output voltage, but stacking cells doesn’t solve the problem of internally controlling or varying the voltage in a cell. We have determined that a fuel cell will produce less than 1 volt by itself, no matter what the size of the anode or the cathode is. Stacking the cells in series will directly increase the voltage of the fuel cell grouping. It is common to have fuel cell stacks into the hundreds or even thousands to generate the necessary voltage and power for the application. Each cell in the stack contains an anode, cathode, membrane, bi-polar plate, and can operate independently and effectively. Stacking cells in series leaves some questions to be answered. Can voltage be regulated by grouping cells within the main stack for various electrical purposes? What happens if a fuel cell in series burns out? Do fuel cells fail and loose voltage slowly or rapidly? Not all of the cells would be needed to run simple operations within a house or a car. Grouping cells together that run at rated H2 density and consumption is more efficient than running all of the cells at low power and then converting the power. Running a fuel cell in series is necessary to generate the needed voltage for many applications, but, much like Christmas lights, if one cell malfunctions, then the whole fuel cell group would fail to generate proper voltage. If this happens rapidly, it would be a very relevant concern for vehicular based applications where loss of power on a highway would be very dangerous. When using the stacking method it is necessary to have a common bus with which to connect the fuel cells. This is so if one cell burns out the remaining cells downstream from that cell will still be able to function and contribute voltage. Another way we can effectively use the stacking method to increase efficiency and maintain our desired output is to use a number of stacks connected in parallel, this allows us to vary the power output by taking an entire stack offline, while still maintaining system voltage. This setup also allows us to take a stack offline for maintenance purposes without shutting down the entire system.
 * Hackin’ It by Stackin’ It- Stacking Fuel Cells to Increase Voltage**



As far as we know, increased temperature within normal operating conditions does not directly affect the voltage output of a hydrogen fuel cell. Aside from losses caused by increased temperature to the wires conducting the electricity away from the fuel cell to whatever it is energizing. However, the increased temperature of the ambient air combined with the moisture generated as a bi-product of the electrochemical reaction can create a more favorable environment for cathode corrosion. This will eventually lead to lower cell voltages and given enough time, total cell failure. There are several ways to vary voltage in a fuel cell, but stacking cells is the most viable and vital method for accomplishing this. Finer and varied regulation can be accomplished by other methods like running parallel circuits or varying the hydrogen pressure. Many questions have been raised on whether fuel cells are a viable fuel source future. Voltage generation and regulation are one of the most important factors governing this new technology, but ingenious solutions, like these, are setting hydrogen based fuel cells into motion to power the next generation. Although internal voltage control is one of the big problems with fuel cells it is not the only one and has clear solutions. Fuel cells are expensive, way more expensive than an internal combustion engine such as a gasoline or diesel. Hydrogen is expensive and not readily produced yet. When the automobile first came out gasoline wasn’t as available as it is today but over time it became popular. If hydrogen fuel cells stick hydrogen fueling stations will become more abundant. But hydrogen isn’t the only gas that we can use for a fuel cell any gas can be used, hydrogen seems to be the best option at this point in time. Even though fuel cells power almost none of today’s cars and trucks over time people will become more convinced and open to the idea of an alternative fuel source. Bio fuels such as ethanol, biodiesel, peanut oil, and vegetable oils, are another alternative to fossil fuels. I’ll discuss bio diesel and vegetable oils as fuels in diesel powered vehicles more in depth then ethanol. Biodiesel is commonly mistaken for Waste Vegetable oil (WVO) but bio is very different. Bio is made using a simple chemical reaction. Heat is used to react a natural oil, vegetable, peanut, canola, etc., with methanol and lye. The process takes place in a series of mixing and washing tanks. The end result is a fuel that can be used as a diesel substitute in warm climates. In cold climates such as New England the bio must then be mixed with diesel to create Bio-diesel. The reacted oil and chemicals have a high gelling temperature which makes them impossible to use in a cold climate without blending diesel. The process is tedious and easy to mess up. Pictured is a home brewing set up for brewing your own Bio diesel. Waste Vegetable Oil, which is commonly mistake for bio diesel, is just that Waste Vegetable Oil. Used for cooking fryed foods in a frialator can be used as a fuel substitute for diesel. What makes WVO different then Bio-diesel is that there is no chemical reaction need to use it in a diesel application. WVO ‘gells’ at a temperature above room so a heated tank must be used for any application burning WVO. The WVO burns just like regular diesel fuel when heated and even smells of French fries.
 * TEMPERATURE EFFECTS ON EFFICIENCY AND VOLTAGE OUTPUT**

Diagram of a WVO set up.

When burning WVO the emissions are no more than same emissions that the plants (used to make the oil) consumed going through photosynthesis. It is virtually emissions free, emitting only emissions that a plant already consumed from the atmosphere. Similarly Bio-diesel has very low emissions too, much less then the emissions of conventional diesel fuels. Diesel burning vehicles aren’t as readily available in the United States as they are in other countries, this poses a problem for anyone who wants to burn Bio and WVO.

Using a fuel cell or bio fuel could help people as a whole to become less reliant on fossil fuels. But more importantly it would help to lower the emissions that people produce when driving. Both bio fuel and fuel cell technology is hardly used. It isn’t readily available to everyone, not everyone has access to a diesel powered car or truck and not every state has a hydrogen fueling stations. The technology could be quickly produced distributed for these things to go into use today.