Piezoelectric: the application of mechanical stress resulting in the creation of an electrical charge
Electromagnetic: The conversion of a magnetic field to an electrical current
Thermoelectrical conversion is being considered as a method to increase the total power generated by means of harnessing any waste heat
Low RPM Permanent Magnet generators seem to be a good option, as (indicated in the name) they do not need to spin at a RPM to generate a useable amount of power.
Source: http://www.pmgenerators.com/products/hydro
The conversion of mechanical to electrical power through the piezoelectric effect is not feasible on a large scale, as piezoelectric materials produce incredible voltage but almost no amperage, meaning that the flow of power is quite limited. For example, a 1cm cube of quarts can produce 12500 volts when 500 lbs of force is correctly applied to it. However, the electrical resistance of quartz is between 5x10^16 ohm-meters and 7.5x10^17 ohm-meters, giving an incredibly small value for current via ohm's law (I=V/R). Similarly, the material PZT (lead-zirconate-titanate), the standard piezo-material, has an extremely high resistance, lessening or removing entirely its potential to generate a useable current.
Piezoelectricity may still be useful in terms of small scale power generation; however at present it is looking like induction generators will be used.
Sources:
https://www.americanpiezo.com/piezo-theory/generators.html
http://en.wikipedia.org/wiki/Piezoelectricity
http://hypertextbook.com/facts/2004/JenniferSchanke.shtml
https://www.memsnet.org/material/leadzirconatetitanatepztfilm/
The locations being considered for the installation of the hydro-turbines have the potential to have a highly variable fluid flow-rate, potentially varying outside of the efficiency range of the low rpm generators, so a dual generator setup is being considered wherein both a high rpm generator and a low rpm generator will be connected to the turbine such that any power above the efficiency limit of the low rpm turbine may be captured. The dual-generator setup also comes with its own inefficiencies, and it remains to be determined if the amount of energy that would be captured by the presence of a high rpm generator would be greater than the amount of energy that would be presumable lost by the presence of that same generator. Factors in the calculation of the necessity of the dual setup include the likelihood that, in a given location, the flow-rate is to exceed the efficiency range of the low rpm generator.
Research has been done on the nature of the electromagnetic force as it pertains to the induction of a current in a material. According to Faraday's law of induction,
, the amount of electromotive force (measured in volts) that can be generated is directly proportional to the change in magnetic flux multiplied by the number of loops in a given coil (N). It would therefore follow that a greater magnetic flux would generate more power. A Hallbach array is being considered in order to augment the magnetic field generated by the permanent magnets in the generator and thereby generate more power.
http://en.wikipedia.org/wiki/Halbach_array
http://www.kjmagnetics.com/proddetail.asp?prod=B888-2PE-N52
http://www.gaussboys.com/store/index.php/magnet-information/halbach-array-info.html
A good general source on building and implementation techniques http://alumni.media.mit.edu/~nathan/nepal/research/research.html#Battery
Greg from TechShop Pittsburgh has advised us to design some sort of pipe assembly that will channel water from the stream or river and increase the flow-rate of the water when it hits the turbine. More research will have to be done in order to determine the most efficient way to go about creating this assembly.
A manual created by the group that built a 5-gallon generator (which served as the inspiration for this specific version of the project) has been found, and will serve as a guide for the construction of the assembly surrounding the turbine.
It has been decided that the dual generator setup will be forgone in favor of a single generator design, as the loss in power that would result from having a second generator is far greater than the amount of power that the second generator would create.
Power storage is being looked at, as the generator is currently a run-of-stream type, meaning that there is no way to store the power being produced by the generator. The batteries will increase the overall cost of the battery quite a bit, as deep cycle batteries are quite expensive and have a relatively short lifespan.
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