Personal Power: DC Motor Generators

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Personal Power: DC Motor Generators
Made by Adam Harvey
Made for Design for UNICEF
Founding Members
Short description Generating power and bridging the "scrap gap" by using a minimum of delivered parts and a maximum of locally available scrap and kinetic energy.
Made Using (Gear)
Relevant Tutorials (Fly-Bys)
Displayed at (Venues) UNICEF Headquarters
Homepage Location
Additional Keywords power, generator, dc, motor, energy, africa, unicef, design

Contents

Description

"Personal Power" is exploring ways of generating power in the field, using a minimum of delivered parts and a maximum of locally available scrap and kinetic energy -- wind, water, human, animal. Our group is looking at various ways to cross the "scrap gap", and connect what's free as a global resource, information, with locally available scrap material. The two target goals of the group are low-power generation, with the goal being to power so-called "ultra-bright" LEDs (which are cheap, easy to ship, and have a useful lifespan of years), and moderate power generation, with the goal of charging a simple mobile phone overnight.

References

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"Personal Power" is exploring ways of generating power in the field, using a minimum of delivered parts and a maximum of locally available scrap and kinetic energy -- wind, water, human, animal. Our group is looking at various ways to cross the "scrap gap", and connect what's free as a global resource, information, with locally available scrap material. The two target goals of the group are low-power generation, with the goal being to power so-called "ultra-bright" LEDs (which are cheap, easy to ship, and have a useful lifespan of years), and moderate power generation, with the goal of charging a simple mobile phone overnight.

 


Research

"Personal Power" is a smaller, simpler alternative to other methods of power generation, such as solar and micro-hydro, which require financial investment. The advantages of making power personal is that it can use locally available resources, saves money for the individual, and bypasses the traditional means of building small to medium sized generators, which can often require changing infrastructure, bureaucratic government approvals, or importing of goods or tools.

Within the framework of "personal power", we evaluated two areas of design: methods for generating power and methods for generation motion.

Generator Devices we looked at were car alternators, DIY permanent magnet alternators, and DC motors. Kinetic motion methods we looked at were small scale hydro generators, wind-turbines, and bike dynamos.

Image:Magnet alternators 2.jpg

Permanent Magnet Alternators (PMA)

The PMA has two main parts; strong magnets and magnet wire wrapped in coils
During our research, we built three designs. Each has rotating magnets that pass through magnetic fields in the coils and creates AC current

  • AC current is what comes out of a wall outlet, DC is what comes out of batteries.
  • Pros: Demonstrates principles of power generation and will work with low rotations per minute.
  • Cons: Precision is needed, magnets and wire are not very easy to come by.

 

Image:Car alternator.jpg

Car Alternators

The next source of power we looked at was a scavenged car alternator.

  • Every car has one, so abandoned or scrapped cars are a good source.
  • Cons: require high RPMs to create useful voltage. Upwards of 1800 RPMs are needed where a wind turbine can only generate 600 RPMs on a strong wind day.
  • Pros: The alternative to high RPMs is to modify the alternator with either stronger magnets or new coils with thinner wire and more turns per coil. It's also manufactured with precision and is very durable.

 

Image:Cardboard turbine.jpg

Micro-Hydro and Wind Turbines

Both of the generators previously mentioned, the permanent magent alternator and the car alternator, are ideal devices for generating power. They've been used several highly successful energy initiatives, including a micro-hydo generator program in Gautamala by Sam Redfield and are also used by the group Practical Action. As good as these devices may be for certain situations, they may not be the ideal device for power generation in Sub Saharan Africa. The problem is not their availability, car alternators are a common item in scrapyards, the problem is that both car alternators and PMA require specialized tools or materials to make them useful.Tools that aren't common or are too expensive. Practically speaking, micro-hydro and PMAs are great, but there are significant obstacles to overcome to before they become practical on a personal level.


Image:DC motor.jpg

DC Motors

Another type of generator that we looked at is the DC motor. Unlike car alternators and PMA, DC motors output a direct current, which is what charges cell phones and powers LEDs. The DC motor in this picture is outputting over 2V. We were powering it by snapping our fingers. The faster it spins, the more electircity it outpus. If we were to spin this one faster, we'd see about 5-6 volts. Smaller motors output less, and larger motors output more. There are various sizes, ranging from the small DC motors that drive the tape heads on a VCR, to slightly larger motors that power comptuer fans. The advantages of a DC motor are that the voltage is already similar to what we would need for charging a cell phone battery. Most mobile phones run on batteries between and 3 and 4 volts and LEDs can also operate at this power. Using a DC motor to charge a battery then is fairly straightforward. To do this with a car alternator or PMA we'd need to step through a few hurdles before we could hook up phone batteries or LEDs. Another advantage of these motors is that they're small and safe, which makes them ideal for anyone who doesn't have a lot of experience with electricity.

 

Conclusions

Many of the tools that bring people together and improve the quality of life in developing countries are also devices that rely on an infrastructure that just isn't there yet, namely electricity. "Personal Power" aims to fill in the "scrap gap" and connect information with locally available scrap materials to produce low-power DC motor generators.

 

 

Using DC Motors as a Power Source

We also looked at methods of harnessing kinetic energy to run these generators. We've seen bicycle dynamos growing in popularity in Sub Saharan Africa. The famous windmill by William Kemkwamba was in fact, a 12V DC motor. DC motors and bicycle dynamos are being made to charge mobile phones while riding, and are capable of producing just the right amount of power for personal items.

With the increased prevalence of bicycle-powered generators, we believe that building on top of this existing trend would be successful way to improve power generation in Sub Saharan Africa.

So how could this achieved? One direction we're exploring is by constructing wind turbines from scrap material. Shown above is <a href="#hydro">one version of a wind turbine</a> that we made in a few minutes from a piece of cardboard. It's simply a shape that catches the wind and it can be made from all sorts of material. The metal or plastic from a junkyard could withstand weather and precision in construction is less important with these designs. By combining the simplicity of DC motors with the simplicity of vertical wind turbines, there is no need for special tools or expensive parts. It could all be sourced locally.

When a bicycle with a dynamo stops moving it stops producing power, so perhaps one design solution could be to park your bike with a personal wind-turbine kickstand. Then you'd be able to generate power even when you're not riding, making your bicycle dynamo an even more useful purchase.

But there's one other crucial thing that's missing, information.



Image:Info scrap power sized.jpg

Field Guide

One potential solution is to produce a paper guide to show these methods of power generation. The guide would include:

  • How to identity discarded objects with usable DC motors
  • Ways of coupling motors to turbines and wheels
  • Creating turbines
  • Steps for modifying car alternator
  • Methods for gearing alternator and motor shafts
  • Instructions for creating permanent magnet alternators

 


Links and References

HYDRO GENERATORS

http://www.picohydro.org.uk/
http://www.wvu.edu/~exten/infores/pubs/ageng/epp13.pdf
http://re-energy.ca/t-i_waterbuild-1.shtml
http://www.re-energy.ca/t-i_waterbuild-2.shtml
http://blog.makezine.com/archive/2008/06/bucketborne_hydroelectric.html?CMP=OTC-0D6B48984890
Water Wheel Charging - http://www.wheelandwater.co.za/solutions.htmv
http://practicalaction.org/video/view/microhydro_ahd/
http://practicalaction.org/video/view/micro_hydro_peru/
http://www.hedon.info/GainingGroundInCommunityMicro-hydroPowerDevelopmentInKenya


GENERATORS & MOTORS
http://micro.magnet.fsu.edu/electromag/electricity/generators/index.html
http://www.fossilfreedom.com/alternator-conversion.html
http://www.dangerouslaboratories.org/altp1.html
http://www.hydrogenappliances.com/powerpmas.html

DYNAMOS
Story on Bike Dynamo - http://news.bbc.co.uk/2/hi/africa/8166196.stm
Instructable Dynamos - http://bit.ly/gpgNk
Wikipedia Dynamo - http://en.wikipedia.org/wiki/Hub_dynamo
Water Desalination -
http://www.instructables.com/id/Multipurpose-Solar-Desalination-Plant/

WIND
http://www.windstuffnow.com/main/alt_from_scratch.htm

SOLAR
Solar Power Tower - http://en.wikipedia.org/wiki/Solar_power_tower
Soloar Power Trough - http://news.cnet.com/8301-11128_3-10228786-54.html
SolarOne - http://solar1.org/

BUSINESS, EDUCATION & OUTREACH
http://www.aidg.org
http://practicalaction.org/our-work/ourwork_energy?id=micro_hydro_faq

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