Calculations show that for a wind of 36 km per hour with a 3 square meter turbine of total efficiency 30% we can obtain about 300 watts. 300 watts are about one half a horsepower which should be enough to power a water pump or about 10 economic light bulbs.
Contacts :
Kathleen D. McCarthy kmccarth at wellesley dot edu
George Alex Popescu popescu at mit dot edu
Motivation and Description
The production of energy is a problem with many human and economic ramifications. Among others, solar and wind energies are very popular but have their own problems, primarily cost. The Physics and Media Group at MIT's Media Laboratory is experimenting with cheap alternative energy sources. A recent study produced by a graduate student of this lab has found that wind energy is more efficient than solar energy. Calculations show that for a wind of 36 km per hour with a 3 square meter turbine of total efficiency 30% we can obtain about 300 watts. 300 watts are about %BD horsepower which should be enough to power a water pump or about 10 economic light bulbs. However to be competitive with the existing invertors such a system shouldn't be more then 400 US$. The windmill should also be reliable and safe.
Site Description
Example of Windmill in Bani ( Dominican Republic)
The Dominican Republic though classified by the World Bank as a lower middle-income country, suffers from daily blackouts due to the lack of electrical infrastructure. Daily blackouts and little sustained use of renewable energy resources, has made the country of considerable interest to the project staff to experiment with renewable resources in this region. We have considered the Maximo Gomez Polytechnic School in Bani, Dominican Republic as the site of its initial experiments because of the Maximo Gomez's reputation as a premier technical high school with a competitive admissions record. However, the Polytechnic school is unique in that there is no cost to the student to attend the school so students from all social economic backgrounds attend the school. The project would likely include Dominican students in the learning process so that they may learn how to produce wind energy on their own. The school also suffers from daily blackouts hindering the learning environment at the school.
Technical description
We would like to build a vertical axis turbine, with an alternator, a redresser and a car battery for energy storage. I believe the easiest would be to use a car alternator. There should be no gear box to reduce the cost of the entire system and therefore the alternator should be able to work at different speeds. The turbine will probably have to be installed on a tower if there isn't enough wind at the ground level.
Means
We give ourselves hand tools and local materials to build the turbine. I will need a covered space with electricity where I could work for about 1 month and a place to install and test the prototypes. I would need the Maximo Gomez Technical School to provide me this space. I would be very happy to teach the school students and stuff everything I am doing in a safe manner.
Schedule
I would like to build a first prototype from January 3rd to February 3rd 2007 in Dominican Republic at the Maximo Gomez Technical School. If the prototype works the Maximo Gomez School will keep it and use and I will try to improve the system and make the knowledge of building such a windmill readily available to anybody who wishes so.
Long term motivation
The long term plan is to for the windmills to be easy to make so that any person could build one. To help with this I intend to help build in Bani a Fab Lab (see http://fab.cba.mit.edu ) which will allow anybody to build a Windmill.
Wind availability in Dominican Republic (data comes from here Repport made by National Renewable Resources Laboratory ):
Should we store energy , use energy , lift water, or just lift water and use it as stored energy ?
Price for a car battery : 60-100$
Store water 2.5 kW for 4 hours = 36 000 000 Joules = 720 000 kg or water lifted at 5m
Best solution : probably just USE the energy.
In 2004, Mr. Meyer a $5,000 (Morris K. Udall scholarship) [ . . . ] he led a student project in the Dominican Republic building a prototype of a household windmill to generate electricity. The prototype cost about $500 to build, compared with the $4,000 that windmills can cost in the Dominican Republic. However, the project needs more work; although the windmill's blades turned, it did not produce any electricity.
link to the article about this
Rotor axis : horizontal or vertical
Power control : stall, variable pitch
Rotor position : upwind/downwind
Yaw control ?
Rotor speed : constant or variable
Number of blades
Rotor ( blades, hub, aerodynamic control surfaces ..)
Drive train ( shaft , couplings, gearbox, mechanical brakes, generator)
Main frame
Yaw system
Tower, foundation and erection
Design choice so far :
(with 3 pallets so that it self-starts). CHEAP, vertical axis ( sometimes no tower needed), easy to make, reliable, less efficient and safe (no flying blades if they brake). For the electronics I am thinking of using car parts for the first one, to show that it works fast and as a starting point. Then I want to make Fab Lab electronics (more dedicated).%0BHere is a list of parts I think I need ( and a schematic of the turbine is on the last slide):%0B
3 plastic barrels cut in half (6 pallets)%0B
1 vertical shaft ( wood, metal tube , 3 cm diam , maybe 5 )%0B
a mounting weather-proof box ( which includes the alternator/rectifier and DC battery).%0B
2 ball-bearings%0B
support structure (wood ? , probably 3 2"x2"x8' pieces of wood) .
1 alternator ( first a used car one)%0B? 1 rectifier (included in car alternator)%0B
1 DC car battery (optional , to be decided)%0B
1 car water pump (for this application , should work with the car alternator)%0B
1 belt and 2 wheels ( to be decided) for the transmission ratio between mill and alternator
Example of Savonius Turbine:
Solid Works model of a possible Realization :
Vertical
Max speed : 90 mph
Rotor Height 4m
Rotor Diameter 1m
Area 4 m2
12 m/s speed : 800 w
2 blades
glass-fiber-reinforced polyester or glass fiber
Other possible geometries ( from the book : Wind Power by Paul Gipe) :
For a horizontal axis turbine using lift forces :
Some vocabulary :
These graphs represent , to my understanding, the percentage ( 1 = 100%) of power that a turbine is "extracting " from the wind
using different forces , as a function of the difference between the wind mills blade speed and the wind speed per unit of area.
BUT a horizontal axis turbine is offering much TOTAL surface toward the wind then a vertical axis PER DOLLAR OF MATERIALS.
This is why I wasnt to build a SAVONIUS TURBINE (see figures up here !)..
Desciption : (The Maximo Gomez Polytechnic High School, built with a donation
from Cuba and by Cuban technicians, will be ready to start classes on 15 November.
It was built on a 13,500 meter lot donated by the Dominican government in the
town of Bani. The Cuban government donated the construction of the polytechnic
to the town of Bani in symbolic appreciation for that town being the birthplace
of Maximo Gomez. Maximo Gomez is known as the liberator of Cuba. The Cuban government
invested RD$45 million in the facility that has capacity for 540 students and
50 internships. The facility includes three small food processors (meat, vegetables
and milk) and specialized classrooms for teaching informatics, microbiology,
chemistry and typing.)
