Week 8

Selecting a Generator:

The initial design of the generator involved the use of a charge controller between the generator and the battery in order to maintain a slow charge (10amps or less). While considering how to make this combination as inexpensive as possible, the idea to use a hand-crank generator instead of a conventional generator was discussed. Instead of having to purchase a charge controller and a generator, a hand-crank generator could be utilized with a gearing design that could maintain a slow charge. The team is exploring ways to design this system.

Turbine Mount Design:

The turbine anchored into the ground (G.L: Ground Level).

Side View

Top View

Front View

Week 7

At the beginning of Week 7 we needed to turn in our Final Report Draft. Writing the draft helped to highlight areas of our project that we need to further develop. Over the final weeks our group needs to work on.

• Selecting a generator
• Developing a way to wire the light sources
• Designing ways to mount the turbine
• Drawing a circuit diagram
• Designing an insulated housing for the battery charging station
• Develop our PowerPoint presentation

We will focus our attention on these tasks in the remaining weeks.

Lighting Requirements

The design is intended to light a classroom, and according to the Rensselaer Polytechnic Institute Lighting Research Center there are minimum recommended lumens (amount of visible light from a source) for reading and writing. Other sources recommended lighting levels of 30 foot-candles for reading. These values of foot-candles and lumens can be used to figure out the square footage (ft²) the recommended amount of light will cover.

Lumens/Foot-Candles = ft²

This information helps find the ideal light bulb to use. The SATCO lamp specification catalog provided the light bulb specifications and helped determine the amount of watts the light bulb requires. Their T2 Ultra Mini Spiral Compact Florescent Bulbs would provide 600-800 lumens and requires 40-60 watts.

The amount of watt-hours 3 bulbs require can then be calculated.

3 bulbs x (40-60watts) = 120-180 watts

5 hours x (120-180watts) = 600-900 watt-hours

Volts & Week 6

The light bulbs are 120 volts and the car batteries that are going to be utilized provide 12 Volts. Different options can be explored to increase the voltage from the battery to the light bulbs.

-Explore cost and practicality of batteries in parallel and series.

-Explore cost and practicality of inverter.

-Explore cost and practicality of different types of batteries.

*Keeping this fundamental “map of requirements” in mind, this would also be a good time to begin exploring some of the negative effects such as power loss through connections and inverters and the effects that the elements might have on our electrical systems.   

Week 5

The graph above shows a theoretical output of both a Savonius Wind Turbine (blue) and a traditional horizontal axis wind turbine against wind speed. The average wind speeds in Africa range between 5 and 20 km/h, but the graph considers extremities of wind speeds up to 35 km/h.

The data was calculated using the following formula, which is the general formula for calculating the revolutions per minute in a wind turbine:

Where λ is the Tip-Speed Ratio

(Source: http://www.raeng.org.uk/education/diploma/maths/pdf/exemplars_advanced/23_wind_turbine.pdf)

The revolutions per minute is directly related to the power and this was calculated using http://www.windstuff.org/calc/calc.php

A simple analysis of the graph shows that both turbines produce similar energy output values, though the Horizontal Axis Turbine is slightly more efficient at higher wind speeds. However, this is not a factor that discredits the choice of a Savonius Turbine over a Horizontal Axis turbine as both of these turbines would probably break down at such high wind speeds.

            Thus, this graph helps to show that the turbine design is sufficiently efficient. The power rating of a wind turbine ranges between 250 watts and 1.8MW. Though the designed turbine’s power rating does not meet up to those, it was only made as a proof of concept and 50% of professional standard output is sufficient to be considered successful. However, it must be noted that these are optimal condition output ratings and errors in design or natural factors may considerably affect the data.