Final Design

Hydro Turbine Design

Originally, there were 3 option designs, a straight pipe, a diverging pipe design and a converging pipe design. All three designs can be seen below.

Image: Straight Pipe Design

Image: Diverging Pipe Design

Image: Converging Pipe Design

The straight piping was ruled out based on experimental results, demonstrating that there is too much pressure loss per turbine.

Both diverging designs and converging designs had the same power output, but upon testing, it was discovered that there is less pressure loss for the converging design

Figure: Diverging Design Chart Figure: Converging Design Chart

For this final design option, it was decided to use the converging design.

Figure: Final Convering Design at Testing Facilities Figure: Final Converging Design Schematic

This design was tested in a closed loop environment, meaning a controlled flow rate was used.

From this, the following results were obtained. As one can see, voltage did increase with only 2 minute irrigation cycles. This proofs the concept one is able to charge

a battery by using the energy the irrigation cycle creates on its' own. The second figure demonstrates how iterations of valve cyclings alone do decrease the voltage of the batteries. Thus

proving the concept can be self-powered, with enough power.

Considering this was done with a limited generator, with a matured design more energy can be obtained, until the point that one irrigation cycle is enough to fully charge the battery,

depending on the specific conditions of that flow rate.

Figure: 2 Minute Irrigation cycles vs. Battery Voltage Figure: Rapid Valve Cycling vs Battery Voltage

The figures below are the corresponding DMM results of each test that was done. These tests were performed in order to double check the previous results.

It was to make sure that the DMM was working correctly, thus double checking our work.

Figure: DMM Results of 2 Minute Irrigation Cycles. Figure: DMM Results of the Rapid Valve Cycling

ThermoElectric Generator (TEG)

In this design, the Seebeck effect was used. Three sensors were put, one 3 cm below the soil, 5 cm below, and the other on the ground exposed. The following figure is the first TEG concept design that was made.

Figure: TEG First Design Setup Figure: TEG First Design Schematic

The temperature difference between the three was obtained throughout 24 hours. The highest temperature was that of 24 degrees Celsius and lowest of 15 degrees Celsius, with a humidity of 51%. The greatest temperature gradient being that of 20 degrees Celsius. As seen below. Through this, analysis was done and it was concluded that in a day it would obtain about 1082.4 Joules. The following data was obtained and conveniently put into graphs in order to facilitate reading.

Figure: Temperature variance between sensors for 24 hours Figure: Temperature difference between ground and soil Figure: Measurement of output voltage vs. temperature difference

For the final design, in order to maximize the temperature difference, a fin and a box for the fin was 3D printed. Below, one could see the final design for the fin and 3D printed box.

Figure: Front side of TEG with fin Figure: Side view of TEG with fin

In order to make sure that the addition of the fin did make a difference, testing inside a lab was performed. The TEG and fin were tested on top of a hot plate with temperature of 50 degrees Celsius, while the fume hood temperature was that of 30 degrees Celsius. The following results were obtained.

Figure: Fin testing results

One could see that the fin design reduces voltage loss from ~72% to ~33%.

An additional test for the TEG was done. TEGs were connected in series in order to see what type of reaction would occur. The results are below.

Figure: Results of TEGs connected in series

As the results demonstrate, the generated voltage is proportional to the number of TEGs connected.

Testing of the final design was done for two different weather conditions, for sunny days in San Diego and for a cold, cloudy San Diego day.

Figure: Test for final hardware design Figure: Schematic for TEG Final design Figure: Another schematic for TEG Final Design

When tested during a cloudy day, the following results were obtained. The lower temperature gradient is due to the entire day being cold and cloudy, with

only 2 hours of direct sunlight. The following results were obtained.

Figure: Cloudy Day Measurement Figure:Cloudy Day Temperature Difference

Figure:Cloudy Day Electrical Power Generation

For San Diego, where the experimental measurements for the TEG were done, an annual temperature variation graph is seen in the figure below. This data is provided by the weather webpage. By using the average temperature data from this Figure, the average energy generated per day can be calculated. Based on the annual average temperature variation, the energy is calculated to be 146.5J, which satisfies 90J energy requirement for daily operation that was previously calculated. This has an energy-based factor of safety (F.S.) of 1.63.

Figure: San Diego Climate graph for a year

If this model where to be applied to national temperature data, the feasibility of TEG design to different locations could be determined. The figure below shows the feasibility of TEG among the United States. Furthermore, energy-based factor of safety was calculated for each different area, the colors of different states indicate different F.S. range, which can be a measure for design feasibility in this area. As one could see, the hotter the area, the more feasible the TEG design would be. This would be because the temperature gradient between the ambient air and the soil would be greatest.

Figure: Feasibility of TEG design in US Map

A summary of the final results for both designs can be seen in the following chart.

Figure: Summary of TEG and Hydroturbine final design results

FINAL RECOMMENDATIONS

There were a couple recommendations that were suggested to the sponsor, in case they want to continue to pursue these designs that were provided, based on the data that was obtained.

1. Integrate both the thermoelectric generator and hydroturbine methods.

Reason: These methods do not depend on each other and are not mutually exclusive, therefore by combining them, harvesting energy would be faster. With this design, the battery would not only charge with the use of the valve actuation, but also charge throughout the day at peak temperatures.

2. Investigate alternate heat exchanger designs and thermal masses for TEG

Reason: The TEG that was used in the experiments was that of the older models and lower qualities and TEGs have only gotten better and stronger now. There is also the option of using the heat of the water inside the pipe, which was not experimented on because of time constraints.

3.Design and integrate turbine+ bypass unit to adjust different flowrates.

Reason: The conditions in which we tested the turbine was less than the ideal flowrate of 5 GPM that was given to us, around 2 GPM, and it was still able to produce charging results towards the battery, which was the goal of this experiment. Therefore including a bypass that would adjust to different flow rates, which would give higher charge thus better results, it can only can get better.