Test Results

Solar Panel

Table 1. Solar Panel Data



Solar Panel Angle: 52 degrees from the horizontal.

Voltage was as expected.

Current was measured using an open circuit current, therefore there are discrepancies between our measurements and the solar panel specification sheet.

Overall, the solar panel was operating as specified.

Rehydrating The Corn For Testing

We obtained approximately 30 bushels of eared corn at 14% moisture content in burlap sacks.

To rehydrate, we placed approximately half of the corn in an environmental chamber for three days:

  • Relative Humidity of Chamber = 70%
  • Temperature = 20C
  • Initial Corn MC = 14.3%
  • After 3 Days Corn MC = 15.3%

After the three days, we dumped the corn out onto the floor of the environmental chamber, thus increasing the surface area for moisture absorption. We adjusted the settings and took the measurements as followed:

  • Relative Humidity of Chamber = 90%
  • Temperature = 25C

3 days later the corn was at 18.3% MC.

The corn was left to rehydrate for 4 more days, but did not pick up more moisture. Testing began.

Figure 1. Initial corn setup for rehydrating.

Testing Setup Trial 1 - Whole System

Figure 2. 8 Bushels loaded into the drying chamber.

Figure 4. Mortar and pestal used to crush up the corn kernels before being placed in the moisture content reader.

Figure 3. (5) 375W heat lamps suspended to simulate sun on the solar collector.

Figure 5. Running samples in the moisture content reader.

Trial 1 Results

Table 2. Corn Drying Data

Logistics: The temperature and relative humidity sensor was placed in the middle of the top shelf in the drying chamber. The heat lamps were placed parallel to the ground and above the solar collector. An ear of corn on the top and bottom shelves were marked using zip ties. The marked ears were placed the furthest distance away from the inlet air duct to ensure uniform drying. 10-15 kernels were taken from the marked ears every hour and placed in a labeled ziplocked bag until the sample could be placed in the moisture content reader. It took two hours per sample to determine the moisture content of the corn. The bottom shelf samples were tested first.

Analysis: Figure 6 shows a decrease in the moisture content of the corn for both the top and bottom shelf samples. The bottom shelf dried by approximately 1.5% whereas the top shelf dried by approximately 3%. Because testing each sample took 2 hours to run, and we had 18 samples to run, which were spread out among a couple days, it is possible that the top shelf samples could have lost moisture outside of the drying chamber. The samples were in ziplocked bags to minimize this risk however. Based on our data, some of our corn was able to reach the desired 14% moisture content at the end of an 8 hour period.

Figure 7 shows the relationship between the temperature and relative humidity in the environmental chamber (T ec & RH ec) versus the temperature and relative humidity of our designed drying chamber (T dc & RH dc). To match Nigeria, our initial conditions in the environmental chamber were set to 25C and 80% RH however the chamber was not holding these conditions. Consequently, the test performed did not accurately depict the location our design was built for. As the figure illustrates, the temperature grew fairly rapidly (nearly 6C) inside the entire environmental chamber due to the heat lamps positioned above the solar collector. The increase in temperature caused a decrease in the relative humidity as expected. While our conditions didn't match that of Nigeria, our drying chamber and solar collector set up did perform as designed. The temperature in the drying chamber after about an hour was consistently 1C+ above that of the ambient air. The relative humidity in the drying chamber after about an hour was also consistently about 1% higher than that of the ambient air, signifying that the air was picking up the moisture from the corn. We would expect the temperature and relative humidity differences to be larger if the drying chamber was placed in the sun.

The heat lamps placed so closely to the solar collector caused some of the plastic to melt. The melted spot can be see in figure 8. Figure 8 also shows the updated heat lamp setup to avoid more plastic melting.

The 400CFM fan operated as expected.

It is also important to note that the initial moisture content of the corn was not at our desired 25% moisture content.

Exclusions: We did not record the quality or state of the corn during the testing of this project. The corn was given to us pre-dried and fairly damaged from animals and mold. Trying to rehydrate the corn caused the growth of more mold which eventually led to us ending testing after exhausting our options.

Figure 6. Graph of the moisture content of the corn over time.

Figure 7. Graph of the temperature and relative humidity of the drying chamber (dc) and environmental chamber (ec).

Solar Collector Testing Setup

Figure 8. Heat lamps suspended parallel over the solar collector for even distribution.

Figure 9. Location of the moisture content and temperature reader.

Solar Collector Results

The heat lamps were placed parallel to the solar collector. The solar collector was run for approximately one hour in the setup above. The plateau in the middle of the graph is the maximum amount of heating that occurred. Once we noticed the graph plateaued for 10 minutes, we turn off the heat lamps and let the system cool. It took approximately 30 minutes to reach the max temperature.

Ambient Conditions:

  • Temperature: 23C
  • Relative Humidity: 39.5%

Maximum Heating:

  • Temperature: 24.54C
  • Relative Humidity: 33.95%

Amount Changed:

  • Temperature: +1.54C
  • Relative Humidity: -5.55%

Figure 10. Solar Collector Data

Discussion

To simulate the sun in Nigeria, we needed 1200W/m^2, or 2400W total, for our solar collector. After extensive research and talking to trusted faculty, we came up with (5) 375W heat lamp bulbs for a total of 1875W. This is was the largest load we could safely put on the environmental chamber circuit without worrying about tripping a circuit breaker.

During the first test, we only measured the moisture content of the corn on the top and bottom shelves to minimize the amount of time samples spent outside of the chamber even though they were placed in ziplocked bags. In addition, our research and coursework showed us that the bottom shelf would likely be the fastest to dry while the top shelf will take the slowest amount of time.

When trying to test the drying chamber a second time, with a space heater instead of the solar collector, the space heater burnt out within two hours of testing. The testing sample was unusable.

After exhausting our options to test the grain drying chamber, and the corn turning into a biological hazard, we stopped testing.

Generally our system's components worked individually. Further testing would need to be done, with all subsystems connected, in an environment more closely resembling Nigeria to conclude this to be a feasible design.