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DC Inverters Make a Buzz



The vision for the Grove City apiary is to become a garden for college students from various majors to contribute in research. Part of creating a community around this apiary means that a basic electrical infrastructure must be in place. The apiary is currently off the grid. This means that the storage shed does not have lighting and the electric maintenance equipment requires batteries to be charged on campus. This is a huge inconvenience to everyone involved in researching in the apiary. A renewable energy system could fix these issues and provide green energy to the apiary. It would also allow for expansion in the future. This semester, Dr. Brooks and Cory Toribio are working on installing solar energy to this facility. This will involve a solar panel, a charge controller, some batteries, and an inverter.

There three main stages towards this goal. First, Dr. Brooks and Cory Toribio will have to conduct site analysis. This step essentially is a way to measure and quantize how much energy can be absorbed throughout the day from the apiary location with the solar panel. This is done over multiple days and with various weather conditions. Stage one is already completed, so will be discussed in more details next. The second stage is to test and collect some data on the inverter, batteries, and charge controller. While the first stage dealt with the solar panel, this step works with the other half of the equipment. This stage does not have to be done on site. The third and last stage is combining these two systems into a working prototype. A prototype verifies that everything is in order before installing professionally.

Dr. Brooks and Cory Toribio have been hard at work to conduct site analysis. They created a testbed for the 230 Watt solar panel and placed it at the location. The solar panel was faced south and inclined about 50 degrees. What the testbed essentially does is take a voltage of the solar panel at a constant load. This voltage is written to an SD card by a microcontroller. A piece of data is taken every 3 minutes for multiple days. These 480 data points per day can then be used to figure out panel irradiance, current, and power characteristics. The solar data is plotted in Excel where it is analyzed.

Here is a zoomed in picture of the back of the solar panel. The main power lines come in the top left corner. This goes into three power resistors which dissipate the energy. Two control lines also come out to transmit a voltage signal to the microcontroller.


This picture is the enclosure which takes in the control wires. These wires go to the microcontroller which writes it to an SD card. Massive batteries are in the enclosure in order to power data collection for many days.


The data from this stage indicates that the solar panel is behaving properly. The four days when data was taken had various weather conditions: Thursday 15th rainy, Friday 16th light cloudy, Saturday 17th sunny and nice, and Sunday 18th cloudy. The data collected here provided a good idea of power from the site. Over 4 days, the power absorbed by the solar panel was 3.66kW-Hrs. This is about enough energy to power an electric oven for an hour. In other words, the solar panel could bake approximately 6 batches of cookies.

This is 4-days of data I have analyzed so far: Thursday, October 15th (rainy), Friday 16th (light cloudy), Saturday 17th (was sunny and nice), Sunday 18th (cloudy).


With some data taken, Dr. Brooks and Cory Toribio are well under way to getting the apiary up and powered in no time.


-Cory Toribio

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