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Citation Information : International Journal on Smart Sensing and Intelligent Systems. Volume 13, Issue 1, Pages 1-6, DOI: https://doi.org/10.21307/ijssis-2020-014
License : (BY-NC-ND-4.0)
Received Date : 30-August-2019 / Published Online: 31-August-2020
The efficiency of the photovoltaic (PV) panel was queried in this research. Past research on spectra response has shown that the maximum solar response, i.e. using color filters is 24%. This result is not very good for a PV system exposed to the harsh weather condition in any part of the African continent. In this research, the bio-filter was used to perform spectral filtering of harmful solar radiation hitting the surface of the solar PV panel. The bio-filter was synthesized from the extract of the hibiscus flower. Hibiscus is a common plant found in almost all parts of Africa. The results show that the bio-filter has a relative efficiency of 94%. This makes the product a novel to be adopted in Africa and other tropical belts to elongate the life span and performance of the solar photovoltaic panel.
Recent clamor to co-opt the solar power grid in Africa has attracted certain criticism-knowing fully well that some countries in Africa still generate less than 15 × 102 kWh (Karekezi and Kithoma, 2002; Choi et al., 2011; Hafner et al., 2018). Africa is blessed with high sunshine hour compared to other continents of the world and it is exposed to over 2.079 × 1015 kWh/year as accruable energy from the sun. Its atmosphere differs from tropical to the subtropical climatic belt. The only challenge Africa has toward developing the solar grid system is the excessive temperatures in recent times. High temperature is found to lower the efficiency of photovoltaic panels (Ishii et al., 2011; Kurnic et al., 2011). For example, the beachfront temperature in the tropical belt infrequently transcends 32°C, while some other parts have running temperature extending in the vicinity of 32°C and 42°C.
The history of capturing solar energy from the sun’s rays began in the seventh century B.C when people learned that magnifying glasses could be used to make fire and burn ants. Apart from this proof of usage of solar energy during the ancient age, other applications of solar energy occurred from twentieth century A.D to date. Even in the 1830s, a Swiss scientist designed and built the world’s first solar collector for cooking food, at other times, solar thermal energy was used to power steam engines (Brandon, 2015).
Solar energy is one of the most important sources of renewable energy that causes it to have advantages and disadvantages, but the advantages majorly outweigh the disadvantages. Some brief advantages of solar energy source according to Bratley (2013) are: it is a renewable (non-conventional) source of energy which means it can be reused over and over again; the usage of solar energy to generate electricity would reduce the dependency on fossil fuels supplies; solar power technologies emit no pollutant materials which assists in reducing the depletion of the ozone layer. In Africa, solar energy options are divided into thermovoltaic and photovoltaic. The solar thermal is used but noticeable only within standalone users for house warming in South Africa, agricultural purposes in Nigeria (Emetere et al., 2018), etc. Solar thermal is the utilization of solar radiation to deliver heat. Solar thermal devices (bureau dryers, broiler, incubation center, and water radiators) are thriving in the solar market in Africa.
Like the solar thermal devices, the photovoltaic (PV) was given the same start-up boost to thrive in the African market. The initial biases of the users were based on high purchasing and maintenance costs. The high purchasing cost of PV panels crashed as solar manufacturers from Asia flooded the African market with different types of PV panels (monocrystalline, polycrystalline, and hybrid PV panels). Domestic or standalone users were the main patronisers of the PV panels. In recent times, the patronage has dropped below expectations due to the realization that the cost of maintenance was still because of the need to change the PV panels within a year or two after purchase. It is believed that the harsh weather conditions over the Africa climate zones have introduced harmful solar radiations that are responsible for destroying PV panels. This challenge had made scientists to examine the spectral responses of different solar PV panels (Cañete et al., 2014; Dirnberger et al., 2015). In this paper, we introduce bio-filters that can be used to filter some of the harmful radiation hitting the surface of the solar panels. The bio-filter used for this research was obtained from plant extract. The plant extract was obtained from Hibiscus Sabdariffa (Figure 1). Before this experiment, it is widely known that the hibiscus extract is used for flavors, medicinal, pharmaceuticals, agrochemicals, fragrances, treatment of wastewaters, and local dyes (Gaur et al., 2009; Jadhav et al., 2009; Al-Snafi, 2018, Hoong et al., 2018). The major component in the flower is the cyanidin 3-sophoroside.
The materials used for thus experiment includes: three 3 W monocrystalline solar panels; three 4 W polycrystalline solar panels; 2 mm connecting wires; data logger; digital multi-meter; retort stand, and solarimeter. The rating of the monocrystalline solar panel is: open circuit voltage (Voc) = 10.8 v; short circuit current (Isc) = 418 mA; maximum power voltage (Vmp) = 8.2 v; and maximum power current (imp) = 366 mA. The rating of the polycrystalline solar panel is: open circuit voltage (Voc) = 22.466 V; short circuit current (Isc) = 0.235 A; maximum power voltage (Vmp) = 18.436 V; and maximum power current (Imp) = 0.220 A.
The Hibiscus sabdariffa flower was blended with butanol and filtered. The filtrate collected into a beaker. The 10 ml of the filtrate was mixed with 0.0045 moles of Cu(NO3)2.3H2O and left a day to enable the proper dissolution of copper. The color of the filtrate changed from light pink to dull blue. This signifies that the Cu(NO3)2.3H2O has naturally diffused through the chemical bonds of the plant extract. The filtrate is stirred vigorously at a certain interval of time. The filtrate was placed in a locally fabricated spray device that is expected to spray 2 ml per spray. Since the uniformity of the spray cannot be ascertained, the sprayed PV module was slated-vertically to drip-off excess filtrate that must have deposited at the surface (Emetere et al., 2019).
The data logger can accommodate four panels in total (two monocrystalline and two polycrystalline) as presented in Figure 1. One monocrystalline and polycrystalline panel was unsprayed and the other two panels (monocrystalline and polycrystalline) were sprayed. The unsprayed panels were used as a control mechanism to monitor the sprayed panels. Before the panels were sprayed, it was cleaned with distilled water. The panels were afterward put under the sun and the readings from the panels were recorded on the logger and stored in an SD card.
Some scientists had mathematically related solar modules and color filters. For example, the relative efficiency is a term used to estimate the ratio between the amount of energy generated in a day by the solar module with the color filter and the energy produced by the module without a filter. The formula is expressed as (Evaldo et al., 2017):
The solar radiation measurement on the monocrystalline PV panel is presented in Figure 2A. Notable fluctuations in solar radiation with respect to time were recorded and the peaks represent the time at which radiation is maximum, i.e. as high as 65 W/m2. Also, Figure 2B shows the solar radiation measurement in the polycrystalline PV panel. The maximum radiation as recorded was 32 W/m2.
The current production per time for the sprayed and unsprayed monocrystalline panel is presented in Figure 3A. The sprayed panel is the panel that has been sprayed with the synthesized bio-filter. It was observed that the current of the sprayed panel was higher than that of the unsprayed panel. Also, the graph takes the same form as the radiation pattern, inferring the amount of solar radiation is directly proportional to the current produced in the monocrystalline panel. In the polycrystalline PV panel, it was observed that the current of the sprayed panel is lower than the current in the unsprayed panel (Figure 3B). Like in the monocrystalline panel, the graph takes almost the same form as radiation pattern, inferring the amount of solar radiation is directly proportional to the current in the polycrystalline PV panel. The relative efficiency was approximately 94%.
The voltage generation per time for the sprayed and unsprayed monocrystalline panel is shown in Figure 4A. It was observed that the voltage of the sprayed panel was higher than the voltage of the unsprayed panel. Like in the case of current, the voltage-generated graph takes almost the same form as radiation pattern, inferring the amount of solar radiation is directly proportional to voltage. The same event took place in the polycrystalline panel, i.e. the voltage of the unsprayed panel was lower than the voltage of the sprayed panel (Figure 4B). The voltage generation almost described the same pattern as the radiation. These results show that the bio-filter is very effective with a relative efficiency greater than 94%.
The power generated per time for the sprayed and unsprayed monocrystalline panel is shown in Figure 5A. It was observed that the sprayed monocrystalline panel is higher than that of the unsprayed monocrystalline panel. Like the voltage and current, the power generated in the monocrystalline panel has almost the same form as radiation pattern, inferring the amount of solar radiation is directly proportional to power generated the monocrystalline solar panel. The reverse event took place in the polycrystalline panel, i.e. the power of the unsprayed panel was slightly higher than the power generated in the sprayed panel (Figure 5B).
The synthesized bio-filter, i.e. copper-coated hibiscus-butanol extract has been found to increase and stabilize the overall output of the monocrystalline and polycrystalline panel at a relative efficiency that is above 94%. This means that the bio-filter is the right candidate for sustaining PV energy generation. By extension, it would help elongate the life span of the solar photovoltaic panel.