Solar Energy Improvement Techniques Hamza Arif L1F11BSEE2046

History: Edmund Becquerel Edmund Becquerel, a French scientist, discovered that some materials would emit an electrical spark when hit with sunlight. This early understanding of solar energy began in the late 1800s and his discovery led to the identification of the first primitive cell material .

Bell Lab Research Bell Labs continued the research in the 1950s but with the use of silicon as a cell material. Solar cells manufactured with silicon can take about four percent of the sun’s energy and convert it to electricity.

How Do Solar Panels Get Energy from the Sun? Solar energy is renewable, environmentally friendly and, by itself, free. However, modern technology is required to convert the sun’s energy. he sun produces about 1,300 watts of energy per square meter. This energy from the sun must be collected and converted to electricity for use. the direct current (DC) electricity from the sun must be converted to alternating current (AC) for regular household or commercial use.

Introduction to Photovoltaics Silicon is not the best conductor on its own. However, when impurities are added, it becomes a semi-conductor. A basic photovoltaic cell consists of two layers of silicon. The top layer contains boron that will produce a positive electrical charge. The bottom layer has phosphorus, to create a negative charge. The area between the two layers is a Positive - Negative (P-N) junction.

Conversion of Energy to Power The collector, or photovoltaic cell, is exposed to sunlight. Sunlight contains energy in the form of photons. Photons hit the collector and knock electrons out of place on the material.

Converting direct current from the sun to AC The electricity used in homes and businesses is AC power. The DC energy is sent through a power inverter - converter that changes the DC supply into the AC power required for home use. There are different types of inverters used, depending on the system. Invertors

Solar cell efficiency  Solar cell efficiency is the ratio of the electrical output of a solar cell to the incident energy in the form of sunlight.

Thermodynamic efficiency limit The maximum theoretically possible conversion efficiency for sunlight is 86% due to the entropy of the photons emitted by the sun's surface. Photons with an energy below the band gap of the absorber material cannot generate a hole-electron pair, and so their energy is not converted to useful output and only generates heat if absorbed. For photons with an energy above the band gap energy, only a fraction of the energy above the band gap can be converted to useful output.

Quantum efficiency Quantum efficiency refers to the percentage of photons that are converted to electric current (i.e., collected carriers) when the cell is operated under short circuit conditions. The "external" quantum efficiency of a silicon solar cell includes the effect of optical losses such as transmission and reflection. If some of these losses can be recaptured by other portions of the solar cell array the aggregate external quantum efficiency of the system may be increased despite a lower internal quantum efficiency.

Maximum power point A solar cell may operate over a wide range of voltages (V) and currents (I). The maximum power point of a photovoltaic varies with incident illumination. For example, accumulation of dust on photovoltaic panels reduces the maximum power point.

Fill factor Another defining term in the overall behavior of a solar cell is the fill factor (FF). This is the available power at the maximum power point (Pm) divided by the open circuit voltage (VOC) and the short circuit current (ISC)

Comparison of energy conversion efficiencies Energy conversion efficiency is measured by dividing the electrical power produced by the cell by the light power falling on the cell.

Dye-sensitized solar cell (DSSC) Dye-sensitized solar cell (DSSC) is a promising candidate owing to its clean, low cost, easy preparation, good durability, and high conversion efficiency Dye-sensitized solar

Solar Panel parameters Most of the solar panels use wafer like crystalline silicon cells or thin film cells. Electrical connections in the solar panel are made in series/parallel to get desired output voltage and current. Electrical characteristics of solar panel includes nominal power PMax measured in Watts (W), open circuit voltage (Voc), short circuit current(Isc) measured in amperes etc.

Load Power consumption The power efficiency of the PV power system depends on the selection of suitable solar panel and battery. Before selecting the battery, inverter and solar panel, it is better to add all the power ratings of the loads together. For example if you wish to connect Four 20 Watts Energy Saver, One 60W TV and One 40W Fan, then the total power consumption of the load is 20+20+20+20+60+40 = 180Watts. This is the minimum power rating of the Inverter system. But consider the power loss also. So it is better to use a higher rated inverter, say 300 VA or 500 VA to run 180W load.

Solar panels power efficiency To calculate the power efficiency, it is necessary to calculate the power consumption in hours also. This can be done by multiplying the total load in watts by the time required. So if you want to run 180 W load for 5 hours, then 180W X 5h = 900Wh(Watts Hour). So a 300 Watts inverter is necessary for the purpose.

Battery efficiency and selection The battery capacity is also important. The battery should have sufficient charging capacity to store 900 Wh energy to run the load and not the 180 watts of the load. Battery capacity is usually represented in Ah (Ampere hour). For example a 40 Ah battery can run 1 ampere load for 40 hours.

If a 12 volt 40 Ah Lead Acid or Tubular battery is used, then the energy storage capacity of the battery is 12 x 40 = 480 Wh. So if the load requires 900 Wh energy, then a 12 volt 80 Ah battery can hold 960 Wh energy which is the minimum rating. Consider the power loss also. Then it is better to use a 100 Ah 12 volt battery so that it can give 1200 Wh efficiency.

Solar panel selection Before selecting the Solar panel, it is necessary to calculate the energy efficiency of the battery. For example, if you want to use a 60 W fan for 10 hours, then total energy requirement is 600 Wh. Using this example, add the wattage of all the appliances and multiply by the hours of use to get the energy efficiency of the power system. If the load rating is 180 watts as the example cited is running for 5 hours, then the energy consumption is 180W x 5 h = 900 Wh.

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