PHOTOVOLTAIC ELECTRIC POWER GENERATING SYSTEM

A basic photovoltaic electric power generating system consists of the following components; photovoltaic panels, charge controllers, batteries and inverters. The solar panels are the engine room of the electric power generation process, so care and attention should be taken in selecting the appropriate one. There are three main types of solar photovoltaic panels; the mono-crystalline, the poly-crystalline and the thin film solar photovoltaic panels. Mono-crystalline photovoltaic panels are made from cells that are grown from a single crystal. The production method is difficult and expensive. They are the most efficient as well as the most expensive. Poly-crystalline photovoltaic panels are made from a process, whose production allows multiple crystalline structures to develop within the cell. It is relatively cheaper than mono-crystalline cells at the expense of lower efficiency. While thin film solar uses less silicon to develop the cell allowing cheaper production cost. It is the least expensive as well as the lowest in efficiency.

The charge controllers are the intermediary between the photovoltaic modules, batteries and the load. They protect the battery from overcharge or excessive discharge by regulating the input and output current.

Batteries are charged during the day and supply power to the load during cloudy days and during the night.

While inverters main function is to convert the direct current (dc) electricity to alternating current (ac), wave shaping the output alternating current ( ac) electricity and regulation of the effective value of the output voltage.

There are three types of photovoltaic power generation systems; the stand alone (off grid), the grid tied or connected, and the hybrid systems.

Standalone systems rely on photovoltaic power only. These systems can comprise only the photovoltaic modules and a load or can include batteries for energy storage. When using batteries charge controllers are necessary to monitor and control the charging process.

A grid connected or grid tied photovoltaic power generation system is connected to the state electricity grid and do not need batteries. The system operates to supplement the grid power during down time or during the day when a substantial amount of solar energy is produced and the excess supplied to the main supply. During the night the grid power alone feeds the load. This system requires additional equipment’s to control voltage, frequency and waveform so to conform to the condition or standard for feeding power onto the grid.

The hybrid photovoltaic power generating system consists of the combination of photovoltaic modules and a complimentary means of electricity generation such as a diesel, gas or wind generator. In order to optimize the operation of the two generators, the hybrid photovoltaic power generating systems typically require more sophiscated controls than standalone photovoltaic systems. The hybrid photovoltaic electric power generation is most suited for loads requiring uninterrupted power supply.

However the standalone photovoltaic power generating system without storage is suitable for remote location power supply where cost of added components like the inverter and battery may be too costly to bear, otherwise if they must operate continuously throughout the day, batteries and inverters are essential or inevitable to provide necessary storage during the peak hours and to supply power to alternating current loads. This configuration is the most suitable for residential and office accommodation to provide critical electric power needs especially where there are often frequent power outages.

There is no reason why we should not complement the main power utility in areas of low power generation, with solar photovoltaic power generating system along the grid to feed the grid with solar electric power during the day. This approach will go a long way in ameliorating the frequent outage experienced especially in developing economies and if possible we may include suitable storage medium along the grid, to extend the time and duration of the supplementary function of the photovoltaic power generating system, thereby increasing the overall efficiency of the grid.

The benefit of photovoltaic power generating system over other power generating system cannot be over emphasized. It’s reliable, scalable, modular, easy to integrate with other power generating system, quick to deploy, with almost zero operating cost, low maintenance cost and above all environmentally friendly. Its main constraints are high initial budget outlay and space constraints.

 

 

Sources

• Markvart L. Castaner,” Practical handbook of photovoltaic: fundamentals and applications. Oxford Elsevier advanced technology, 2003.
• Luque, S.Hegedus, “Handbook of photovoltaic science and engineering” , Wiley, New york (2003).
• Estimating photovoltaic system size and cost,(online), infinitepower.org
• A.Duffie, W.A. Beckman,” solar engineering of thermal processes”,3^rd edition,wiley,New york(2006).
• gov (n.d).grid –connected renewable energy system. www.energy.gov
• B(2016) September 23, global energy consumption the number for now and in the future.