Solar Power pack is systems used to generate electricity that make use of Solar power. These systems are ideal for locations where grid is inaccessible or the access is prohibitively expensive. The Solar power pack can also be used in conjunction with existing grid to enhance the energy delivered at that particular location.
TYPES OF SYSTEMS:
A. GRID INTERACTIVE PV SYSTEMS:
Photovoltaic power systems are generally classified according to their functional and operational requirements, their component configurations, and how the equipment is connected to other power sources and electrical loads. The two principle classifications are grid-connected or utility-interactive systems and stand- alone systems. Photovoltaic systems can be designed to provide DC and/or AC power service, can operate interconnected with or independent of the utility grid.
Grid-connected or utility-interactive PV systems are designed to operate in parallel with and interconnected with the electric utility grid. The primary component in grid connected PV systems is the inver ter, or power conditioning unit (PCU). The PCU converts the DC power produced by the PV array into AC power consistent with the voltage and power quality requirements of the utility grid, and automatically stops supplying power to the grid when the utility grid is not energized. This allows the AC power produced by the PV system to either supply on-site electrical loads, or to back feed the grid when the PV system output is greater than the on -site load demand. At night and during other periods when the electrical loads are greater than the PV system output, the balance of power required by the loads is received from the electric utility This safety feature is required in all grid-connected PV systems, and ensures that the PV system will not continue to operate and feed back onto the utility grid when the grid is down for service or repair.
Photovoltaic Grid-Interactive systems use the light available from the sun to generate electricity and feed this into the main electricity grid. These systems differ from a 'Stand Alone' or 'Remote Area PV system in that there are no batteries to store the energy produced. The houses are connected to the electricity mains and use the same appliances as found in other houses. If at a particular moment in time more power is being produced than is required in the house, the extra power is sent back onto the grid At night or when there is insufficient power being produced to supply the households needs, electricity is drawn from the grid in the same manner
B. STAND-ALONE PHOTOVOLTAIC SYSTEMS
Stand- alone PV systems are designed to operate independent of the electric utility grid, and are generally designed and sized to supply certain DC and/or AC electrical loads. These types of systems may be powered by a PV array only, or m ay use wind, an engine- generator or utility power as an auxiliary power source in what is called a PV-hybrid system. The simplest type of stand-alone PV system is a directcoupled system, where the DC output of a PV module or array is directly connected to a DC load (Figure 5). Since there is no electrical energy storage (batteries) in direct coupled systems, the load only operates during sunlight hours, making these designs suitable for common applications such as ventilation fans, water pumps, and small circulation pumps for solar thermal water heating systems. Matching the impedance of the electrical load to the maximum power output of the PV array is a critical part of designing well-performing direct-coupled system. For certain loads such as positivedisplacement water pumps, a type of electronic DC -DC converter, called a maximum power point tracker (MPPT) is used between the array and load to help better utilize the available array maximum power output.
In many stand -alone PV systems, batteries are used for energy storage. Figure 6 shows a diagram of a typical stand-alone PV system powering DC and AC loads. Shows how a typical PV hybrid system might be configured.
Solar power pack consists of the following:
The electricity generated by the Solar array is stored in the Battery through Charge Controller. The loads are activated when required and is powered by the Battery through an Inverter. A change over switch is provided to transfer the load from Solar to grid and vice versa. In general, the back up period for the full load is 4 –5 hours per day.