Solupro Renewable Energy » Solar Photovoltaic
Solar photovoltaic (commonly known as solar PV) refers to the method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect; where after the current is inverted and stored in a battery bank from which the consumer may draw power for daily appliance running.
The afore is stated is noted in the simplest of terms, and it is of utmost importance to acknowledge the fact that the design and implementation of a suited Photovoltaic system, that will ultimately satisfy the consumer’s need and demand, requires a skilled approach and insistent attention to the individual household’s load.
Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaic has declined steadily since the first solar cells were manufactured, although the scale and purpose suited type of application will determine the ultimate cost incurrence.
Four system types exist, each intended to suit a particular purpose and need:
- DC System
DC Systems are the most basic form of energy for domestic applications. DC Appliances are generally more expensive but can supply the simplest needs, including lighting and 12 Volt fridges and freezers.
Since the range of DC appliances is limited, the option of appliances is subsequently limited to rather basic loads.
Advantages of the DC System:
- Affordability: Basic power requirements can be satisfied at a reasonable cost incurrence;
- Low Voltage: Hazards and dangers are limited;
- Accommodating: Easily expandable.
- Island System (Off-Grid System)
Energy can be harnessed from solar, wind or water, and stored in batteries to supply energy when needed. These systems typically have an inverter to invert DC battery power to 220V used by normal household appliances. In the instance that prolonged periods of overcast weather conditions occur, alternative backup may be established in the form of generators. Various methods of backup control exist, including manual or automatic / programmed switchover.
Accurate and premeditated design is of paramount importance, since an inadequate inverter, batteries or charger could lead to dire disappointment and secondary cost of rectification.
Advantages of the Island System:
- Purpose Focussed: Conventional household appliances are accommodated;
- Design Focussed: Increased capacity can be facilitated by stacking inverters to increase capacity without having to split appliances into separate circuits;
- Source Accommodative: Wind, Solar and Hydro sources may be utilized;
- Phase Accommodative: Single or three phase enabled;
- Accessible: System status may be monitored via internet or SMS;
- Adaptive: Grid independence can be achieved gradually.
- Multi Hybrid System
Multi-Hybrid systems consist of a combination of Grid-tie and Island systems. A Multi Hybrid system offers an advantage in that no cycling would occur during Grid Mode, resulting in a significant extension in battery life. Backup is all automatically controlled via the Island inverter that would utilize battery power as primary source and generator as standby.
Grid Mode
When grid power is available the energy would be fed into the energy utility’s network and thus reduce energy requirements from energy suppliers. No cycling of batteries occur, subsequently extending battery life expectancy. (This is not currently allowed in all the provinces and are limited to Gauteng, West and Northern Cape Provinces)
Island Mode
Island mode initiates in the event that grid failure occurs. The grid inverter feeds power directly to the appliances during daytime. Surplus power generated by photovoltaic solar panels or wind turbines will be charged into batteries by Island inverters. During night or high peak demand times the Island system will supply power to the appliances.
Advantages of the Multi Hybrid System:
- Reliability: Flexible and reliable;
- Battery Preserving: No cycling of batteries will occur during Grid Node;
- Backup Adaptive: Grid or Generator backup may be established in the event that demand exceeds inverter capacity;
- Accommodating: Easily upgradable by stacking similar inverters in parallel on a common distribution line;
- Phase Friendly: Single and three phase enabled;
- Inverter Friendly: Capacity can be increased during daytime by making use of Grid inverters;
- Charge Smart: Additional power generated by grid inverters charged to batteries;
- Accessible: System status may be monitored via internet or SMS;
- Adaptive: Grid independence can be achieved gradually.
- Contingent: Backup is readily available in the event that excessive draw or battery failure (low power) occurs.
- Grid-tie System
Power generated by photovoltaic modules are fed into the national utility grid by grid synchronized inverters. This would reduce the electricity required from main utility supplier.Grid-tie systems are commonly known in the European counties, however as yet a fairly new concept for many in Southern Africa.
Until NERSA has approved a feed-in tariff for small generators (residential), small scale generation only becomes viable once one can utilize the bulk of power generated without allowing surplus to be fed back. This is ideal for businesses that operate during daytime and would consume the entirety of power generated.
Since no batteries exist in a grid-tie system, the maintenance cost of these systems is reduced significantly; the PV modules and inverters typically have a much longer life expectancy than even the finest batteries.
Grid-tie systems are also used in Multi-Hybrid Systems to increase capacity during generation times.
Advantages of the Grid-tie System:
- Module Susceptive: An initial small scale grid feed system can be established initially and be expanded in time;
- Maintenance: The absence of batteries ensures affordable maintenance;
- Source Accommodative: Wind, Solar and Hydro sources may be utilized;
- Feed: Power can be fed to main grid, i.e. meter is ‘reversed’;
- Design Smart: Capacity specific off-grid system can be established.
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