A solar power plant, also known as Pembangkit Listrik Tenaga Surya (PLTS) in Indonesian, is a power generation system that uses solar cells (photovoltaic, PV) to convert sunlight into electrical energy.

Indonesia has vast landmass, a lot of which are remote areas. Thus, it is not possible for all to be connected to the grid (PLN = Perusahaan Listrik Negara = State Electricity Enterprise). However, with abundant sunshine all year round, Indonesia has the ideal setting with a high potential for solar power.

Currently, there are hundreds of small islands in Indonesia that have been installed with a Centralized PLTS. For islands or remote areas that receive general government assistance, the standalone PLTS have an output capacity of 5, 10, 15 and 30 kWp.

Solar Power Energy – Standalone PLTS

Image by Free Sun Power (http://freesunpower.com)

Called a standalone System or Off-Grid System because the system relies solely on solar energy as the main energy source. It utilizes a solar module circuit to generate electrical energy in accordance with the needs that have been planned.

Solar energy can be converted into electrical energy through the use of solar cells (photovoltaic). Solar cells are components that can convert solar light energy into electrical energy using the principle of the Photovoltaic effect.

The working principle of the photovoltaic effect is the emergence of an electric voltage due to the connection or contact of two electrodes connected to a solid or liquid system when obtaining light energy.

Image by University of Calgary – Energy Education (http://energyeducation.ca/wiki/images/1/11/Photovoltaiceffect.png)

Benefits of using Solar Energy :

1. Solar energy is abundant and free
2. Environmentally friendly
3. Long life time period of use around 25 – 30 years
4. Cheap maintenance costs
5. Not Noise (Silent)

Disadvantage of using Solar Energy :

1. Dependency on the weather
2. Requires large area for installation of solar modules
3. Big investment for initial installation solar energy

Efficiency of the PLTS (commonly around 80% – 93%) is determined by the degree of irradiation of the sun (the greater the irradiation value, the greater the power it can generate), the environmental (mountain or sea) temperature, dust and type of solar module, controller, inverter, losses of long cables.

So what makes up a PLTS Standalone System/Off-grid system:

1. Solar Module
   The main function of a solar module is to convert solar energy into electrical energy. A Solar module consists of a number of silicon cells which when illuminated by the sun, will produce photons that can generate electrical current. A set of Solar Panels in one system is called an Array. Generally the most widely used solar modules are crystalline type either Monocrystalline or Polycrystalline. While thin film solar modules are still rarely used (in Indonesia). A solar cell can produce a voltage of approximately 0.5 volts. So a 12 volt solar cell consist of about 36 cells.PLTS Off-grid will consist of several solar modules according to their capacity. For example, a 10 kWp PLTS will consist of 50 units of 200 Wp solar modules or 100 units of 100 Wp solar modules. These solar module is arranged in series and parallel with certain configuration.

2. Combiner Box
   In a solar power plant, solar panels can be arrayed in parallel to produce a larger current. Combiner boxes are  used to connect the positive foot of solar panels to one another. Similarly, for negative legs. The positive foot end of the solar panel is connected to the positive charge controller leg and so is the negative leg. The resulting solar panel voltage will be used by the charge controller to charge the battery.
3. Fuse
   The fuse is a component to protect PLTS / PV network system. In the event of a short circuit or over-current on the circuit or other load, it cuts the flow of electricity.
4. Charge Controller
   A tool to regulate the current and voltage both to the incoming current and voltage of the PV panel as well as outflow / used load currents. The voltage and current entering the battery should be as intended. When either is larger or smaller than the specified range, then the battery or other equipment will be damaged. In addition, the charge controller also serves as a guard to ensure the resulting output power remains optimal, in order to achieve Maximum Power Point Tracking (MPPT).
5. Inverter
   Inverter is a converter that will change the DC voltage (48VDC, 24VDC or 12VDC) on the battery into AC voltage (220VAC or 120VAC) at the output will be channeled to the load. Off-grid inverter can adjust the amount of output power based on the amount of load. so it can be used to turn on household electricity such as lamps, fans, television, etc.
6. Battery
   In a standalone system , the battery serves to store the solar energy generated during the day so that the energy can be used both in the day and night.The voltage on the battery bank PLTS is generally 48VDC, 24VDC or 12VDC. The battery type that is widely used for such applications is usually a Lead-Acid type, either OPzS (wet battery) or OPzV (dry battery). Batteries used in the PLTS system are a deep cycle type  which means the battery can be discharged up to 80% capacity (80% DOD).In addition to Lead Acid, the other battery type that can be used on a PLTS system is the  Lithium battery. As with any battery on our mobile phone, lithium batteries are known as batteries with high energy density which means the same volume of energy that can be stored by lithium batteries larger than other batteries.
7. AC Breaker
   The AC Breaker is required to limit the power of the inverter so that the power being injected does not exceed the existing load, resulting in a fire.
8. KWH Meter
   To measure the amount of electrical energy that has been produced by solar panel can be used kwh meter.

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