UBNT Solar Power Home Automation Networking



PV Power Systems


PV power is one of the two technologies known today of harnessing electrical energy directly from the sun. Unlike concentrated solar power (CSP) which uses the sun’s heat, Photovoltaic (PV) technology utilizes the energy carried by sunrays, specifically the photons in the light. This is done through PV panels that are made from semiconductor material; usually doped Silicon.


Even though the Photovoltaic effect was discovered in the early 19th century (by Edmond Becquerel) it was not until the mid-20th century that the first practical PV cell was created (by Bell Laboratories) and the first commercial PV panel much later.


Today’s urge for solar power rises from the fear of the imminent running out of fossil fuels on which our entire lifestyle relies so heavily. And with the threat of global warming materializing more and more every day, the need for power from green renewable sources, such as the sun, have never been as dire.


This is even more so the case here in Lebanon with the unreliable grid power, the increasing rationing hours and hence the desperate need for new sources of backup power amid the astronomical monetary as well as environmental prices of diesel generators.


Types and Components

There are three main types of solar PV power systems: Grid-tie, stand-alone, and grid-interactive systems. Grid-tie systems require no batteries, but are reliant on the power from the grid to work and cannot operate as a backup system. Thus they are ineffective here in Lebanon. Stand-alone or off-grid systems are usually used in remote sites that cannot be reached by the grid or cases where the user wishes to be completely independent from grid power. They become the sole source of energy on the site and thus need to be oversized in order to provide this very high availability of power. Finally, grid-interactive systems basically combines the previous two. They can operate in parallel and exchange power with the grid while still providing backup power from the batteries when the grid is off.







On grid only


Least Expensive


Off grid only


Most Expensive


On and off grid




Here in Lebanon, the vast majority of cases, especially for homes, will be grid-interactive systems (without actually putting extra energy back on the grid). The main components of such system would usually be:




1)      Solar Panels: Provide DC power from the sun. Their size depends on the size of the load and the duration in which the system is supposed to provide backup power.

2)      Charge Controller: Charges the batteries and prolongs their lifetime by regulating how they are charged (PWM) and preventing overcharging and over discharging. Some chargers (MPPT) can increase the power drawn from the panels.

3)      Battery Bank: Stores energy to be used during outages and rationing hours. The battery bank of grid-interactive systems is usually smaller than that for stand-alone ones.

4)      Grid-Interactive Inverter: Operates as a grid-tie inverter when the grid is functioning normally and the battery bank is full, then as a stand-alone inverter when the power from the grid is down. The grid-interactive inverter is off when the grid is on and the battery bank is still charging from the panels. It is a programmable device that can be programed to not put energy on the grid

5)      Main Switchboard: To connect and distribute the power to the loads.

6)      Consumer Loads: Basically the home appliances, electronics…etc. that need to be fed with electric energy.

7)      Power Meter: Measures the amount of energy drawn by the load from the grid. In cases where the user is allowed to put extra power from the panels back on the grid, the meter either measures the difference between the power consumed from and supplied to the grid if (net-metering) or a second meter is installed to measure the power placed on the grid separately if the powers supplied to and consumed from it go for different rates (feed-in tarrif).

8)      Utility Service: Or grid. Connects the power provided by the state (usually from power plants) to your home. When available, it is usually the main source of power for the loads.

9)      Emergency Power Source: Optional. Provides emergency power in extreme cases such as unaccounted for prolonged grid outages and drastic weather conditions. Usually a diesel generator*.


*Note: If a diesel generator is used, it is advised that the system be designed in a manner that allows the generator to run at least once every two months and for at least several hours straight or the expected lifetime of the generator will suffer and its maintenance cost likely increase.

Comments Comments
All the comments below reflect the opinions of the visitors only,
and this site is not responsible for it
Number Comments: 0
No comments, be the first and add a comment.