Wondering what solar energy system to install?

With so many solar energy system packages that are being offered in the market today, have you ever wondered which of these would be applicable to your home energy needs? For a start, we will introduce the basics of a solar energy system. As most of us would now know, sunlight can be converted into usable household electricity to power our appliances and lights. But for this to happen, sunlight needs to be processed through appropriate devices.

The device where sunlight is captured is the solar panel which are made up of several photovoltaic cells connected together to produce direct current (DC) electricity. Since sunlight that hits the photovoltaic cells varies in intensity because of shading (due to clouds mostly or nearby structures) and temperature, the DC electricity may either be strong or weak. In order to stablize this, the current passes thru another device called the solar controller (may be an SCC or MPPT which will be discussed in another topic) that will limit the current output to acceptable DC voltage range. If equipment or appliances to be used run on batteries (runs on direct current or DC), then the set-up may be enough. But the typical household uses equipment and appliances that run on power supplied by the electric grid which is alternating current (AC). So, to make use of the DC output from the solar controller and make the typical household appliances run, direct current (DC) would have to be converted to alternating current (AC).

Direct current can be converted into alternating current with an inverter. For most of the household appliances and equipment, a pure sinewave inverter will be appropriate (There are other types of inverters which are not pure sinewave and will not work properly with many household appliances). This will match the alternating current that comes from the electric utility company.

So far, we have discussed how sunlight is converted to usable current, either direct current (DC) or alternating current (AC) using three basic devices: solar panel and solar controller to convert sunlight to direct current (DC) and then convert DC to AC through an inverter. Our succeeding topics will lean mostly on alternating current which a typical modern household have access to. This means that we will generally discuss solar energy systems that have inverters.

There are two general types of solar energy systems that will be presented. Grid-tie system and off-grid system.

Grid-tie system

A grid tie solar energy system is one which has the following components: the solar panels, solar controller and the inverter. It provides power to the household during the day when it is connected to the grid (and does not generate power at night). The system can operate only if connected to the grid. When the grid is down, even when there is sunlight, the grid-tie system will not provide electricity. A grid-tie inverter, as a safety precaution to linemen or others who might be fixing the power line connections, is designed to shut down.

The grid-tie system somehow acts like a supplementary power plant for grid. If the load at the household cannot make use of the power generated by the solar system, excess power can be given to the grid. In short, when there is no load at the household, the solar energy system acts like a small power plant that contributes to the total power generation of the grid. At night though, when there is no sunlight, the system does not generate power and the household draws its power mainly from the grid.

Off-grid system

An off-grid solar energy system is one which operates even without the grid. This system is usually connected to a battery through a solar charge controller. As most of the appliances in the market is AC powered, an off-grid energy system converts the DC to AC through pure sine wave inverter. Generally, the system powers the energy requirements at home and charges the batteries during the day. At night, with no available sunlight, the battery provides the power.

Hybrid Systems

There are variations to the grid-tie system and the off-grid systems with the introduction of the hybrid inverters. There can be a hybrid grid-tie and hybrid off-grid. The hybrids can be connected to the grid as some sort of a supplement and a complement.

A hybrid grid-tie operates like an grid-tie system but can operate at night or during brownouts with a battery. On the other hand, a hybrid off-grid can be connected to the grid so that it will operate even when the batteries are discharged. The grid can likewise charge the batteries if sunlight is not available or sufficient.