Off-grid solar systems are those installations that are isolated from the electrical grid. All the electrical energy generated by the solar panels is consumed directly.
An off-grid solar system is designed for cases where the cost of maintenance and installation of power lines is not profitable. For example, this would be the case of mountain refuges that need an electrical generation system to cover their needs.
These isolated systems, as they are not connected to the electricity grid, require a solar battery system. Solar batteries store the energy produced by off-grid solar panels when production is higher than the energy needed.
Examples and applications of off-grid solar systems
The main applications and uses of the off-grid solar system are:
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To supply electricity at home and buildings, mainly for lighting and low-power devices.
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Street lighting.
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Agricultural and livestock use.
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For pumping and water treatment.
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Supply energy in telephone antennas built in remote areas, far from the grid.
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Signaling and communications.
These facilities are used above all in those locations where there is no access to the electrical grid. Moreover, installing a PV system is cheaper than laying a line between the grid and the point of consumption. The electricity generated is used for self-consumption.
What is the difference between an on-grid and an off-grid solar system?
Off-grid solar systems are not connected to the utility grid. They are independent of the power grid and can generate electricity. Off-grid solar systems are usually used in remote locations where it is not feasible to connect to the utility grid. Some people also use it in cases where they want to be self-sufficient.
There are a few other key differences between these two types of solar systems:
Off-grid systems are usually more expensive than on-grid systems because they require more equipment (such as batteries) to store energy when there is no sun.
On-grid systems can take advantage of net metering, which means you can get credit from your utility company for any excess electricity your system produces (and you don’t use). It is not possible with an off-grid system since you are not connected to the grid.
Off-grid systems require more maintenance than on-grid systems because they have more components that can break down (such as batteries).
Pros and cons of off-grid solar systems
Off-grid solar systems have pros and cons. The most important advantage is that they do not depend on external elements to supply energy, and the direct cost of a kilowatt hour of power is zero.
On the other hand, it has certain drawbacks. The main disadvantage of this type of renewable energy source is the dependence on the variation of the solar radiation received. In other words, the solar radiation that the PV panel will receive depends on the solar time, the inclination of the Sun at different times of the day and at other times of the year, and the weather.
Solar hours of radiation can be calculated. However, what cannot be estimated is the number of hours and cloudy days that will be experienced precisely.
Unlike grid-connected solar systems, an energy storage system must be provided to use during those hours when the solar panels do not generate electricity because they do not receive radiation.
Components of an off-grid solar power system for homes
The essential elements for off-grid solar energy systems are:
1. Off-grid solar panels
Solar panels are a crucial component of an off-grid solar power system. Off-grid solar panels are typically used in remote locations where there is no access to the grid or in emergencies where the grid is down. Solar panels convert sunlight into electricity, which can then be used to power lights, appliances, and other devices.
2. Battery bank
The battery banks are responsible for storing the energy generated by the solar panels at times of low consumption so that they can be used at times of energy demand.
These are generally batteries, although some off-grid solar energy systems are mixed with hydraulic power. In these cases, the energy generated using off-grid solar panels is used to activate a pump and raise water again so that it can pass through the turbines at a certain height.
On-grid solar systems can also have batteries in case of power outages.
3. Solar charge controller
Solar charge controllers ensure that solar batteries are always within the correct operating conditions. Therefore, it is necessary for any solar system with a battery, mainly when fully charged, to cut any excess energy.
Of course, the control is carried out both in the loading and unloading processes.
4. Power inverters
Inverters are responsible for converting the energy in the form of direct current obtained in the solar panel to alternating current.
Since solar panels generate electricity in DC and most of the electrical devices we will use require that the current input is in AC, we will need to carry out this conversion.
Configuration of an off-grid solar energy system
The basic configuration of off-grid facilities comprises a photovoltaic generator, a charge regulator, and a battery.
The battery is the element in charge of storing the energy delivered by the panels during the hours of most remarkable radiation for its use during the hours of low or no insolation. The charge regulator controls the battery charge, preventing excessive overcharging or discharging that decreases its useful life.
Another basic configuration is solar pumping, made up of panels, a small piece of equipment, and the pump, in which water is pumped when there is sun, not requiring batteries.
The most used configuration in home solar kits comprises PV panels, a charge controller, batteries, and a power inverter. The power inverter converts the energy stored in the batteries into AC, which is used for most applications.
The design criteria are different for calculating this type of facility. In on-grid solar systems, an attempt is made to maximize annual production, facing south and with the most favorable inclination.
On the other hand, one criterion for off-grid solar energy systems can be for them to produce at their maximum in the worst month, December. Therefore, the rest of the year will have at least the energy calculated for the worst month, always covering the needs.
