How To Build Your Off Grid Solar System

What is Off Grid Solar System?

Off grid solar system is a house or a stand-alone building power line that requires its own generator to produce electricity to support regular use. Off solar grid system are particularly common among people in remote areas where grid access is expensive. It is also common in suburban homes that are withdrawn from local distribution lines nowadays.

Several reasons motivate people to purchase off grid solar system: one is to save money over the life of the system without paying the local electricity supplier. The other is to slow the rate of increase in carbon emissions. Having your own power system to meet all your electricity needs means a significant reduction in the amount of greenhouse gases produced by using power from your local electricity supplier.

Mostly, people install solar panels and wind energy systems in off grid houses. These cannot be done in a few days and sometimes take months. Solar panels and wind turbines can be purchased at reasonable prices. Some off-grid people are showing another trend of building their own solar panels and wind turbines. With some basic building or electrical skills, we can all DIY our proprietary generators.

Batteries play an important role in off grid solar systems as they are used as the primary storage device. It is best to use deep cycle batteries and having deeper levels of energy storage is an effective feature for using electricity at night. Choosing the right power converter is also important as they are the main component in converting electrical energy into a usable form. The converter also needs to be achievable for use with solar panels or wind turbines at any given time. Learn more about battery suppliers: Best Lithium ion Battery Manufacturers in the world.

Along with other renewable energy systems such as solar systems, hot water and land batteries, they will also benefit greatly from an off-network system, which can be used to power hot water and external lighting that consumes a lot of electricity.

Energy efficiency throughout the house is important when choosing an off-grid electrical system. Based on the daily economic activities that require the installation of wastewater drainage systems and energy systems, it means using energy-efficient electrical equipment that needs to keep your home well insulated and leak-free.

Choosing an off grid solar system means you will no longer be dependent on traditional electricity and will have a significant positive impact on the environment, consuming 100% green energy!

Design selection of PV off grid solar system

PV off grid system design is not really complicated. However, it is found in daily life that many people are afraid of off grid solar system, they want to do off-grid project, but they don’t know how to start, and often in a dilemma. The following content hopes to make it clear how to successfully do a set of photovoltaic off-grid power plant through simple and plain language.

1. Value of off grid systems

The off grid solar system is based on the following starting points, as summarized over time:

  1. In places without access to utility power (grid), such as on mountains, on boats, in cars, and in the field. This is the most typical demand for off grid solar systems; more than 80% of the users want to be powered by an off grid system because they are not comfortable with mains electricity.
  2. Areas with utility power, but with frequent and irregular power outages. When the power goes out, loads can continue to be supplied through the PV off grid solar system to meet the continuous power demand.
  3. Having utility power but wishing to reduce electricity costs through off grid systems. Off grid solar systems can not only charge the batteries through the PV modules, but also by setting the utility to charge the batteries at low rates and then discharging the batteries to supply the loads at high rates.

2. Typical off grid system composition

The above diagram shows the components of a typical off grid solar system. These points need to be noted:

  1. Off grid solar system means that the output of the system is not required to be connected to the utility grid as in the case of a grid-connected PV system. The off-grid system’s output is what supplies the load.
  2. The off-grid system provides a V-F source, which is equivalent to the role of a power grid.
  3. The main equipment in the off-grid system are: PV modules, off-grid inverter, battery, convergence device, distribution box, and electrical load.
  4. The leanest off grid solar system can contain only 2 parts: off-grid inverter, battery.

3. Off grid solar system design process

(1)Confirmation of Requirements: Designing an off grid solar system is a customized process, as different users typically have varying loads and electricity usage patterns. The correct approach is to first confirm the requirements: what loads need to be powered? What is their power rating? How many hours are they used daily? Based on this information, the system size can be calculated. For example, a customer in the North China region requires an off-grid power station to run a 3500W blower for 3 hours daily, with a backup power requirement for one day. From this information, we know that the load’s power is 3.5KW, and the daily energy consumption is 10.5kWh.

(2)Inverter Selection: In the early stages, off grid solar system control was executed by combining an MPPT controller with a DC/AC converter. With technological advancements, integrated control and inverter units are now mainstream, such as the NPP series off-grid inverters. After confirming the requirements, a suitable off-grid inverter can be selected. The chosen inverter’s output must cover the rated power of the load and leave some margin for system reliability. In the example mentioned earlier, with a load rated at 3.5kW, an NPP off-grid inverter with a 5kW output can fulfill the power supply.

The number of inverters required to cover the load power depends on the backup power requirement, known as the “continuous rainy days.” If the backup power demand is significant, a single inverter and its associated components might not be able to meet the needs, necessitating the use of multiple inverters.

(3)PV Module Selection: In any photovoltaic system, energy is sourced from photovoltaic modules (and, in the case of off grid solar systems, sometimes from the grid). The chosen off-grid inverter will have a specified acceptable module capacity, which can be directly matched based on the inverter’s specifications.

For instance, using the mainstream 182 modules with 550Wp capacity, 8 modules in parallel provide a rated power of 4.4kWp, generating an average daily energy of approximately 16kWh. The modules can be installed in a series or parallel configuration based on the inverter’s maximum allowed input voltage and the chosen modules’ parameters.

(4)Battery Selection: One significant difference between off-grid and grid-tied systems is the use of batteries in off grid solar system, which act as a buffer for energy storage to avoid the system becoming isolated.

Choosing solar battery manufacturers is really important. When selecting batteries, it is essential to consider the user’s electricity consumption requirements. In the example above, the customer requires 10.5kWh of backup power. This means that the batteries must provide 10.5kWh of electricity when there is no sunlight to meet the load’s demand.

However, whether it’s lead-acid or lithium-ion batteries, they have a concept or characteristic known as Depth of Discharge (DoD). This refers to the portion of stored energy that can be discharged without causing damage to the battery. It is not advisable to fully discharge the battery every time, as it could lead to premature battery failure. Lead-acid batteries generally have a DoD of around 60%, while lithium-ion batteries can reach up to 90%.

When choosing the battery capacity, the depth of discharge also affects the overall battery capacity. In the example above, using lead-acid batteries with a DoD of 60%, the total battery capacity required would be 10.5kWh ÷ 0.6 = 17.5kWh. The batteries act as containers to store the system’s generated electricity and release it when the load requires it.

To simplify the calculation of individual battery capacity, for a 5kW off grid inverter, batteries with a capacity of 200Ah or higher should be used. Based on this information, adjust the number of batteries to achieve the desired total battery capacity.

Currently, the main specifications of lead-acid batteries available in the market include 2V, 6V, and 12V options. Typically, the 12V specification is chosen, which means the capacity of one battery is 12V * 200Ah = 2400VAh = 2.4kWh. To determine the number of battery units needed, we divide the total capacity (17.5kWh) by the capacity of one battery (2.4kWh). Hence, the required number of battery units is 17.5kWh ÷ 2.4kWh = 7.2916…… Since batteries cannot be divided, they need to be rounded up, so 8 battery units should be configured. Let’s verify this calculation: 8 units * 12V * 200Ah = 19200VAh = 19.2kWh, meeting the load’s backup power demand.

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(5)Main Equipment List: A general configuration of the off grid solar system equipment list is as follows:

1Off Grid Inverter1
2Photovoltaic Module550Wp8
There are two situations where multiple machines are required:
  1. When the load demand is not significant, and one inverter can handle it, but the backup power requirement is substantial.
  2. When the load power exceeds the rated output power of a single inverter. Off grid inverters support 2 to 6 units working in parallel, providing an output range of 10kW to 30kW. When additional inverters are added, the number of PV modules must be increased accordingly, especially for systems with high backup power requirements. It is crucial to have enough PV modules to generate and store electricity to meet the load demand.

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