The Difference Between Off-Grid and On-Grid Solar Energy
Off-grid vs. grid-tied solar. Ground mount vs. roof mount. Polycrystalline panels vs monocrystalline.
When it comes to installing a solar power system, there are a lot of decisions to make. And because you’re investing in equipment that will last many years, you want to make the right choices.
If you partner with a reputable solar installer. they’ll be able to guide you through these decisions to get you the perfect system for your situation. However, doing a little homework on the front end can’t hurt either. That’s why we’re sharing the four differences between on-grid and off-grid solar power to help you decide which is best for your solar project.
What Is Off-Grid and On-Grid Solar Energy?
An off-grid solar energy system is not connected to the utility grid, whereas an on-grid (aka grid-tied) solar energy system is connected to the utility grid. Whether off-grid or on-grid system will determine your access to electricity, what equipment is needed for excess production, what happens when the grid goes down, and how you’re billed for electricity.
System components simplified for graphic
The Differences Between Off-Grid and On-Grid Solar Energy
Difference #1: Your Access to Electricity
Electricity Access with Off-Grid Solar
What is meant by off-grid solar systems? With an off-grid solar system, you’re completely reliant on the sun and energy stored in batteries to power your home or business.
If you opt for a solar system that is not tied to the electric grid and you do not have a generator, you will only have electricity at two points:
- When the sun is shining and your solar system is producing electricity.
- When you’re pulling electricity previously generated by your solar system from a solar storage device, like batteries.
If you do not have batteries or a means to store your energy, you will have less or no electricity when it’s cloudy, and you will not have electricity at night.
With an off-grid system, you will not have access to extra electricity if you need it. What you are producing and what you have stored is all that’s there to power your equipment.
Electricity Access with On-Grid Solar
If you decide to install an on-grid solar system, you will always have access to electricity (unless the grid goes down), whether or not your solar system is producing or if you have batteries.
If your system is not producing any electricity or not producing enough electricity to power the devices, lights, machines, etc. that you’re using, you can pull energy from the utility grid to supplement it. This ensures you always have enough electricity for what you need.
Difference #2: What Happens to Excess Production
Excess Production with Off-Grid Solar
Depending on the size of the system you install, how much electricity you use, and when you use that electricity, there will likely be times when your system is producing more electricity than you’re using. What happens to this excess energy depends on the equipment you install.
Most off-grid solar systems are designed to produce a certain amount of “extra” electricity in the daytime, which is sent to batteries for storage. The energy stored in those batteries can then be accessed when the system is not producing, like at night or during cloudy weather.
Depending on your energy goals, systems can be sized to produce enough excess electricity in the daytime to cover your entire energy usage around the clock.
However, despite even the best and most accurate estimates, the weather is unpredictable. If you experience abnormally cloudy weather several days in a row, your system may not be able to produce enough electricity to charge the batteries and fulfill all your needs.
While having extra batteries offers peace of mind and can provide a bank of stored electricity just in case this happens, they’re also expensive. Purchasing more batteries than you need may be cost-prohibitive, depending on your budget.
Excess Production with On-Grid Solar
Just like off-grid solar systems, many who choose to install an on-grid solar system want to cover 100% or nearly 100% of their energy usage. This can be achieved with on-grid systems as well.
Depending on the time of day you use electricity, your solar system can produce excess energy. Instead of sending it to batteries as you would in an off-grid system, you can send it to the grid and you will be compensated for that electricity.
For many in the United States, they’ll be compensated through something called net metering. Net metering is when the utility company compensates or credits your account for electricity generated by your solar system and sent to the grid. Then, whenever you need to draw energy off the grid, you’ll be drawing on those credits to get your electricity without racking up charges on your electricity bill.
There are currently mandatory net metering rules for 39 states. 11 states are either transitioning or are currently implementing compensation methods other than net metering (like the Value Stack in New York ).
Map from www.eenews.net via https://www.dsireusa.org/
Grid-connected solar power has a distinct advantage over off-grid systems because net metering and other compensation methods from utility companies offer what is essentially free storage.
Difference #3: What Happens When the Grid Goes Down
Power Outages with Off-Grid Systems
Your solar system is working independently from the power grid. If there’s a bad storm or event that knocks out the power, your solar system can continue operating. You won’t notice changes in your service or access to electricity.
Power Outages with Grid-Tied Systems
By connecting to the grid, you get access to electricity whenever you need it. However, you’re also subject to some rules. If you have a grid-tied solar system and the grid goes down. you will not have electricity, unless you opt for a grid-tied solar system with battery backup.
Why is this? The shutdown of solar systems when the grid goes down is required by the Underwriters Laboratories (UL 1741). This is for the safety of utility workers who are fixing the power lines.
While this is a disadvantage of grid-tied systems over off-grid systems, if keeping things up and running during a power outage is important to you, then you may be interested in adding batteries to your grid-tied system.
Difference #4: How You’re Billed for Electricity
Electricity Bills with an Off-Grid System
If your PV system is not tied to a grid, you won’t receive an electric bill at all. However, even with no electric bill, off-grid systems are often more expensive because of the additional equipment like batteries that are needed to make it viable.
Electricity Bills with a Grid-Tied System
If you opt for a grid-tied system, you could still see a few minimal charges on your electricity bill, even if your solar system provides 100% of your electricity.
One type of charge you may continue to see is the service fee or delivery charge. This is the cost levied on customers for connecting their home or business to the grid. For many utilities, this fee is a flat rate that is not impacted by how much electricity you use.
Another type of charge you can see is demand charges. Demand charges are typically levied on commercial properties and are the increased electric rate you pay for the power you use during a peak demand period. The peak demand period is typically the 15-minute period in which your business uses the most electricity.
Because using a large amount of electricity at one time puts a strain on the grid, the utility will charge a higher rate for the electricity used during that period.
If your peak demand period is during the day, you may be able to reduce it with solar, as energy produced by your system will compensate for some of the energy you use from the grid. If you pay very high demand charges, you may also want to look into peak demand shaving with solar and batteries.
Depending on how much energy your solar system produces and how much energy your home or business uses, you may see an electric charge for the electricity you pulled off the grid and used that wasn’t covered by your net metering credit.
Hybrid Solar Energy Systems
A hybrid solar energy system is one that is tied to the grid but also has a battery bank to store unused electricity. Hybrid systems, though more expensive due to the added cost of batteries, allow their owners to keep the lights on when the grid goes down, and can even help reduce demand charges for businesses.
If you’re interested in learning more about a hybrid solar energy system, check out our blog: How to Size Batteries for a Solar System
There are two ways for grid-tied solar systems to be connected to batteries: DC Coupling and AC Coupling.
While there are distinct differences between off-grid and grid-tied solar systems, the one that is best for you is dependent on your situation. Off-grid systems allow for complete freedom from the utility, but they’re often more expensive. Grid-tied systems marry significant electricity savings with grid-backed dependence, so you’ll never have to worry about not having the electricity needed to power your house or business.
Learn more about the advantages and disadvantages of both options in our blog Grid-Tied Solar vs. Off-Grid Solar: What are the pros and cons of both?
Simulation Model of PV System Function in Stand-Alone Mode for Grid Blackout Area
PV systems are frequently used in a stand-alone configuration. In a solar PV-based energy-producing system, power fluctuation is a natural occurrence. Alternative sources of energy, including such hybrid grid-tied or energy storage systems, could be discovered when solar PV systems run off-grid to satisfy regional power demands for reliable power supply. This research uses an unusual PV system that can function in both grid-connected and stand-alone states to propose an efficient approach for the power generation challenge in the residential segment. A block of storage battery with sufficient dimensions is included in the system to make sure the constant power supply of such a residential building with an average electricity demand of 10 kWh. An atypical 3.2 kWp PV system and a 19.2 kWh storage battery brick was determined to be capable of meeting the house’s whole daily energy requirements, as well as the defined electrical shutdown times, to simulate the system, which took into account the day load profile, network cutoff times, and monthly radiation from the sun. The collected simulation results showed that during 9 months of each year, the generated PV energy surpasses the load needs, resulting in a maximum battery state-of-charge (SOC) in the range of 74-85%. The generated PV energy is an approximately proportional requirement as during 3 months of minimum solar irradiance (Dec-Feb), whereas the sequence’s SOC differs between
demonstrating the validity of the proposed photovoltaic system. In January and July, the PV service’s daily energy produced ranges between 2.6 and 5.4 kWh/kWp, corresponding to a conversion efficiency of 90% and 66.25%, correspondingly.
Microgrids are low-voltage networks that include combination of distributed (DG) units, energy storage systems (ESS), and load, controlled demand that can operate either as stand-alone modes . In a state, the microgrid modifies power leveling in free enterprise activities by getting power from the main system or providing electricity to the grid to improve operational benefits. The microgrid is separated from upstream distribution systems in stand-alone operation, to maintain a constant power supply to the customers who use DG. Different types of methods are used as elements of the microgrid to minimize the power swings of nondispatchable DG units, such power dynamic of every distributed energy generating unit, charge and discharging of ESS, and load variations.
A network-controlled dependent voltage-sourced converter (VSC) or a networking framing agrees to take two modulation techniques utilized in a microgrid. To achieve stable and cost-effective functioning, a microgrid normally requires a powerful platform to enable dynamic referencing power factor, ensuring collaboration among the controlled components. With the quick rise in fossil fuel prices, and also the sharp rise in the construction price of building normalized pattern facilities, there is a renewed FOCUS on alternative generating systems that use energy more efficiently . The electricity sector gets increasingly competitive as a result of activities and reorganization of power networks. Solar, freshwater, air, geological, and wastes generated are the most common alternative energy sources. Solar energy is widely available and may be used in practically anyplace. Many countries have taken major steps in the new millennium to tap into the vast and environmentally benign solar energy supplies. These countries invest much in both development and public awareness campaigns aimed at environmental protection. High-quality studies will lower manufacturing costs while also improving the efficiency of allied solar energy-harvesting equipment . Furthermore, public understanding will raise the demand for these devices in the industry. As a result, the technology will be given out at a cost-effective rate.
Renewable energy systems (RES) present a cleaner solution capable of fulfilling the growing electrical requirements of linked and remote communities. Microgrids (MGs) have piqued the scientific group’s interest in recent years, as well as being a possible alternative for future conventional power generation. MGs are being considered as a potential solution for integrating intermittent renewable energy supplies into traditional grids . Many implementations have been applied in SG, notably in the construction of controller and electronic Band converters, as a result of the advent of new communications technology such as microprocesses devices and developments in power electronics. Experts had made major contributions that can have a substantial influence in such domains in recent years, particularly in the context of data collecting, mechanization, and management of MGs. MGs not just reliably and cleanly connect electricity renewable to the main grid, as well as provide greater validity in its design to function within the face of natural disasters and interconnected power grids, resulting in lower energy failures in distribution and transmission, as well as reduced building and financial moment.
Connecting terminals with defined and estimated capacities are used to transmit and supply electricity generation. Electrical supply increases in some circumstances, forcing distribution networks to plan electricity supply over multiple periods ranging from 6 to 10 hours each day . Communities and other industries face a serious problem as a result of this situation. This problem has existed for more than ten years, and there are no signs that it will be resolved in the coming years given the political scenario remaining constant . Mounting PV systems on private residences and other privately or publicly facilities with pretty modest minimum fuel use, on either hand, is a viable solution for a wide spectrum of such users, who account for a significant portion of Gaza’s overall consumption of electricity. Throughout grid outages, the PV power systems should provide a constant supply of energy, and during the day, this can feed extra produced electricity into the electricity network.
Due to such island operation of the converter, which is a necessary significant aspect with each grid-connected converter to fulfill the safety requirements, grid-connected PV systems may continue to deliver electricity generation during grid shutdown hours . As a result, if the PV system does not have energy storage, the electricity generation produced by the PV system throughout blackout periods would be lost. This results in significant energy waste and lengthens the time it takes for photovoltaic systems to repay for themselves. Stand-alone PV systems are two types of photovoltaic (PV) systems that utilize solar fuel to power electricity. The stand-alone PV system is represented in Figure 1. The grid kind is linked directly to the power grid and operates in comparison only with resource load demand . There is also no requirement for battery storage in this PV system because it does not allow for autonomy. Its size ranges from a small-scale distributed roofing system with a few kW to a large central grid-connected system with an MW capacity, and it uses an inverter to translate DC electricity produced by aPV arrays back AC power that can be delivered into the grid. On either side, a stand-alone or off-grid photovoltaic system does not connect to the power system.
This kind of PV system includes a PV system for producing power, energy storage equipment including such battery, energy ventilation system, or AC or DC electrical demands. A grid-connected PV system reduces electricity and capability inefficiencies in the distribution systems, as well as delays or prevents distribution and transmission systems upgrades . Consumer demands are also unconstrained because energy is delivered to the electric grid. The grid integration service’s functioning, on the other side, is contingent on the occurrence of the power scheme. Stand-alone photovoltaic systems, on either side, have found use in rural places where the grid connection is limited. For instance, rural electricity, telecommunications, and pumping systems are all examples. They demand more upkeep but also give you a great sense of freedom.
The goal of the research is to recommend the solution to these problems by providing a different PV system that includes storage batteries, charging controller, grid-attached, AC/DC bilateral change, and process regulator. That means savings can be saved by the battery. This can prevent excessive energy without wasting. It also helps monitor and categorize the submissions charging through the circuit . The technology was developed to accommodate the advantage of all available network hours, not just for providing the demand but also for recharging batteries. On either side, it will use all of the PV-generated electricity to charge batteries, provide the load, and feed the extra electricity back into the grid. In comparison to another traditional photovoltaic system, the proposed solar system is unique in that it can function in both stand-alone states without compromising the islanding security features. On either side, unlike traditional grid-connected photovoltaic system, which typically functions at a voltage source of 400–600 V, the suggested system operates at a drastically reduced voltage source of 48 V, which is safer and allows the required number lithium batteries to be reduced with only
cells . The simulation outcomes of this research verify the correctness of the advanced software architecture and demonstrate that its manufactured and preserved electricity generation is fully sufficient to cover overall load requirements throughout the year, indicating that the advanced system design is a viable solution to address the grid outage issue for a huge proportion of a residential market. However, leading to a shortage of papers upon an unusual PV system that is created for a specific scenario, the received testing data could not have been matched to other analogous findings.
This paper offers a grid-tied photovoltaic (PV) control adaptation topology with a new grid resynchronization mechanism. The goal of this plan is to provide continuous energy to the system while also nourishing control to the network. The control strategy aids in a harmonic compensation and energy quality improvement while obtaining the most generated by the PV array. The suggested arrangement is managed to utilize three ways, characterized as the grid control scheme, points of conventional connection (PCC) voltage regulation, and purposeful transient stability with resynchronization, dependent on the amount of grid energy. Within these modes, a basic error signal controller controls grid frequency, voltage output, batteries, and the direct current (DC) connection amplitude. A control strategy is also presented for Rapid and horizontal evolutions between modes. The system’s durability in the face of irregular solar irradiance, linear model, and grid supplies interruptions makes it a good fit for a home application. The findings of the controls, architecture, and simulations are given to illustrate that the suggested system operates satisfactorily .
Photovoltaic (PV), that could be independent, off-grid linked, or a grid-connected, is viewed as among the most promising alternatives for underdeveloped countries like Rwanda to minimize difficulties associated with energy shortages. Despite developments in renewable technology, Rwanda’s present electricity rate is projected to be 59.7%, and hydroelectric maintains the country’s principal source of energy. Rwanda’s administration has vowed to attain 48 percent of its overall electricity targets through off-grid photovoltaic panels by 2024 to supply inexpensive energy to low-income homes. By constructing an easy and low off-grid photovoltaic system, a comparison of results among a single household as well as a microgrid photovoltaic is undertaken. For a private household, the battery model is 1.6 kWh everyday demand with 0.30 kW peak demand, while for the off PV network, the storage model is 193.05 kWh/day and 20.64 kW peak load. For each of these energy generation representations, the hybrid optimization model for electric renewable (HOMER) software is utilized that estimate a network size or life cycles cost, which includes the net present cost (NPC) and levelized cost of energy (LCOE). The optimal program’s LCOE, NPC, electricity generation, and operational cost are predicted to be 1,166,898.0 USD, 1.28 (USD/kWh), 221, and 715.0 USD for the grid and 9284.4 USD, 1.23 (USD/kWh), and 2426.0 USD for an only one stand-alone, correspondingly, according to the analysis. When evaluated to a regional PV network that provides power to a remote county in Rwanda, the LCOE of such a stand-alone PV scheme for individual residence is shown to be charge-effective .
Stand-alone mode offers the highest effectiveness of the control of a matrix converter, stand-alone PV converter. Initially, a DC-DC boost converter with quadratic back-stepping regulator was modeled and designed. The suggested converter extracts the maximum power point (MPP) by the properly reacting to variable atmospheric circumstances by using a standard voltage supplied by the perturb and observe (PO) technique. One purpose of the boost converter is to increase the voltage at the inverter’s intake while needing a transformer; proposed system is less small and less costly. Next, the single-phase on H-bridge converter was regulated with back-stepping control to minimize the error among the inverter’s voltage level and the target variable; however, there was a significant load variation at the inverter’s production. Lyapunov’s stable concept was used to verify the boost conversion and H-bridge inverter’s reliability. The suggested photovoltaic system using back-stepping controls has a strong recovery of the MPP, with effectiveness of 99.83% and a speed of response of 1 ms, according to simulation findings. Furthermore, the inverter’s voltage output is regulated to 220 V in its sine format, and the overall harmonic component of the output power is little more than 1% .
The Rapid development in the production of renewable power generation to the power process is due to the use of conventional energy sources and environmental concerns. The reduction of power loss and voltage profile might be significant advantages of distributed energy resources (DG). Nevertheless, studies reveal that inappropriate ESS design and size result in unintended energy losses and risk of voltage stability, particularly in areas where renewable power adoption is strong. To address the issue, this study establishes a microgrid created on IEEE 34-bus distribution network that includes wind power, photovoltaic system, and production of diesel, including energy storage systems about particular types of loads. Furthermore, the research proposes the particle swarm optimization (PSO) technique for minimizing power loss and improving system output voltages by efficiently managing various types of renewable power under the worst-case scenario of renewable power. Case educations were approved out using the well-established IEEE 34-bus system. The thorough simulation results for each example highlight the importance of optimal configuration organizational structure as well as the efficacy of the proposed approach .
A single-phase freestanding PV device with two steps of converters is shown in this research. The goal of this project is to track the MPPT so that the extreme possible control can be transferred to the load, as well as to manage the production of current so that the AC load may be fed with a sinusoidal waveform. These objectives are met by designing control rules for the boost DC-DC and an inverter switch utilizing the slipping mode. As a result, a sliding mode MPPT and outputs control technique are presented. The work’s unique feature is that it proposes a freestanding PV system using controls based exclusively on adaptive control. Under quick fluctuations of irradiance level, the suggested system is designed and analyzed in MATLAB/Simulink environment. The findings obtained with the proposed MPPT are instead compared with the results with the incremental conductance (IC) approach. These findings show that the sliding manner (SM) MPPT outperforms the fixed mode MPPT in terms of timing velocity, effectiveness, and responsiveness. Furthermore, the current controller produces a high-quality control signal with a THD of 3.47%. over, these controls are assessed under the changes of two daily meteorological patterns and contrasted to the IC approach for valid results. The findings show that the trajectory tracking MPPT can generate more electric power than an IC MPPT, with advantages of up to 13.12% for the bright daily pattern and 27.67% for a gloomy day pattern .
Materials and Methods
3.1. Characteristics of PV Cell
The majority of solar panel is made up of a series of modules. A p-n connection, which creates small amounts of electricity to the reflected light, can be used to depict this organism. Various analogous circuit designs are provided to investigate the electrical characteristics of the PV cell , because of its strong performance concerning substantial fluctuations in temperature and irradiance. The most commonly used designs for PV cell modeling is shown in Figure 2.
Off-Grid Solar Energy Systems — Pros and Cons
Many homeowners consider installing off-grid solar energy systems, which allow them to sever ties with the local utility company. But while cutting all ties with the power company is certainly possible (and can even be practical) for many people, investing in a stand-alone photovoltaic power system isn’t right for everyone.
If you’re trying to weigh the pros and cons of off-grid solar power, scheduling a consultation with a professional photovoltaic contractor is a great way to get all your questions answered. In the meantime, however, we have put together some basic information about the advantages and disadvantages of going off-grid with solar power.
Advantages of Off-Grid Solar Energy Systems
Disconnecting from your municipal power company comes with several benefits — no doubt the following advantages play a part in your desire to install an off-grid photovoltaic system:
- Independence — Go with an off-grid system, and you’re no longer subject to the terms and policies of the utility company. Getting away from the ongoing rate increase may be reason enough to cut ties.
- No Blackouts — When the power is out and everyone else has no electricity, your home will still have full power. This can be particularly important for people with health conditions that require electronic devices or refrigerated medicine.
- No Electricity Bills — You’ll never again have to give the utility company a slice of your monthly paycheck after you go off-grid with solar power.
Disadvantages of Off-Grid Solar Energy Systems
Installing an off-grid photovoltaic system does come with some drawbacks, however. Here are a few reasons homeowners end up deciding against going off-grid:
- Higher Initial Cost — If you disconnect fully from the power company, you’ll need source of backup power for when the sun isn’t shining. Adding a battery bank and/or generator bumps up your solar costs.
- Limited Solar Energy Storage — Even with backup power, energy storage is limited. Given a few days of cloudy weather, you may run out of stored electricity.
- Energy Efficiency is a Must — When you live off-grid, you have to be careful about your household energy use or you run the risk of not having enough power for your home.
Should You Go Off-Grid with Solar Power?
What is your main motivation for wanting to go off-grid? Answer that question, and you will have a better idea of whether to install an off-grid PV system.
If energy independence, an end to blackouts or eliminating your electricity bills is your primary reason, cutting ties with the power company may be right for you. The same may be true if your home isn’t already connected with electric utility service, as running new lines to a property can cost tens of thousands of dollars, depending on how far the nearest lines are.
If, on the other hand, you simply want to save money by creating your own electricity, you might want to consider a grid-tied photovoltaic system instead.
The professionals at Intermountain Wind Solar provide high-quality, affordable grid-tied and off-grid photovoltaic solutions to homeowners throughout Utah, Idaho, Colorado, Nevada and Wyoming. Contact us today to schedule a free, no-hassle consultation for more information on installing off-grid solar energy systems.
Off-Grid Solar System
All solar power systems work on the same basic principles. Solar modules first convert solar energy or sunlight into DC power using what is known as the photovoltaic (PV) effect. An off-grid solar energy system is not connected to the utility grid, whereas an on-grid solar energy system is connected to the utility grid. Your choice of an off-grid system or on-grid system will determine your access to electricity, what equipment is needed for excess production, what happens when the grid goes down, and how you’re billed for electricity. In this article, we will be looking into the main components used in off-grid systems.
Off-Grid system types. AC or DC coupled
Off-grid systems are built using either AC or DC coupled power sources. AC-coupled generation sources include common solar inverters while DC-coupled sources include MPPT solar charge controllers. Whether a system is AC or DC coupled is generally based on the size of the system. Most small-scale systems are DC coupled and use efficient MPPT solar charge controllers. Larger off-grid systems can be either AC or DC coupled depending on the type of off-grid inverter-charger used, and compatibility with different solar inverters (AC) or solar charge controllers (DC).
Off-Grid Battery Banks
Off-grid batteries should charge efficiently so as not to waste valuable energy generated by the solar array or a diesel generator. Off-grid batteries need high power capability to support the high surge draw, discharge and charge current of off-grid inverter chargers. Access to off-grid sites is not always easy, so a maintenance-free battery is highly desirable. Temperature changes must be considered as this will affect the lifetime of the battery.
State of Charge (SoC) is the level of charge of an electric battery relative to its capacity. The units of SoC are percentage points 0% = empty; 100% = full. SoC is normally used when discussing the current state of a battery in use. Off-grid solar battery systems will be deeply cycled and regularly operated in a partial state of charge (PSOC) condition. So, SoC monitoring is critical for off-grid users.
Lead Acid Battery vs. lithium-Ion Battery in Off-Grid
This all boils down to the number of cycles a battery has and its depth of discharge, how many times the battery can be drained, and how much power can be used. Lead-acid batteries degrade more with every cycle. Where a lithium battery may come with a 10,000-cycle guarantee. Lead-acid batteries are lower in cost for the same voltage and capacity but do not last for many cycles whereas, for lithium-ion batteries with higher discharge cycles, the initial cost is low. Despite having higher upfront costs, lithium-ion batteries are usually more valuable than lead-acid options. lead-acid batteries may be the better decision is in a scenario with an off-grid solar installation that isn’t used very frequently due to lower usage rates a lead-acid battery would be a good solution instead of lithium-ion batteries.
Solar Charge Controller
It regulates the charging of batteries and prevents them from over-charging and further damage. Simple charge controllers stop charging a battery when they exceed a set high voltage level and re-enable charging when battery voltage drops back below that level. Charge controllers may also monitor battery temperature to prevent overheating. Some charge controller systems also display data, transmit data to remote displays over time.
The most common DC-coupled systems use solar charge controllers (also known as solar regulators) to charge a battery directly from solar, plus a battery inverter to supply AC power to the household appliances. For microsystems, such as those used in caravans/boats or huts, the simple PWM (Pulse Width Modulation) type solar controllers are a very low-cost way to connect 1 or 2 solar panels to charge a 12-volt battery. For larger systems, MPPT (Maximum Power Point Tracking) solar charge controllers are used. Unlike the simple PWM controllers, MPPT systems can operate at much higher string voltages.
Off-Grid Solar Inverters
Grid-tied inverters are simpler and easier to wire since there are usually only two main components but an off-grid inverter needs a battery bank to function. In the case of an off-grid system, the solar panels feed DC power to the batteries. Then the inverter takes that power and converts it into AC power for your home. This works essentially like a miniature power grid. One main difference between off-grid solar inverts and on-grid is they don’t have to match the frequency of the utility power grid compared to a grid-tied inverter.
A hybrid inverter, otherwise known as a battery-based inverter, combines two separate components–a solar inverter and a battery inverter–into a single piece of equipment. it can function as both an inverter for electricity from your solar panels and a solar battery. One of the biggest benefits of a hybrid inverter is that it combines the functionality of two separate pieces of equipment into one. This can mean an easier installation process for your solar installer. Other than this a hybrid inverter allows for centralized monitoring of both battery and solar panels.
AC and DC Disconnects
The purpose of these disconnects is to make sure you can shut off incoming power from the solar panels. DC disconnects are places between solar panels and inverters. AC disconnects are placed after the inverter.
AC disconnects are typically mounted on the exterior wall of the customer’s home near the electric meter. The necessity of these disconnects arises from the fact that in case of an emergency like fire or extreme weather conditions to protect the installations from getting damaged and even during maintenance, it is required to shut off the power completely for safety purposes. AC/DC disconnects are just one piece of the BOS (balance of system) components you’ll need for a successful solar installation.
Off-grid systems are more complicated, thanks to additional components like the charge controller, battery monitor, and additional AC and DC circuit breakers. All of these things tend to make off-grid systems more difficult to wire and install.