Solar Interconnection: How Solar Farms Connect to the Grid

Utility solar interconnection is vital to completing a successful project. Therefore, successfully managing this critical step helps keep projects on schedule and budget. Unfortunately, solar interconnection issues can degrade customer satisfaction, so effective management is essential. Understanding how solar farms connects to the grid and the point of interconnection for solar projects is critical.

The Importance Of Solar Interconnection

Solar interconnection is critical for commercial solar projects to connect to the power grid and earn compensation for electricity generated from distributed generation. Without utility compensation, most commercial solar installations are not financially sustainable. The solar interconnection process depends on the electric utility, property specifics, and local regulations, including load-side and line-side requirements.

The utility company must authorize this connection to receive approval to interconnect. In addition, the solar panels and equipment must meet specific qualifications to ensure the proper voltage, power quality, and reliability.

Therefore, solar interconnection management can be relatively complex, especially for larger projects. However, utility interconnection might not be much more complicated for small commercial projects than residential solar installations.

Not correctly identifying all the costs related to solar interconnection can result in numerous change orders and can increase the total cost of the solar system. This can lead to dissatisfied customers and delays.

The Commercial Solar Interconnection Process

In the United States, state-level public utility commissions (PUCs) create interconnection policies that utility companies and solar installers must follow. Many states have also enacted safety requirements based on IEEE 1547 and UL 1741 standards.

This also means the interconnection policies vary by state, with some having more complicated and unclear standards than others. Unfortunately, this increases the soft costs of installing a solar PV project. Also, varying requirements make it more difficult for solar contractors that operate in numerous states because they need to learn the requirements in all states where they complete installations.

In general, the solar system must satisfy grounding, power quality, and voltage requirements to navigate the process successfully. In addition, some commercial solar projects will require an impact study. The solar interconnection process consists of two main steps that need to be completed in the correct order.

Solar Interconnection Application Process

Like residential projects, commercial projects require filling out an interconnection application. The applications contain basic information, such as the system size, solar PV equipment, location, and solar electricity production estimates. For large commercial projects, this application can be relatively complicated. In particular, solar with battery storage can be incredibly complex because of the impact of the battery on the electric grid.

During the solar interconnection application process, contractors and project developers need to show that the renewable energy system meets various requirements. The application must also explain the point of interconnection for solar. If changes or modifications are made to the solar project, the solar contractor or developer must update the application.

Permission To Operate

Before a system can be turned on, it must receive permission to operate (PTO) and an approved interconnection agreement. The system must be installed, inspected, and approved by the utility provider. Now, the solar system has the authorization to operate and connect to the utility grid because it fulfills all the interconnection requirements.

How Long Can Commercial Solar Interconnection Take?

The length of the process depends a lot on the utility company, if there are complications, and how quickly the solar contractor or developer responds to requests from the utility company. Also, solar systems with energy storage can take longer to receive approval. This is because the solar installation is both a load and a generator, depending on how the project is operating. Some jurisdictions have simplified solar interconnection approval processes, especially for residential and small commercial solar systems. Other jurisdictions have not.

According to a 2015 study by the National Renewable Energy Laboratory, the average small commercial project (10 – 50 kilowatts) took an average of 62 days from when the contractor applied for interconnection to when they received permission to operate. Keep in mind that solar interconnection timeframes vary a lot by the jurisdiction and scale of the photovoltaic solar project. Large commercial projects can take significantly longer.

What Causes Solar Interconnection Delays?

Solar interconnection delays often stem from utility administrative processes, permitting issues, technical reviews, and grid capacity limitations. Lengthy paperwork, regulatory approvals, and coordination with utilities can slow progress. In some cases, required upgrades to grid infrastructure to support solar integration add to the timeline. Local regulations and the complexity of the solar interconnection process may vary, influencing the overall timeframe.

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The Difference Between Residential & Commercial Solar Interconnection

Residential solar interconnection is generally straightforward, with most systems connecting to the power grid without significant equipment upgrades beyond the meter. In contrast, commercial solar interconnection is often more complex due to the larger scale and higher voltage requirements of commercial projects. These systems frequently require additional modifications and infrastructure to ensure proper integration with the grid.

Point Of Interconnection for Solar

It is typically not cost-effective to connect a small solar project to a high-voltage transmission line because the cost of interconnection typically increases by the voltage of the power line.

Larger commercial projects, such as a community solar farm, usually need to be connected to a three-phase distribution line. Utility-scale projects either connect directly to a substation or a transmission line of 69 kV or higher.

Unless a solar farm is installed next to transmission lines or substations, the solar contractor needs to install a generation tie to connect the clean energy project to the grid. These are expensive to construct and can have a significant impact on the project’s return on investment. Therefore, close proximity to transmission lines or a solar farm substation is preferable.

Unfortunately, just because a high-voltage line is located near a proposed solar farm doesn’t mean that it has the capacity to handle the additional power from the solar project. Sometimes, electrical equipment needs to be upgraded to increase its capacity, which can be costly.

Solar Interconnection Voltage

Interconnection voltage is a critical consideration for commercial solar installations. While utilities typically supply 208V to commercial customers, most inverters over 20 kilowatts operate at 480V. As a result, many commercial solar systems require a transformer to step down the voltage for compatibility.

Also, larger solar systems with multiple inverters need a combiner panel to merge their outputs. This panel is commonly installed on the roof but may also be located in a mechanical room or basement, depending on the system design and site requirements.

Utility Compensation

Under net metering laws, many residential and some commercial solar customers are compensated for solar electricity at the retail rate. However, laws vary by state, and some states don’t have a net energy metering program. For commercial power customers, policies also vary by the type of commercial account. For example, some commercial customers can offset demand charges on their power bills with solar power, while others cannot.

What is a Solar Farm Substation?

A solar farm substation is a key infrastructure component that facilitates the connection of a solar farm to the electrical grid. Here’s a breakdown of its role and function:

Step Up Voltage

The solar farm substation houses transformers that increase the voltage of the electricity produced at the solar farm. Solar panels typically produce electricity at a lower voltage, which is then converted to a much higher voltage needed for efficient transmission over long distances.

Point of Interconnection

The substation is the point of interconnection between the solar farm and the grid. It ensures that the electricity generated by the solar farm is synchronized with the grid’s voltage, frequency, and phase, allowing it to be fed into the wider electrical network.

Protection and Control

Modern solar farm substations are equipped with protection devices, such as circuit breakers and relays, that safeguard both the solar farm and the grid from electrical faults or anomalies. It also includes control systems that manage the flow of electricity, ensuring that the power output meets the grid’s requirements.

Monitoring and Communication

Solar farm substations often include monitoring and communication systems that track the performance of the solar farm, control the operation of the transformers and other equipment, and report data back to the utility or solar farm operators.

Energy Storage

Solar farm substations often include energy storage systems, like batteries, to capture surplus energy produced during peak sunlight hours. This stored energy can be released during periods of low solar generation, improving the reliability and consistency of the solar power supply.

Solar Interconnection FAQs

Read on to gain answers to common questions about the solar interconnection process and the point of interconnection for solar.

How does a solar farm connect to the grid?

Solar farms connect to the grid by converting the direct current (DC) generated by solar panels into alternating current (AC) through inverters. The AC electricity is then transmitted to a substation within the solar farm, where it is further transformed and connected to the broader electrical grid. This allows the solar farm to distribute the generated electricity across the grid for consumption by homes, businesses, and other users.

What role do transformers play in connecting a solar farm to the grid?

Transformers or substations play a crucial role in connecting a solar farm to the grid by stepping up the voltage of the electricity generated by the solar panels to match the grid’s high voltage levels. This is essential for efficient long-distance electricity transmission from the solar farm to the grid. Without transformers or solar farm substations, the generated power would not be compatible with the grid's infrastructure, hindering its distribution.

When do solar farms need a substation vs a transformer?

Transformers step up voltage in small—to medium-sized solar farms to connect to local distribution grids. Large-scale solar farms require substations to provide additional protection and control and step up voltage for high-voltage transmission. Solar farm substations are essential when connecting solar farms to the high-voltage transmission network.

What is the point of interconnection for solar?

The point of interconnection (POI) in a solar energy system is where the solar power project connects to the electrical grid. It’s the physical and electrical point where the electricity produced by the solar panels is fed to the utility grid or used within a building. This connection is essential for integrating solar power into the broader energy infrastructure.

It includes:

• Location: The point of interconnection for solar can be at the main service panel (for residential or commercial systems) or at a utility substation (for larger-scale solar farms).

• Grid Connection: At the POI, the AC power generated by the solar system (after being converted from DC by the inverter) is synchronized with the grid. This allows excess electricity to be fed back into the grid (often through net metering), or it enables the building to draw power from the grid when solar production is insufficient.

• Safety and Compliance: The point of interconnection is critical for safety, and its design and installation must comply with local electrical codes and utility requirements to ensure proper operation and avoid issues like backfeeding, which can be dangerous to utility workers during a grid outage.

Connecting Solar Farms to the Grid

The interconnection process becomes easier with experience, especially if the technical requirements remain consistent or are streamlined.

Bringing expert knowledge to the interconnection process is critical. Unfortunately, many solar companies lack this knowledge in-house, or they simply don’t have the time to properly manage the interconnection process and site solar equipment optimally.

GreenLancer solar interconnection and engineering services can help mitigate costs and ensure project success through their professional solar development services. To learn more, sign up for free and shop our interconnection services, or complete the form below to learn more.