Okay, this is a common situation with SolarEdge, and your constraints make for an interesting challenge. Let's break it down

Regarding: "If I have 12 panels in an array (A1) and I connect 1 panel (P1) of the array to an optimizer (O1) and connect O1 to an inverter (I1) can I connect the rest of the panels in array A1 to inverter I1 without any connection to any other optimizers?"

The Answer is: Absolutely Not.

Here's why: SolarEdge Inverters Require a Complete and Compatible Optimizer String

SolarEdge inverters are designed to only function with optimizers on every panel in the string. They don't just improve efficiency; they're integral to the inverter's operation. The inverter needs the communication and voltage regulation provided by the optimizers to operate. Trying to mix panels with and without optimizers will result in the inverter not working at all or producing error messages.

Impedance Mismatch and Voltage Issues

Even if the inverter did start, you'd likely experience significant performance problems. Panels connected directly to the inverter would have different voltage/current characteristics than the panel connected through an optimizer. This mismatch can cause the entire string to operate at a suboptimal point, severely reducing power output.

The Inverter Won't Recognize a Partial String

The inverter constantly monitors the number and type of optimizers in the string. A missing or incorrect optimizer will cause the system to fault and shut down.

Regarding: "Also it appears that SE has features within their optimizers which have their systems compliant with NEC rapid shutdown requirements. Would connecting panels to an inverter that didn't have optimizers (but having at least 1 panel with an optimizer going to the inverter) negate or compromise these safety features?"The Answer is: Yes. You would be negating and compromising the rapid shutdown feature.

Here's why: Rapid Shutdown is Optimizer-Dependent

The rapid shutdown functionality in SolarEdge relies completely on the optimizers. When the inverter detects a rapid shutdown command (usually triggered by a disconnect switch), it signals the optimizers to reduce the voltage of each panel to a safe level (typically under 30V).

Unsafe Voltage

If you bypass the optimizers on some panels, those panels will continue to operate at their full voltage when a rapid shutdown event occurs. This would violate NEC rapid shutdown requirements and create a dangerous situation for first responders.

Compliance Issues

Using a mixed system will void the UL listing for the system and make it non-compliant with local electrical codes. This can lead to fines, rejection of the installation, and liability issues.

Recommendations for your situation

Given your limited budget and the fact that the primary goal is a proof of concept, here's how I'd approach this:1.

Talk to SolarEdge

Seriously. Contact SolarEdge directly. Explain your situation and your research/educational goals. They might be willing to offer a discount on the optimizers, provide educational materials, or even offer a different inverter option that's better suited for your specific needs. They have an interest in promoting their technology and might be willing to work with you.2.

Consider Returning the SolarEdge Inverters

If you can return the SolarEdge inverters without a major penalty, it might be the most cost-effective option. You could then:

Buy a Traditional String Inverter

A standard string inverter from a reputable brand would be significantly cheaper than purchasing all the required SolarEdge optimizers. While you won't get the individual panel monitoring or some of the advanced features, it will work for basic power generation. Look for an inverter that can handle the voltage and current characteristics of your VSUN panels in strings of 12.

Explore Microinverters

Microinverters (like Enphase) are another option. Each panel has its own microinverter, eliminating the need for a central inverter. They are more expensive up-front compared to string inverters, but might be cheaper than buying all the SolarEdge optimizers.

Off-Grid System

If you don't need to connect to the grid, you could build a small off-grid system with a charge controller, battery bank, and a stand-alone inverter. This would allow you to use the panels and bypass the need for grid-tie inverters and optimizers altogether. (Though batteries can be costly).3.

Scale Down the Array

If returning the inverters isn't an option, consider scaling down the size of the array to match the number of optimizers you can afford. Install a smaller, fully optimized system. It's better to have a small, functioning system than a large, non-compliant one.4.

Used/Refurbished Optimizers

You might be able to find used or refurbished SolarEdge optimizers online. However, be very cautious when buying used electrical equipment. Ensure the optimizers are compatible with your inverter and panels and that they are in good working condition. Test them thoroughly before installation.

Important Considerations



NEC Compliance

Always ensure your installation meets all applicable electrical codes. Improper installations can be dangerous and can result in fines and rejection by the local authority having jurisdiction (AHJ).

Electrical Safety

If you're not a qualified electrician, hire one to perform the installation. Working with electricity can be dangerous, and a mistake can be fatal.

Documentation

Keep detailed records of all components used, the installation process, and any testing performed. This documentation will be essential for troubleshooting and maintenance.*

Insurance: Check with your insurance provider to ensure your solar installation is covered.In summary, trying to "hack" the SolarEdge system by bypassing optimizers is not a viable or safe option. You need to either fully commit to the SolarEdge system (by buying all the necessary optimizers) or explore alternative inverter technologies. Given your budget constraints and project goals, a different inverter solution is likely the best path forward. Good luck! Flag for review