by Greentech Media

As solar developers in the U.S. prepare for a steep reduction in the federal Investment Tax Credit at the end of 2016, they're hustling to get projects in the ground. Making good decisions under this time crunch will be key to maximizing the value of projects and limiting risk.

According to GTM Research, more than 7 gigawatts of utility-scale solar will be placed in operation before the 30 percent tax credit drops down to 10 percent. A similar push will take place in the residential and commercial sectors as well, likely bringing total 2016 installations above 12 gigawatts.

This robust installation activity will undoubtedly be a good thing for the industry. But it will also force developers to make quick decisions about equipment procurement. In this time-sensitive environment, it's vital that developers consider their options wisely.

"The key to success is early engagement with vendors who have project experience from the system perspective, and not just at the component or equipment level," said Rob Weber, director of utility inverter sales at ABB. 

One of the most important decisions will be the inverter -- both the backbone and lifeline of any solar installation.

In order to ensure a successful interconnection by the end of 2016, developers of large-scale PV projects must consider how to minimize logistical constraints created by inverters.

Three-phase string inverters: A simple and flexible option

Utility-scale developers in the U.S. have long favored central inverters. While central inverters are a vital offering from companies like ABB, they do require longer lead times and also bring more complex shipping and infrastructure requirements. Generally, the lead time for a central inverter is double that of a string inverter.

As a result, more companies are considering three-phase string inverters for their large commercial and smaller utility-scale projects.

"The three-phase string inverter is quickly gaining traction," said Chavonne Yee, the director of product management for ABB's inverter business. "Many companies are seeing there's an alternative to central inverters in order to get a project done quickly and reduce some of their constraints."

The technology offers many benefits to the time-constrained developer eyeing the ITC deadline at the end of 2016.


Flexibility is one important benefit. When installing large central inverters, companies must hire cranes, schedule special delivery trucks, and consider other infrastructure needs when shipping the product. String inverters come on standard palettes, greatly simplifying shipping and other on-site logistics.

Developers can also buy inverters in smaller block sizes, thus avoiding an over-purchase of power capabilities. This will cut down on under-loaded inverters that are not operating at their optimal points, thus boosting the levelized cost of energy.

Improved monitoring is another benefit. String inverters offer two maximum power point trackers, allowing for deeper insight into panel performance. Three-phase string inverters can provide up to 30 times more granularity in maximum power point tracking than an equivalent central inverter.

"There's a whole list of things on the balance-of-equipment side that are much more standard and easier to order, therefore reducing lead times," explained Yee.

No single solution: Central inverters stand up to greater power demand

This is not to say that string inverters are the ideal choice for every situation. For many large projects, it makes much more financial and logistical sense to install a central inverter. Large-scale string inverters can meet up to 3 megawatts of capacity.

Central inverters don't have to be overly complicated. By applying a system-level approach to inverter integration through standardized skid platforms, the entire process from design and deployment can be improved.

“Finding a partner with experience and capabilities can result in specific product configurations and features that can help reduce lead time, installation time and complexity, and potentially unforeseen issues that may arise during construction, commissioning and operation," said Weber.

For example, self-contained enclosures eliminate the need to build an E-house around the inverter -- cutting the need for fans, filters, controls and dampers. In turn, that reduces labor costs, time of installation, and operational complications.

As an example, ABB’s ULTRA inverters are also designed to simplify integration. The units have 690 Vac output voltage for coupling with a medium-voltage transformer, allowing for standardization in transformer design. This standardization encourages competition because the developer is able to buy transformers from a broader range of vendors. With competition comes lower costs.

Integration considerations

As an engineering company working on complex grid challenges worldwide, ABB brings expertise from other areas of its business to inverters. ABB's deep experience in the development of substations ensures that its large-scale inverter technologies are made with the most reliable components and are easily connected to transformer stations.

It is important to look at inverter design as an overall package -- for example, by eliminating the need for separate DC cabinets, reducing transformer investments through direct coupling or including multi-stage topology that prevents any major grid events, like voltage spikes, from dissipating back into the modules. 

"We're always looking at ways to optimize the inverter for customers, whether they integrate it on their own or we do it for them," said Weber. "We are always looking at what it takes to be the best in reliability -- to keep things simple, yet strong."

There are a lot of inverter options to choose from. Customers should evaluate the range of functionality and integration options to understand what's best for their project.

"While inverter specific features and characteristics can be beneficial in a successful and timely project completion, selecting and engaging with a vendor that understands the application of the inverter in the scope of the entire project can help identify additional opportunities for cost, performance and deployment optimization," said Weber.

With more and more developers rushing to meet tight project deadlines, finding that peace of mind is critical when making such important equipment decisions.

Don't miss ABB's upcoming webinar with GTM on the ITC deadline: Best Practices for Successful and Timely Project Completion. The webinar will be held on Wednesday, October 21 at 2 p.m. EST. Sign up here.

ABB is working hard on the challenges associated with solar integration. Learn more about the company's offerings in the video below.


This article was sponsored by ABB.