Researchers at the National Renewable Energy Laboratory (NREL) worked with the Sacramento Municipal Utility District (SMUD) in a bid to solve a pain point in the interconnection process: how to streamline the solar application process while remaining technically thorough.

The solution is a tool known as PRECISE—PREconfiguring and Controlling Inverter SEt-points—which is designed to perform fast and automated interconnection assessments while also integrating with SMUD’s existing business interconnection workflow.

“PV interconnection evaluation is becoming a time-consuming process as each proposed solar power system must be individually reviewed in detail to make sure it works safely with our grid,” said Sheikh Hassan, a principal distribution engineer at SMUD. He said that PRECISE “significantly reduces” this evaluation time by “instantly determining optimal inverter settings for a given location.”

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The high volume of interconnection requests shows no signs of slowing down as the price of photovoltaic (PV) systems falls and as states and local governments set higher renewable energy goals for their communities.

The crush of solar interconnection requests poses challenges for utilities as each application received requires a technical evaluation to assess the potential grid impacts of the new solar installation. 

PRECISE went live at SMUD in February and, to date, has processed more than 1,700 applications, an average of 13 applications each business day and as many as nearly 30 applications in one day. 

Hundreds of applications

NREL said the tool itself can scale to process any number of applications. Through automation, data integration, and fast computing techniques, PRECISE can handle hundreds of applications daily.

To be technically rigorous, PRECISE automates the modeling of all of SMUD’s 40,000-plus distribution secondaries and pulls in advanced metering infrastructure (AMI) data as required. 

The tool also uses local irradiance measurements across SMUD’s service area and creates mathematical models of each incoming PV system. This involves modeling every component of the solar panels and their orientations, as well as the inverters and smart inverter capabilities.

The process is automated to enable PRECISE to pull in data as soon as a customer’s interconnection application is created. It updates business teams downstream (functions such as planning, metering, and line design) once its calculations are complete.

One common scenario for SMUD customers involves requests to interconnect solar power systems larger than the grid could accommodate in a specific location. PRECISE automates an assessment of what size system the grid can accommodate and how advanced inverter functions can support approval. In these sorts of scenarios, planning engineers can work with the customer to find a solution to enable the PV system to interconnect successfully.

For every residential solar PV interconnection application, PRECISE assesses the impact of the interconnection proposal and evaluates the need to use smart inverter functions.

To build the assessment tool, NREL worked with a SMUD team that included more than 20 personnel working over multiple departments at the utility—including geographical information system (GIS) experts, advanced metering infrastructure leads, distribution engineers, database administrators, application administrators, information technology project managers, and business process experts.

NREL’s project team included Kapil Duwadi, who played the role of application developer, Aadil Latif, who automated the modeling of SMUD’s entire distribution system, and Killian McKenna, who oversaw the effort.

The project is considered to be one of the first automations of the technical interconnection evaluation process of its kind, and could serve as a template for utilities that wish to automate the increasing challenge of evaluating new interconnection requests.