For years, the cumulative amount of distributed generation (DG) on the grid was akin to a drop of water in a glass.  That is, a tiny drop in a big glass.  But look how far we’ve come in the past few years. Last year the U.S. installed more than 90,000 photovoltaic installations, with a total capacity of 3.3 GW. This represents an 80% increase over installations completed in 2011 (see graph below).  If we were to sustain this growth rate, we could expect to see close to 20 GW of solar installed in 2015.

grid connected

Annual Installed Grid-Connected PV Capacity

Source: IREC’s 2012 U.S. Solar Market Trends Report.  Larry Sherwood, expected publication, July 2013.

This is great news for distributed generation industries, but how do we plan for that kind of growth? In highly active DG states, we are already seeing stalled DG development, as distribution circuits surpass the ubiquitous 15% penetration level that serves as a review checkpoint in most state interconnection procedures. As a result, it’s becoming increasingly difficult for developers to find circuits with available capacity to host additional DG.

To address this challenge, last month IREC, in collaboration with Sandia National Laboratories, published an extensive report titled Integrated Distribution Planning (IDP) Concept Paper, A Proactive Approach for Accommodating High Penetrations of Distributed Generation Resources.  This paper combines the planning processes of several forward-thinking utilities around the country to propose the proactive study of the grid’s ability to accommodate further DG capacity.

As explained in the concept paper, IDP leverages existing tools from distribution system planning to allow utilities to estimate the hosting capacity of distribution circuits before studying a particular interconnection request. It also identifies and analyzes any potential infrastruc­ture upgrades needed to accommodate anticipated DG growth.  The paper summarizes the IDP process into five-steps:

1) Forecasting DG growth on the circuit;

2) Establishing the hosting capacity and allowable penetration level;

3) Determining available capacity on the distribution circuit;

4) Planning upgrades and expedited interconnection procedures based on IDP; and

5) Publishing the results.

While most utilities aren’t yet to this stage of DG development, we can look forward to a greater interest and need for innovative approaches like this as DG growth continues its upward mobility.

Now that we’ve moved well beyond the original drop in the glass, we’d like to see DG fill that glass with a steady flow of projects in the coming years.  IDP can help get us there.