In general terms, we’ve known for a while that the current condition of the grid would be a limiting factor in the growth of renewable energy. But now, as utilities are introducing significant new programs to meet state Renewable Portfolio Standards (RPS), the reality of grid limitation is quickly coming into focus, in a very visible way.
For instance, grid limitations on Hawaii’s most populous island, Oahu, mean that no solar photovoltaic (PV) system can be more than 100 kW, and renewable energy capacity is restricted to 10 MW for the entire island. To put this in perspective, the total yearly revenue possible from 10 MW of solar power purchase agreements (PPAs) would be roughly equivalent to the annual sales volume of a single grocery store.
As part of its massive 500 MW solar program, Southern California Edison (SCE) has created a map of places within their distribution system where “wholesale” distributed generation PV (500 kW to 10 MW) will be easier to connect (see below or view on Google Earth). Speculation is that SCE doesn’t think that areas outside the red boxes can handle the addition of variable PV power — and that’s a big deal. If SCE won’t approve requests for PV outside the preferred areas, it narrows the playing field for PV developers — a lot.
So, where do we go from here? Southern California Edison has taken the necessary first steps. Their map tells PV developers, “this is where you can connect, no problem.” A working group trying to tackle this problem is the new Renewable Distributed Energy Collaborative (Re-DEC)launched by the State of California. This is an effort that may lead to what SCE has done, but on a rooftop-by-rooftop basis across the state. The benefit is that one can know immediately how much PV can be put on each roof, based on grid capacity.
Other possible solutions come into play as we look further out over time. One longer-term possibility is bolstering the grid for PV in populated areas, which can be done using smart grid technology. Another longer-range solution is envisioned by the Renewable Energy Transmission Initiative (RETI), which is sponsored by the State of California, but could be expanded across the nation. RETI is working toward a completely remodeled grid that includes renewable energy sources and transmission by identifying the best locations for wind, solar, and geothermal in California and adjacent states, and then proposing locations for new transmission lines.
Finally, for those who dream big–including Bob Ready at the Florida Solar Energy Center, AltaTerra’s Jon Previtali, and Ben Kroposki, senior engineer at NREL, leader of the Distributed Power Systems Integration Team, and our featured guest for next week’s “Scaling Up PV-Grid Integration” online conference–there is the future possibility that PV could produce as much as 200% of the power needed in a particular area, allowing half of the power produced to be used in local buildings and the other half transmitted out of the area using smart grid technology.
At a minimum and in the near-term, the grid will have to accommodate new commercial and utility-scale renewable energy installations on a widespread basis. And lest we forget, mass-market electric vehicles are just around the corner. So the grid must be ready for major pattern changes in both supply and demand. Stay tuned.
Don Bray, Jon Previtali, and Anneke Hohl contributed to this blog.
