You are exactly right. Transmission is usually about moving energy 10s or 100s of miles getting energy from one area to another. Historically it was primarily to get power from the very big remote power plants to where the energy is needed as well as interconnect energy load centers to allow more redundancy and trading to allow access to cheaper energy in other markets. Distribution (smaller wires/towers/voltages) is normally the last mile or so of the journey. Capacity related infrastructure are always sized to moment of greatest need, otherwise you see system failures. This means any solution that doesn’t reduce usage during all hours, only reduces reliance on a particular piece of equipment to the extent the new peak usage hour is lower than the prior peak. Historical energy peaks were in the 3 to 5 hours, but since the 6 to 8 pm hours usage is usually only slightly lower, abundant energy at 3 to 5pm doesn’t remove need for transmission lines at 6 to 8pm. Also the vast majority of solar customers still rely on the grid at night so they still need those miles of transmission lines from sometimes remote power plants to keep their power on. Regarding my claim of transmission expansion needs, this only becomes an issue once an area expands beyond say 5 to 10% (actual amount varies by grid) solar penetration (few are there today, but most have that in their goals for the near future). Germany is well into these area of need. I believe the most obvious signs of this in California would be increasing solar curtailments year over year and transmission expansion projects. California would absolutely prefer to ship the solar that extends beyond their own needs to other states rather than curtail (turn off plants giving up free marginal cost energy), but the availability and capacity of lines are the limitation, thus the reference to solar leading to transmission expansion. When you’re the only solar system in the neighborhood your production that is likely 2 to 5 times your needs on a sunny spring day goes to your 2 to 5 closest neighbors only touching distribution line drops and a transformer bus bar (fraction of distribution system). If you get say all 6 customers in a neighborhood on the same transformer, you’re now likely using that transformer more heavily running in reverse during a sunny spring day than it gets used during even the hottest days of summer and sending that power up distribution lines all the way to a substation. If an entire development is largely solar, you will get the same phenomenon, but it will basically reverse direction for part of the day and become a “step up” voltage transformer rather than a “step down” voltage transformer. I guess my point is the equipment still tends to be heavily used and necessary. NEM often offsets some or much of these costs that aren’t significantly reduced in many cases and this is the challenge that I believe utilities will continue to try to address through updated rate structures. A more justified structure might offset fuel and energy type costs and a limited amount of grid type benefit, which is why I believe these proposals will keep coming. Sorry about the novel. These topics are very technical and deep. To your question I will disclose that I’m an avid believer we need to do more to clean up grids and really all outsized sources of pollution or non-sustainable practices, but I consult in the utility arenas and often conduct detailed analysis of the relative economics of many types of renewables including both rooftop and utility scale solar plants. My view is that the more relevant information that is out there, the more informed decisions we make. This response is already really long so I’ll comment on the LLNL rejected energy study separately.
