Battery Alone

In the last post we discussed where it makes most sense (from a carbon footprint reduction standpoint) to install Solar Panels plus a Home Battery (California). In this post we go somewhere that seems strange -- where you would want to install a Home Battery alone.

Meet Hawaii. More specifically the islands of Oahu and Kauai. The short version of the story is that Oahu and Kauai have so much Solar (and more specifically Solar on homeowner rooftops) that the grid on those islands simply can't handle any more. If you've read the previous posts you know that once Solar gets above the 13% range it becomes quite difficult for grid operators to deal with it. In Hawaii they are up to 18%! So how did this happen?

Hawaii has a few unique qualities that have lead them quickly to the "redline" of Solar. First is that electricity there is very expensive. Most of their electricity comes from burning oil in steam electric plants (similar to coal plants but using oil instead of coal) The oil has to be shipped allllll the halfway across the Pacific. Therefore Solar energy, especially at first, made a lot of economic sense. Second... it's sunny. Third is that each island is, well, an island. Each is its own small grid. There are plans out there to lay power lines between some of the islands but as of this writing none exist. In California if they have an excess of Solar they can send some to Nevada... no such luck in Hawaii. Finally, because most of the Solar on Oahu and Kauai are on homeowners' rooftops, the utilities have no way to turn them down (i.e. curtail) the output -- they have no choice but to accept it. All of these factors have led to Solar PV getting "max'ed out" quite quickly in Hawaii.

To better understand what we mean by "max'ed out" let's see how all that Solar looks to a Hawaiian grid operator:

A couple of notes. First Hawaii does not go on Daylight Savings, so the Solar is centered right at noon. Second because Hawaii is pretty far south the sun is up a fairly long time, so I spread the Solar over 10 hours instead of 8.

In the figure above we can see that the 18% Solar generation provides a huge percentage of the grid's electricity around midday. This requires the grid operators to turn their oil plants way down. A steam power plant can usually only turn down to 40% of capacity, but all this Solar is demanding the steam power plant turn down to only 23% of capacity. This really puts grid operators in a bind. 

Also remember that 18% is the average... some days Solar provides even more! For example below is a graph showing a day during which Solar was providing so much electricity that power in the lines started running backwards!


This kind of situation can damage utility equipment and result in power outages. The bottom line is that the grids on the Hawaiian Islands simply cannot handle any more solar. For this reason, on many areas of the islands the utilities have been forced to halt homeowners from installing any new Solar. Now you should have a pretty good idea of why.

It should be pretty obvious by now that if you are a homeowner in Hawaii and you want to reduce the carbon footprint of your electricity use... you should install a Home Battery alone. Because there is so much Solar power already flooding the grid during midday, you could charge your battery during that time and then use the stored energy to power your home the whole rest of the day. You would be helping the grid because you would be using up electricity when there is too much, and you would be decreasing the evening peak demand, thereby lowering the amount of oil burned in the old steam generators! With enough batteries, Hawaii could move to 100% Solar energy. 

So basically Hawaii can't use any more Solar until it gets a bunch of batteries. And in fact Hawaii has started to do just that. Recently the company AES announced that they are building a Solar + Battery Storage plant on Kauai, which is expected to go live in late 2018.

The average homeowner in Hawaii equates Solar Panels with green energy, and so there is no shortage of people wanting to put them up. My hope is that, from the perspective of reducing one's carbon footprint, Hawaiians will start to view the Home Battery in just the same light.