It’s my Clean Energy Microgrid-iversary!

…and my solar-iversary, my battery-iversary.

Reflections on one year living with an energy independent system on my home

A year ago, a crew of men arrived at my house and installed a rooftop solar array, coupled it to a battery system three stories below, and ran it in such a way that I could isolate my house from the larger electrical grid and be entirely independent. My very own microgrid! My entire home is backed up with this system…but it isn’t designed as a backup system only. This is my main system energy system, running in a mode better described as “self-sufficient”. Basically I use the electrical grid as my backup, and help out the grid when I can by exporting power when it is most needed.

The completed installation of the solar array — actually there are two equal sized arrays here…one is AC coupled and mine is D-coupled.

The system is comprised of a 4.7kw solar array and a 16kwh Blue Ion energy storage system from Blue Planet Energy (disclosure: I am part of that company!). The system also includes an Automatic Transfer Switch (ATS) located next to my main electrical panel that, in the event of a grid outage, throws a giant switch and allows the system to run isolated from the main grid. This allows the house to “island” itself from the grid and is an essential capability for a microgrid. My main panel has relatively few breakers, so I was able to add them all into the ATS, so all the circuits in the house are backed up in the event of an outage.

A key component to a clean energy microgrid is reliable, safe batteries. One of the advantages of Blue Ion batteries is that they are very robust, designed to be fully charged and discharged (eg “cycled”) thousands of times in their lifetime. They also have a high power rating, so they can handle the load for the entire house!

My Blue Ion 2.0 system…still in the process of being tweaked during the first days, but at least we got the blue lights on!

Unlike battery installations intended for backup use only (rarely cycles the batteries), my microgrid uses the grid as a backup, only pulling power from the grid if there is not enough solar or battery. Every day I am charging and discharging the battery as much as possible (saving just a few % in the battery each night). This makes for a better impact on the grid, as well (see below). By using the battery, I am able to save up extra solar during the day and shift it’s usage to the evening, when it is most challenging for the grid to provide (and also most expensive to me if I buy from the utility!).

I am very pleased at what it means to have “gone solar+storage” and, more importantly, created a microgrid. There have been a couple days were the whole block was without power and we were able to keep working from home. Additionally, using my battery to consume as much of the solar means I’m doing my part to be a “good grid citizen.”

Some stats for this first year:

  • Solar generation is at exactly 6 MWh, which beat the Helioscope estimate by about 20%! Guess the drought months meant better solar production. For reference, this is about twice what my EV used during a year.
  • Battery has been cycled 100% an awesome 190 times! (only 2.4% of warranty cycles!), totally over 3MWh of energy throughput!
  • Grid energy was still used (in large part due to having an electric vehicle, lower solar production in winter, electrifying large loads), and this comprised about 20% of the 7.7MWh of total energy consumption for the year. Almost all that consumption from the grid happened outside the late afternoon/evening hours, when electricity is dirtiest on the grid.

In California, where I live, there is excess solar energy available during the day and then a very stressful increase in energy usage in the evening. This creates a phenomenon that has made electricity prices in the middle of the day about $0(!) and in the evening, prices get very high (and also the electricity is made from carbon-intense resources).

Unfortunately it is very confusing to talk about some of the stats. When my account at PG&E was switched to a NEM (Net Energy Metering) one, all the data tracking on the PG&E website stopped. So now I am dependent on 20-page paper statements that run about two months behind actuals (and are really confusing, even for someone in the industry). So, my estimate is that:

  • 650kWh were exported to the grid (eg ONLY 10% of my solar production!)
  • 1,750kWh were consumed from the grid
  • Total energy consumption was around 7,700 kWh

To note here is that, the battery made my solar system an asset for the grid in two ways:

  • With the battery, I was able to consume almost ALL my solar production, exporting only 10% of the total electricity generated (during those long, sunny summer days…when it was gobbled up to power air conditioning a few miles inland!). This means the system is also gentler on the grid than a solar-only installation, which would be pumping out a much higher amount of excess energy during the day, using the grid like a battery and contributing to the “duck curve” problem.
  • The battery enables me to NOT draw power from the grid during the evening hours (the “head of the duck” problem). This saves me money by not consuming electricity from the grid when it is most expensive (and carbon-intense) and reduces the need for the grid to provide power when it is most stressed.

For the next level analysis, I will attempt to get the data about when the excess electricity was exported and some other insights from the time series data. Qualitatively, I know that it is later in the day before any export happens, since the battery first charges from the solar, which takes until the afternoon before it fills up. I’ll also use the next level analysis to estimate cost savings of using the battery.

We can’t talk about rooftop solar in California right now without acknowledging that the ability to have this kind of system is under direct attack by the utility regulators and the utilities themselves. They attacked the ability to have energy independent systems in the legislator last session, and we beat them…barely. Now they are dumping million$$$$ in lobbying dollars (that we pay for!!!) to influence the California Public Utilities Commission and other stakeholders to tax, block, and otherwise make it harder and more expensive for anyone to have a system like this. I urge you to sign on your support with the Save California Solar coalition. And look out for more calls to action in the coming weeks as the decision advances.

Anything else you would like to see as a reflection or analysis on living with a microgrid? Thanks for reading and I welcome your comments!



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