Thoughts on Solar

Last month during Intersolar, I (along with colleagues Sara and Victoria) was lucky enough to get invited to see a microgrid demonstration featuring the Enphase next-gen IQ8 at their headquarters in Petaluma, California.  As I had to sign an NDA as the price of admission, I was unable to write about what I had seen until today, when Enphase hosted their annual Analyst’s Day.  But I am no longer bound by that agreement, and can now tell you about what I saw. 

To say that I was impressed would be a gross understatement - quite simply, it was the most astonishing thing I have ever seen in the solar industry.  Settle in and let me tell you what I saw…

What Happens Today

Before I launch into describing the demo, let me remind you of what happens today.  All of the systems that we have installed are what is referred to as “grid-tied” which means that if the grid goes down, the PV system that is capable of back-feeding the grid also goes down, and remains down until the grid comes back.  (This is to prevent your house from being an island of energy, feeding the grid, and potentially injuring a worker trying to restore grid service.  As a result, this feature is known as “anti-islanding” and it is required of all inverter systems that are connected to the grid.)

Normally this is not a problem, but last month, when it got super hot out here (think 115° F hot!), both SCE and LADWP suffered dozens of outages, taking down PV systems across large swathes of LA County, and leaving frustrated PV owners without power, or A/C, just like their PV-less brethren.  Not good.

What I Saw in the Lab

Which brings us to what I saw at Enphase last month.

The lab looked like an ordinary industrial space, but with a series of household appliances and tools at one side.  There was a simulated array feeding a bank of IQ8 inverters, and a display that showed the output of the array (i.e., PV production), the total consumption from the loads, and any power being exported or imported to support those loads.  At the start of the demo the only load was a single red lamp, and the display indicated that it was drawing roughly 90 Watts.  The PV array was producing roughly 1.9 kWs, so the excess 1,800 Watts was being exported to the grid.  All super normal stuff.

But then things got interesting…

One of the engineers switched off the breaker that connected the PV array to the grid… and nothing happened!  Well, actually, a lot happened, but what didn’t happen was that the red light did not go off.  It didn’t even flicker to the extent that we could detect it.  But then when you looked at the display you noticed something amazing.  Not only had the microinverters created a grid on their own in fractions of a second, but they had throttled the output down so that now the production of the PV array exactly matched the load of the red light!  And here’s the kicker - there were no batteries attached to this system!!!

But what fun is just having a light on?  How about some toast?  So they switched on a toaster, and it lit up, and the total load jumped by about 1,000 Watts, making the total load now around 1.1 kW, and the PV array scaled up to meet it!  Still no batteries.  And how about this - there was no central controller, no master-slave relationship between the microinverters.  Rather, this was the “hive mind” at work, as the micros sensed the demand and scaled up or down as necessary to meet that load!

But wait, there’s more!

The next load to be added was a grinder like you might find on your workbench in the garage.  All by itself, that device drew roughly 1,200 Watts, bring our total load to roughly 2.3 kW - more than the maximum output of our simulated array.  What would happen when that was added to the mix?  Surprisingly little.  The grinder spun normally, but the red light dimmed slightly.  What was going on?  The system’s “hive mind” had lowered the voltage slightly (a microgrid equivalent of a brown out) to meet the amperage demand of the new load mix!  So slightly slower than normal, cooler than normal, dimmer than normal, but all operating.

Of course, all good things must come to an end.  Our already overloaded microgrid faced one more challenge - a vacuum cleaner with a significant in-rush current, far in excess of what the grid could sustain.  Indeed, as soon as they switched the vacuum cleaner to “on", everything shut off.  Nothing was damaged, the microinverters just shut off to protect themselves.

Turning on the vacuum cleaner served as the “ah-ha” moment for the potential homeowner - I guess I can’t run everything in grid outage mode.  So what do you do when something you just did produced an undesired result?  Well if you can, you undo it!  Turning the vacuum cleaner off, immediately restored the microgrid to its previous state of operation!  No delay.  No human intervention - just turn off that latest (over)load, and the system recovers on its own!

How cool is that?  Pretty damn cool, if you ask me!

Batteries Please?

So what about batteries, how do they play with this new system?  Just exactly as you would want.

The engineers added a bank of batteries to the mix, each with an IQ8 installed.  Now the display also indicated the battery’s overall state of charge, and whether they were charging or discharging.  Reset the demo to just the red light as a load and the batteries at 30% state of charge.  The PV array output jumped back to its maximum, with the surplus energy being used to charge the batteries.  As more loads were added, the PV array remained at maximum output, and as needed, drew power from the batteries.  Should the batteries reach full capacity and the PV output is greater than the loads, the microinverters will once again throttle down.

Sweet!

What’s Next?

I hope you agree that this was an amazing demo, and the IQ8 (or Ensemble, as Enphase refers to the overall system) has tremendous potential, both for Enphase as a company, and for so many nascent markets.  Think of how this product could have helped out in Puerto Rico, or in parts of Africa which have never, ever seen a grid!  Makes me want to book a trip to bring power to a village somewhere - hey Laurel, what do you say?

For our own clients, this has the potential to be the answer we have been seeking ever since Elon’s whoppers got people thinking about storage for the first time ever.

A point we raised with Enphase management is the need to have a reasonable upgrade path for existing clients.  Indeed, I have a call with Enphase tomorrow to discuss that very topic.  We know that current Enphase IQ products (the 6+ and 7+ we have been installing this year) will be compatible with Ensemble.  We expect to be able to work with older systems, though there may be a higher retrofit cost.  When we have that information, we will surely let you know!  The IQ8 is expected to be available in 1H2019… watch this space!

Our recent heatwave is a potent reminder of a sad solar fact: generally speaking, if you have a solar power system and the grid goes down, or even just drops really low as it did in Altadena this past weekend, your solar power will also go out, leaving you sweltering in the heat with everyone else. 

But why?  And what can you do about it?

Anti-Islanding

Every system that Run on Sun has installed is what is known as grid-tied.  Those systems are designed to shut down when the grid goes departs from a fairly narrow range of voltage and/or frequency.  The reason for this is simple - safety.  Imagine this scenario: a tree snaps in the wind and takes down a power line.  What does the utility do?  They shut off power in that area - causing any grid-tied solar systems to shut off -  and then they send a crew out to restring the line.  Once that is done, they restore power to the area and all is well.  The grid-tied systems sense the restored grid and turn back on automagically.

But now consider this - what if your solar system didn’t shut off when the grid failed?  Well you might be happy because your A/C would still be running, but what about that excess energy that your system is feeding back to the grid?  It is possible that you would energize the very line that the utility workers are coming to repair.  Your solar system is now its own “island” of energy production, and it could pose an extreme hazard to the unwitting linespeople.  And that would be bad.

Thus the need for “anti-islanding” - the intelligence built into your inverter to keep workers safe.

Comfort is just a Microgrid Away!

So what can you do about it?  How can you keep your solar investment running even when the grid fails?  The answer is in a microgrid which requires two key features: isolation and self-starting.  The isolation follows from the anti-islanding discussion above - you need to make sure that your system cannot export power back to the grid.  This is generally handled by installing a “transfer switch” which can be either manual or automatic.  

The second step is harder - you need something to emulate the grid.  In off-grid systems that involves a bank of batteries and a special battery inverter that can use the power of the battery bank to start-up and create what appears to be a grid.  Now the solar system “sees” what looks like a stable grid and can come back online.  That sounds pretty easy, but there are complications.  In particular, the inverter that forms the grid must also be able to match the output of the solar system precisely to the needs of the house.  Remember, there is no grid out there to absorb excess energy, so you need a way to throttle the output of the array up and down to avoid over production.  

Storage is generally a key component here, as it can absorb excess power (at least until the battery is full) and help smooth out the energy flow.  All of which has historically made for an expensive addition to a solar system just to hedge against an infrequent occurrence.

Perhaps this past weekend’s outages will cause some folks to reconsider.

Cue Intersolar

Which makes the timing of this year’s Intersolar trade show ideal.  Running Tuesday-Thursday of this week (in cool San Francisco, thank you!), Intersolar is bringing together solar and storage manufacturers as they demonstrate their latest and greatest gear.  Finding a cost-effective microgrid solution is our number one mission this week, and we will be pressing our friends at Enphase for as many details as possible about their approach to solving this problem - watch this space!