Thoughts on Solar

UPDATE - We got a message back from Enphase about a viable approach to the whole-house connection issue discussed below.  

The end of March found me in San Diego attending the annual NABCEP Continuing Education Conference.  As part of being NABCEP certified, I am required to recertify every three years, and my third recertification occurs this year.  The Conference is a convenient way to earn the credit hours needed as part of the recertification process. 

While much of that is bone dry (such as a full day talking about the most recent changes to the National Electrical Code, made tolerable only by the wit of the presenter, Ryan Mayfield), or surprisingly cool (such as our discovery of Scanifly), nothing was more anticipated than our chance to attend a talk presented by Enphase titled, “Design and Specification of Grid-Agnostic Enphase Ensemble™ based Systems."  (Enphase describes the Ensemble system as being “grid-agnostic” because it is intended to switch seamlessly between grid connected and grid isolated operation.) Here is our take…

The room for this talk, as was the case with a number of talks, was way too small for the number of interested participants.  I arrived early and was rewarded with a seat.  Late arrivals were SRO.  The talk was presented by Peter Lum, with an assist from Field Applications Engineer, Nathan Charles. 

Key Takeaways

For folks looking for just the highlights, here are some (in no particular order):

1. Initial rollout of the IQ8 in the U.S. will be as part of the Encharge energy storage system
2. Encharge will come in two basic flavors, a 3.3 kWh, 1.28 kW unit, and a 10 kWh, 3.8 kW - both with a peak surge output of 150% rated power for one second
3. The 3.3 kWh unit will be 24″ high, 13″ wide, and 12″ deep, weighing 88 lbs, mountable either on the floor or the wall, and it can be mounted outdoors
4. Cells are LFP, cooling is passive, and comms are - surprise - Zigbee
5. The 3.3 kWh unit has four IQ8 microinverters inside, that are field replaceable should one fail
6. The battery cells are not tied to any one microinverter; if a microinverter fails the storage capacity is unaffected, but peak output power is diminished
7. Warranty will be for 4,000 cycles (100% DoD) or 10 years, whichever comes first
8. For a microgrid to form, there must be roughly the same amount of IQ8 power as there is IQ6 or IQ7 power in the system
9. Not compatible with M-series microinverters, “at launch”
10. No word yet on pricing, anticipated deliveries to begin Q4

A Little More Depth

So those are some highlights, let’s talk about some details. The smarts inside the IQ8 is an Application Specific Integrated Circuit (ASIC) with some 5 million gates. As a result, the IQ8 is able to update its control vectors every 20 ns.  Thus, the individual IQ8 provides the primary control over the microgrid, and there is no master/slave relationship.  However, the IQ6 and IQ7 do not have that level of independent control functionality, and so they rely on secondary control, via the Envoy, to stay in sync with the microgrid.

As with its other IQ cousins, the IQ8 is a bi-directional inverter, meaning the same device that can be in an array, converting DC to AC, can be in the battery, converting AC to DC to charge the cells.

Keying off the 2017 NEC (which California will adopt come January), we were introduced to a new acronym: MID - which stands for Microgrid Interconnect Device, and is defined as, “A device that allows a microgrid system to separate from and reconnect to a primary power source.” (705.2)  The Enphase MID is referred to as Enpower, and it essentially has three components: an automatic transfer switch, a neutral forming transformer (recall that the IQ series just uses the two hots, L1 and L2, so the NFT is necessary to power 120 volt loads when off grid), and a control device.  Comms are - you guessed it - Zigbee.

Use Cases

There are two primary use cases for the new Encharge component, Energy Optimization, and Storage with Backup.  Let’s look at each one in turn.

Energy Optimization

Energy optimization, or more to the point, Time-of-Use arbitrage, involves storing energy during the peak production portion of the day (instead of exporting it to the grid) and using it later in the day for local consumption.  This becomes important as utilities - think SCE - switch to TOU rates where energy in the middle of the day is significantly cheaper than energy during the peak TOU period (more and more, something like 4-9 p.m.). 

Our friends over at Energy Toolbase just blogged about, “A Historic Moment for Residential Energy Storage Economics: California’s new Time-of-Use Rates,” noting that for the first time it was possible to model a more economically advantageous system adding storage, than just solar alone.  Which means that the Energy Optimization use case may pencil out on its own - though that is hard to say for sure until we have some actual pricing!

Enphase provided the following illustration (sorry for the lousy images, taken from the side with my phone!). You can click on the image to see a larger version.  

 

On the far left is the Encharge 3.3 kWh storage system showing the four IQ8’s.  To the right is an array built on an equal number of IQ7 microinverters - but note well, this is not a microgrid configuration.  Why?   Because it doesn’t have a MID, and per the 2017 NEC, you can’t have a grid-agnostic microgrid without a MID. 

In the middle is the latest version of the IQ combiner box.  (We just installed one of these and frankly, I’m not a big fan.  The wiring for consumption CTs requires you to cross reference an unmarked connection block to the lid for the wiring diagram.  This is going to be error prone, IMHO.  Also the Envoy has been reduced to just a circuit board w/out its own case.  Ok, it’s in a NEMA 4 box so the case is probably not needed, but if you are trying to operate it with the deadfront off (say during testing), you need to watch where you put your fingers!  A false economy here, I’d say.)  

Note the green boxes which denote updated software both in the cloud and in the Envoy.  Also, the Envoy picks up a Zigbee device (to communicate with Encharge) to be attached to one of the two USB ports on the Envoy.  (As we noted before, Zigbee is built into Encharge, though not called out on this slide.

This is super easy to set up as the Encharge just lands on one of the breakers in the IQ combiner.  And while it may - assuming our friends at ET are correct - pencil out, it isn’t what all the buzz has been about, so let’s turn to that use case, shall we?

Storage with Backup

Ever since I made my pilgrimage to Petaluma last summer, the amazing microgrid has been the feature that everyone is eager to see.  The good news is, we are closer!  The bad news is, this isn’t going to be as easy as we had hoped.  So here is the key diagram from last week:

There is really only one change from the prior diagram and that is in the upper right hand corner, where the Enphase MID - dubbed the Enpower 200G, has been added.  The switch is rated at 200 A (that is the significance of the 200, G stands for grid), and in theory could be an all home setup.  In a grid outage, the Enpower ATF switches and the microgrid forms - automagically.  Depending on the actual array and storage configuration deployed, will determine how much of the house loads could actually be powered here. 

There is one fly in the ointment in this illustration.  In many parts of the country, the utility meter is mounted outdoors and the distribution panel - the Main Load Center in the slide - is located indoors.  In such a scenario, the Enpower MID could be wired in between those two components with minimal disruption or cost.

Alas, in California, at least in Southern California, that is not how we do things.  99.9% of the services that I have ever looked at consisted of a combination meter and load center “all-in-one".  The rub here is that there is no easy way to physically interconnect the Enpower device between the meter and the load center.  When pressed on that issue, Enphase - accurately, if not helpfully - pointed out that we would have the same problem with any such storage solution and the combo meter/load centers.  True enough, but we have been talking about this product for a long time now, and you would like to think that they would have a clean solution in mind as to how to make this work by now.

UPDATE: I spoke with Enphase Field Applications Engineer Nick Dadikozian about the following possible solution.  Assuming that the utility and the AHJ go along, you could add a separate meter socket and wire the line side to the service, with the load side of the socket connecting to the line side of the Enpower MID, and the load side of the MID to the load side of the meter socket in the combo panel, or if no way to do that, wire to the line side of the combo meter socket and install appropriately rated jumpers in lieu of the relocated meter. 

Of course, another approach is to have a critical loads subpanel, with a breaker on the main panel and the Enpower in between.  That, I suspect, will be the approach most commonly taken.

So there you have it – all that I could absorb from our relatively short session, and some follow-on conversations with Peter over the next couple of days.  (My thanks to him for his patience in dealing with my myriad questions.)

Eager to hear your thoughts on how you will be using this system.

Last week I spent four intense days in San Diego for the annual NABCEP Continuing Education conference.  This is a great event, with lots of super smart, experienced installers from around the country gathering to sharpen their skills and share information.  Lots of vendors are there providing workshops, and there are heavyweight course sessions like two hours on Worker Safety, and an entire day on the National Electrical Code.  (Ok, so those two are a bit like eating your vegetables as a kid - but super important information, nonetheless.)  But there was one thing that stood out for having the highest cool factor - and that was courtesy of the folks at Scanifly.  Here’s our take…

Site Evaluations Re-imagined

One of the most crucial aspects of the solar installation business is performing proper site evaluations.  Some companies brag about being able to provide you with a proposal for adding solar to your home or business without ever bothering to go there.  We categorically reject that approach - online imagery is fine, but it won’t tell you whether the grounding is complete or the service panel has so many doubles in it already that it is a fire waiting to happen.  Nor can you look a prospective client in the eye, answer their questions, and build the confidence that is so important to doing this right.

But every time you have someone go up on a roof, there is a chance for injury.  And while roof work is a necessary part of this business, going up on a dangerous roof before you have even won the job, means most of the time you are exposing your employee to risk for potentially no gain.  Moreover, it is time-consuming and error prone to be making measurements while on the roof.  Things get overlooked - like just how far is that vent from the ridge? - and often you bring the evaluation results back to the office, only to realize that you missed a key detail!  Frustrating (and expensive) if you have to go back to the site a second time.

What if you could be assured that you would gather all the detail you could possibly need the first time?  And what if you could turn that - automagically - into a 3-D model complete with all the shading on the site from both trees and other obstructions?  Now that would be cool, and that is what the folks at Scanifly have achieved.

Here’s how it works.  You take a drone (typical price range: $700-1,500) and fly it on an automatic setting that flies a complete circle around the site at a set height, and radius from the center of the building in question - typically less than 100′ AGL and maybe 75′ radius (the site obstructions will dictate most of this).  The drone will fly that course automatically, and will take pictures with a roughly 85% or so overlap.  (No drone? No problem, they can hook you up with a drone pilot to do the image gathering.)

Once you have the photos, you upload them to the Scanifly site, and after some amount of data crunching, you now have a 3-D model onto which you can add your modules.  The software understands the shading at the site and can produce production modelling data that can then be imported into a savings modeling tool like that provided by our friends at Energy Toolbase.

Even cooler, you can give your prospective client a link to the model so that they can see what their house will look like with the system installed (including the boxes on the wall!) in full 3-D!  

Now that is really cool, and no one had to go up a ladder onto a roof to do it!

We are super excited about this system and we cannot wait to try it out for ourselves.