Panel Optimization Part 2

My analysis of module optimizers is now complete.  If you recall, there were three under consideration:

• SolarMagic™ by National Semiconductor
• TIGO Energy™ Module Maximizer
• SolarMizer™ by Xandex

And the winner is...

Tigo Energy Module Maximizer-ES 60

It was actually a fairly straightforward decision.

All three optimizers provide power maximization at the module level. This will minimize the degradation of the power output for an entire series based on an issue for a single module, such as shading.

But the one feature that sets the Tigo product apart from the others is the module monitoring.  Much as the Enphase micro-inverters, the Tigo maximizers provide per-module information which is collected by a central sensor/combiner and managed by a Maximizer Management Unit (MMU).  Monitoring can be shared with Tigo so that their engineers can diagnose module problems should they occur.

Tigo components are approximately:

• $56 per maximizer.  One per module.
• $650 for the MMU.
• $0 for 6 months of monitoring by Tigo.
• $350 for 5 years of monitoring.

Module performance can be monitored using a web browser and the display can be customized so that individual solar panels are shown visually matching the actual installation.

Unfortunately, the technical information available from the Tigo website is minimal and the options are varied so decisions are tough to make without requesting additional information. For example, the website does not mention several important facts:

• A 'sensor/combiner' is required.  This is the box that communicates with each module maximizer and forwards that information for monitoring.
• The pictures give the impression that there are four connections to each but there is a fifth connection that is made to the 'sensor/combiner' over which the module control signals are sent and the module performance information is retrieved.
• The maximizers can communicate with the 'sensor/combiner' either wired or wirelessly.
• The interconnections between the modules is done via Tigo custom connector.  I'm sure that is deliberate so that incorrect connections cannot be made and damage the maximizer or the module.
• Nothing is said about how the 'sensor/maximizer' connects to the Internet for monitoring. Is a wired Cat-5 connection required or is WiFi supported? Can the monitoring information be collected locally or am I locked into Tigo's monitoring?

But the Tigo's are brand new and are only now becoming available so it's not surprising that information is only now trickling out and even dealers have little information. I've been working with Tigo directly and am now working one of their distributors, AEE Solar, to figure out the proper configuration. Once I get a configuration finalized I'll have to work with one of AEE Solar's local dealers to place the order.  

Panel Optimization

Perviously I mentioned that there are some minor shading challenges for the main house from a tall cottonwood tree.  That tree will cast some shade on the house on the non-summer days.  The Enphase micro-inverters would effectively address this problem but they are not available yet for the 210 watt panels that I'm specified.

An alternative technology has recently come on the scene in the form of 'module maximizers' (also called 'power optimizers').  Like the Enphase micro-inverter, one module maximizer is attached to each panel and performs "dynamic module balancing".

I know of three such products:

• SolarMagic™ by National Semiconductor
• TIGO Energy™ Module Maximizer
• SolarMizer™ by Xandex

The SolarMagic product purportedly reclaims up to 50% of lost energy due to shading.  TIGO claims "Up to 20% more Energy."  And Xandex says their SolarMizer can be selectively installed on only those panels subject to shading. More research is needed!

One immediate advantage of the TIGO system is the availability of individual panel system monitoring.  Monitoring is very important in diagnosing panel issues.  One large bird dropping can rob an entire series of panels half as effective.  Monitoring can quickly identify the panel in trouble so that you can remedy the problem.

The Enphase micro-inverters also offer monitoring. Monitoring is not mentioned for SolarMagic and SolarMizer.

I've been concerned about how to best monitor my system and have even considered building my own micro-controller board that talks to the inverter and sends data to my Macintosh once a minute (or so).  While that would be great fun it sure would be nice to have monitoring from Day One.

TIGO, like Enphase, offers a system monitoring device and web-hosting of data.  It costs: first six months free, then $350 for five years.  But it also offers remote system management including the ability to completely shut down the system for safety in case some service was required.

Another advantage of a monitoring system of this kind is that it is independent of the kind of inverter being used.

I'm off to do more research and the check availability.

Getting Serious

Since I'd decided to be my own solar contractor it was time to get serious. The primary objective was to make sure that I was not overlooking anything — those 'gotchas' that can really make a hash of things.

So I dusted off my copy of Photovoltaics: Design and Installation Manual and did all of the exercises pertinent to my project.  Photovoltaics is an excellent book and the only recommendations I could offer would be 1) add more checklists, and 2) eliminate the "Solar Data" section (just put the latter on-line).

Everything checks out okay:

• House:
• 24 panels (3 strings of 8)
• Medium size inverter capable of handling ~350 VDC
• Inverter to be placed immediately adjacent to the main power panel
• Garage
• 16 panels (2 strings of 8)
• Medium size inverter capable of handling ~350 VDC
• Inverter to be placed next to the auxiliary panel in the garage

About this time, after visiting with some of the neighbors, I started thinking about cutting back to just the house-mounted portion of the system and leaving the garage as a possible future expansion.  There would be no real penalties for postponing the garage and there were a few minor benefits: 1) I wouldn't have to get Architectural Committee approval for the project, and 2) I wouldn't have to remove a tree:

The garage is on the right and this picture is taken facing to the south-southwest.  The tree immediately to the left of the garage shades the south-facing roof of the garage too much and would have to be removed.

The house will have a bit of a tree-shading problem from a large cottonwood tree located in the southwest corner of our lot:

This picture is taken facing almost directly east.  The cottonwood can be seen beyond the garage and is about 60' tall and growing taller each year.  It will cast a shadow on a portion of the house roof during non-summer days until about 11 AM.  The Enphase micro-inverters would help minimize the impact of that shading but since they are not available in the size I need I will consider using Tigo Energy's Module Maximizer or National Semiconductor's Solar Magic Power Optimizer, both of which can be retrofitted after the initial installation.

Having decided to eliminate the garage portion of the project I'm ready to move ahead.  That means getting a final equipment bid for the panels, inverter and railings and talking to my electrician.

Professional Residential Solar Bid Analysis

I mentioned in an earlier post that I'd been disappointed by the bids I'd received from three of our local professional solar firms.  Now that I've gone over the various layouts and configurations it might be interesting to examine those bids and see how they stack up.

Bid #1 provided pretty good detail.  Bid #2 just provided a bottom-line number.  Bid #3 was essentially given by phone.  And 'My Est' was based on prices for components I could purchase as an individual (mostly from from Wholesale Solar) plus estimated labor by an electrician.  (The companies providing bids will not be identified.)

                      Bid #1    Bid #2    Bid #3    My Est
------------------  --------  --------  --------  --------
Total Wattage          5,250     4,800     4,800     8,400
Panels Total        $ 28,673                      $ 34,440
  Each                 $ 956                         $ 861
  Type            Solarworld     Sanyo       REC     Sanyo
  Wattage Ea.            175       200       200       210
  Count                   30        24        24        40
Inverters Total      $ 6,213                       $ 7,070
  Each                 $ 207                       $ 3,535
  Type               Enphase   Enphase   Enphase Sunny Boy
  Count                   30        24        24         2
Racking Total        $ 3,784                       $ 2,218
Labor Total          $ 2,870                      $ ~3,000
System Discount          $ 0       $ 0       $ 0  $ -3,269
------------------  --------  --------  --------  --------
Grant Total $       $ 41,541  $ 40,870  $ 38,040  $ 43,459
Cost per Watt         $ 7.91    $ 8.51    $ 7.93    $ 5.17

------------------  --------  --------  --------  --------
Federal Tax Credit  $ 12,462  $ 12,261  $ 11,412  $ 13,078
Net System Cost     $ 29,079  $ 28,609  $ 26,628  $ 30,381
Effective per Watt    $ 5.54    $ 5.96    $ 5.55    $ 3.62

For comparison purposes, at the time of writing this blog entry, the prices for various components from Wholesale Solar are as follows:

  Solarworld 175 W panels         $ 855
  Sanyo 200 W panels                N/A
  REC Solar 205 W panels          $ 564
  Enphase 175 W microinverters    $ 197
  Enphase 205 W microinverters      N/A

Doing the work myself (hiring out the electrical expertise and roof labor, of course) has a distinct advantage in terms of price per watt.

For only 4% more money I can get 60% more electrons!

It was pretty easy for me to make a decision: I'll be my own solar contractor and work with an electrician.

On Being a Neighbor

Looking over the house and garage configuration I realized that the detached garage installation might be something the neighbors must appreciate some conversation about.  Plus, our subdivision has CC&Rs* governing the type of roofing material we can use on our house.  Solar panels would certainly qualify a 'roofing material'.

Some counties and states have laws which nullify subdivision restrictions.  That may soon happen in Utah, but I would check with my neighbors even if there were no restrictions.

In order to moderate the CC&Rs our subdivision has an 'Architectural Committee', supposedly made up of a few neighbors with one servicing as the committee chairman.  In our case, the original subdivision developer is still the 'Architectural Committee' — a common situation.  (He tried to talk me into becoming the Committee!  Ha ha!)  So I called him and he was fine with my solar panels but asked me to canvas the neighbors and let him know their reaction.

I spoke with our most immediate neighbors and none of them offered any resistance to my solar plans though I noticed some slight concern by one.  So I decided to mull it over for a few days.

* — Codes, Covenants and Restrictions