Tigo Energy optimisers are the quiet achiever of the Solar industry. In part one of this blog, I’ll explain how installing solar panels in shade will affect your solar production. I’ll show, through a series of tests, how solar panel bypass diodes work reasonably well to combat shade, but I’ll also explain why solar panel diodes are not the solution. Next, I’ll explain how Tigo optimisers work, and I’ll give three reasons why Tigo optimisers are significantly better than bypass diodes. In part two, I’ll discuss why I believe Tigo is a better solution that SolarEdge. Then I’ll discuss my findings on the Tigo optimiser failure rate, and I’ll expose two weaknesses of Tigo Energy.
About Tigo Energy
Tigo Energy is a Californian based solar panel optimiser company. They began in 2007, and today they operate with a lean 45 staff worldwide. Only one of their staff, Jeff Routelage, based in Australia.
Interestingly, it’s an Australian who is the patent-holder for Tigo Energy’s core technology. I emailed Peter to ask him about his invention. He replied:
Nearly 20 years ago I had a solar car team and I developed some single cell maximum power point tracking devices. This resulted in some patents on distributed maximum power point tracking that were held by my university on my behalf …. Tigo Energy built their business in the US and then found they overlapped my patents. They asked for the rights to use my patents and I agreed to sell them these. I was quite happy that they saw some value in my work.
Professor Peter J Wolfs
CQ University, Rockhampton Queensland
That’s good enough for me. Tigo optimisers are an Aussie invention.
In 2016, inverter manufacturing giant SMA bought 27 % of Tigo Energy. I reckon SMA were onto something. This blog explains why.
Part one: Why we need optimisers
Shade is no friend of solar. In fact, just a little bit of shade on one solar panel can reduce the output to all of your panels. When solar panels are “daisy-chained”, or wired together in series, shade on one panel acts like a kink in a hose and reduces the output of the rest of the solar panels.
Going on this logic, let’s say we had ten panels all producing 200W, a total of 2000W. Suddenly one solar panel is partly shaded and can only produce 100W. If the logic above follows, then every panel could only do 100 W, so we would lose half of the power just because of one solar panel in shade.
Solar Panel Bypass Diodes
In reality, solar panels work better than that, thanks to the help of solar panel bypass diodes. Solar cells within a panel are usually wired in 3 columns called cell strings. Each cell string has a bypass diode connected to it.
If a panel is significantly shaded, the solar panel diodes will engage. As a result, the shaded portion of the panel will be bypassed. The shaded cell string won’t produce any power, but at least it won’t drag the other panels down. That’s the theory, now time to test it.
Introducing Tigo TS4M
The product that made my testing so much fun was the Tigo TS4M. The Tigo TS4M is a dumbed down version of a Tigo optimiser. It’s a device that monitors what a panel does but doesn’t optimise.
You may think it’s a dumb idea to pay extra just to monitor your panels. But for testing how solar panels react to shade without an optimiser, the Tigo Ts4 is a perfect tool. When a bypass diode engages, the panel voltage reduces by a third – and the Tigo monitoring reveals this. In the image below, a bollard is shading the middle panel on one cell string, so the voltage is reduced by one third.
How much shade do you need before a solar panel bypass diode engages? First I set up two strings of panels as shown below. I then ran multiple tests, shading with fly screen, stink pipes, rail, branches and fold up tables. I was up and down the warehouse roof almost every day for a month. This paper pusher rediscovered his calf muscles. Here’s a summary of what I learnt the hard way.
Unoptimised panel results
- Figure #1. Partial shade on four cells does not activate a diode, so all five panels are dragged down.
- Figure #2. A vent pipe partly shading one cell does activate a bypass diode. Production of a third of 1 panel is lost.
- Figure #3. Partial shade on six cells activated a bypass diode. Production of only one cell string is lost.
- Figure #4. Heavy shade on three panels across 1½ cells. Bypass diode does not engage so all five panels are dragged down.
When solar panel diodes work
It was interesting how easily one bypass diode engaged when a single panel was in partial shade (fig 2 & 3). In figure 4, when three panels were heavily shaded, the bypass diode did not engage. But this was actually the best option: had they engaged, the entire string would have shut down due to a low string voltage.
How does a simple solar panel bypass diode know when it is best to bypass and when not to?
The inverter tells it!
The job of the inverter’s Maximum Power Point Tracker (MPPT) is to dictate the current and voltage, so the entire string produces the most power. Sometimes this means the inverter lowers the current so low that the bypass diode does not engage. Sometimes it increases the current so high that a little bit of shade activates the solar panel bypass diode.
What I found interesting is how effectively this inverter and solar panel bypass diode interaction works. In most cases, the bypass diodes significantly reduce the impact of shading.
So if solar panel bypass diodes are doing a good job, why the need for solar panel optimisers? Lets first look into what the optimiser does.
What is a solar panel optimiser?
A solar panel optimiser is a black box of power electronics that you can install behind solar panels to allow each panel to work more independently of the other panels.
Each brand of optimisation does this slightly differently, but Tigo Energy does it by “impedance matching”.
/ɪmˈpiːd/ To delay, prevent or restrict (someone or something) by obstructing them.
/ɪmˈpiːd(ə)ns/ A fancy word that has close enough to the same meaning as electrical resistance. Impedence restricts current flow in an electrical circuit. Shade on a solar panel will cause impedance in that panel.
Before a bypass diode has the time to engage, the Tigo optimisers see the impedance caused by the shade and open a bypass tunnel to match the impeded current. This allows the inverter to work at a higher current without affecting the solar panel bypass diode.
Bypassing the current from higher panels around a bypass tunnel is a far more effective method than relying on a bypass diode for at least three reasons:
Reason 1 – Optimising prevents shaded solar panels from dragging the entire string down.
One of the shade tests I performed showed what happened when solar panel diodes do not engage.
In this test, the left three panels were significantly shaded. To prevent the inverter from turning off from under-voltage, the inverter reduced the current, so the bypass diodes did not engage. This meant each panel still produced 30 volts, but only 0.5 amps.
With the same amount of shade on the optimised panels, the shaded solar panels performed poorly. But the unshaded solar panels were able to run at a higher current, (so higher power). That high current was redirected through the Tigo optimisers on the shaded panels.
Reason 2: Optimisers allows partial production on shaded solar panels
When I compared scattered shade on an optimised vs non-optimised panels, the advantages of optimisers were clear. The optimised panel still produced 20 watts while more than a third of the panel was in the shade. The non-optimised panel was bypassed with minimal shade.
Reason 3 – Solar panel diodes are not optimisers
The primary purpose of a solar panel bypass diode IS NOT to increase production but to prevent panel damage caused during shade. If bypass diodes were not installed in solar panels, the shaded section of the solar panel would have a high resistance. The high resistance will cause excessive heat as current flows through. So solar panel bypass diodes are primarily designed to prevent damage caused by hot spots from infrequent shading.
Diodes are a simple semiconductor device with a limited duty cycle. The more the solar panel diode engages, the shorter its lifespan. If you install unoptimised panels in significant shade, the bypass diode will eventually fail, and your panel will no longer be protected from hot spots. Interestingly one of the more reputable panels, LG, state that their panel warranty does not cover:
Improper installation or reinstallation and poor solar system design. (Examples of improper installations and very poor system design are modules installed in conditions which put long term stress on the bypass diodes in the modules, and also reduce the system output for the owner – for example prolonged significant strong shadowing of the modules e.g. via trees, walls, gables, overhangs, valleys, chimneys, satellite dishes etc (In such situations a professional solar designer will suggest a micro-inverter or optimiser solution and with such a proper solar system design solution the module warranty is fully applicable).
While not specifically stated in many other solar panel warranty documents, most panels brands have the same issue. (Sunpower’s Maxeon cell is different from others, but investigating how Sunpower panels respond to shade is for another blog.)
Part 2: Why Tigo Optimisers
We’ve identified that Solar panel optimisation not only increases your production, but it also protects your solar panel diodes. In reality, there are only three optimisers in the Australian market, Tigo Energy, SolarEdge and Huawei. So why Tigo Energy?
The simplicity of Tigo Optimisers
One aspect of Tigo optimisers that makes it stand out from SolarEdge is the limited work Tigo optimisers are required to do. SolarEdge optimisers require you to use a SolarEdge inverter. The SolarEdge inverter does not have a “Maximum Power Point tracker” (MPPT) and as a result, it requires each SolarEdge optimiser on the roof to continually adjust the voltages and current throughout the day to achieve the Maximum Power Point.
In contrast, when you use Tigo optimisers, you choose any brand of inverter. It’s the job of that inverter to do the heavy lifting of the Maximum Power Point Tracking. The Tigo optimisers get off easy and are only required to work when their panel is “impeding” the other panels.
While Solaredge optimisers are forced to work anytime the sun is shining, Tigo optimisers are only required to work when the shade is … shading.
This simple Tigo Energy architecture has two clear advantages
- If your inverter fails outside of warranty, you can replace it with any brand of inverter.
- The power electronics on the roof are required to work significantly less, logically increasing their lifespan.
Tigo optimisers are better in shade
In my SolarEdge post, I showed how SolarEdge usually requires a minimum of 8 panels to operate efficiently. This is because the SolarEdge inverter requires a combined 360 volts from all the optimisers, and standard optimisers only boost to a maximum of 60 volts. If you have less than six panels un-bypassed, the inverter will go offline. In short, the SolarEdge system does not work well in heavy shade.
Tigo is different. We would normally match Tigo optimisers with a Fronius inverter which has a minimum voltage of 80 volts. All the inverter needs to operate is three un-bypassed panels.
Tigo Energy Selective deployment
One of the advantages Tigo Energy has over SolarEdge is you get to choose which panels to optimise. If you only have one or two panels that will ever be in the shade, you can optimise just them. Selectively deploying optimisers has taught me a lot about the importance of optimisation. I ran a test on panels on my warehouse to demonstrate:
Using the same installation, I removed the Tigo optimiser on all panels except two. I placed bollards and posts in front of panels to mimic vent pipes.
As the shadow moved over the unoptimised panels, I could see bypass diodes kicking in and out. When the shade was not significant enough to engage a diode, the shaded solar panel dragged down the rest of the array.
The optimised panel performed significantly better. Not once did a bypass diode engage with this level of shade, and the unshaded solar panels saw no loss in production
Selective Deployment not only cuts down on cost, but it also reduces the number of power electronics sitting on your roof. If there is one thing I learnt from SolarEdge, it is that power electronics can and will fail. I don’t care what bells and whistles you get with this fancy module level power electronics. If you are interested in reliability, you might consider avoiding wacking a bunch of power electronics on your roof – unless you absolutely need to. But should I tar all optimisers with the same SolarEdge brush? How reliable are Tigo optimisers?
Tigo Optimiser Failure Rate
My problem with analysing Tigo optimiser failures is that most of the Tigo Energy systems we selectively deployed without monitoring. We have only installed six measly systems with full monitoring, and one of those is at my office. So I called a bunch of installers who have monitored Tigo Energy systems. I talked to nine installation companies who had anywhere from 2 to 30 sites monitored. Some of these sites were commercial sites and had over 1000 Tigo optimisers. The total number of optimisers for this sample was almost ten thousand. I asked three key questions:
- How many Tigo optimisers you have you installed?
- What is your failure rate on TS4 optimisers or earlier Tigo products?
- Are you sure there are not more failures?
The two companies with the larger sites told me they had someone in their office that checked the systems weekly or monthly. They can do this because it only takes a couple of clicks on the Tigo platform to check. The other companies were not so diligent, so I asked for their Tigo portal logins and manually checked all systems myself.
To summarise the commonalities of the feedback I received:
- Many had failures with Tigo Energy products before Tigo released their TS4 optimiser.
- Most of the issues were with embedded panels, (the optimiser is sold as part of the solar panel) and were a result of ribbon failures. It’s a fault of the panel manufacturer.
- Everyone said Jeff Routledge from Tigo Australia is legendary for his technical and warranty support.
- One person reported one Tigo TS4’s failure.
ONE failure in about TEN THOUSAND optimisers. Ok, take that with a grain of salt, I hardly believe it myself. I asked Jeff from Tigo how many reported failures Tigo Australia had.
FIVE TS4 failures claimed in Australia.
Na, I like Jeff, but he must be counting wrong. That’s stupidly unbelievably reliable. But Jeff read this blog before I published it. He puts his good name to his bold claim. Have you had a Tigo TS4 failure?
Tigo Energy Monitoring
If you choose to purchase Tigo Energy monitoring, it comes with individual panel monitoring for the customer as the base offering. While the amount of information we can gather from the Tigo portal is impressive, it does not tell us what is happening at the inverter level. But that’s easily fixed. We use Fronius inverters, which has the best inverter monitoring available. While it’s not perfectly elegant having to use two websites to get your data, the level of monitoring you get is second to none.
One small confusion between the two platforms is that production figures are different. This is because Tigo records the daily kWh before the inverter, but Fronius record the daily kWh after inversion. Because there is always an efficiency loss through the inverter, Fronius records a lower production figure than the Tigo Energy platform does.
Tigo Energy offers basic alerts via email or SMS. If you subscribe to premium for another $20 a year you get production alerts, in theory giving you alerts when you have lower production than expected from a panel or an array.
I jumped on the roof to test how well the alerts worked. I started off slowly by shading the panels, but it was obviously not enough to trigger an alert. So I got serious.
- First I replaced 300 w panels for 190W panels and removed and shorted bypass diodes.
- Next, I shaded several solar panels with varying amounts of cardboard and fly screen.
- In an attempt to fry a Tigo optimiser and trigger an alert, I connected 4 x 345-watt panels in parallel into one optimiser. These bad boys are unstoppable; I couldn’t kill it.
- Finally, I had success at blowing up a Tigo optimiser by putting three panels in series and running 120 volts through the optimiser that would normally run at 35 volts or less.
I set my premium alerts to send me alerts every day via text message and email. However, the only alerts I received were daily heartwarming congratulations about my system’s outstanding performance, including this one:
Considering this system produces 60kWh the day before, I don’t think 0.1kW deserved congratulations. I never received a low panel performance alert or a failed optimiser alert. I never received a single text message. Fair to say Tigo premium alerts currently don’t work. Tigo has advised me they are working on it. I’ll update this post if they get it working.
Tigo Energy marketing
And I’m going to have one more jab at Tigo. The Tigo Energy sales and marketing department is … underwhelming. SolarEdge has gained market dominance with a product that is fundamentally flawed. Imagine what the SolarEdge sales and marketing team could do if they marketed a product like Tigo!
While solar panel bypass diodes work reasonably well to reduce the impact shade has on performance, it is not what they were designed for. If a solar panel is installed in significant shade, an optimiser should be used. Optimisers not only increase solar production, they prevent bypass diodes from burning out. Tigo optimisers are a superior optimiser because of the simplicity of the design. They perform better in heavy shade, can be selectively deployed, and are only required to work during shaded times. It’s not surprising then that Tigo optimisers seem to be far more reliable than SolarEdge. Tigo still has issues: their premium alerts are not working. But if Tigo Energy were to up their marketing, they deserve to gain more market share.