The highly anticipated award-winning SolarEdge HD Wave inverter is now available. In part one of this post, I’ll explain solar panel optimisation and panel level shutdown; then I’ll explain why you may want to individually monitor every solar panel on your roof. In part two, I’ll look more specifically into SolarEdges’s new model. I’ll discuss my findings on the HD Wave efficiency claims, investigate the inverter’s operating temperature, and discuss a key component of the HD Wave: film capacitors. Next, I’ll briefly cover Zigbee, a protocol they use for load control, and finally, I’ll discuss SolarEdge’s warranty.
Part One: Why SolarEdge?
SolarEdge is a huge player in today’s solar inverter market. Compared to their competitors, they are the new kids on the block. They only kicked off in 2006 with the first inverter sales in Australia in 2008. Today they are second only to SMA for the number residential inverters they are moving, and the way I read it, they are making bucketloads of cash, and are here for the long run. So what are they doing right?
It’s probably got something to do with their staff. While writing this post, I met with SolarEdge’s Country Manager Gavin Merchant and his technical marketing manager Adrian Hawke while they were in Brisbane. Both gents are infectiously passionate about SolarEdge although they approach the product from different mindsets. They corrected me several times on what might otherwise have been dodgy info on this blog. But SolarEdge is a whole lot bigger than Gavin and Adrian, so again, what are they doing so right?
To step back a bit, let’s look at one of the key components of any solar inverter: the Maximum Power Point Tracker (or MPPT). Standard string inverters have two MPPT’s. The panels on a house are divided into two groups (or strings) and connected to the two MPPT’s in the inverter. As the sun’s intensity changes throughout the day, the two MPPT’s will continually adjust the voltage and the current from the panels to achieve maximum power.
The problem with standard string inverters is that a string of panels works kind of like old school Christmas tree lights: if one panel is affected by shade or dirt, then all the panels in the string are affected. SolarEdge offers one solution to this problem. It takes the MPPT’s out of the inverter and effectively puts one MPPT (or optimiser) behind every panel. So if one panel is shaded, it does not drag down the performance of the next.
SolarEdge is just one product that offers a solution to shade. The other contenders are Enphase (micro-inverters), Tigo, and the newcomer, Maxim. In my last post, I discussed how my test results showed Maxim outperformed SolarEdge in the shade. But what Maxim can’t do (at least not yet) is offer what SolarEdge does extremely well: panel level shutdown and panel level monitoring.
Panel Level Shutdown
I deliberately didn’t call this section “enhanced safety” or “SafeDC” as SolarEdge brand it, because that infers other solar systems are not safe. If solar systems are installed by electricians who follow today’s standards, your solar is arguably as safe as the rest of the electrical wiring in your home. The nature of electricity is that it is not 100 percent safe, but we can put measures in place to make it safer.
So Sunday BBQ lunch goes wrong, and suddenly your house is on fire. That’s bad. You run to your switchboard like a good boy scout and turn the main switch off. Although your inverter turns off, your solar panels will still be pumping 600 volts potential through the solar cable in your roofspace. The firefighters are not amused as the solar cable arcs, and your roof potentially becomes live. It’s then that you realise you shoulda gone SolarEdge.
SolarEdge brings another level of safety. SolarEdge relies on communication between the inverter and the optimisers in order for it to operate. If the main switch is turned off, the inverter will turn off, and the optimised panels will produce a safe 1 volt each. This added level of safety may not be a be a major consideration for an individual purchase, but a collective higher level of safety in the solar industry is of huge importance. SolarEdge is raising the bar for safer solar systems. The rest of the industry will follow.
Panel Level Monitoring
Every system we install today has an in-depth level of monitoring. With Fronius monitoring, we can see the DC voltage, DC current and power in individual strings. We can monitor AC voltage, AC current, power and even power factor in five-minute intervals. We can even see import/export power assuming a Fronius Smart Meter was installed. All this is historically recorded to infinitum assuming your inverter is online.
How much data can we possibly need from a solar system? I mean, it’s not like we’re sending it to Mars! Why would we possibly want to monitor individual panels? Get your nerd on – I’m going to give you four reasons.
i) To identify shading for tree growth and soiling,
ii) to identify panel degradation,
iii) to identify bypass diode failure, and,
iv) education. Because there is always more to learn about solar.
i) Identifying tree growth
SolarEdge works at it’s best on shaded roofs because shaded panels with optimisers will not affect the rest of the panels in that string. The problem is: as trees grow, the impact of that shade will increase. As this happens, you could jump on SolarEdge’s online monitoring platform and see the impact of this shading, and identify if it’s then worth the effort of getting out your sabre saw. Obviously, this only works if you are the type of person that would nerd it up and actually use this info.
To be the devil’s advocate, if you were that nerd, with a little more know-how, you could less specifically pick up shading issues with Fronius online monitoring, and jump up on your roof and have an educated guess about the offending branch. Let’s move on to the second and more compelling reason you might need panel level monitoring.
ii) Panel degradation
Most solar panels lose about 1% of their production per year, as shown in this “linear performance warranty” waste of space. But what if a few of your panels reduced their output to say 80% after five years? In your typical string system, it is extremely difficult to prove this, and your so-called “performance guarantee” isn’t really worth the paper it is written on. However, in theory, if one panel was running significantly worse than others on a SolarEdge system (assuming no shade or dirt) you should have enough information to go to the panel manufacturer to claim warranty.
In the past, I’ve not been too excited about individual panel monitoring, but I’m starting to think that this may be SolarEdge’s strongest hand. Assuming you purchase a decent panel with a warranty that covers parts and labour, and a manufacturer that actually honours their warranty without insurmountable conditions, then the ability to monitor the performance of panels individually may be invaluable in helping you identify a warranty case in years to come.
iii) Bypass diode failure
Bypass diodes are installed in solar panels to protect a panel against “hot spots”. If a panel (or a third of a panel) is shaded, it is “bypassed” instead of dragging down the production of the entire string of panels. However, bypass diodes can fail. If one does, it reduces the production of that panel by one-third. This would be hard to pick it up with string system monitoring, but you can with SolarEdge’s individual panel monitoring. Although, it would require the user to keep their eye on the system performance and know the difference between a shaded panel and a failed panel. Again, in the years to come, panel level monitoring may help us detect a fault in your panel that could otherwise go unnoticed.
This is why I like individual panel monitoring: it helps me nerd it up. Last year, on one of our SolarEdge installs, we were supposed to relocate a TV antenna during the installation. Because of the age of the antenna, we asked a professional to install a new one. Something was lost in translation, and he never did the job. A month later we checked out the system online and noticed one panel had lost about 20 percent in production! Ooops! Obviously, we relocated the aerial immediately. Since then I have performed multiple tests to determine how SolarEdge performs in different situations. This knowledge helps us greatly in the design and installation of all kinds of systems.
SolarEdge has always had the advantages of optimisation, panel level shutdown, and individual panel monitoring over traditional unoptimised string systems. The New HD Wave was designed to lift the bar even higher. Let’s see if it has.
Part II – The revolutionary SolarEdge HD Wave
In the early days, inverters used a heavy copper-wound transformer. Over the last ten years, inverters became “transformerless” which made them heaps lighter and more efficient. All inverter manufacturers today use SMA’s H5 Bridge technology – all except … the new SolarEdge inverter.
SolarEdge claims to have lifted the bar. They have replaced electrolytic capacitors with film capacitors and heavy magnetics with digital processing. There are three claims that SolarEdge makes that I’ll examine:
i) The HD Wave is more efficient.
ii) The HD Wave produces less heat and requires less cooling
iii) Film capacitors last longer than electrolytic capacitors.
Of course, I wasn’t going to take SolarEdge’s word that the HD Wave was more efficient, so earlier this year I gave Gavin Merchant, the Country Manager of SolarEdge a call to hit him up for an early HD Wave to test out. Gavin generously sent me his functional display HD Wave – one of only two in the country. I shuffled around the panels on my warehouse and set up this comparative test.
- As an early control, I removed the external optimisers and ran both systems on two separate Fronius inverters. The panels were working identically.
- Both the Fronius 3kW and the SolarEdge 2.5kW inverters use the same components as their respective 5kW models, so the comparison was fair.
- Because the test was run during the winter months, we never saw clipping of the inverters. Monitoring was via Solar Analytics.
- I refer to my previous blog where compared a Fronius 5kW vs a Solaredge 5kW in unshaded conditions. My tests showed that “over a 7 day period, SolarEdge and Maxim / Fronius were performing almost identically.”
The earth-shattering HD Wave test results
Over a 3 week period, the new SolarEdge HD wave performed about 1.5 percent better than the earlier model SolarEdge and the Fronius inverter!
Interestingly, SolarEdge generally only outperformed when production was low. It’s at the times you produce less, that you are more likely to self-consume solar power. The 1.5 percent performance increase could save you up to $40 dollars a year on a 6.5kW system. If you compared that to un-optimised systems and accounted for future mismatch and soiling (not to mention shading), then that figure can only increase.
ii) Less heat requires less cooling
I presumed that if the SolarEdge inverter produced less heat, it meant it would run cooler. It was EOFYS while I was writing this blog so I used the need to test this presumption as justification to buy a thermal imaging camera. Because the taxman was going halvesies on my new toy, I went all-out and bought a FLIR E8.
I repositioned my test wall so I had both my HD Wave and Fronius sitting at the same height.
This is what I measured.
Because the SolarEdge inverter requires less magnetics, it produces less heat, so it doesn’t need to do as much to dissipate that heat. This allowed them to put it all in a smaller enclosure and leave out the fan.
As you can easily see Fronius produces more heat, however, an internal fan expels the heat on top.
But which one actually runs cooler? Umm, yeah, well… While learning to use the thermal camera I learnt about a word called “emissivity”. When measuring the temperature metallic cap of a capacitor, I need to set a different setting for when I am reading a resin coating of a coil, and so on. That neighbours impossible. Bugger. So, I pulled out my old $50 aircon thermometer and used high-tech sticky tape to attach the probe above the capacitors. I put the lid back on and waited for them to warm up.
Apples for Apples
It didn’t work out well for SolarEdge. My results show the 2.5kW SolarEdge was running significantly hotter than the 3kW Fronius. But was this apples for apples? I knew the Fronius 3kW was the same build as the Fronius 5kW. From reading the SolarEdge HD Wave specifications, it seemed the SolarEdge 3 and 5 were also the same. However literally minutes before I intended posting this blog I received our first shipment of 5kW HD Wave inverters. I opened one to double check. The 5kW HD Wave has a much bigger heat-sink! (The HD Wave specifications/ data sheet doesn’t reflect that it is heavier). Rookie mistake.
The next morning I swapped both inverters for their 5kW models and tested again. I heated the room with the aircon and a couple of jaffle makers. NASA would be proud.
The test results were as follow:
At 2300 watts and 30 degrees ambient, SolarEdge ran a few degrees cooler than Fronius. It appears SolarEdge does run cooler internally, at least at half capacity. Surprisingly the “lower heat dissipation” claim of SolarEdge does seem to stack up.
Notice I didn’t run this test on a 40-degree ambient temperature at 5000W of production. On these days, all three of the Fronius fans would be cranking and would be more efficient at cooling. However, presumably, it would also be generating comparatively more heat.
The thermal image camera showed the heat dissipation remained the same, and although the test period was short, the 1.5 percent increase in production seemed to remain accurate.
iii) Film Capacitors last longer than Electrolytic capacitors
Are film capacitors actually better than their electrolytic cousins? SolarEdge have claimed electrolytics only last an average of 10 years, and by using film capacitors they significantly increase the expected life of the inverter. I consulted leading inverter manufacturers.
An anonymous comment from a well-respected figure was pertinent:
If correctly specified and chosen, and an inverter’s internal heat dissipation properly designed and tested, electrolytic capacitors have no problem to continue to operate for a product design life of 20-25 years. But the same is of course true for ANY component within an inverter.
I called my mate Andy from Sungrow. Sungrow is a quality but more affordable Chinese built inverter.
We design our electrolytics to last 15 to 20 years, tested at 50 degrees celsius. It is true though, that the 2 weak points on inverters are the electrolytics and the internal fans.
Joseph from ABB replied:
ABB have had power conversion devices which have been installed and are still running 25 years into their life. These devices … use extremely similar technology to solar inverters and tend to have an even more demanding load as they work 24 hours a day rather than only when the sun is shining.
Many products have been proven to last 20-25 years using electrolytic capacitors. The biggest factor is that the device is designed correctly to utilise the chosen capacitor type. The only advantage I can think of for remaining electrolytic free, is for the products to have a longer shelf life …
I didn’t need to ask Fronius because a few months ago they took me on a tour of their R&D facility in Austria. So I’ll quote my good, eloquent and uncensored self:
Fronius has had an inverter on accelerated testing in their labs for 18 months. I can’t exactly remember what they said that accelerated time equates to, but it embarresed the figure “25 years”. The idea that electrolytics only last for ten years is total bulI$h1+.
Thanks for your input M.C.
SolarEdge has a point that internal fans and electrolytic capacitors are a weak point in inverters, but I think a 20 year+ design life on electrolytics is fairly acceptable.
Zigbee Load Control
Load control is the ability to run an appliance automatically with excess solar power. Instead of heating your hot water from the grid and paying 28 c/kWh, you could heat your hot water with the solar that you would have otherwise sent back to the grid for 10c/kWh. Simple, affordable and reliable load control is, in my opinion, the most important “feature” of any inverter.
SolarEdge is handling load control in an interesting way. The are using a wireless communication network called ZigBee. At the time of writing, we cannot use both Wifi and Zigbee, and the hot water controller is not yet released. It’s a huge topic, so once the Zigbee is tweaked and I’ve have had a chance to play around with it, I’ll post another review.
The ugly inbuilt DC Isolator
The version of the HD wave that was on display at Intersolar in Germany looked small and schmicko. Australia, however, has this stupid regulation about inbuilt DC isolators that made SolarEdge feel obliged to favour function over form.
To match Fronius, their biggest rival, the Australian edition of the HD Wave added an enclosure below the inverter to house a DC isolator. The isolator works fine and I’m not doubting that it is ‘fit for purpose’. It just feels flimsy. You get the vibe that the engineers snuck it past the design department to get it to market in a hurry. To be honest, I’m not convinced it was necessary. I might have preferred a more competitively priced inverter without an inbuilt isolator. It certainly would have looked better.
At least they kept the display screen. Many inverter manufacturers are moving away from display screens and are forcing Grandpa Technophobe to keep his inverter online if he wants to monitor basic inverter production.
Earlier this year I was asked to give a short presentation about “Solar Optimisation” at Fronius International in Austria. I’ve never had an issue with SolarEdge inverters, but during the presentation, I raised the point that I have had 7 SolarEdge optimisers fail out of only 55 SolarEdge systems we have installed. In that room full of Fronius love, the lads unexpectedly defended the Fronius rival saying their experience of SolarEdge optimisers was one of reliability. Recently I called one of those gentlemen to get clarity on his position.
Rohan is the residential manager for Infinite Energy, a huge and reputable solar company based in Perth. They have installed over a megawatt of solar using SolarEdge, which is a truckload, or actually about six truckloads of panels. Rohan tells me their failure rate for embedded optimisers is .00212 percent. If you multiply that by six truckloads of panels, it adds up to just a little bit more than zero failures.
To balance this, not all companies have always found SolarEdge’s warranty process a walk in the park.
I’m keen to hear installer experiences, both good and bad in the comments below.
The SolarEdge warranty document reveals their own confidence in their product – kind of.
- 25-year warranty on optimisers.
- 12 years on the inverter
- 5-years on the Zigbee and WiFi and the SolarEdge Meter.
- It’s a limited warranty, and when you read the warranty document this means they pay for the replacement product or parts, but not labour.
However, SolarEdge has a labour reimbursement programme that would cover the cost (but not really any profit) for certified SolarEdge installers. I’d just like to see that reflected in their SolarEdge-warranty document.
SolarEdge is a financially stable company with a unique product. Optimisation will allow your panels to perform at their maximum, particularly in shaded conditions. SolarEdge offers an increased level of safety in case of a fire. More importantly, the production of individual panels can be monitored which may help identify a future panel warranty claim.
The new HD Wave is a redesigned inverter that I found operates 1.5% more efficiently than its predecessor. The inverter does not produce as much heat as a Fronius inverter. In my tests, although it did not dissipate the heat, the 5kW SolarEdge ran cooler internally than the Fronius even without the use of internal fans. SolarEdge believes they have solved a significant problem by replacing electrolytic with film capacitors. However, the industry does not entirely agree this problem needed to be solved. SolarEdge seems to be more reliable than my relatively limited experience. While it would be good to see the warranty document changed for it to reflect the SolarEdge’s labour reimbursement programme, you can’t help but be impressed with the duration of their warranty.
After my mixed review, I hope SolarEdge still considers me a friend.