Can Microinverters Take The Heat?

Microinverter heat tolerance

A black box of electronics sitting beneath a solar panel baking in the hot Australian summer sun. How do microinverters hold up in Australia’s scorching summers?

A little while back I received an email from someone who recently had a solar power system installed, and while researching solar inverters prior to the purchase was tossing up whether to install a single string inverter or micro-inverters.

A string inverter is the most common choice – generally one per installation, with strings of solar panels connected to it (hence the name). It’s usually installed on the wall beside a home’s switchboard/meter.

A microinverter  is much smaller device and one is used per panel. It’s attached to the racking below the panel, or in the case of an AC solar panel it’s factory-integrated and takes the place of the junction box on the back of the module. Microinverters offer a number of benefits, including enhanced system design flexibility and safety, redundancy and panel level monitoring – but they add to system cost.

Anyhow, this fellow ended up opting for a single string inverter – one of his concerns being the temperature microinverters will have to endure during Sydney summers, which can get pretty toasty; particularly out west.

Some Like Tolerate It Hot

While this may not apply to all devices of this nature, Enphase microinverters are built to take the heat. The company says they can withstand up to 65°C ambient (air) temperature and 85°C internal operating temperature.

While it doesn’t reach 65°C anywhere in Australia1, temperatures in the space between the solar panel and the roof 2 can be higher than official temperature readings, which are often taken by a thermometer inside a box called a Stevenson screen. This is a ventilated wooden box that protects instruments from direct heat radiation from outside sources.

There’s also the heat generated by the microinverter itself, which plays a bigger role on internal temperature. Enphase says based on 97% efficiency, for a 5kW string inverter running at maximum capacity 150W of heat must be dissipated. For a microinverter running at 300W, only 9W of heat needs to be dissipated. Additionally, Enphase microinverters have a significant amount of surface area to dissipate heat  (IQ7+ = 212 mm x 175 mm x 30.2 mm).

Enphase has evidence from the field on how its microinverters fare in extreme heat conditions. The following data is based on what the company says were the hottest days in Australian capitals last year (sourced from the Bureau of Meteorology) and the corresponding maximum internal temperature of the Enphase microinverters, which was grabbed from Enlighten servers – the company’s solar monitoring system.

Date Location Max ambient
temp
Max microinverter
temp
4 Jan 2020 Penrith 48.9°C 63°C
31 Jan 2020 Melbourne 42.9°C 64°C
30 Jan 2020 Adelaide 43.9°C 70°C
4 Feb 2020 Perth 42.7°C 68°C
6 Dec 2020 Brisbane 43.5°C 52°C

There are some interesting/curious results in that table. For example, the highest internal temperature recorded was in Adelaide, yet the highest ambient temperature was in Penrith, Sydney by quite a margin – and what a stinker of a day that was for Penrith folks. In fact, it was claimed to be the hottest place in the world on that day.

So, what gives?  The company’s explanation is hot days can be cloudy and windy. This means less power generation, better cooling, and lower internal temperatures. Enphase indicates on the hottest day at the Adelaide site, it was pretty sunny. It doesn’t mention the conditions in Penrith. And the Brisbane data looks a bit iffy – it looks like the maximum temperature on that day was 33.2°C.

That aside, it’s worth noting in none of the examples did the microinverters get even close to the maximum internal operating temperature of 85°C.

Enphase has a fair bit riding on its confidence in these microinverters being able to withstand hot days over a long period given the company offers a 10-year product warranty in Australia.

Footnotes

  1. According to the Bureau of Meteorology, the highest temperature recorded in Australia was 50.7°C on January 2, 1960 at Oodnadatta Airport.
  2. ~ 135mm including the racking lift and gap between the base of the frame and the panel face.
About Michael Bloch

Michael caught the solar power bug after purchasing components to cobble together a small off-grid PV system in 2008. He's been reporting on Australian and international solar energy news ever since.

Comments

  1. Chris Thaler says

    Find the specs on each component used in the electronics with, in particular, the max temp rating.
    Most normal components are rated as performing at a max of 85 deg. C. though some are rated at up to 105 deg. C .

  2. Michael Bloch,
    You state: “While it doesn’t reach 65°C anywhere in Australia[1], temperatures in the space between the solar panel and the roof [2] can be higher than official temperature readings…

    Give it time…

    From phys.org news, published on 4 Oct 2017:

    “Major Australian cities, such as Sydney and Melbourne, may experience unprecedented temperatures of 50 degrees Celsius under 2.0 degrees of global warming,” said lead author and ANU climate scientist Sophie Lewis, adding it could occur by the 2040s.

    “The increase in Australian summer temperatures indicates that other major cities should also be prepared for unprecedented future extreme heat.”

    The study’s climate modelling projected daily temperatures of up to 3.8C above existing records in the states of Victoria and New South Wales, despite efforts to curb warming.

    https://phys.org/news/2017-10-sydney-melbourne-degree-days.html

    From Degrees of Risk: Can the banking system survive climate warming of 3˚C?, on page 10 (bold text my emphasis):

    Prof. Andy Pitman, Director of the ARC Centre of Excellence for Climate Extremes in Australia notes that global mean warming is badly understood. As a general rule of thumb, global average warming of 4°C (covering land and ocean) is consistent with 6°C over land, and 8°C in the average warming over mid-latitude land. That risks 10°C in the summer average, or perhaps 12°C in heatwaves. Western Sydney has already reached 48°C. If you add 12°C to the 48°C you get summer heatwaves of 60°C.

    https://www.breakthroughonline.org.au/dor

    Heat is a killer for electronic devices. The future will be hotter, so microinverters on hot roofs need to be able to endure those projected conditions now, or they likely won’t last long.

  3. John Bennett says

    It puzzles me why the microinverters are black. Surely that is a recipe for overheating when they are exposed to the sun.
    I enquired from Tindo why their panel frames are black, and received the answer “for aesthetics”. Although the panel efficiency might be compromised little by the absorbed heating, why compromise at all?

    • Ronald Brakels says

      Well, they go under panels and so shouldn’t be in the sun. In the shade, black can be better for radiating heat.

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