[LINK] A Clean Energy Revolution -- Now

Marghanita da Cruz marghanita at ramin.com.au
Sun Sep 22 15:57:11 AEST 2013

Hi Stephen,

My 2c worth is there are a few things about the article and I think we need 
to question some of the assumptions around electricity. There are a lot of 
DC appliances around, mainly aimed at the Carvan market, but then the 
Laptop and other mobile devices lead to energy efficiencies in Computrers. 
AC Wiring for Lighting is no longer a given.

> In the War of Currents era (sometimes, War of the Currents or Battle of Currents) in the late 1880s, George Westinghouse and Thomas Edison became adversaries due to Edison's promotion of direct current (DC) for electric power distribution over alternating current (AC) advocated by several European companies [1] and Westinghouse Electric based in Pittsburgh, Pennsylvania.


stephen at melbpc.org.au wrote:
> Here's a somewhat simplistic but interesting discussion of solar panel 
> inverters. Any linker have more information regarding this technology?  
> http://www.solarquotes.com.au/inverters/micro/
> Micro Inverters and AC Solar Panels. The Future of Solar Power?
> In the beginning, there were solar panels which produced electricity as 
> Direct Current.
> To make that electricity useful for powering appliances or connecting to 
> the grid, it was converted to Alternating Current (AC) using a large box of 
> electronics called an inverter.
> In Grid Connected systems, the solar panels were connected together in 
> series (called strings) to create higher voltage DC which is good for 
> reducing losses. However, this also created some problems.
> Hence the Micro Inverter was invented.
> Micro Inverter
> A Micro Inverter is simply a miniaturised inverter, sized to suit 
> individual solar panels rather than a string of solar panels.
> They aren�t new; they first appeared in the late 1990�s but arguably it was 
> a bit too early and the technology suffered a bit from reliability issues 
> and high price. In the last few years however, they have re-surfaced and 
> are starting to really take off.
> Around the world there are at least twenty one different brands of Micro 
> Inverters. In Australia, about 8 brands of Micro Inverters are approved for 
> use with more on the way.
> AC Solar Panels
> An AC Solar panel is simply a solar panel that has been fitted with a Micro 
> Inverter so that it produces Alternating Current instead of Direct Current.
> What's good about AC Panels and micro inverters?
> There are a number of complexities caused by the traditional way of 
> connecting solar panels together (in series) which Micro Inverters can help 
> overcome including:
> High Voltage DC
> High Voltage DC can create a risk of very high temperature arcing and 
> potentially fire. Because Micro Inverters convert to AC the potential for 
> this to occur is greatly minimised.
> Switchgear
> High voltage DC requires relatively expensive protective switches and 
> fuses. By using AC, switchgear is more commonly available and thus cheaper.
> Shading
> When solar panels are connected together in a series string, shading just 
> one of them can dramatically affect the entire array; (kind of like 
> standing on a hose).
> As an example: Imagine an array of 3 solar panels connected to a 
> conventional, central inverter. One of the panels has been pooed on by a 
> bird, which could easily reduce its output by 50%. However, it will also 
> reduce every other panels' output by the same amount.
> But by having a Micro Inverter on each solar panel, the outputs are 
> completely independent of each other. So that bird poo is going to only 
> affect the soiled panel:
> According to the US National Renewable Energy Laboratory, this effect can 
> yield as much as 12% more energy.
> Solar panel mismatch
> When solar panels are made they each have slightly different electrical 
> characteristics due to imperfect manufacturing tolerances. When you connect 
> them together in series string, this effect is called "mismatch". Micro 
> Inverters can adapt to the individual characteristics of each panel, 
> avoiding mismatch.
> Maximum Power Point Tracking
> Like the effect of mismatch, different electrical characteristics also 
> create different Maximum Power Points for each solar panel. The maximum 
> Power Point is the perfect point for extracting maximum power from a solar 
> panel and Micro Inverters attached to individual solar panels can therefore 
> target this point better.
> Monitoring and fault finding
> Almost all inverters have some level of monitoring and fault finding 
> however; it can only see the combined output from every solar panel in the 
> series string. A Micro Inverter however, can monitor each solar panel 
> individually, allowing you to easily identify exactly what's happening more 
> quickly and easily. 
> Factory fitted
> Assembling and connecting components in a factory environment is inevitably 
> a more controlled environment and can potentially save time and money. A 
> number of solar panel manufacturers now factory assemble Micro Inverters to 
> produce AC Panels.
> Redundancy
> If your series string inverter develops a fault, your entire solar array 
> stops producing power until it is fixed. If a Micro Inverter develops a 
> fault, the remaining Micro Inverters can continue to operate, so you should 
> have a more reliable system.
> Modularity
> Series string inverters can only accept specific number of solar panels per 
> inverter so it's not always possible to simply add a few more panels at a 
> later date. AC Solar Panels however, can be added much more easily because 
> they are independent of each other.
> Orientation
> In a series string, all your solar panels need to be connected in the same 
> orientation so they are combining to produce the right voltage at the same 
> time to fire up the inverter. Because they operate independently, AC Solar 
> Panels can be oriented in any direction and will not affect the operation 
> of other solar panels.
> What's bad about AC panels and micro inverters?
> Nothing is perfect however, and Micro Inverters do have some downsides 
> including:
> On the roof
> If your Micro Inverter develops a fault, someone has to get up on the roof 
> and disconnect it from under your solar panel. This can add time and cost, 
> compared to simply taking a series string inverter off the wall.
> Weather effects
> Because Micro Inverters are on the roof (albeit under the solar panels) 
> they do suffer from more extremes of weather including heat, cold and 
> moisture. This means they have to be really carefully built and in many 
> cases, use electronic components that are more robust than would otherwise 
> be required. As a general rule, extremes of temperature reduce the 
> efficiency of electronic devices and shorten their life.
> Efficiency
> Although they are getting close, Micro Inverters have not yet reached the 
> same efficiency levels of series string inverters, so they can't convert as 
> much solar energy into electrical energy.
> Price
> Again, they are getting close, but Micro Inverters remain about forty to 
> fifty percent more expensive than high quality series string inverters and 
> almost three times the price of low cost series string inverters.
> When is an AC Solar Panel or Micro Inverter a better choice?
> As you can see, there are a number of advantages to AC Solar Panels using 
> Micro Inverters. The most common reason people choose them is because they 
> have shading or they need to use different orientations on their roof to 
> generate the power they require.
> An increasing number of people are also choosing them because they are 
> prepared to pay a premium to avoid mismatch, increase their redundancy and 
> allow for future expansion. The other benefits described tend to strengthen 
> the case and some people just love the idea of having the latest/newest 
> technology.
> Clearly, if you have shading or sub optimal orientation Micro Inverters are 
> an ideal choice and could end up being cheaper in the long run because they 
> will produce more energy.
> Beyond this, Micro Inverters become a personal choice about how much you 
> are prepared to pay balanced against the extra features and advantages.
> How popular are they?
> A few years ago there were virtually no Micro Inverters or AC Panels 
> installed around the world. However, in California it is estimated that 
> around 40% of all inverters installed in 2012 were Micro Inverters, so they 
> taking market share rapidly, particularly in the US. They are growing in 
> other countries too, but are best suited to Residential markets where the 
> price difference is less noticeable.
> The Australian solar market is around 98% residential, so it is logical 
> that we will see pretty strong growth here too. In fact, we know that in 
> the last 6 months from a base of effectively zero, more than 10,000 Micro 
> Inverters have been sold and we have only just started. Although this 
> represents a small fraction of the market, within a couple of years it's 
> quite reasonable to predict that around 20% of the market or more, could be 
> utilising Micro Inverters.
> Who sells AC Solar Panels and Micro Inverters?
> We know of twenty one Micro Inverter manufacturers around the world 
> including: Enecsys, Apparent, Sparq, Kaco, Power One, Tigo, Array 
> Converter, Solar Bridge, , GreenRay Solar, Azuray Technologies, Petra 
> Solar, Direct Grid, Accurate Solar, OKE/SMA, Exeltech, National 
> Semiconductor, Larankelo, Enphase, APS, SWEA & Plug & Power.
> Enecsys and Enphase are undoubtedly the market leaders with APS not far 
> behind however SMA and Power One (both huge Inverter manufacturers) are 
> sure to shake things up a bit once they get going. A new kid on the 
> (Australian) block is Solarbridge who, instead of selling the inverters 
> individually, team up with solar panel manufacturers to sell the AC panel 
> as a complete, factory assembled unit.
> http://www.enecsys.co.uk/
> http://enphase.com/
> http://solarbridgetech.com/
> There is a growing list of big name PV companies around the world who have 
> partnered with Micro Inverter companies to produce and sell AC Solar panels 
> including Westinghouse Solar, BenQ, Canadian Solar, Suntech, SunPower, 
> NESL, Hanwha SolarOne, Sharp and probably more that we haven't heard of 
> yet.
> In Australia, we have (at the time of writing) one company producing AC 
> Solar Panels. Adelaide's Tindo Solar manufacturer solar panels and use the 
> SolarBridge Micro Inverter providing our only true, locally made AC Solar 
> Module. AC Solar Warehouse based in QLD also sell a good range of Micro 
> Inverters.
> http://www.tindosolar.com.au/
> http://acsolarwarehouse.com/
> Beyond these two companies, a growing number of Distributors and Dealers 
> can access Micro Inverters and fit them to pretty much any solar panel you 
> like with APS the biggest selling Micro Inverter to date.
> The last word
> A few readers have asked if AC inverters represent a "Do-It-Yourself" 
> option and the short answer is no, although it is tantalisingly close. 
> Because you are dealing with 240V AC power, a licenced electrician is still 
> required to connect them and for rebates or FIT's you'll need an accredited 
> installer.
> Just how much of the market Micro Inverter equipped AC Solar Panels take 
> remains to be seen but one thing is for sure; they do solve some hairy 
> problems and have a big future.
> If they can get the cost down just a little bit more, then they may well 
> become the dominant solar inverter technology.
> --
> Cheers,
> Stephen
> Message sent using MelbPC WebMail Server
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Marghanita da Cruz
Ramin Communications Pty Ltd

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