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The power of microgrids

Why is there a lot of research and commercial interest in microgrids right now? Mitchell Lennard explains.

The term ‘microgrid’ covers a large range of energy system architectures. Researchers with a background in utility-scale electrical engineering tend to refer to any system smaller than, for example, the Victorian state grid, as a microgrid. At the other end of the scale, many designers see remote area power systems (RAPS) as the best representation.


The Microgrids at Berkeley project, one of the centres of excellence in this area of research (, uses the following definition.

“Microgrids are electricity distribution systems containing loads and distributed energy resources (such as distributed generators, storage devices or controllable loads) that can be operated in a controlled, coordinated way either while connected to the main power network or while islanded (disconnected from the grid).”

This definition covers a wide range of system capacities and technologies. It certainly covers the sorts of systems that ATA members have been perfecting over several decades. It could even cover power systems in ships and aircraft.

The main reason there is growing interest in microgrids is that many of the generating technologies referred to as renewable (think PV, small wind, small hydro, solar thermal, wave) are all suited to and in some cases best used in microgrid or distributed energy system configurations.

The 2009 CSIRO report A Value Proposition for Distributed Energy in Australia concluded that: “In general, distributed generation appears to be an effective early action greenhouse gas mitigation option for Australia when it is considered within a portfolio of other mitigation options…but before distributed energy achieves wide-scale uptake, technology and market development needs to be focused on reducing costs and improving reliability.”

This notion that distributed energy systems and microgrids are a quick way to get greenhouse advantageous renewable generation into the energy mix is the main driver for most microgrid development work presently underway.

While it is possible to categorise microgrids in a range of different ways (have a look at the Berkeley site for one such set of definitions) the main projects running around the world can be seen as falling into two broad categories: campus-scale and remote-area microgrids.

Read the full article in ReNew 128

Sourcing a green builder

Elizabeth Wheeler explains how to find a ‘deep green builder’ who can deliver a quality, environmentally sensitive home.

One of the things I hear most when I speak with people about their builder is, “He said he was open to incorporating our ideas about green building.” Sadly, the context for our conversations is almost always their disappointment, frustration and even anger at how their home was ultimately constructed. And quite frequently these people say that, upon reflection, they didn’t enquire deeply enough about the builder’s knowledge, values and experience.


I suspect that fear is often what stops people asking ‘too many’ questions of prospective builders. It is common for people to worry that the builder won’t want to quote on their job and/or that the builder will apply a premium to the contract for a client they perceive to be pushy or ‘hard work’. Sometimes time pressures are also in play—for example, wanting to be in by Christmas or before the baby comes. Almost always, clients seem to feel that it is the builder, not them, who is in a position of power.

Yet for most people the cost of a house or major renovation is the most significant one-off bill they will ever pay. And in ecological terms, what happens in construction is critical—a well-designed house will still perform badly if the builder hasn’t done their job properly. What’s more, given that working drawings rarely specify products and brands for the building fabric, issues such as VOCs, embodied energy and ethically sourced timber are usually the domain of the builder.

From both a personal and environmental perspective, it’s critical for people to work through their fears and expectations and contract a builder who can deliver a quality, environmentally sensitive home.

What shade of green?

In environmental terms, I put builders in three categories: conventional, green and deep green.

Conventional builders might or might not have any idea about environmentally sensitive construction.

Green builders have some sort of training in environmentally sensitive construction (for example, certification by the Master Builders Association as a Green Living Builder), but (for most) it is not their core business.

Deep green builders might or might not have Green Living Builder certification, but environmental thinking is at the core of their business and they can demonstrate that it’s part of their lives.

Read the full article in ReNew 128

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Backyard chickens

Keeping chickens in your backyard can have many advantages, and not just for you, as Justin Brasier explains.

I once heard about a man who recovered from serious depression after acquiring a small backyard flock of chooks. Observing the complex, often hilarious social hierarchy of his chooks as they foraged and explored his backyard gave the man a focus, helped him wrestle with his own inner demons and reminded him of the simple pleasures of life. His story is proof that eggs aren’t the only benefit of backyard chook-keeping.


Chickens are indeed beautiful, giving creatures and while they may not have the same apparent therapeutic impact on you as they did the above-mentioned man, I promise they will change your life for the good and, in the process, transform your backyard in a productive and positive way!

As most backyard chook-keepers already know, chooks really do have their own personalities. We grow to appreciate this in our daily routine of feeding and egg collecting, or when we take a moment to observe them as they entertain us with their antics. One of the greatest motivations to start up your own flock of chooks is that they encourage you to actually venture into your backyard and experience your immediate outdoor environment.

Chickens are the ideal backyard companions and are truly giving pets. For a start they feed you—one to three hens will usually provide the average family with more than enough eggs. They are relatively easy to keep, although some thought and preparation is required for their overnight housing (more on that later). And chooks are not particularly needy. Unlike dogs, they don’t have to be exercised daily nor like cats do they need to be constantly stroked and fussed over.

Sustainable ‘pets’

Many of you who are reading ReNew are already trying to make a difference at home with your environmental footprint. Some will have water tanks, others solar panels; worm farms and compost heaps are also popular. Well, chooks can help complete the picture. In fact, chooks are also champion composters. Since I got chooks I have had next to no food rubbish. With the exception of citrus and potato and some vegetable peel and coffee grounds, all kitchen scraps are decimated.

Chook-keeping is becoming trendy. Normally, I’m not interested in the latest fads but I don’t mind being on board this bandwagon. Maybe you’ve had a similar epiphany—well, you’re not alone. There’s a groundswell rejecting the multinationals who are dictating our food choices, and much of this movement is occurring in the suburbs. We seem to be returning to the ways of previous generations when keeping chooks was commonplace.

Read the full article in ReNew 128

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Know your renewables: off-grid basics

There’s been renewed interest in giving energy companies the flick. Lance Turner takes a look at the how and why of going off-grid.

Most people never think about their electricity supply until it isn’t there. Most blackouts are short-lived events caused by car crashes or fallen tree limbs and are, at most, an annoyance. But what if your electrical supply disappeared for days, even weeks?


Anyone who has experienced a natural disaster knows that an extended power outage can have serious consequences. For instance, you might be dependent on a bore pump for your water supply or for pumps in a bushfire, or you might be in the depths of a cold winter and find yourself without heat.

Even if you are an optimist and believe that such an event won’t happen to you, there are still other reasons to get off the grid.

Energy independence

It’s not just the thought of days without electricity that makes people think about becoming their own energy generators. Another incentive is the variability of energy prices and the steady transfer of costs towards the fixed component of energy bills—so even energy-conscious people are receiving high bills.

Being responsible for your own energy also means that you are more aware of your energy use. Additionally, the sense of being independent for your energy needs and generating energy from renewable sources such as solar panels instead of using grid power from dirty generation sources can be enormously satisfying. One comment I have heard repeatedly over the years is just how good it feels to be independent of the big generators and retailers.

And, of course, for many remote properties the cost of connecting to the grid may be higher than installing even a large independent energy system. In those cases, there’s simply no reason to connect to the grid.

There are some disadvantages to being off-grid. The most obvious is that you can only use the energy available from your generation system. Use too much and your system will run down and simply shut down from low battery voltage. If you have a backup source of energy such as a petrol, diesel or even steam-powered generator (yes, they do exist, such as those from Strath Steam, www., then you are truly independent.

Read the full article in ReNew 128


The economics of going off-grid

Recent ATA research explores Australia’s ‘unplugged’ potential, and just how financially viable it is to go off-grid.

While rising energy prices are leading some to unplug their appliances, others are considering unplugging their homes and entire communities. In a new report, What Happens When We Unplug?, researchers at Energy For The People and the Alternative Technology Association have examined when it will become economically viable for households and communities to free themselves from electricity and gas networks using off-grid solar photovoltaic (PV) and battery storage systems—often called stand-alone power systems (SAPS).


Their report highlights the strong economic case for some regional and outer-suburban communities to unplug today, while noting that unplugging could be cost-effective for others by the end of this decade.

The story of solar PV should be all too familiar to readers of ReNew: prices have fallen by around 90% since 2009, and there is now over 3.2 GW of installed capacity across Australia1 (equivalent to nearly 6% of total electricity generation capacity2), including solar panels on the roofs of 1 in 8 Australian homes3. Combine this with lithium-ion battery storage—the price of which is expected to fall 40% by 20204—and you have the ideal ingredients to develop SAPS for single households or entire communities.

Why go off-grid? A key motivation is the increasing risk of the ‘utility death spiral’: as demand for electricity continues to fall, for reasons including behaviour change, energy efficiency and solar PV, distributors may be forced to increase prices in order to remain viable. The flow-on in higher retail energy prices drives consumers to use even less electricity. The end result is that centralised electricity generators (power plants) and distribution infrastructure (poles and wires) are increasingly becoming stranded assets, with the costs of keeping them alive passed on to consumers. And so the death spiral continues.

Modelling an energy transformation

In modelling Australia’s unplugged potential (see box), the researchers used scenarios of typical Victorian housing types found in the inner-Melbourne suburb of Preston, the outer- Melbourne greenfield suburb of Werribee and the regional town of Bendigo. Victoria was chosen as a ‘worst-case scenario’ region—in most of the remainder of the country, due to better solar insolation and often higher grid prices for energy, the value proposition for SAPS would be more attractive.

Read the full article in ReNew 128


Off-grid in the tropics

Designed for the tropics, Andrew Spiers’s tropical off-grid home exists to look after this conservation block, writes Robyn Deed.

When I call to speak to Andrew Spiers about his off-grid home near Darwin, he’s out ‘chasing weeds’ on the property. It’s a conservation block, which Andrew and Helen Spiers bought in 2002 while living in Darwin. They had planned to retire to the block down the track, but it proved difficult managing the land conservation on weekends only. So they decided to build a house and move there before retiring. Thus, Andrew describes the house they built as “existing to look after the block”.


An ex-ranger and current educator in sustainability, Andrew’s trying to stop the native savannah woodlands from all becoming grasslands. It’s a greater risk to the tropical environment than cane toads, he says.

The weeds he’s fighting are mainly African grasses, introduced for pastoralists as they’re preferred by grazing animals. Australian grasses, he says, have “spent their lives making themselves unpalatable to kangaroos”. Kangaroos prefer the African grasses too. That’s how Andrew can track down the invasive grasses: they’re the chewed patches in between the native grasses.

Living lightly in the tropics

Within the savannah woodland environment that he’s protecting sits a completely off-grid and passively cooled home. The home’s design was initiated by Andrew—he has a background in planning and was interested in demonstrating just what’s possible, in terms of living comfortably and lightly in the tropics.

He’d started thinking about the design in 2002 when they first bought the block. Over several years, Andrew and his partner Helen went along to what were then called Solar House Open Days (now Sustainable House Days), talking to owners, and going back several times to some houses.

A modern Burnett design

Even more importantly, he says, he also studied the heritage houses designed by Beni Burnett in the 1940s in Darwin.

Burnett was a government architect of Scottish extraction who grew up in South-East Asia. He understood tropical design, but also was able to come up with a compromise to suit the mainly British immigrants. In addition, he was dealing with a town without electricity or running water, so his house designs provided comfort in the tropics without even the cooling effect of electric fans.

A Burnett design centres around air flow, critical to a passively cooled house in the tropics. Andrew’s house is skewed from an east-west orientation to pick up breezes which come from the southeast in the dry season and the northwest in the wet. This is something that’s been lost in so many Darwin developments, says Andrew. There’s no room between the houses for breezes, and orientation just doesn’t seem to play a part.

The two-bedroom house is also just one room wide. Andrew says, “In a Burnett house, and in my house, the verandah becomes the house.” Any internal walls that block breezes are louvred to allow the breeze through when it’s needed.

Read the full article in ReNew 128

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No wires and too much power!

Kevin White describes his off-grid home in Queensland as a renewable energy ‘power station’, with more energy than they can use!

It all began with eighty-three acres in southeast Queensland, an almost clean slate, up for sale by a good friend who’d fallen in love and was emigrating. Suddenly we had acquired a property with a bit of everything— dairy pastures running out to steeply treed hills, peaking at a ridge before descending into remnant rainforest; a 300-foot hill rising from the flats completes the picture.


Buying the property was the easy bit; deciding what to do with it was more evolution than plan. The flats had been used for grazing so we decided to continue that. In went cattle yards and a reasonably large shed—your shed can never be big enough! We decided to build a studio within the shed as temporary accommodation while we planned our build.

As ex-yachties who’d swallowed the anchor for the country life, we knew we wanted to maintain our independence. The ‘reasonably large shed’ had plenty of roof area to supply a water tank and there was plenty of fallen timber nearby for heating.

We wired the studio for both 12 and 240 volt power. We had no idea where on the property we wanted to build so we didn’t consider getting a quote for grid power at the time. However, we did get a telephone connection put into the shed.

At that time (just a few years ago!), solar panels were a rather costly item, so for our interim system we decided to mount four 80 W panels on a frame and have them track the sun for peak efficiency, along with using an MPPT charge controller and 400 Ah of Trojan T105 batteries.

Being an ex-electronics tech I built the tracking system—from an old C-band satellite dish mount, coupled to a homemade trackin  controller. ‘Noddy’ did his duty, day in and day out. We were always delighted when guests asked, “Did your solar panels just move?”

With 12 volt LED lighting, a modest 12 volt fridge/freezer, 12 volt entertainment devices, a laptop and a pot belly stove (with a year’s worth of cut timber), my tolerant wife Gudrun spent over a year living in our temporary home while I went to work in Antarctica for a year.

Read the full article in ReNew 128

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A DIY no-care worm farm

Discarded plaster or paint cans get put to good use in Valerie Yule’s simple and cheap worm farm.

This simple design for a homemade worm farm is rat-proof and fits a small shady space. It suits a family of four, as the worms eat the kitchen scraps so fast!


All you need are two empty plaster or paint buckets or cans, often thrown out from building sites, and two cheap plastic garden sieves. Builders and plasterers at a building site will usually be happy to give you the used cans rather than throw them into a rubbish skip.

Place one can in a depression in a shady space on damp ground. Put a sieve on top. Cut the bottom from the second can. Place the can on the sieve. Top it with the second sieve (if there are very clever rats around, weight this sieve with half a brick, so vermin can’t lift it).

The sieves stop rats, mice and blowflies getting in, but allow worms perfect freedom to come and go.

Start off the worm farm by putting some damp earth with a few worms into the top can. They will multiply quickly, so there is no need to buy worms.

Read the full article in ReNew 128

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Energy storage buyers guide

There has been a steady increase in the number of ready-to-use energy storage systems available. In this mini-guide, we take a look at the options so far.

Providing electricity to off-grid homes has always required the use of a suitably sized battery bank for energy storage.


In recent months, there has also been a lot of interest in energy storage for homes with a grid-connected solar system—whether for avoiding export at times of excess solar generation, load shifting (buying energy when cheap, storing it and then using it to offset energy use at more expensive peak times) or for supply backup, for times of mains power grid failure. The latter is especially important for users with critical needs, such as telecommuters, people with medical appliances and the like.

Both on- and off-grid storage systems need a battery bank sized to suit the requirements. This is coupled with energy generation equipment such as solar panels, a charge controller, an inverter and various other components.

There has been a move in recent years towards storage systems that contain the batteries and other components in a pre-configured ‘storage in a box’ module that is simply connected to a generator such as a PV array. These sorts of pre-configured energy storage systems are the focus of this buyers guide. We have included any unit that contains a battery bank and associated safety gear, as well as at least one other system component such as the charge controller or inverter.

We do not cover individual batteries/cells, as they have their own buyers guide, the most recent of which appeared in ReNew 113.

Pros and cons

There are several advantages to this sort of ‘storage in a box’ system. Firstly, installation is usually quick as much of the wiring between components has been done. Secondly, it often makes for a neater system as many components and their associated wiring are enclosed in a single cabinet.

There are some disadvantages too, including less flexible system sizing—most suppliers have a few standard battery bank sizes that they offer. However, storage units may be modular so that multiple units can be used to make up the required capacity.

Read the full article in ReNew 128


Remote pumping buyers guide

Moving water is a requirement on nearly every remote and rural property. We take a look at the different types of pumping systems and what pumps are available.


On many rural properties, pumping water is critical, whether it be for watering stock, irrigating crops or providing potable water for household use. Mains power may not be available on the property or the pump may be far removed from the house, so these pumps often require an alternative energy source, such as solar panels or wind power.

For both rural and non-rural off-grid properties, off-grid pumps are also often used for circulating water, for example in a remote-coupled solar hot water system.

These pumping requirements may also be critical to the operation of a farm business. Such off-grid pumps thus need to be reliable, easy to maintain, long-lived and cost-effective.

So what are some of the features of pumps that need to be considered? Firstly, different tasks require different pumps: for example, the pump for drawing water from a well or bore will be different from a pump to circulate water through a hot water system. Secondly, the amount of water and the height it needs to be pumped to (the ‘head’) also vary from site to site, and the pump needs to cater for these requirements.

To meet these variations in pumping requirements, there are many different types of pump on the market. These include the well-known windmill-powered bore pumps, solar bore pumps, reticulation pumps and pressure pumps. There are also numerous types in each of these categories, adding to the confusion in choosing a pump.

This guide looks at pumps designed to be powered from renewable energy sources—solar, wind and water. It includes DC electric pumps as well as pumps directly driven by wind or water power.

To read the pumping guide in full (PDF format), click here

Alan Pears

The Pears Report: The war on renewable energy

With neighbouring Asian countries investing millions or billions of dollars in renewable energy and energy efficiency, Alan Pears reflects on Australian policy in 2014.

Life is certainly interesting in Australia in 2014. What is most tragic is that our leaders seem to be uninterested in having transparent, balanced processes to work things through to a consensus position that is in the interests of society.


Every inquiry or audit seems to be stacked with partisan people, and has inadequate process to allow consensus to be built. Every announcement is full of PR spin and provides little information, much of which is selected to support a particular view. This is a serious challenge for democracy. Of course, in the energy sector, we’re used to this kind of behaviour.

Science also seems to be in disrepute. We are paying a high price for the lack of scientific training of our leaders and their advisers.

I visited China recently for an APEC sustainability workshop. I was the only westerner present at the invitation-only session, which made me feel very honoured. I was given the task of explaining Australia’s renewable energy policy to the attendees: they were all completely bemused. I then had to sit and listen as they took turns telling the group about the hundreds of millions or billions of dollars they were all investing in renewable energy and energy efficiency.

Appliance efficiency

A recent report on Australia’s appliance energy efficiency program (at www. provided some great news, however. From a base year of 2000, the program is cutting greenhouse gas emissions by 13.5 million tonnes annually at a cost of minus $119 per tonne avoided (based on purchase and operating costs over appliance lifetime per tonne of emissions avoided). By my estimate, it is saving $3.2 billion on energy bills each year, $2.7 billion of which is saved by households. That’s around $300 per household on average. Just think, the average annual energy bill of $2000 could have been $300 higher! If we look at carbon pricing as part of a broader package, it is quite clear we can deliver a lot of abatement at zero or low cost by using a combination of policy tools.

Electricity developments

Things are moving fast. On the one hand we have even more aggressive attempts to kill renewable energy and energy efficiency. But on the other hand, the incumbent industry is beginning to fragment and shift, as players come to accept the futility of trying to hold back the tide.

Apparently the Western Australian and Queensland governments, and the networks they own, are now subsidising fringe-of-grid consumers by more than a billion dollars a year. Two of their network operators have announced that they will help people in these areas go off-grid. It will save their governments a lot of money.

There may be a role for local governments to take over existing grids and manage a transition to microgrids. Network operators can offer services such as maintenance, monitoring and sale of equipment to make a profit—as I suggested in my column in ReNew 123. I hope there’s a nice big cheque in the mail in recognition of my advice!

This is not news. In its 1991–92 annual report, the State Electricity Commission of Victoria pointed out that residents in rural towns cost 50% more to supply than they paid, while rural outlying homes cost double what they paid. Most state governments have maintained these subsidies for political reasons.

The retailer sector is also undergoing rapid change. A number of community groups are serious about setting up not-for-profit energy retailing businesses. And some new business models are appearing, such as the (presently) Victoria-only PowerShop. Check out the blog on PowerShop’s website for some interesting views on the direction of energy markets.

The Productivity Commission and the federal government are keen to see more privatisation of the electricity industry. PV, shifting off-grid, investment in large renewable energy projects, energy efficiency and demand management all do that: so why is the government opposed to them? The government’s Green Paper is due out in May, so it will be interesting to see what position it takes.

RET review

This review’s design is a clear declaration of war on renewable energy by government on behalf of the incumbent electricity industry. It will be very interesting to watch the attempts to manipulate economic analysis and policy objectives to fit the outcome.

I have made a submission to the Inquiry pointing out that renewable energy policy operates within a broader context, and that, when this is considered, a stable RET is a sensible and financially responsible policy— as concluded by the 2012 Climate Change Authority Review.

From the limited information available, the Emission Reduction Fund will cost around $12 per tonne of avoided emissions. This alone justifies a RET if its net cost is under 1.2 cents per kilowatt-hour—which most agree it is. While the incumbent industry wants to shift to a (lower) target based on the actual percentage of 2020 electricity sales, keeping the existing fixed target is very important for investor certainty. The industry itself has argued strongly for a fixed target in the past, when that option suited them. They can’t have it both ways.

Indeed, the uncertainty created by this review has unnecessarily increased the cost and difficulty of meeting the 2020 target by undermining investment. That extra cost should not be counted against the RET: it is an outcome of poor policy.

A 2009 report by the Australian Academy of Technological Sciences estimated that air pollution from coal-fired power stations cost Australians 1.3 cents per kilowatt-hour. The RET reduces this cost.

The decline in electricity demand is largely due to a range of separate factors and policies implemented by government such as successful energy efficiency programs (which are saving consumers much more than any RET cost); the high exchange rate driven by the mining boom that has made Australian industry uncompetitive; and big increases in electricity prices caused by unnecessary investment in electricity network infrastructure. So why is the RET blamed for these impacts on the incumbent electricity industry?

The electricity industry is supposed to be a competitive market. The incumbent industry can choose to invest in renewable energy and other emerging technologies to make profits from the RET—as they have done in the past, and WA and Qld network operators seem poised to do. They can even write off losses from existing infrastructure against profits from new activities.

The present high electricity costs are outcomes of their decisions. Independent consultant Bruce Mountain estimates that networks need not have spent about $20 billion of the $40 billion invested over the past few years. If they had saved this money, electricity prices would be at least a cent per kilowatt-hour cheaper: this would have offset much of the claimed RET cost for consumers.

So when we look at claimed costs for the RET, we see they are small compared with the outcomes of many other decisions, some taken by governments, and others by existing industries. On this basis, the RET looks like good value for money. It is also positioning Australia for a better, more competitive future.

In any case, how many Australians outside the energy sector would see the RET over-achieving as a bad thing? For decades, surveys have shown that most Australians want an efficient, renewable energy future. Governments and the industry has chosen not to deliver what we want. This is their chance to catch up.

We must remember that change usually brings challenges, creates winners and losers, and can even create some short-term costs. But just think where we would be if the government had helped Telstra’s landline business to block the rollout of mobile phones and the internet.

Alan Pears has worked on sustainable energy issues since the late 1970s. He is one of Australia’s best recognised and most highly awarded commentators on sustainable energy and climate issues. He teaches part time at RMIT University and is co-director of Sustainable Solutions, a small consultancy.

Read more articles on energy efficiency in ReNew 128.


Product profile: Portable solar generators

When most people think of portable power supplies, they think of a genset. But gensets require maintenance and fuel, and are quite polluting, especially when run at low loads, as most are for a large percentage of their runtime.


Ecoboxx provide a great alternative with their portable solar power systems. Just set up the panel, connect it to the main Ecoboxx unit and you are done.

There are three models—the 160, 600 (to be released in August) and the 1500. They feature 100, 600 and 1500 watt inverters respectively, with the two larger models having sinewave outputs. Storage capacities are 13 Ah and 45 Ah at 12 V for the 160 and 600 respectively using sealed AGM batteries. The Ecoboxx 1500 can use batteries from 100 Ah to 300 Ah, but it is supplied without a battery as standard. To make the most of the solar panels, the Ecoboxx 1500 also features a MPPT solar charge controller.

The solar panels for each unit are rated at 20, 80 and 130 watts respectively (the 1500 can handle up to 300 watts in total) and each Ecoboxx comes with a 3W LED bulb and lead set, and an AC charger, for when you need to charge the unit from mains power.

RRP: $299 for the Ecoboxx 160 and $1299 for the Ecoboxx 1500. The 600 will be priced around $800 when released. For more information and to find your closest dealer, contact Ecoboxx, ph: (02) 9724 3344,

For more product profiles, buy ReNew 128

Q&A: Microinverter advantages

Can you please tell me the pros and cons of using AC solar panels versus DC solar panels?


Tim Clarke

For a grid-interactive system, both have some advantages. AC panels (with attached microinverters) mean that all the wiring can be done by a suitably knowledgeable electrician and there is no DC wiring or disconnects etc required. All of the panels operate independently too, so if one fails or is shaded, it doesn’t affect the others. Further, if the mains fails or there is a problem with the house, such as a fire, the highest voltage on the roof is that of a single panel, provided the mains is disconnected. The datalogging of the separate inverters also lets you see the performance on a per-panel basis.

With DC panels and a string inverter, the inverter is away from the high temperatures of the solar array (assuming it isn’t mounted on a sunny wall, as in some systems I have seen) so the inverter runs cooler and is likely to have a long lifespan. However, modern microinverters use electronic components that are more heat resistant than previous models (e.g. ceramic capacitors instead of electrolytics), so the thermal advantage of a large single inverter is less than it used to be.

So, with progressing tech, microinverters are starting to gain advantages over the traditional way of doing grid-interactive systems (although not everyone in the industry agrees with this). We will be looking at the advantages of microinverters in a coming issue of ReNew.

Lance Turner

To read more questions and answers, buy ReNew 128