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ReNew Editor, Robyn Deed

ReNew 129 editorial: Community energy special

I like the term community energy, conjuring up, as it does, a picture of enthusiastic community contributors—aptly illustrated in the photo of exuberant delegates at the recent community energy congress on page 40!


The idea of community energy is a simple one—energy projects funded by the (usually local) community. However, its genesis in Australia has been anything but simple, with planning, financial and regulatory hurdles slowing down or preventing the development of many projects.

But it seems a pleasing shift is happening. A notable milestone was the community energy congress, held in June, which brought together groups and individuals with bucketloads of energy to get projects started, and share ideas.

That’s one of the things you notice straight away about community energy—there’s a whole lot of information sharing going on. From the Difference Incubator’s legal templates, to Embark’s governance structures, to ATA’s Sunulator, and much more besides, there are many ideas and models to borrow from—with some now proven in the field (or on the bowling club roof, as with Shoalhaven’s Repower One project!).

This issue we take a tour of community energy projects happening in Australia right now, including community solar, a bioenergy project that could transform a rural town, and the installation of two wind farms. We also consider the sorts of issues that can arise in community energy projects, around such things as metering and management.

Plus, we take a step back and look at community action more generally. Dr Samuel Alexander from the Simplicity Institute has examined the ‘disruptive potential’ of a range of social movements. Covering collaborative consumption, divestment, transition towns and community energy (and more in the original paper), his review of all these areas carefully considers just how effective they can be in initiating a low-carbon shift.

Our cover house sits somewhere in that world of social sharing. Built with the help of travellers, exchanging their work for board and lodging via HelpX, it’s also a great example of reuse and sustainability. We were also excited to find out about OpenShed, a website enabling the sharing of tools!

There’s much more to consider in this issue too, from a pioneering owner-build using hempcrete, to a discussion of how EVs could affect the grid, to a power station in a backyard in Tassie. We cover the basics of inverters, present an efficient hot water buyers guide, and delve into what’s available in renewable energy courses. Collyn Rivers explains how to improve the performance of fridges in caravans (with many of the tips just as applicable to domestic fridges). We also present our Winter Energy Challenge winner and notable entries, all innovative and practical. Enjoy!

Robyn Deed

ReNew Editor

disruptive tech

Changing the World: Disruptive Innovations

With the need for action on climate change getting ever more urgent, Samuel Alexander considers just how far community action can go to help build a more sustainable future.

We consider four social movements or social innovations that at least have the potential to change the current trajectory of history acutely in the direction of a low-carbon world.

Fossil fuel divestment campaign


This movements was initiated late in 2012 by climate activist Bill McKibben and his team at In the 18 months since then, this campaign has taken on a life of its own, as nascent social movements tend to do.

The disruptive potential of this campaign lies in how directly it challenges the financial foundations of the fossil fuel industry— without finance the industry cannot support itself or develop new projects.

Motivated by this possibility, McKibben and his team organised a divestment campaign, which calls on individuals, communities, institutions and governments to withdraw or ‘divest’ their financial support from the fossil fuel industry with the ultimate aim of crippling it. Without investment, the fossil fuel industry cannot exist; without the fossil fuel industry, the primary cause of climate change is eliminated.

The campaign appears to be gaining momentum. In the USA, 380 college campuses have committed to divestment, with successful divestment already achieved in nine universities and colleges, 22 cities and 10 religious organisations, with further campaigns under way in Canada, the United Kingdom, Sweden, Finland, India, Bangladesh, as well as Australia and New Zealand.

While the campaign encourages individuals to divest wherever possible, the main focus is on larger institutions and organisations where the real financial power lies, especially banks, superannuation schemes, universities, churches and governments. A recent report from Oxford University concludes that this is the fastest growing divestment campaign in history.

Transition Towns

If the fossil fuel divestment campaign is one of the most promising social movements opposing and undermining the carbon-based society, the Transition Towns movement is arguably one of the most promising and coherent social movements focused on building an alternative society.

This movement burst onto the scene in Ireland in 2005, and already there are more than 1000 Transition Towns around the world, in more than 40 countries, including Australia. The movement runs counter to the dominant narrative of globalisation, and instead offers a positive, highly localised vision of a low-carbon future, as well as an evolving roadmap for getting there through grassroots activism.

The rationale for engaging in grassroots activity is that “if we wait for governments, it’ll be too little, too late. If we act as individuals, it’ll be too little. But if we act as communities, it might just be enough, just in time” (Hopkins, 2013: 45).

According to some commentators, this approach represents a pragmatic turn insofar as it focuses on doing sustainability here and now. In other words, it is a form of DIY politics, one that does not involve waiting for governments to provide solutions, but rather depends upon an actively engaged citizenry.

This approach is particularly relevant here in Australia, where the government is showing no signs of progressing the nation toward a low-carbon future. Of course, whether grassroots movements for a low-carbon world ultimately march under the banner of ‘transition’ is of little importance; what is necessary and important is that people do not wait for governments to act or lead the way.

Collaborative consumption

The term ‘collaborative consumption’ has emerged as one of the socio-economic buzzwords of recent times, with Time magazine in 2011 listing it as one of the big ideas that will change the world. Surprisingly, perhaps, collaborative consumption is in many ways just a fancy name for ‘sharing’, although as the prime website ( dedicated to this concept notes, it is “sharing reinvented through technology”.

But if human beings have been sharing their wealth, possessions and skills (to varying extents) throughout history, what role could collaborative consumption play in the transition to a low-carbon world? And to what extent could something as mundane-sounding as sharing have disruptive potential?

The innovation here is that people are using online forums and technologies to offer or acquire access to things without necessarily buying or selling them; instead, they often share, hire or gift them in more or less informal ways—facilitated by online peer communities which make it easy to list or search for available goods and services. In economic parlance, the transaction costs of sharing or trading are markedly reduced through the use of the internet, making it more efficient than ever to connect formal or informal sharers and traders.

Examples of collaborative consumption are many, varied and expanding. A representative example is the upsurge in car-sharing businesses, which involve either a central business purchasing limited cars that are then used by a community of people (e.g. Zipcar, Flexicar and GoGet), or alternatively, the central business can facilitate peer-to-peer car sharing (e.g. Car-Next-Door). The genius here was in recognising that many, if not most, cars sit idle for a huge portion of the day or week, opening up space to utilise them more efficiently through sharing access.

Renewable energy financed from below

As the climate situation worsens, a louder chorus is forming amongst scientists, educators and activists that an urgent top down political response is needed to facilitate a rapid transition away from fossil fuels toward an economy based on renewables.

Lester Brown in World on the Edge (2011), among others, uses the metaphor of “war time mobilisation” to signify the urgency needed. The US economy changed almost overnight with the bombing of Pearl Harbour in 1942, responding to an urgent security threat by reconfiguring, among other things, car factories to produce tanks, planes and ammunition.

The shrinking carbon budget suggests that a similar mobilisation is needed now, this time to confront the threat of climate change, by mass-producing solar panels, wind turbines and other renewable technologies. Nevertheless, the failures at Copenhagen and later international climate-related conferences don’t provide many grounds for hope that politicians are going to be the prime movers in the transition to a low-carbon society.

However, in recent years there has been a multitude of innovations in the socio-cultural sphere that suggest that, even in the absence of serious top down political action, the transition to renewable energy supply could be driven from below.

The preeminent example is Germany, which globally produces the most solar energy per capita. The interesting point about the example of Germany is not simply how much renewable energy it is producing, but that approximately 65% of that production is owned by individuals and communities, as opposed to being funded by the public purse (although attractive subsidies exist).

Beyond Germany, there are a growing number of inspiring examples—such as the Westmill Cooperative, in the UK, and Hepburn Wind, in Victoria, Australia—where communities with less attractive subsidies have still taken the transition to renewables into their own hands.

This is an edited extract from the article. Read the full article in ReNew 129.

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Winter Energy Challenge

We asked ReNew readers how they are reducing their winter energy use. We received some interesting and novel ideas—here is the winner!

We had many great entries from ReNew readers for our Winter Energy Challenge, from the simple to the complex, from a single lifestyle change to an entire lifestyle choice (see Karen Cheah’s excellent presentation at www.


The ATA crew particularly like the Trombe wall that replaces conventional heating in the home, making John S our Winter Energy Challenge winner. Read all about his trombe wall below.

John will receive a portable ‘Sydney Tube’ solar BBQ from Run on Sun worth $550.

WINNER—John’s Trombe wall

John S 

I had this idea for a solar heater many years ago, and thought if I ever built a house it would be a main part of the energy efficient design. Well, I had been beaten to the idea by a guy named Trombe—so it won’t be named John’s wall!


John used black painted corrugated steel to make a trombe wall to heat his home in winter.


Trombe made it using glass, but mine uses black painted corrugated steel. The principle is based on getting the sun to heat a cavity, with the warmed air thermosyphoning into the building. I had the advantage of computer fans to make the extraction of the warm air more efficient. The air enters the house through five vents.

The black corrugated steel wall is 2.4 m high and about 12 m along a 20 m north-facing wall. Windows break up the sections. The wall is 15° west of north facing. A veranda shades the wall to varying degrees, but completely from November to April.

The best winter days are clear, calm and cool. As soon as the sun hits the black wall it starts to warm, and by 11 am the air coming from the vent will be 28° C and as high as 49.7° C at 3 pm. I have saved running the reverse cycle air conditioner and still keep warm; saving money and the planet.

We’ll share more great entries with you over the coming weeks, or read the full article in ReNew 129.

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People power

In a year of milestones for community energy in Australia, Craig Memery takes us on a tour of how the ATA is helping projects with the strategies and resources they need.

It won’t come as a surprise to ReNew readers to hear that ReNew’s publisher, the Alternative Technology Association (ATA), is excited about community energy in Australia. Having been the collective owners of the Breamlea wind turbine two decades ago, some ATA members are probably more surprised that community energy is yet to take off here!


There are a handful of groundbreaking community energy projects up and running today, and here are a few of the ways we are doing our bit to help more than 50 communities bring future energy projects into being.


ATA is a founding partner and steering group member of the Coalition for Community Energy (C4CE), alongside some stalwarts of the community energy sector. C4CE exists to empower and grow the community energy sector. The Coalition is moving from its formative stages to incorporate new members, with membership and governance arrangements being formalised as this goes to print. Find out more at

With welcome support from ARENA (Australian Renewable Energy Agency), C4CE is developing a national strategy for community energy. This work is being led by the Institute for Sustainable Futures and Community Power Agency, with ATA providing specialist input in areas such as energy policy, markets and regulations. Look out for the strategy, which will be released later this year.

In July, C4CE held the inaugural Community Energy Congress in Canberra, bringing together over 300 community energy supporters from across Australia, as well as international delegates. The event was a resounding success, and I think we will look back on the congress in coming years as a milestone for the community energy movement.

Getting a better deal for local generation

Our friends at Total Environment Centre (TEC) have been working hard to improve the incentives for generating energy that is sustainable, locally consumed, improves competition and minimises burden on electricity networks.

ATA is helping TEC’s work on virtual net metering as a member of the project steering group. We are also advising TEC, who, on behalf of a consortium of NSW Northern Rivers organisations, is on a quest to form a community energy retailer. With the spotlight shone on the poor environmental performance of most energy retailers (see GP-TGEG), a community retailer will not only provide a more sustainable business model, but raise the bar for the integrity of the existing retail sector.

Directly engaging with communities

The support of the NSW Office for Environment and Heritage has been vital in allowing ATA to reach NSW communities and help them progress their energy projects.

Most recently we spent some time with the Cowra community (read more about their project here) and in October we’ll be presenting at the North Coast Energy Forum. Straight after that we’ll be travelling to central NSW to meet with local community energy proponents and speak at the AGMs of the Bathurst Community Climate Action Network and Central NSW Renewable Energy Cooperative (CENREC). With the support of Infigen, CENREC grew out of action that took shape three years ago when ATA ran a series of regional community energy workshops around NSW, so seeing how far they have developed is particularly rewarding.

Energy market advocacy and research

As ATA’s energy consumer advocate, my main role is to promote affordable, sustainable energy for all Australian energy consumers, through more demand-side participation, fairer pricing, better regulation and improved competition. ATA punches well above our weight in the energy policy ring, but with tens of billions of dollars behind incumbent businesses in the red corner, we have a long fight ahead of us. Of course, there are many more ways ATA is supporting community energy—from our groundbreaking research into community scale microgrids to Sunulator. Dive into the rest of ReNew 129 for a closer look at the many projects and resources in the works!

Craig Memery is an energy consumer advocate at the ATA and a specialist in community energy.

Read the full article in ReNew 129.

corena - Tulgeen 7kW 450

Community solar: energy from the ground up

With support resources now readily available, Taryn Lane from Embark explains how individuals, groups and businesses can work together and benefit from setting up community solar projects.

Already a mainstream model internationally in countries such as Denmark, USA, Germany and Scotland, community solar is about to hit Australia in a big way. There are around 50 active projects in Australia and it is a tangible pathway for all communities—whether they be urban, regional or remote—to participate in transforming their energy supply.


Community solar can take on a myriad of identities, depending on a community’s exact needs and opportunities. From community bulk-buy rooftop models, through to small crowd-funded systems, up to more sizable solar parks, they provide real opportunities for installation efficiencies and more inclusive ownership.

Several models of community-owned solar projects feasible within Australia’s current legislative and energy market boundaries will be explored in this article. Although we can learn from international models, we also have unique restrictions in the Australian landscape that we all need to navigate. Our aim at Embark is to both create innovative business models and collate from the broader sector what’s been learnt from the first generation of systems—thereby accelerating the uptake of, and social licence for, renewable energy in communities in Australia.

Why community solar?

The move to a low-carbon economy requires a magnitude of capital that charity alone cannot provide: community investment with reasonable returns will provide a necessary part of the solution.

There is still a significant portion of the community who can’t invest in solar technology. This includes renters, apartment owners, those living in homes with shaded roofs or heritage overlays, and those who can’t afford to install a residential system on their own home.

Community solar projects enable neighbourhoods to develop and own their own renewable energy infrastructure. It answers the calls for social equity for solar in Australia, as renters, apartment dwellers and low-income households can have the opportunity to make a direct investment in solar PV.

Shared ownership schemes will soon drive significant growth in the medium-scale solar space. A business installing 100 kW on a factory roof will result in the same abatement as a community that installs 100 kW in the same location, but the latter has the opportunity to engage a hundred (or more) community members on an ongoing basis.

Read the full article in ReNew 129.

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Renovating with HelpX

Allowing a steady flow of international strangers to live in your home may feel uncomfortable for some, but Katerina Gaita has had them back-to-back for almost two years. Kiara Pecenko investigates the world of HelpX.

Katerina Gaita and her husband Joel bought their home in Melbourne’s west ten years ago, complete with a rustic old Edwardian shopfront and a train carriage in the backyard. Their shared passion for sustainable living saw them plan a revamp of the property, creating a smarter, more efficient home in its place. But, while juggling paid work, a not-for-profit start-up, two small children and a renovation that forced the family into the small front section of their house, Katerina decided to search for helpers, which she found in abundance online at HelpX.



Help Exchange, or HelpX for short, is a listing service connecting host organisations and families with working travellers looking to exchange their skills and time for short-term accommodation. Katerina registered herself as a host, and within days had multiple travellers enquiring to come and stay with her. In exchange for a place to stay and food, she asked helpers for 20 hours of work a week.

“I needed help with a variety of things. I would ask them to clean the house once a week, pick my son up from swimming lessons, and sometimes cook dinner—just enough to keep me afloat.” Since registering

in January 2012, she has lost count of the number of helpers she has had come through their door. While five months of that year were taken up by intensive renovations, she has now had back-to-back HelpX helpers with her since October 2012.

Helpers joined in on the renovations: painting, laying grass, even shopping for shelves in IKEA. They helped by cleaning and restoring salvaged studs and bricks from the original house and neighbouring houses that were used for new fences and exteriors. “Most of the time all they could offer was unskilled labour. We did however have a French man here for five months, who happened to be a carpenter by trade. The family built such a strong relationship with him that he plans to return through HelpX to help finish the rest of the house.”

Over the years, HelpX has grown in both helpers and hosts, and offers travellers a wide range of work to undertake all over the world. Each position is different, with tasks from babysitting and cleaning, to fruit-picking, carpentry and working with animals. While most HelpX helpers are unskilled backpackers in their twenties, many pick up skills as they travel around working through the service. Katerina recalls helpers that had worked on building sites driving trucks, or on farms herding cattle before coming through her door.

Aside from receiving much-needed help around the house, Katerina and her family developed strong bonds with many of the helpers. In October 2012, they housed a few HelpX helpers to support them in the final part of the back-end renovations. “We had some great helpers during that time that were with us when we were moving in. It was all very exciting. It was a really important time of our lives, so they were happy to follow our progress. We will keep in touch with them.”

Find out more about HelpX at

Read the full article in ReNew 129.

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Biomass potential in rural communities

This community energy project is not just about energy, it’s also about improving agricultural practices and creating a new industry—definitely a trickier proposition, but potentially more rewarding, writes Robyn Deed.

Not that long ago, say about 60 years ago, before we moved to a more centralised grid, it used to be the norm in regional Australia for country towns to manage their own power supply. Residents in Cowra, 300 kilometres west of Sydney in NSW, are exploring options that could reinstate that local control, and at the same time bring new industries to the area.


CLEAN (Cowra Low Emissions Action Network), a local group of sustainability advocates, is working on a pilot system to run a portion of the town of Cowra on a microgrid using energy produced from biomass, and start up a bioenergy regional hub.

The proposal has gained broad support— from industry, the council, locals and farmers. The proponents believe it could provide a way of improving sustainable agriculture practices and reducing reliance on the grid, potentially decreasing costs for the local community.

Architect and local Dylan Gower, one of the people involved in initiating and developing the proposal, says that community engagement is particularly important for this type of project.

“It’s a community energy project that relies on creating a new industry around what’s already there, and in some ways that’s more complex than importing in renewable technologies such as solar and wind,” says Dylan.

The ‘what’s already there’ is the resource stream for a biomass-based plant. There are two streams that the proposal is considering as input, one of ‘dry’ waste from agriculture and the other from ‘wet’ municipal waste, such as green waste and waste water.

The latter is one reason that the local council is behind the project: pre-treatment of waste water by a biomass system could reduce the running costs of the local (newly built) waste water treatment plant, which currently has high energy needs—and would also yield energy in the form of biogas to run the plant.

In this mixed farming community with intensive cropping of canola and wheat, plus dairy and poultry, there’s also a lot of residual material from agriculture that could feed into a biomass plant.

Dylan resists calling the residual material ‘waste’, as much of the agricultural by-products are already reused. For example, the stubble from canola or wheat production (the two intensively farmed crops in the area) is currently left on the soil as mulch or used to create compost.

“That is something we’re discussing with farmers,” he says: whether there is higher value in using the stubble as compost or mulch (as is done currently), or in using it in the biomass process to generate biogas and biofertiliser.

The feasibility of a pilot system to power an industrial estate in Cowra on biogas is currently being investigated.

Read the full article in ReNew 129.

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Building with hemp

Hemp has the potential to become one of the greener building materials on the market. Kiara Pecenko visits Neil and Sandy Garrett to see how they are using hemp in their new sustainable home.

Avid travellers Neil and Sandy Garrett are currently living in a cosy shed on their six acre property in Violet Town, complete with solar panels and induction cooktop. They built the shed immediately after buying the land, packed it full of their possessions, then began to draw up plans for their dream home—and they are using hemp to build it.


Neil has built a number of houses in his time and been involved in the construction of mudbrick and strawbale houses, but was initially taken by the idea of using rammed earth for their new home. A stay in a rammed earth home in Mandurang, Victoria, prompted the couple to seek out how they could achieve a similar outcome in their build.

Their research, though, proved a little disheartening. Neil says, “Although it is a tremendous final product, rammed earth isn’t a great insulator, and required a lot of hard work to build with. I’m 69 years old!” The process of ramming the earth to make the walls is very labour-intensive, and for the retired owner-builder couple it was no longer a viable option.

Through Neil’s research, he had made contact with people who were using a hemp-lime composite to build interior and exterior walls. The practice has a European origin, developed in the 80s by builders refurbishing old French Tudor homes. Builders took the woody interior of the hemp plant (called the hurd), which was primarily considered a waste product, and combined it with a lime-based binder and water. The hemp-lime composite (now commonly called hempcrete) proved to be easy to construct with and to manipulate, strong yet flexible, breathable and environmentally friendly.

Building performance

Neil says that every quality one could want in a non-structural wall material can be found in the hemp-lime composite. Hemp hurd is a cellular material that easily traps air and holds it over a long period of time. This means it is a great insulating material, so hempcrete can achieve a rating of up to R4 for a 250 mm thick wall, depending on how much it is compressed. The material has good insulating qualities, and high thermal mass compared to other insulating materials. It is also breathable (moisture permeable) so condensation and mould won’t form. The composite is also highly alkaline, which deters both vermin and white ants.

The finished product in Neil’s build is one continuous, unbroken wall that makes up the home, meaning it has high thermal performance and good sound attenuation— which the couple found imperative. “Our block sits between a freeway bypass and a railway line, and we have the Melbourne– Sydney flight path above our heads.” They wanted to ensure that they had the peace and quiet they sought in the country.

Read the full article in ReNew 129.


Electric vehicles and the grid

Increased EV uptake means challenges for the grid, but the good news is that demand-side management could help. Marcus Brazil and Julian de Hoog explain.

The last few years have seen a rapid increase across the globe in the uptake of electric vehicles (EVs). A recent report by the US Department of Energy points out that sales of EVs are increasing faster than those of hybrids, if you compare the same stages of the technology life cycle. One of the leading manufacturers of EVs, Tesla, is now valued at more than $30 billion and has been projected to be a major disrupter of the automotive industry. Many major car makers are planning to introduce electric and hybrid models into the Australian market in the near future.


An important question that is often overlooked in discussions on electric vehicles is: what will be their impact on the electricity grid? An EV with a typical daily commute of 40 km requires roughly 6–8 kWh of energy to recharge; this is equivalent to the daily needs of a small household. In other words, if you buy an electric vehicle, the impact on the local electricity network is about the same as adding a small house to the neighbourhood. Furthermore, in an unregulated environment, most EV owners are likely to plug in when they arrive home, around 6 pm, at exactly the time that residential electricity networks experience peak demand.

The impact of EVs on the electricity grid

The main challenges to the grid arising from the increased uptake of electric vehicles fall into three categories.

Peak load

Perhaps the most well known of the problems, peak load occurs at the time of day when the highest demand for electricity occurs. Our networks are sized to withstand peak demand, but if electric vehicles are added to the network, then the additional demand may be too much for the local lines and transformer to handle. New infrastructure may need to be installed, the cost of which is inevitably borne by the consumer.

Voltage drop

The lines in a local distribution network have an impedance of their own. As current travels from the transformer to your house, this impedance leads to a decrease in voltage. The more current you draw, the more the voltage drops. An electric vehicle can draw a lot of current for long periods of time, and therefore cause a significant, sustained drop in your voltage. Low voltage can mean that some appliances may not run properly, or may run inefficiently (reducing their lifetimes). What’s more, the drop in voltage caused by an EV does not affect only its owner; it can affect other houses in the network too, particularly those furthest from the transformer.

Phase unbalance and power quality

Most distribution networks in Australia are 3-phase, and most houses connect to only one of these phases. If several people in a neighbourhood buy EVs, and by chance these are connected to the same phase, then there can be significant losses in efficiency in the network due to the resulting unbalance. There is also the potential that an EV and its charge point could affect the overall quality of the power in the network, for example by distorting the 50 Hz grid waveform.

When are these problems likely to arise? A study of two networks in Australia suggests that there can already be problems at fairly low vehicle uptake rates—for example at only 10% in a network based in Melbourne. While even a 10% uptake of EVs is some years away, now is a good time to start thinking about how to prepare for these problems.

The solution: shifting of demand

The good news is that many of these problems can be prevented. Electric vehicles are among the most ‘flexible’ loads in the grid: they can be shifted to other times of the day, such as overnight, when there is more capacity in the network.

Read the full article in ReNew 129.

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River Power

Dr Catriona McLeod reports on a project harnessing a large renewable resource, at a smaller scale, in Tasmania.

In south Tasmania, Nigel and Josh Tomlin, founders of River Power Tasmania, have designed, and custom built, a hydroelectric generator. This might not seem so unusual as the market is awash with domestic and micro-generators. These small-scale operations are designed to power one domestic site; however, even Nigel’s first ‘backyard’ working prototype, built several years ago, powers about 30 houses, near his property at Ellendale.


The prototype takes water from the Jones River, which runs through the Tomlin’s property. This small generator generates about 80 megawatt hours per year and is powered by water falling 30 metres along 500 metres of pipeline.

The newer, second and larger hydroelectric generator is on the Humboldt River, which starts below Tyenna peak, in Mt Field National Park, at an elevation of 896 m, and ends at an elevation of 248 m. The Humboldt River drops approximately 648 m over 10.3 km. The fall and water content of this river make it ideal for a hydro scheme.

The generator captures water in the last 2 km of river, where it flows through forested areas used for industrial-scale softwood plantations; over the last 2 km it falls 98 m vertically. It demonstrates the efficiency of physics: the energy of falling water is enormously powerful in terms of generating electricity, even at a smaller-than-commercial scale. This new system is expected to generate 2.2 gigawatt-hours per year.

Turbine technology

Manufactured in Australia by Pentair Southern Cross, the Turgo impulse turbine installed by the Tomlins is a medium-to-high head turbine. It’s designed for ‘run of river’ schemes as it can tolerate some so-called ‘dirty water’ (although the water entering this system is incredibly clean) and has good efficiency over a wide flow range. It’s also designed for minimal maintenance; this is vital to the Tomlins as they also run a large, diverse farm in the area. Monitoring can be done remotely via the Citect program, with error alarms sent out via SMS.

This model can be manufactured in a range of materials to suit the customer’s requirements. Here, Nigel’s 30-plus years in the hydroelectric industry—dreaming on the job of his own generators—meant he was very clear about how he wanted his machines to be configured. He notes the system is actually incredibly simple: an induction generator converts the water’s energy, much like a large washing machine motor being run in reverse.


The hurdles to construct this turbine have, however, been anything but simple. As mini-hydro projects are rare, there are no local precendents for the authorities to observe, and no specialists who properly understand the project. For example, the water management board required the installation of expensive monitoring equipment on the assumption the tailrace would be a trench dug into the earth. However, as the tailrace has been constructed from concrete to the river’s edge, to avoid creating any muddy turbidity, the Tomlins’ are arranging to have this requirement lifted. The outwardly tapering tailrace also slows the water’s velocity as it rejoins the river, some two and a half kilometres downstream from its point of diversion.

Around 48% of the river’s flow will be diverted, and returned as clean as it enters the pipeline. Baseline levels of micro flora, micro fauna and water quality have been taken by consultants, for ongoing monitoring once the system is in operation. The project has required close liaison with the local forestry landowner, Norske Skog Boyer Mills, and other local and state stakeholders.

Read the full article in ReNew 129.

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As easy as DC to AC: inverter basics

Almost all renewable energy systems use at least one inverter. But what exactly are they and how do they work? Lance Turner explains.

Solar panels produce DC electricity, and batteries store DC. However, common household appliances are all designed for the AC mains power grid and so can’t be used with DC electricity directly. The inverter solves this problem by converting DC into AC. There are a number of different types of inverters for different uses, and inverters have a number of different ratings that it is important to understand.

DC versus AC


Firstly, let’s explain those two terms—DC and AC. DC is short for direct current. This means that current only flows in one direction. This is the type of current produced by batteries and solar panels. AC stands for alternating current. This is the type of current supplied by the mains power grid. It rapidly reverses direction 100 times per second and there are two reversals per cycle, so the mains grid frequency (in Australia) is 50 cycles per second, or 50 Hertz (Hz).

The reason AC is used in the mains grid is that, firstly, this is the type of electricity produced by rotating generators (more accurately called alternators) used to generate electricity in large power stations. Also, AC allows for simple voltage conversion using transformers, so power can be transported long distances at very high voltages and then stepped down using a simple transformer (basically a block of iron with some insulated copper windings wrapped around it) to voltages safe for domestic use. Converting DC to a different voltage takes a lot more effort— something that couldn’t be done efficiently when the grid was first designed. So too does converting DC to AC, but thanks to modern semiconductors, producing AC mains power from a DC source is now quite easy.

Inverter types


Grid-interactive inverters are now the most common type of inverter, with over 1 million of them installed across Australia as a part of rooftop solar systems. They take DC power from a renewable energy source, such as a solar panel array, and convert it into AC power.

Note that a grid-interactive inverter can’t supply power to the house if the mains grid is down. This is a safety feature called anti-islanding; it prevents export of power at the time of a grid failure, thus protecting people working on the powerlines. The inverter can’t just disconnect from the grid and still power the home as the output from the solar panels varies depending on conditions, so the inverter output is unknown at any given time. By shutting down, the inverter also prevents your appliances from being affected by fluctuations in voltage that could occur if powered directly

The power from grid-interactive inverters is used inside the home or, if you’re generating in excess of what you’re using, the excess gets fed in to the grid.

Microinverters are a subset of grid-interactive inverters. Rather than having one large inverter that all of the solar panels feed into (often called a string inverter), microinverters are tiny inverters that are mounted on the back of each solar panel. They only convert the energy from their own panel (or sometimes a pair of panels), so they are much smaller and lighter than a string inverter, and each microinverter feeds AC power independently into the grid/ home. This makes them better suited to some installations, such as when one or more panels in an array might be shaded or become dirty, as the reduced output from one panel has no effect on the rest.

Read the full article in ReNew 129.


Sunulator solar calculator

The ATA’s new tool for calculating the economics of solar installations can use half-hourly consumption and insolation data to give a much more accurate view of the benefits. Andrew Reddaway explains.

If you’re trying to get a community solar project off the ground, a major issue is economics. How much electricity would the system generate? What kind of deal might you offer the host site? What rate of return can investors expect, if any? To answer such questions, you need to do some homework.


This is where you can use Sunulator, ATA’s free tool, which estimates the economic feasibility of a grid-connected solar photovoltaic system.

Is it like Tankulator?

Readers may be familiar with the ATA’s popular tool at Just as Tankulator helps you plan for a rainwater tank based on historical rainfall data, Sunulator helps you plan a solar system based on sunshine data. However, there are more variables in solar systems, so Sunulator had to be more complex.

How it works

Sunulator uses a simulation approach. You provide information on the host site’s current electricity consumption, ideally for a full year. You also tell Sunulator some details on the proposed solar system, electricity tariffs and costs. Sunulator then simulates a year in half-hourly intervals.

For each interval it determines the position of the sun in the sky and estimates electricity generation, based on sunlight intensity and the angle at which it hits the solar panels. It then compares this generation to on-site electricity consumption to estimate the amount of electricity imported from the grid and/or exported to the grid. Finally it applies the tariffs to calculate the interval’s contribution to the annual electricity bill.

A key result from this simulation is the overall percentage of solar generation that gets exported to the grid rather than consumed on-site. For example, 15% of generation might be exported, or it might be 70%. This percentage has a big impact on economic feasibility, as the typical value of exports (via feed-in tariffs) is only a third to a fifth of the value of electricity consumed on-site. Most other solar calculators require you to estimate this percentage, whereas Sunulator calculates it based on electricity consumption versus simulated solar generation.

After the detailed simulation is complete, Sunulator totals the annual generation, bill savings and investor returns and extrapolates them up to 35 years into the future, based on user-defined future changes in tariffs etc. This future cash flow is used to calculate economic measures such as return on investment, net present value and payback period.

Electricity consumption data

You have a couple of options to provide consumption data. Ideally you will have access to data from the host site’s electricity meter, in which case you can format it in another spreadsheet, then copy and paste it into Sunulator. If not, Sunulator will help you to construct data from estimated monthly and daily profiles.

Climate data and locations

Sunulator is currently setup to work for sites in NSW and Victoria (as the funding for its development came from organisations in those states). ATA selected a total of 45 locations throughout NSW and Victoria based on population, climate variability and proximity to an automatic weather station. For each location, we extracted satellite-based hourly sunshine data purchased from the Australian Bureau of Meteorology from the 1990s up to the end of 2013. Months with too much missing data were excluded. We filled gaps in the remaining data and interpolated to half-hourly values.

We then prepared a typical meteorological year (TMY) for each location. For a TMY, each of the twelve months of the year is considered separately. Data is not averaged, as that would understate the variability in actual sunshine. Instead, the most typical full month from the data set is selected.

Let’s say 10 years of sunshine data are available. Each of the ten Januarys has its sunshine totalled, and the average of these ten figures is calculated. The January whose total sunshine is closest to the average (e.g. January 2000) is selected. Then we move to February. For example, the February data might be copied from February 2013, if that was the most typical February. This results in a full year of data made up from months selected from several different years.


In Sunulator you can define up to six different scenarios for comparison. One is the ‘business as usual’ scenario, which typically has no solar system. In the other scenarios you can explore a range of options for a solar system, for example varying system size or tilt angle. Or you might consider the impact of different system installation costs or electricity tariffs.

When you run Sunulator it calculates all the scenarios at once, and you can then compare the different scenarios side-by-side.


ATA was fortunate to obtain assistance from several volunteers. They ran simulations for a range of locations using 2013 sunshine data and compared Sunulator’s results to reported actual 2013 generation data from the website Often, reported data was influenced by site-specific factors (e.g. shading from trees or buildings). An intriguing example was Falls Creek—some sunny winter days matched very well, but others did not. After much head-scratching, we realised it was likely due to snow lying on the solar panels! This reinforces an important point: don’t rely on Sunulator alone, make sure you carefully consider local conditions. On the other hand, some sites gave very ‘clean’ matches.

We also checked Sunulator’s generation estimates against some other solar calculators and found a good match when looking at aggregate results.

Community investment options

Although most solar installations in Australia are owned directly by the electricity consumer, Sunulator is designed to assist community organisations to install solar systems via additional investment options. For example, it might be used by a community organisation planning to install a system and sell electricity to the host site, or to install a system through a loan, or for a community organisation acting as an electricity retailer. There’s more info on the different ways it could be used on the Sunulator page, in the presentation links.

Can a homeowner use Sunulator?

Sunulator is very suitable for estimating economic feasibility of a grid-connected home solar system. However, it does require some persistence and prior knowledge to use it effectively. It also requires a computer with Microsoft Excel 2003 or later. Please see the user manual for more details.

Future development

As useful as Sunulator is, it could be improved! If funding permits, our first priority is to extend Sunulator to all states and territories. Battery storage would be an important enhancement, allowing users to evaluate the economics of battery-enabled grid-connect solar systems. As covered in ReNew 128, these are already commercially available and receiving a lot of interest.

For more information, including a full user guide:

The ATA has run two training courses so far and hopes to hold other training courses and publish an online webinar. Keep an eye on the ATA website for updates.

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Renewable energy courses guide

With enrolment time for next year approaching, we’ve updated our renewable energy courses guide. Mischa Vickas investigates what’s on offer and the opportunities available.

“Things will keep happening, almost regardless of what happens on the political stage,” says Associate Professor Alistair Sproul from the School of Photovoltaic and Renewable Energy Engineering at the University of NSW; a promising remark at a time of great uncertainty for the renewable energy industry in Australia.


Despite this uncertainty, there still remain many opportunities to become involved in renewable energy (RE) through study and training, whether you are a school-leaver or professional looking to diversify your career. TAFE, university and distance-education courses all provide avenues to entering an industry bound to flourish as Australia looks for sustainable, reliable and affordable energy.

TAFE qualifications

At the front line of the industry are those who directly handle RE technologies. According to the Clean Energy Council, 21,000 people were directly employed by the industry in Australia in construction, installation, operation and maintenance roles at the end of 20131. As a comparison, 27,600 people were employed in oil and gas extraction as of May 20142.

David Tolliday, Renewable Energy Training Coordinator at Holmesglen Institute in Victoria, says the greatest opportunities are for licensed electricians looking to be trained in the design and installation of photovoltaic (PV) systems (both grid-connected and stand-alone) and small wind systems. David says the motivation for undertaking such study is often the prospect of new employment or business development, but at the core of this can be a personal drive to see RE developed in Australia; “I’ve got a passion for it,” he says. David, who has also worked as an electrician for 35 years, undertook training in RE about 10 years ago, and has since benefitted from opportunities to work and teach in RE both in Australia and overseas.

Importantly, RE training is additional to a basic electricians qualification, meaning electricians can diversify into RE while continuing to offer standard products and services.

These courses are offered at over 15 training schools across Australia. If you are not a qualified electrician, a small handful of schools also offer courses in related areas, such as solar sales, carbon accounting and energy auditing, and wind energy site assessment, as well as generalist RE courses that are most suited to architects, engineers and project managers in the construction industry.


An engineering qualification at the undergraduate or postgraduate level can also enable a career in RE research and project management, particularly for emerging large-scale solar and wind technologies. “Renewable energy and energy efficiency is going to be very disruptive to what we are doing now and we need people who can figure it out,” says Alistair.

Whilst a mechanical or electrical engineering degree can provide you with the general skills relevant to RE, students can also undertake engineering degrees majoring in RE, PV and solar, sustainable systems, as well as environmental engineering.

Although the majority of students at university are school leavers, Alistair says that some students are already professionals in engineering or the physical sciences looking to update their qualifications, and some of these go on to start up their own businesses in RE and energy efficiency.

Read the full article in ReNew 129, or download our extensive renewable energy courses table.

Alan Pears

The Pears Report: Future Global Energy Giants

Alan Pears considers the interesting future for energy providers and energy efficiency in Australia, and globally.

Energy and climate policy are certainly entertaining at present. The dominance of crude politics over reality continues.


Australia becomes a world leader at being a climate laggard by dumping its carbon price. Electricity companies apply further restrictions and charges to rooftop PV (but not to air conditioner owners). Governments use shonky economic analysis to justify dumping carbon pricing, the Energy Efficiency Opportunities program, Victorian Energy Efficiency Target and, possibly, the Renewable Energy Target. And the PUPs gambol.

Meanwhile, electricity consumption continues to decline, gas prices accelerate upwards, global coal prices continue to fall and it looks as though we may have a record hot year globally. Then, Senator Ricky Muir turns out to be a renewable energy enthusiast: maybe when camping he uses renewable energy? Or perhaps he’s just an ‘ordinary Australian’: most of us support renewable energy.

Is it time for energy efficiency to shine?

President Obama and PM Abbott have apparently agreed that the November G20 meeting in Brisbane will discuss energy efficiency as a proxy for climate policy. There are also whispers around Canberra that ‘energy productivity’ (more economic output per unit of energy consumed) is gaining support.

The International Energy Agency has declared energy efficiency to be the biggest ‘source’ of energy for OECD countries. IEA also sees energy efficiency as the biggest and lowest cost contributor to climate response.

So maybe the signs are looking good—at last. It would be really nice to stop bashing my head on brick walls after 35 years!

But I’ll believe it when I see it. Unfortunately, many policy makers still believe that since energy efficiency is often cost-effective, the market will just adopt it, maybe with a bit of extra information. But it’s not that simple, and most effective energy efficiency policies involve measures that are unpopular with deregulatory, ‘small government’ thinking and powerful vested interests.

Why are developing countries shifting away from fossil fuels?

Fossil fuels create problems for developing countries, including China, despite the development benefits they bring. A US Agriculture Department study estimated that the $137 billion increase in oil import costs for developing countries in 2005 exceeded the official aid ($84 billion) they received.

Many governments subsidise energy, adding to budget pressures. Then there’s the indoor and outdoor air pollution, health impacts, fuel spills, inequity, fuel theft and more.

Governments are realising that improving energy efficiency, renewable energy and distributed energy systems can help solve all these problems. Shifting to efficient renewables (e.g. LED lighting powered by solar) reduces energy costs, improves quality of services, cuts the need for fossil fuel subsidies and reduces import bills. And it also happens to cut their greenhouse gas emissions.

Australian government and fossil fuel energy policy advisers have underestimated the significance of these benefits and overestimated the amount of energy needed in predicting export demand for their products. So they are repeatedly surprised as their profits decline.

Future global energy giants

It’s easy to get bogged down in the short-term battles for success in both climate change policy and our rapidly changing, cut-throat energy markets. But it is interesting to take a broader view.

We need to remember that energy is a ‘derived need’. That is, what we actually want are services, rather than energy. Receiving those services may involve consumption of more or less energy of different forms at different times, depending on technologies and behaviour. So the amount of energy we actually need can be very different from, and much less than, what we now use.


Businesses that sell high-efficiency, smart, flexible ways to provide services linked to energy will be winners. That’s appliance and equipment manufacturers, retailers and installers, builders, building product suppliers, financiers, internet-based businesses and specialist advisers who can market attractive packages. This could include smart systems that manage energy use to match availability, minimise costs and work with storage and on-site renewable energy. Integrating their energy-related offerings with other non-energy services will amplify opportunities. Finance schemes, home performance monitoring, maintenance contracts and optimised insurance packages are just a few possibilities.


Businesses that combine distributed energy, energy storage, energy efficiency and smart management are also looking good, especially in developing countries and at fringe-of-grid in developed countries.

Many niche markets are actually quite big. For example, many developing country electricity grids suffer frequent blackouts that impact on business productivity and quality of life. Many now use small petrol and diesel generators to cope, but this is expensive, dangerous, noisy and polluting. Energy-efficient equipment combined with storage, on-site low-emission electricity generation and grid-interactive capabilities can solve these problems.

Even larger markets will become available as our electricity industry shifts to time-of-use pricing or other pricing options, and all consumers, not just those with solar, see stronger signals to manage the amount and timing of energy use. For example, in NSW, afternoon to evening time-of-use prices are now over 50 cents per kilowatt-hour—a strong incentive to reduce usage from the grid at those times. And, if adopted, ‘capacity charges’ (which involve charging consumers for the peak supply capacity they use instead of the amount of electricity they consume) will drive more rapid adoption of storage and smarts to limit peak demand at a consumer level and avoid high costs.


At the other end of the scale we have energy-intensive industries that are global in scale: miners, mineral processors, metal processors, chemical companies and large-scale manufacturers and their like. Traditionally, they have sought large amounts of cheap and reliable energy.

But their world is changing. ‘Ores’ from landfill sites, wastes and replacement of existing building and equipment stock provide an increasing resource that can be more concentrated than that from traditional mining. For example, one tonne of old mobile phones contains 400 grams of gold, 80 times as much as is present in a tonne of typical gold ore (

3-D printing, biomimicry, green chemistry, dematerialisation, material switching and other changes are also transforming the fundamentals of energy-intensive industries. 3-D printing supports decentralised manufacturing and involves building up a product, instead of wasteful machining; green chemistry allows new materials to be created that are stronger, lighter, more effective or improve process efficiency; and dematerialisation uses less (or no) material to deliver a given service.

So it’s not at all clear how much energy these industries will actually need in the future, but it will be a lot less than conventional analysts predict.

Nevertheless, the bulk energy supply sector will still have a big market. But what forms of energy will it supply?

There are synergies between the oil industry’s drilling expertise and countries with large geothermal energy resources: sophisticated drilling capabilities are critical. The Pacific ‘ring of fire’ countries and others near boundaries of tectonic plates seem well positioned to access enormous amounts of reliable energy. The Philippines has been developing geothermal technologies since the 1970s, while Iceland has already attracted energy-intensive industries to use its geothermal and hydro energy resources.

Companies that can mobilise and adapt existing expertise and large amounts of capital are well positioned, as they can leverage these to gain market share in emerging markets. Countries with large renewable energy and mineral resources (both recovered and virgin) and whose governments support their development could also benefit—if they can capture a fair share of the returns from their exploitation. Australia’s solar resources offer opportunities: as Ross Garnaut has suggested, we could become a sustainable energy powerhouse by utilising our enormous renewable energy resources.

Countries and businesses that can produce forms of renewable energy suited to export and storage, and businesses that can link these to existing and new energy-consuming equipment that delivers valued services, will be well positioned.

Supply chains that can deliver sustainable transport solutions, in particular, will grow. Electric vehicles (including public transport and low-speed vehicles) will benefit from improving battery technologies and expanded renewable electricity generation. Technologies that use heat or electricity to produce renewable liquid or gaseous fuels for export and that are usable by existing vehicles will be of increasing interest. Oil-producing countries may be able to use their existing cashflow to fund such developments to maintain their market position in a zero-emission world.

Just as discovery of oil and gas in Bass Strait and the North West Shelf transformed Australia’s energy prospects and industrial development, the new renewable energy revolution will create surprises. Countries traditionally seen as importers of energy, such as Japan, could become energy giants, and threaten existing major energy suppliers.

There’s a message here for Australia, as we could be a big winner in the global race towards an energy-efficient, renewable energy future. But it would mean cannibalising our existing energy industries, a bit like the situation Kodak faced when it developed digital photography. Kodak lacked the courage to embrace the future. Will we?

Alan Pears 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.

This article was first published in ReNew 129


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Efficient hot water buyers guide

If your old hot water system has seen better days, maybe it’s time for an efficient replacement. We show you how solar and heat pump hot water systems work, what’s available and how to choose one to best suit your needs.

As the price of energy keeps escalating, the idea of being able to reduce energy use has never been more attractive. One of the biggest energy users in any home is water heating—it can account for around 21% of total energy use (on average, according to YourHome). Water-efficient appliances are one way you can reduce energy use, but far greater energy reductions are possible if you replace a conventional water heater with a solar or heat pump system.


Such systems have the added advantage of also reducing your greenhouse emissions. For example, for an average family the reduction can be as much as four tonnes of CO2 per year— the equivalent of taking a car off the road!

Currently only SA and Victoria offer state government rebates for solar and heat pump water heaters, but STCs (small-scale technology certificates; each STC is equivalent to the one megawatt hour of electricity the system will displace over a 10-year period) are still available across Australia.

STCs can save you a great deal on the cost of a new water heater, making it more economically viable. Note that the rebates and STCs are usually arranged by the supplier so you don’t need to do any paperwork to receive the discount. The price will probably still be higher than a similarly sized conventional water heater but the savings made in running costs will pay for this difference in 5 to 10 years in most cases.

How they work


A solar hot water system usually consists of a hot water storage tank connected via pipework to solar collector panels. These collector panels are placed on a (preferably) north-facing roof. The tank can be situated immediately above the panels on the roof (a close-coupled system), above and a small distance away from the panels within the roof cavity, or at ground level (a split or remote-coupled system). For split systems, a pump and controller are required to circulate water through the panels. The collectors are usually mounted at an angle of no less than 15° from the horizontal (the minimum angle for close coupled systems to ensure correct thermosyphon operation), although often a lot steeper to optimise the system performance for winter.

As the sun shines on a collector panel, the water in the pipes inside the collectors becomes hot. This heated water is circulated up the collector and out through a pipe to the storage tank. Cooler water from the bottom of the tank is then returned to the bottom of the collector, replacing the warmer water.

Some systems don’t heat the water directly but instead heat a fluid similar to antifreeze used in vehicle cooling systems. This fluid flows in a closed loop and transfers the collected heat to the water in the tank via a heat exchanger.


A heat pump is a process used in refrigeration where heat is moved, or ‘pumped’, from one medium into another. Air conditioners and refrigerators are the most common forms of heat pumps. For example, in a refrigerator, heat is pumped from the food and dumped to the air outside the fridge via the coil at the back.

Heat pump hot water systems are electric water heaters that concentrate low-grade heat from the air and dump it into the water storage tank. They are much more efficient than conventional resistive electric water heaters: compared to resistive heaters, they are generally capable of reducing year-round energy requirements for hot water by at least 50%, and by as much as 78% depending on the climate, brand and model.

The most common systems are air-source heat pumps, but ground-source heat pumps are also available. While their efficiency can be even higher than an air-source heat pump, they are a great deal more expensive and are often not economically viable. But if efficiency is the primary goal then they should be considered, especially if you are in the market for both water and space heating systems. We looked at ground-source heat pumps in ReNew 112.

The complete article looks at solar versus heat pumps, sizing, installation, retrofitting existing systems, warranties and more.

Read the full Efficient Hot Water Buyers Guide in ReNew 129.

Download the full table of manufacturers, suppliers and their systems.


Microinverter potential: your questions answered

Are microinverters a passing fad or a serious contender in the solar inverter market? Industry analyst Nigel Morris from Solar Business Services looks at some of the common issues people ask him about.


A microinverter is quite simply a very small inverter which converts DC electricity from solar panels into AC. The major difference between micro and string inverters is that microinverters convert the power from each solar panel individually, whereas string inverters convert the energy from a string of solar panels connected together in series. Microinverters are typically attached to the back of a solar panel whereas string inverters are usually mounted on the wall near your switchboard.

There are pros and cons to each type of technology, but after being involved in the industry for more than 20 years, one thing is clear: microinverters have a rightful place— and that place is growing.

A good place to start with the microinverter story is a bit of history. Many people don’t realise that they have been around for a long time; my former employer was supplying a company who successfully sold them in the late 1990s. True, they struggled a bit with reliability but the majority are still out there plugging away on Australian roofs. So they aren’t new and there has been some good long-term experience with the technology.

Having said this, string inverters have dominated sales and it’s only in the last few years that microinverters have come back with a vengeance. So what’s changed?

Clearly, technology has evolved a lot in the last 20 years.

It stands to reason that both string and microinverters have benefitted from this evolution. However, it could be argued that, in recent years, miniaturisation and electronics development has had a far bigger impact on the potential for microinverters, and that’s part of the reason they have taken off.

To put it in context, around 40% of all inverters sold in California (one of the world’s largest residential solar markets) are now microinverters, and locally, more than 10% of all sales are now microinverters. The world’s biggest microinverter company recently announced it had sold its five millionth microinverter; so the numbers are becoming very substantial.

To help understand more about microinverters, here are the issues I am most often asked about.

1: “It’s really hot on the roof. It doesn’t make sense to put electronics there and their life must be shorter as a result.” 

This is sound logic and pretty rational thinking. However, the reality is that well-designed microinverters can deal with this stress and most have 10 to 20 year warranties as standard. The big companies making good products recognised this challenge and set out to build in very high levels of quality and so dominate the market. Also, being smaller, microinverters don’t create or have to dissipate as much heat.

There are also a number of independent studies that demonstrate how microinverters perform under high-temperature situations which show that the reliability is very high.

With the better companies, we are also seeing very large-scale, micro-level manufacturing, which lends itself to really sophisticated quality systems; many are working with the same companies who make smart phones, as an example. One manufacturer also described to me how, by monitoring so many microinverters around the world remotely, they can feed back the data into their processes in almost real-time—a perpetual and real-time quality feedback loop.

So, these inverters are very sophisticated and can cope with high temperatures.

Read the full article in ReNew 129.

Disclosure: Solar Business Services consults to government, installers, retailers, wholesalers and manufacturers of solar equipment, including microinverters. This article was not paid for by any manufacturer and was produced at the request of the ATA.
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Fridges for caravans

Collyn Rivers looks at simple ways to improve the performance of fridges in caravans—particularly important when they’re running off batteries.

The energy use and cooling performance of fridges installed in caravans and motor homes is related more to installation than technical differences between the fridges. Few are fitted as makers advise, leading to increased energy draw and hence cost; this also applies to domestic fridges, many of which are enclosed on three sides and inadequately ventilated.


Fridges are simply boxes from which heat is removed from inside the cabinet and dumped outside. It is vital this dumped heat is removed effectively. Owners, many builders, carpenters and even some electricians perceive fridges as ‘back to front’ ovens that generate cold. This approach often leads to ventilation being ignored, resulting in poor installation—the bane of fridge makers.

Ventilation vital

All fridges require adequate ventilation spaces at their rear. However, that alone is not enough. Cool air must be routed to flow unhindered over the cooling coils (also called fins) and the heated rising air must be routed to where it cannot heat the fridge again. With caravans, this is outside the van, and for homes, it is also preferably outside. This is often poorly done in RVs, and all but ignored for self-installed domestic fridges.

Most caravan/motor-home fridges have rear-coil cooling. For this to work, cool air at the fridge base must be directed to flow over the coils. This is assisted by baffles (flat plates inserted into the airflow to change its direction and make it more effective); even baffles made from cardboard will work well. A high exit for the warmed air provides enough suction to draw in cool air.

With such fridges, adding more insulation on their sides, top and (if feasible) to the door also helps hugely. Even 100 mm is not overkill.

Skin ventilating

Some caravan and domestic fridges dissipate heat from their outer skin; these fridges have an enclosed back without cooling coils. These need a 50 mm side gap and ideally the top area should be vented to the outside. Cool air needs to be directed to the base of their sides, and back if it is used for heat dissipation (you can tell which sides are used for heat dissipation as they will get warm when running). Obviously, you must not insulate the sides and/or back of this type of fridge!

Chest fridges need provision for cool air entry, and ideally nothing located above them to roof or domestic ceiling height. Some have a fan that draws cool air in via vents in their sides and over the compressor’s associated cooling fins.

Chest fridges with coil cooling are aided by adding insulation. However, a few (such as the Indel and Ozefridge) dissipate heat from their side walls and so need a minimum 50 mm gap around the walls.

Collyn Rivers has published several books on solar electrical systems and caravanning. Visit Caravan and Motorhome Books

Read the full article in ReNew 129.