Do It Yourself

ReNew articles to make home more sustainable


Efficiency on a budget: Easy, low-cost retrofitting

Alan Cotterill takes us on his journey retrofitting a standard brick-veneer home for energy savings.

Eleven years ago we bought a near-new four-bedroom brick-veneer house in Wagga Wagga, an inland town in NSW, in an area that experiences hot summers and cold winters.


It’s a fairly standard house for the area, set on a concrete slab, with a verandah running the length of the eastern side. The house is long and narrow, on a north–south axis, with only the double garage facing north. Excluding the double garage and verandah, the house size is 183 m2 and the window area is 19% of the floor area.

R3.3 batts were already installed in the ceiling, along with reflective foil in the walls and under the colorbond roof. We found that an evaporative cooler provided effective summer cooling on most days and later-fitted gas central heating provided winter heating, albeit at a cost.

There were several areas, however, where we found we could significantly increase comfort and decrease bills, through simple retrofits. Some of these are detailed below, including information on any issues we encountered and how we overcame them. Hopefully this will be of assistance to others planning similar retrofits.

Downlight gaps

The house’s original lights were 12 V, 20 W halogen downlights. A 30 cm clearance without insulation batts is required around each downlight to guard against overheating and fire. There were 18 halogen downlights, meaning 18 gaps in the insulation. Thus, there was about 6 m2 of ceiling without insulation.

So, four years ago I did a simple changeover from 20 W halogen globes to 3 W LEDs ($15 each at the time), using the existing fittings and transformers. I later covered each downlight with a downlight mitt ($18 each) and, ensuring that all transformers were held above any insulation to prevent overheating, I filled in the insulation gaps up to the mitts.

Each mitt comes with a wire support to secure it to the plasterboard and a wire tower to secure each transformer above the mitt and batts. Installation of the mitts was easily done from below, standing on a ladder. Because they are soft, you can simply collapse them, insert them through the hole for the light fitting, and open them up inside the roof cavity and position them over the hole. Then you just push the light fitting back in place, as they are held in the ceiling with spring clips.

The main energy saving wasn’t from the significantly lower wattage for lighting, but from the improved ceiling insulation, which reduced energy costs, especially from winter heating.

There were some problems, however. The original transformers were designed to run with a higher wattage than the 3 W LED globes I used, resulting in some flickering and some transformers failing. With what is available today, I would, instead, plug in an entire new 12V LED downlight unit, which includes a matched transformer ($28 from a specialist electrical trade/retail outlet).

Also, the 3W LED bulbs were bright enough for general socialising, but a little dim for reading. We’ve since added newer 8 W LED bulbs selectively, such as over a chair used for reading or over a work area in the kitchen. Not only is there now plenty of light, but the beam angle of 95 degrees (rather than a narrow 33 degrees) gives wider and more even illumination.

The choice of downlight mitt also needs to be considered carefully. Mitts need to be matched to the type of light fitting and may need a ventilation hole. Mitts without ventilation holes can be used with fittings of the gimble type, where the light can be tilted in its fitting. This tilting action requires a small circular air gap, flush with the ceiling, and this allows some ventilation around the bulb. But, where fixed fittings are used, mitts with ventilation holes are required. We used mitts with ventilation holes to avoid any risk in the future; for example, a new homeowner could unwittingly replace a gimble fitting with a fixed fitting.

Read the full article in ReNew 130.

run on sun

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.

fridges caravans

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.

IMG_5557 400px

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

vy wormfarm 400px

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

Raspberry Pi and meter

Low-power, low-cost computing

If you need to be energy frugal, you can still have a real computer for real tasks that won’t cost the earth. Lance Turner shows you how.

OVER the years we have looked at many low-power computers in ReNew, and there are new models out on a regular basis. Many of these have considerable computing power for their size, but most cost in the realm of several hundred dollars and many are simply not available in Australia.


The needs of computer users vary widely—some need higher processing power whereas others, who do everything in a web browser, need far less. The same applies to energy consumption. If you live with a small renewable energy system, your main priority may be to minimise energy consumption.

So just what options are there for really low-energy computing? Let’s take a look at the options, and then look a bit more closely at a low-cost option with surprising power.

Phones, tablets and phablets

Mobile phones, tablets and phablets (basically big-screen phones) are everywhere, and they may be all many people ever need to get connected. They have considerable processing power, are portable and are, by design, energy sippers. But they also have numerous drawbacks that make them unsuitable for many computer users.

Trying to type anything more than a few words on a tablet’s on-screen keyboard is a real pain, at least to anyone used to using a ‘real’ keyboard. Most tablets can take some basic peripherals, such as Bluetooth keyboards, or come with optional keyboard docks that also extend battery life. These can make a tablet more like a tiny PC and can push them into the realms of usability for users who may otherwise have overlooked them as an option.

Read the full article in ReNew 127.

Solar hydronic collector on roof

Low-cost solar heating

Solar hydronic systems don’t have to be complex and expensive. Chris Hooley describes his simple and low-cost solar hydronic heater.

WINTERS in Melbourne used to be predictable: four months of sog from May to September. However, whether due to climate change, El Niño or simple drought, the winter of 2010 had a particular impact on me in that I kept coming home in the late afternoon to a very cold house, lit by shafts of brilliant winter sunshine. “Wouldn’t it be good,” I thought to myself, “if I could catch some of that energy and keep the house warm?”


I had a rough idea of what was available to make water hot using sunlight. Being a devoted handyman and incurable tinkerer, the seed of an idea took root and grew. My basic parameters were simple: I wanted a completely off-grid, stand-alone system that would ‘catch’ some energy in cooler months and put it to good use, without having to be plugged in or modified seasonally. Since the house already had gas central heating, the system would not need to meet all heating requirements but would rather take the edge off the cold on days when the sun happened to shine.

With this in mind I prowled eBay and mentally drew up plans until I could stand it no more and started buying parts. The key elements consisted of an evacuated-tube array piped to a fan-forced radiator. The collector heats the water and a pump transfers the hot water to the radiator in the house. A fan forces air through the radiator and into the room, heating it.

The system would be controlled by a thermo-switch and powered by a pair of 20 W PV panels. To avoid it freezing solid overnight or boiling away in summer and to eliminate the need for seasonal draining and refilling, I resolved to fill the whole system with car radiator coolant.

Read the full article in ReNew 127.


Warm sun, cool house

Martin Chape describes how he put an old evaporative cooler to good use, automating the system in the process.

Last year I promised myself that I was going to try and use the excess heat that my solar hot water system generates to cool my home.It was my intention to do this by extracting the heat from the hot water tank, either directly or with a heat exchanger replacing the redundant electric heating element, and use either an absorption or adsorption cooling process.


However, after one or two unsuccessful experiments, I put this idea aside for a while and instead decided on a much easier build: an evaporative cooler using solar PV to power it directly.

My plan was to source a discarded evaporative cooler rooftop box and replace the AC-powered fan and pump with 24 volt DC versions to be powered by a solar PV/battery system. I would also add a control system for monitoring and controlling the system remotely. Evaporative coolers are simple devices that draw air through wet absorbent pads. This cools the air through evaporation, and has the advantage of using a lot less energy than a refrigerated air conditioner. The main issue with using a second-hand unit is the cost of replacement pads, as they degrade over time and may become mouldy if unused for a while.

Step 1: sourcing the cooler rooftop box
I figured there ought to be plenty of those evaporative cooler rooftop boxes discarded after they wear out, break down or folks switch to other forms of air conditioning. I put the word out and within days my nephews had dropped off the parts for a Bonaire Brivis they’d found on the side of the road!

However, I ended up deciding to use a Bonaire Celair instead, which I bought for $50, as the Celair has thicker pads than the Brivis and the cost of pad replacement is lower.

Step 2: replacing the fan
I decided to source a fan used in the automotive industry, an 18 inch (457 mm) 24 volt DC fan, commonly used to cool the radiators of the big haul pack mining trucks.

The Celair’s removable fan mount made modifying it easy. However, the original fan was larger (19 inches), so I got a plastics company to make me a spacer to close the gap at the outer edge of the blades.

Read the full article in ReNew 126


Monitoring a rooftop solar hot water system

David Gobbett is using a Netduino microcontroller to monitor the temperature fluctuations in his rooftop solar hot water system.

For decades, the first or only solar appliance installed by many Australian households was a rooftop solar hot water system. My parents installed one on our family home in Adelaide in the mid 1970s. In my current home we installed a conventional 300-litre rooftop system in 2006. Superficially at least, the design seemed to have changed little over the intervening years. In both cases an electric booster was connected to off-peak power, which is switched on automatically by the power meter from midnight to 7 am each day.


To reduce our energy consumption over summer, we turn off the electric booster at the main switch during late November to late March, and we still have adequate hot water most of the time. However, occasionally we unexpectedly get caught short of hot water, and at those times it’s been frustrating having no way of knowing how hot the water in the tank actually is.

Another concern with switching off the booster is that there are potential health issues when hot water system temperatures are allowed to drop below 60 °C. Lévesque et al. (2004) indicate that Legionella bacteria can grow in water temperatures up to 45 °C, but that growth stops above 55 °C, and over 60 °C the bacteria are killed. Even in hot water systems with the thermostat set to 60 °C, the lower part of the tank can remain at temperatures that are optimal for Legionella growth. It would be nice to avoid this—but that would entail having a way to sense the temperatures in the tank, which is high up on the house roof.

A project idea was sparked when a friend showed me that he was using a small microprocessor board to log solar PV power outputs. He had also connected a sensor on his water meter so he could log household water consumption. This inspired me to start on my own project to get a better understanding of what the temperatures in my solar hot water system were doing.

My interests in this project were to:
• minimise unnecessary power usage
• know when we’re running low on solar hot water, so the booster can be turned on
• minimise any risk associated with Legionella.

Setting up the temperature logging

Although I have experience as a computer programmer, I had never programmed microprocessors or worked with such things as temperature sensors. After some internet research I decided to use 1-wire devices (1-wire is a technology by which sensors and other devices can communicate). I took the plunge and purchased:
• 1-wire temperature sensors (DS18S20; 10 of these cost $18). These sensors operate over a temperature range of -55 °C to +125 °C. Several of these sensors can be connected to a single cable to form a mini network where each sensor has its own unique identification.
• a USB to 1-wire adaptor, to allow me to connect the sensors to my PC for testing (DS9490R; $28)
• a Netduino Plus microcontroller (US$70) which included a network socket and micro SD memory card slot. (See side box ‘Arduino style microcontroller boards’).

I proceeded to build the system in small steps. First I soldered three of the 1-wire sensors to a length of old telephone extension cable and then used the 1-wire to USB adaptor to connect them to my PC. Using free software (from I was reassured that I had wired them correctly (phew!). Then with some extra lengths of phone extension leads, I inserted the sensors under the insulation at one end of my hot water tank and immediately saw big differences between the top, middle and bottom of the tank, as well as temperature changes in response to hot water use in the house. This was encouraging since it showed that I could get useful temperature readings from the outside of the tank.

Read the full article in ReNew 125


An introduction to making biochar

John Hermans explains what biochar is, its environmental benefits and the process he uses to make it.

It was not until I read The Biochar Revolution by Paul Taylor that I began to think about biochar’s agricultural and environmental value, and decided to make the effort to make biochar at home. This article won’t attempt to summarise the book but rather focus on how I’ve used its approach to benefit our household.


What is biochar?

In a word, biochar is charcoal. Crushed into small particles, the charcoal can be used to improve the nutrient- and water-holding capacity of soil, and so improve plant growth and productivity.

Biochar is a relatively new word, but biochar’s use has been documented as far back as the Amazonian Indians, who created tera preta or ‘black earth’. These nutrient-enriched soils retain much of their higher fertility, and their char, thousands of years after they were created.

Biochar can also permanently lock up carbon to help neutralise our carbon footprint. In this world where governments are largely failing to mitigate a climate catastrophe, this is another path for a ‘bottom-up’ global effort.

Why make biochar?

Biochar is now commercially available as a soil conditioner, at around $10/kg, but if you are not confined by allotment size, it is quite easy and cheap to make instead. You can also then control what goes into it.

In my case, I have been using the sticks and leaves that I would otherwise have burnt to reduce summer bushfire risk.
Making it has also given our household another option for becoming truly carbon neutral, other than planting trees. Biochar means we can now lock up atmospheric carbon in the soil, potentially for thousands of years, rather than have it re-enter the atmosphere when the ground litter rots or is burnt. Once it is added to the soil, it remains mostly inert to oxidation and hence does not re-enter the carbon cycle. At the same time, it increases the soil fertility in our extensive food garden.

Biochar chemistry

When organic matter is burnt in the open air, it nearly all burns to ash, with only very small amounts of unburnt black char. It is possible to make char in a controlled open-air fire by extinguishing it early with water, but smoke, heat, flames and gas emissions will result.

In biochar manufacture it is preferable to use enclosed steel drums to control oxygen delivery and to burn most, if not all, of the carbon monoxide, hydrogen and methane which otherwise are given off in smoke. If unburnt, most of these gases have a far higher greenhouse gas effect than CO2. When the fuel is burnt in controlled conditions, they are converted to CO2. An added advantage is that it is a fairly smoke-free production process—far more neighbour-friendly than open-air fuel reduction burning.

Read the full article in ReNew 124


Urban strawbale

THERE has been no shortage of vision and hard work poured into this lovely strawbale house built on a suburban block in Melbourne’s west.

Built with non-toxic materials to be energy-efficient, long lasting and with a small footprint, it was a pleasure to visit and take a look at this home over lunch.


The house has the beautiful feeling inside that is characteristic of strawbale houses. It’s a settled quiet that puts you at ease. “The straw was chosen for its insulation quality and also for its beauty. Straw also creates such a melodic ambience in the house,” says owner-builder Nikki.

The first thing I noticed is how the house enables the many social and creative visions of its makers. Designed to feel and function a little like a small town hall, the central space of their urban strawbale home includes a stage (complete with power and AV concealed in the floor) and a commercial kitchen where Nikki plans future cooking classes, drawing inspiration from their abundant edible garden.

The house is the product of two years visioning, planning and designing and one year of hard work by a committed team led by Nikki. The core building team was made up of Nikki and her son, his friend and two building apprentices in the process of retraining from chefs (is this why the kitchen is so great?), with skilled tradespeople coming in and out as needed.

Nikki says, “We chose the vacant lot (500 m2) as the land was close to main street shops, ten minutes walk to the railway station and most importantly, right next to the beautiful, magnificent Werribee river.“

They did the design themselves, and included a lot of what they wanted in their three-room house. It has two-storey high ceilings, storage cupboards that stretch almost to the roof (accessed by a ladder), a 19,000 litre galvanised water tank, a Wattworks greywater treatment system and solar hot water. In summer it keeps them cool with fans, insulation, moveable outside shades and semi-transparent inside blinds. As they plan to stay for a while, they also designed the single-storey house for wheelchair access.

Read the full article in ReNew 123


A lithium battery lawnmower retrofit

When it comes to high power and high capacity for less weight, nothing beats lithium batteries. Lance Turner describes his rechargeable mower upgrade.

Mowing lawns is a bit of a chore but it seems hard to avoid. Unlike most people, I don’t have to futz around with petrol, oil and pull starts to get my mower going, I just turn the key and off it goes.


There’s a lot to be said for rechargeable electric mowers, even ancient ones like my 11-year-old Husqvarna. Despite its age, the only real maintenance it’s had was a replacement set of lead-acid batteries a few years back. But like all lead-acid batteries, deep cycling means they only last a few hundred cycles at best, and these had begun struggling to give me more than 15 minutes run time. So it was time for an upgrade.

I looked around for replacements and realised that a pair of good quality 12 V, 20 Ah deep cycle lead-acid batteries were going to cost me close to $200 after shipping, so I decided to use a lithium battery pack instead.

I checked to see what was available and wasn’t really happy with the standard 24 volt lithium battery packs designed for electric bikes and the like, as they were generally made from many small cells, often around 3 Ah capacity, connected in a series/parallel arrangement. I don’t like batteries that contain paralleled strings of cells, even if they are all fitted with a proper battery management system, so I decided to assemble a pack myself.

There were a few options but I decided to use eight 15 Ah cells from Lithium Batteries Australia, as they have been around a long time, and are known to be robust and have very long lifespans, even when undergoing deep discharges. These cells are supplied with hexagonal end-caps that slide together to let you make a solid battery pack without the need for an external case. Copper battery linking bars and bolts are also supplied.

I assembled the pack in a 3–2–3 arrangement as can be seen in the photos. This gave me a pack with the closest approximation to the original battery size. Even so, the battery was longer than the original units were wide, so I had to mount the battery pack running front to back instead of side to side like the original batteries.

Read the full article in ReNew 123


Making a shed liveable

Vadim Pantall explains how he and his family converted an ordinary shed into a comfortable off-grid home while planning a more permanent dwelling.

We wanted to set up the way we live on our farm to have minimal impact on the surroundings and to be as self-sufficient as possible, but without losing too many luxuries. Some of the decisions were made for us, given the farm was never going to get a phone or mains water, and power was a little distance away and therefore would have needed a few poles (at a fair cost) to get it to our dwelling.


Our current dwelling is a shed converted into a house, so we call it the Shouse. Below is how we provided for the energy and water needs, as well as what we did to make the Shouse liveable for our family of three.

Well supplied with water
Council required us to have a minimum 90 kL of water storage. When pricing tanks, it worked out only a few thousand dollars more to get a tank that was significantly bigger, so we settled on a 255,000 L steel tank. With over 200 acres we figured space wasn’t an issue! This tank filled up in a winter and a half, with no water consumption. We’ve since also added an additional 23,000 L tank and have plans for more as I do have a bit of a fear of losing our whole water supply should a pipe burst or the water in one tank get contaminated.

Off-grid generation
For the first few years we ran on a diesel generator. Unfortunately, much of this energy was wasted as the generator produced more power than we needed. It was actually quite convenient for us and not for the power companies that while we were looking at both grid and renewable options (including combinations of both), a couple of things happened.

WA was having significant power price increases, and these didn’t (and still don’t) look like easing up. Also, we had a few arguments with Western Power about some changes in billing practices for a house we were renting. It was perfect timing for a power company to annoy us, so we settled on not hooking up to the grid at all!

We checked out a couple of options and initially signed up for a package that would use the diesel generator, but included batteries and an inverter. This would reduce our generator run time to around four hours a day. Renewable generation could then be an add-on for the future.

Read the full article in ReNew 123

The cold-air intake at the back of the ash compartment underneath the firebox (ash tray removed) after a few months of use. Note the shiny appearance
of the duct with no trace of smoke presence. The stove is 10 years old.

Improve wood heater efficiency with a cold-air intake

In ReNew 123, Tom Chalko describes a simple modification to make wood heaters more efficient.

SOME people argue that there is no benefit in using a cool-air intake for wood stoves; that the best source of combustion air for a wood stove is the room that they are trying to heat. But if that’s the case, why then isn’t combustion air for car engines drawn from inside car cabins? All modern cars strive to draw the coldest air possible for fuel combustion. The colder the air, the denser it is and more oxygen per unit volume it contains, which should then assist combustion.


Cold-air intake experiment
To test this, I installed an outside cold-air intake in the ash compartment of my Morso 2110 wood stove in a way that enabled me to compare the behaviour of the stove with different combustion air supplies—just by opening and closing valves under various atmospheric and other conditions, without touching the fuel or altering the fire.

I found the cold-air intake was astonishingly better than a room-air intake. I would say that there was no comparison, and with so many advantages it makes me wonder how I lived without a cold-air intake for so many years.

Read the full PDF of the article here: Improve wood heater efficiency.

Or buy ReNew 123

My computer

DIY: Make that old PC run like new

Every year, many thousands of computers are replaced by new ones in Australia. But is this really necessary? Lance Turner explains how to make that old PC run like new.

THE BIG problem with so many computers being replaced is that most areas of Australia still don’t have convenient recycling facilities. Sure, councils offer hard waste collection, but most of that goes to landfill. For computers, especially older ones which contain toxic materials such as lead and brominated fire retardants (BFRs), placing them in landfill is about the worst thing that can happen to them, as the toxic materials will eventually leach out and end up in groundwater.


But is it possible to make an older computer run much faster—fast enough to compete with a more modern machine? Provided you’re not into heavy video editing or gaming, the answer is, yes, you can. If you’re like the average person and mostly browse the web, write letters and edit your happy snaps, then an older machine can easily take the place of a newer model. Even for more demanding tasks, an older PC can be made to perform very well.

What slows them down?
Computers get slower for two main reasons.Firstly, the demands on them increase over time. As new versions of software are released with more features, the amount of code in the software and hence the memory it requires to run also increases. Whether it is your operating system or one of your favourite applications, new releases can slowly degrade performance until the computer feels like it’s running at a snail’s pace.

Also, many people have a habit of installing software they simply don’t need. Google, Yahoo and Ask toolbars in browsers and iTunes, Google and Adobe updaters are common forms of this, but there are many others. And what makes things a whole lot worse is that many of these applications will load part or all of themselves when the computer first boots. If you are not using that application, then it is running for no reason and simply sucking up computer resources (memory and processor time) for no reason. The more programs running on your PC at any one time, the slower it runs.

Read the full article in ReNew 120.

Making my home free from the grid

Martin Chape has made an independent power supply for his lights and home office. Next it will be the whole home as he tries to escape his electricity retailer.

As a semi-retired engineer I have always dabbled in technical projects and probably always will. This latest project came about when my electricity retailer Synergy cut the rate paid per kilowatt-hour of electricity sent to the grid to 7c per kWh, to coincide with the introduction of the West Australian government’s feed-in tariff in 2010.


The thought that, after my solar feed-in tariff ended in ten years, my system would become merely a cheap generator supplying all the local air conditioners at a profit to my power company annoyed me. Especially as I would have to fund any maintenance to the solar PV system from my pension.

So I decided not to invest further in additional grid-connect panels but rather, to put my dollars into making my home office totally independent of the grid. I built an off-grid solar power system with 12 volt battery storage, supplying a 240 volt inverter at the lowest cost possible.

Online shopping for parts
I sourced a pair of new 6 volt deep cycle lead-acid batteries from a local retailer. The brand was Interstate Batteries model GC2-HD-UTL, with a capacity of 216 amp-hours each. I purchased a 200 watt, 12 volt monocrystalline solar panel for $500 from eBay store LHP Power, which came with a 25-year warranty, and found a low cost 10 amp solar controller from a Chinese eBay supplier.

The solar controller has three sets of connectors, one for the PV panel, one for the load, and the third for the battery bank. The solar controller prevents overcharging the batteries, unwanted discharge of the batteries through the PV system at night, and disconnects the load to prevent battery damage if it becomes run down.

After purchasing a couple of low cost 800 watt 12-240 volt inverters from another Chinese eBay store I was ready to roll with my first system.

Read the full article in ReNew 119.

DIY cargo bike – A recycling adventure

Inspired by the abundance of cargo bikes across Europe, Simon Waugh built one at home from salvaged materials.

A while back I was lucky enough to enjoy a trip to Europe, where I was struck by the widespread use of bikes for everyday use. In Amsterdam I was particularly impressed by the ubiquitous cargo bike, to be seen at every turn ferrying children to and from primary school, bringing home the groceries or delivering goods for small businesses.


Often the next step after looking at a bike is trying it out, but unfortunately the opportunity never presented itself and I returned home wondering what it would be like to use one of these amazing machines for real.

I started looking at them on the internet and discovered that I could purchase an imported Bakfiets cargo bike quite easily, but the prices were enough to make my eyes water.

Birth of a shed project
Somehow the idea of owning a cargo bike just wouldn’t go away and six months later I hit on an answer—I’d build my own! Perhaps I have too much spare time, but all of those shed projects have to start somewhere.

What about raw materials? During an early morning walk around the local streets I noticed that the piles of junk waiting for the next council kerbside collection included several bikes, in various states of repair. Some were complete wrecks, while others were in reasonable condition and even too good for what I had in mind. I returned home with a couple of likely candidates: a venerable Malvern Star ‘racer’ and a ‘supermarket’ mountain bike, complete with sprung fork.

A conventional cargo bike has a smaller front wheel, typically about 20 inches (51 centimetres). This is for practical purposes, allowing the front fork to fit in front of the cargo box and making it easier to arrange a steering linkage. However, among my collection of ‘it’ll be useful some day’ bits and pieces, I had a front wheel complete with a 200 watt motor, which seemed like a worthwhile addition to the project. I couldn’t see any way of building the motor into a smaller wheel, so I decided that my cargo bike would have a full size front wheel.

Read the full article in ReNew 119.

Cute little ute

Ralph Hibble has driven more than 3000 kilometres in his electric Citroën since registering it last July.

Knowing that Citroëns are lightweight vehicles suitable for electric car conversions, I have taken a Citroën 2CV, previously crashed between two four-wheel drives and converted it to electric. I am an electric vehicle and Citroën enthusiast and already own a vintage Citroën AK van, plus a more modern Citroën hatchback.


With a badly damaged boot from the crash, I decided to make it a utility, with 160kg of batteries bolted to the back tray. The original gearbox and disc brake have been retained, close coupled to the electric motor, while the engine, exhaust, fuel tank and air cleaner have all been removed.

The front and rear bumpers were destroyed in the crash and have been replaced with aluminium bumpers. Standard 2cv tail lights have been recessed into the ute back and a Citroën logo has been glued in place.

To read the full version of this article in PDF format, click here.

eVolvo: A Swedish EVolution

Looking for the perfect medium-sized car for an EV conversion, Greg Sievert and Wayne Bowers decided it just had to be a Volvo!

Click here to download the extended version of this article.


A shortened version of this article originally appeared in ReNew 117.

Sth view of finished collector rack400px

Farmhouse solar hydronics

In issue 116 we visit Ian Hill’s 1970s home which has been retrofitted with solar-powered water and household heating. Here’s is a detailed version of that article, with more of the nitty gritty on system design for those about to embark on such a project.

Nearly nine years ago we made a tree change to active, semi-retirement. We bought a farm in West Gippsland, left behind seaside Frankston, and went niche beef farming for a change in lifestyle. We’re happy to say it was a good decision.


The farm came with a large home—16 rooms over five levels with two open-plan living and entertaining areas—the main selling point being we liked this style years ago.

The three concrete slabs stepping down the rolling red soil hills already had hydronic in-slab tubing, heated from a diesel furnace along with the tap water. Cooking was done by bottled gas, and there were three slow-combustion wood heaters in the two living areas.

Philosophy and design

We are very keen on sustainability and want to minimise our carbon footprint, both in the home and our farm’s beef production. We were prepared to spend some money converting the heating system for a large reduction in running costs and emissions. The farm has many large trees and limbs are always falling, so using solar-powered heating and hot water, boosted by a wood-fired heater, seemed like a sensible idea.

We found the solar collectors we wanted and set system parameters. Our plumber designed and built the conversion, changed the skylights, re-flashed the house and updated much of the water collection. We added ideas as it was built over several months.

The home

The climate is cool temperate with few frosts and the house is sited on a southern slope in foothills.

We are at latitude 38.005°. There is some unavoidable morning shading in winter from a roadside glider possum habitat of magnificent eucalypt trees over 40 meters high, 30 meters away and uphill on the northern road boundary. The outside temperature ranges between 2°C and 42°C but the house has such a large thermal time constant that living areas stay between 17°C and 22°C in winter, and no more than 25°C after a run of hot days.

The house design is classic 1970s double brick with rough-sawn, exposed beams in eight meter cathedral ceilings.It had hardwood french and other windows with single-glazing throughout, and sad plastic-vented skylights. Everything was coloured mission brown.

The designer ignored the 16 kilometre view to the Strzelecki Ranges and the valley below, and modern principles of house alignment for passive heating and cooling. However, at least the sun does not load up the interior. There are a few, small windows to the east, with excellent shading from canvas blinds, and large french windows to the west. These are shaded by a pergola and close battens. The home’s north face is stepped into the hill and the windows are totally shaded by a brick cloister with archways: a very sensible design providing a great spring breakfast area.

The kitchen, living and lounge rooms, study and billiards rooms are open plan and interconnected on three levels, which does create air currents, especially with such high ceilings. We have been slowly renovating, as one does with a retirement income.

The aim is to convert major glass in living areas to high-efficiency glass and to install as much double glazing as we can afford. So far our plumber has retrofitted seven double-glazed, openable skylights. The local glazier replaced 11 clearstory windows and made three panels openable to draw up cooling air from the lower levels when a summer cool change arrives.

We use pressurised tank water for most of the home, buildings and farm animals. There are 245,000 litres available in concrete tanks, linked by a 50mm buried ring main. Our local irrigation contractor built a fire sprinkler system for all buildings on the farm, which was essential when the wind changed during the Black Saturday bushfires in 2009. Our 100-year average rainfall is 1100mm; we received 1178mm in 2010 so we always have an excess of stored water.

There is a 1.5kW solar power system on the roof, bringing an income and well offsetting the minor energy drain from the small pumps moving water into the hydronic heating and up to the solar collectors.

Hydronic system components

Our heating system has three sources of heat:

• 36 solar-collecting vacuum tubes (rated at 5.8kW)
• wood-fired, slow combustion fire, with flue water jacket
• two gas-fired instantaneous hot water boilers.

The service courtyard where most of this hybrid heating and hot water system is hidden looks Heath Robinson, but it is a credit to our local green-accredited plumber at Baw Baw Plumbing and his team. He always knows about the latest efficiency innovations and was a terrific speaker at our Landcare group’s Green Energy field day.

Heat storage

A custom made 1000 litre stainless steel tank with 75mm of insulation and a small header tank is the heat storage. It’s similar to those made for the local dairy industry. Hot water is not drawn from this water but via three heat exchanger coils in the tank, with the solar one at the base, the hydronics one at the centre and the hot water service at the top. Each is 11 metres long.

Solar collectors

I contacted eight retailers advertising evacuated tubes. Disappointingly, not many responded.

From sellers’ claims, the most efficient collectors I could find were Ritter (labelled APR), a Chinese-made German design imported by Sunplus CPC. We bought 1.6m long evacuated tubes in banks of six, with parabolic mirrors to direct extra sunlight under the tubes. Our budget limited us to triple the normal number of tubes recommended for hot tap water and a 1000 litre hot water storage tank.

The collector bank of 36 tubes is fixed to a 1.6m by 4.4m aluminium frame facing 15° west of north. I asked for it to be tilted steeper than the roof’s 17° at a calculated winter solstice angle of 60° to collect maximum energy for winter. This reduces excess summer yield and steam problems.

Importantly, the plumbing route for the tubes allows us to add more down the track.

The north roof with evacuated tube collectors for the heating system and a 1.5kW solar power system.

Inside the solar control and storage area

Solar-heated water pumping

This is a rainwater-filled closed loop heat-exchanger. Water from the storage tank coil is lifted about five metres up to the solar array by a 3-speed 30 watt 240v hot water pump with throttling valve, giving infinitely variable flow. It usually runs at 0.2 bar boost. A Zilmet model 20013 50 litre cylinder stores system over-pressure up to four bar from summer days, backed up by a blow-off valve to save water loss on hot days.

Relief valves

Four high spots in the solar array and wood heater circuits have auto air-bleed valves, allowing only air and steam to escape.

Wood-fired slow combustion heater

We changed the third wood heater to a gas unit for quick response to a cold home.

After the first winter with the new system, an existing free-standing Saxon unit in the living room was retrofitted with a 550mm tall stainless steel heat exchanger in the first part of the flue. It burns quietly from late autumn to early spring on wind-fallen mountain ash and blackwood harvested around the farm. Water to the flue exchanger is drawn from the base of the storage tank and delivered back to the top. Piping is about 25 metres long and rises about 3 metres. It is insulated with 25mm thick foam tubing and cased in colorbond. A 240v thermostat in the output pipe in a wall behind the heater senses output temperature and controls another small circulating pump at the storage tank, moving two litre slugs of hot water at 50 °C into the storage tank every few minutes. This heater provides around half our total hydronic heating in winter.

Gas boilers

Tap water is delivered via an instantaneous Rinnai V1500 gas boiler which adds heat if stored water is not 50°C. There are no adjustments for the home owner. Electronics in this unit can be damaged by our emergency home generator, so we cannot run the hot water when mains power fails, which it does for several hours at least four times per year.

Hydronic water supply is delivered to the mixing valve via a Sime Format 34e instantaneous gas boiler, rated at 11.2kW to 34kW, large enough to heat the whole home on its own. It adds heat if needed and has user-adjustments for output temp (set to 35°C). Its instruments display output temperature and pressure. The pump within this unit is also triggered by the thermostat in the master bathroom, sending heated water to a Hydrotherm P-600 Platinum tower rail, 2.2m by 600mm wide, helping provide some extra hydronic heating to the bathroom.

Both boilers stay on in summer as they do not use any gas unless heating water.

Heat users

The house is heated by hydronic coils in five zones in three concrete slabs at descending levels in the house, plus a fan-assisted radiator in the living room. Two manifolds are fed from a mixing valve, and water circulated by five, 240v Grunfos thermostatically-controlled 3-speed pumps.

We have only activated the outer coil on the lower slab coils. We are very fortunate that it flows via the master toilet and bathroom, laundry, kitchen, two guest bedrooms and to the living room on the lowest slab.
Hot tap water runs throughout the house with all piping insulated with 25mm thick foam tubing. External piping is further encased in 90mm stormwater piping.

Water delivery controls

Hydronic water is blended by the original tempering valve supplying two hydronic manifolds. Tap water is held to 50°C by a Reliance Heatguard Ultra tempering valve. This setting can be altered.

The three room thermostats in the home are very clever Honeywell model CM 907. They can be programmed in time blocks for every day of the week, can be over-ridden for one time block, set to a fixed temperature and adjusted for daylight savings. The lower slab thermostat in the living area also masters the upper slab in the entertainment area. The second thermostat in the upper level study controls the mid slab. The third thermostat in the master bathroom controls water to the towel rail.

Solar control

The electronic differential controller, made by Whitnic Services of NSW, gets its data from 10volt thermistors, one at the array output and one at the storage tank top. It has three modes and a red light indicates the pump is on, which I positioned to see from the back door.

Gas supply

Gas was originally supplied by a bank of 40kg cylinders. These were replaced by a 190kg truck-filled tank, with pressure reducers at two boilers, and a circuit supplying the guest kitchen and fast-response gas heater in the living room.

Owner adjustments and monitoring

I wanted to monitor input and tank temperatures, so I bought three $10 electronic indoor/outdoor thermometers with remote sensors and mounted them next to the differential controller. I can feel the input arriving from the solar array, with one attached to the lowest hot connection on the storage tank, indicating roughly how much hot water is in the tank, and the other reads water delivery to the taps. These have max/min displays as well, useful for checking array performance or pump adjustments. An old clock-type dial indicator measures the temperature of water returning from the hydronic system, a rough indication of how much heat is in the slabs.
The electronic gauges are particularly useful to know how much heated water is available for a big load such as a spa fill or running the lounge room radiator. Monitoring incoming temperatures from the array allows me to tune up the flow rate for best performance just below steam occurring, and tells me if we have any problems when it’s pumping. An improvement would be digital readings from the differential controller’s thermistors.
We can adjust slab heating times in two zones and towel rail temperature, and boost heat in the lounge room by activating the fan-assisted radiator. We can control the temperature of the water leaving the fire water jacket. We cannot alter the temperature trigger points for the solar array. It might be useful to keep it pumping above 80°C to stop a steam blockage occurring.

Current settings

Thermostats have six available time block settings, with the initial settings for the slab thermostats listed below:
6am          20°C
8                18°C
Midday   18°C
5.30pm   18°C
8.40pm   13°C
10.30pm 8°C

When there’s a run of low solar-energy days we run the wood fire hotter. When there’s sunny days predicted, we can use less wood, or not light it.

As autumn starts, we open the hydronic valves and drive the wood heater hard to put as much heat as possible into selected slabs prior to cold snaps and overcast winter days. On a run of overcast days we open the damper on the wood heater.

Fine tuning and problems

We run the collector pump at the lowest of three speeds and fine-tuned the flow to 1.5l/min on the advice of the plumber. We’ve learnt that in summer we need to double the flow rate to avoid excessive pressure build-up.
The original thermistor on the solar array burnt out after one year and the surrounding insulation was charred! The new importer tells me the replacement thermistor is a tougher type.

Anything that stops the circulating pump while there’s sun on the vacuum tubes can create a blockage in the circuit that the circulating pump cannot overcome. When the thermistor on the roof fried, and when we lose power when the sun’s on the tubes, pressure builds up and the closed loop finally drops below it’s 0.2 bar pre-set pressure. This stops circulation for that day and we lose a little water as steam. When the pump is alive again it fails to get water circulating if the array is in sun. So if the system pressure gauge is zero, I know circulation has stopped and must be topped up. To fix it we fit the garden hose onto the fill point just below the pump, and run cold water until there are no bubbles passing the sight gauge. Our plumber has suggested an automatic supply for this.


Particle filters in the inlets to the tap boiler and both tempering/mixing valves need to be cleaned annually, the latter by removing the fitting gland, which is not a good design.

The Zilmet pressure storage tank needs its quiescent air pressure checked annually, and the whole tank replaced every five years. Pressure cylinders on my Citroen last indefinitely, with re-gassing, so we’ll see. The system needs to be de-pressured for accurate pressure checks.

The solar collector array needs to be hosed periodically to remove leaves.


Our gas costs about $730 for 550 litres per year, but my urban mate pays a fraction of our price! We really only use significant gas when we have guests, then it goes through the litres when the large boiler is doing a lot of the home heating. We average about 66 mjoules of gas per day in winter, and as little as 19 at other times. The Elgas truck doesn’t come from October to late April. In 2010 we used half the gas of 2009, mainly due to better windows and remembering to keep bedroom doors closed. We will get further significant reductions when our window conversions and internal glass partition are finished.

Total changeover cost, including towel rail and some bathroom alterations, was about $11,500 against an estimated $17,000. The local shire gave us a rebate of $250 and we received another $6900 in rebates. If hydronic slab heating was built into a new home, it may not be any more than other hot water and heating systems. Our 44 RECs were not sold because the supplier did not have an approved system with the tank size we used, so we missed out on around $1500. That’s a little plus for the environment as energy companies had to find an extra 44 RECs somewhere else.

Changed family habits

The dog is often asleep on the hottest sections of the hydronic loop, always in doorways or on the top of stairs. The cats love the laundry benches in winter.

To minimise the generation of greenhouse gas and gas bills we use most of our hot water first thing in the morning, giving the solar array the first opportunity to recover hot water lost. We built a wooden, pull-down rack below the laundry ceiling which now dries much of our cold weather washing.

We need to shut off the hydronic valve when spring is well-entrenched and must remember to open it when the first cool weather is predicted after Easter.

What next?

We are part-way through replacing most open-plan area windows with double glazing, with low U and SHGC value glass and argon gas in the space.

At the moment glaziers are installing a glass, openable air barrier at the top of the living area. This will zone the home into separate living and entertaining zones, reducing wood demands and cold air currents up the kitchen.
Stopping heat escaping is next. After a government-funded home assessment, this air entrapment work was to be financed by the now defunct Green Loans scheme. Another task is resealing all doors, and chasing air leaks along the brick-ceiling interfaces throughout the living spaces and external walls. This is to stop bushfire embers and smoke ingress; the home is to be a refuge as we’ve spent a lot of money on a 10-hour fire sprinkler system for all buildings.

I’m also planning to have the roof re-pointed; it’s amazing how much heat escapes from the fabric of the cathedral ceiling when you remove a capping tile on a cold day.

Much of the living room slab could be heated, in cooler weather, by direct sunlight, and possible when we replace dark green fibreglass on the pergola outside with clear sheets and retractable shade cloth.

I’d like an automatic system to over-ride the pump control in the main gas boiler, so the rail can be heated when the slab hydronics are off. This will probably involve some extra 240v relays to override the pump’s under-temperature and gas supply controls, which stop the pump when the hydronics are not on.

Due to firebox corrosion we will soon replace the wood heater. The next one will have a wet-back for more hydronic capability.


Green-accredited plumbers—Baw Baw Plumbing, Buln Buln East

Solar equipment suppliers—Phazer, Warragul

Glaziers—Walkies’s windows and glazing, and Warragul glass and glazing

Flue heat exchanger, gas room heater—Cosy heaters, Warragul

Monitoring thermometers—Dahlsens, Warragul

Fire protection system—The Farm Depot, Warragul

Gas heater installation—West Gippsland gas services, Warragul