Editorial ReNew 126
ReNew takes to the road this issue, for our first-ever sustainable travel issue. Choices made when travelling can shed a different light on sustainability. Issues arise of fuel use, of impact on the places we travel to, and the energy and water use of the places we visit. Our route this issue focuses on the technologies and approaches that can help.READ MORE »
Our first stop comes courtesy of ReNew readers, with the innovative entries in our sustainable travel competition. We kept expanding the space allocation for this as your amazing stories kept coming, but we had to stop at 4 pages and 14 stories; we apologise to those not included, though we may follow up your stories down the track! From PV-powered river voyages to ingenious water saving to getting by on the smell of an oily family—these are great reads, and great examples of sustainability in practice.
Our journey continues as Olivia Wykes tracks down sustainable places to stay. The criteria were simple: we looked for use of renewable energy and water saving technologies along with a green philosophy. Some were nominated by people in our office and some we found online. Clearly, eco can be a selling point, not just for us, but for the wider online world.
Next, we hitch up the van and consider the technologies that can help reduce energy use when caravanning and camping. Collyn Rivers look at some possible traps for caravan owners using solar PV to power their travel. We examine the range of DC appliances available for van use, the weighty advantages of lithium batteries in caravans and just what you can cook in a solar oven (quite a lot!).
From travel to transport: A team at Swinburne University has plans to manufacture a commercial solar car and they’re taking ReNew along for the ride, with a series of articles as their design and build progresses. We also ‘mythbust’ what’s possible in EV charging right now, with Bryce Gaton explaining why an EV battery doesn’t equal a tank of fuel and just how fast an EV can be charged. And finally on our transport theme: cargo bikes are bikes with built-in carrying capacity, making it possible to cart kids and shopping with ease—and can be a viable car-replacement, as in Adam Peck’s case, documented here.
There’s much more inside, including all our regulars and three great DIYs. Our basics article explains common electrical terms with the nitty gritty of power, energy and what’s watt. Plus, we introduce a new regular section, Living Off-grid, showing off a home that’s off the grid for energy and water. We delve into the systems the home has, the appliances they can run and any issues they’ve had along the way.
Enjoy! We hope you have a safe, sustainable and relaxing summer. Let us know your stories and see you in the new year.
IN the past few months, the ATA has been busy conducting research and speaking with a number of groups across the country about community renewable energy. More than 1 million homes in Australia now have rooftop solar panels and many people are now exploring further possibilities in larger-scale community-owned projects. The Hepburn wind farm in Victoria, Denmark wind farm in WA and many other success stories overseas have been profiled in past issues of ReNew.
With funding from the City of Sydney and the Lord Mayor’s Charitable Fund, the ATA is developing an assessment tool for community-owned renewable energy. The tool will give groups guidance on the economics of their project—particularly important in the early stages of understanding feasibility and building community support.
The ATA is also a partner in a program headed by the UTS Institute for Sustainable Futures to develop a strategy to grow the community renewables sector. The Australian Renewable Energy Agency (ARENA) has recently announced funding for the program, which will include a National Community Energy Congress in Canberra next year.
If you are thinking of establishing a community renewable energy project in your area, get in touch with us here at the ATA.
Communities taking control of their own energy—clean and green energy—is the way of the future.
To keep up with ATA news and developments, go to our new website at www.ata.org.au.
Olivia Wykes tracks down sustainable stays in ReNew 126: holiday places that use sustainable technologies and/or have a green philosophy.
The criteria were simple – Olivia looked for places which noted sustainable technology or a green philosophy on their websites. Some were found by referral and some by searching on the web.READ MORE »
Olivia collected a bit more information on the sustainable technologies and design features of the places listed in the article. You can find these in the attached sustainable stays table.
Places were found either by referrals or online. Please note that we haven’t visited the places listed and inclusion in the table is not meant as an endorsement of one venue over another. Some information we received direct from the owners and some we found on their websites.
Read the full article in ReNew 126.
Solar panel buyers guide
We’ve contacted photovoltaics manufacturers for details on warranties, cell types, size and price to help you decide which solar panels are best for you.
Solar photovoltaic (PV) panels have a range of uses from powerful grid-interactive or off-grid rooftop installations to small DIY applications such as for camping or pumping water.READ MORE »
Over the last few years, grid-interactive rooftop installations have emerged as the most popular use of PV in Australia. Well over a million homes are now enjoying reductions in their electricity bills. Worldwide, demand from rooftop systems and solar farms has produced economies of scale leading to significant reductions in panel prices, especially for the larger panels used in such applications.
A solar installation consists of several components, depending on the application. This guide focuses on panels. For information on other components, system sizing and economic returns, see ‘More info’ at the end of the article.
How solar cells work
Solar cells produce DC electricity, similar to that from a battery. The amount of current produced by a panel of cells is proportional to the amount of light hitting the panel.
The basic mechanism of operation for a solar cell is as follows.
A solar cell is made of a thin slice of a material such as silicon. The silicon is modified by a process called doping with elements like boron and phosphorus to form what’s called a semiconductor P-N (positive-negative) junction inside the cell.
As photons in light strike the solar cell, they cause electrons (electrically negative sub-atomic particles) to cross the P-N junction, causing a voltage across the junction.
By connecting a load from one side of the cell to the other, the electrons will flow through the load, allowing the electrons to be harvested as an electric current.
The different technologies
A typical solar cell only produces around half a volt, which is too low to be of much use. Photovoltaic panels are made of a group of solar cells, usually with the cells connected in series to produce a much higher, usable voltage. There are three common types of solar cells: monocrystalline, polycrystalline and thin film.
Read the full article in ReNew 126
Solar on the move
Collyn Rivers has a long history of self-sufficient caravanning. He explains some of the traps when designing solar systems for caravans.
The number of caravans, motor homes and camper trailers currently registered in Australia is estimated at about 450,000. Many such recreational vehicles (RVs) are bought with solar panels factory-fitted while some have solar retrofitted or added as an expansion to an existing system.READ MORE »
However, feedback (from readers of my books, TAFE lecturers and auto-electricians I deal with in my business) suggests that many of these mobile solar systems fail to meet user expectations.
The problems are in many cases particular to mobile systems. Both exaggeration of what’s feasible and overly optimistic user expectations have a role to play in user disappointment, but there are also easily fixable issues that often are not addressed in the design and setup of such systems.
A major problem is that many RV solar systems assume that users will have overnight access to a 230-volt supply for recharging of batteries and overnight electricity usage. Most RVs include solar/battery systems sized for daytime use only, with only occasional (single) nights away from mains power (or without alternator charging via driving).
However, a substantial proportion of RV owners ‘free camp’, without access to mains power, often for many days on end. One estimate suggests that half of all regular RV travellers avoid staying in caravan parks whenever feasible. This type of usage is rarely allowed for in standard production RVs.
Installing mobile solar systems is also very different from domestic practice. Domestic installers rarely understand the complexities of RV electrical systems, in particular of interfacing solar with alternator charging, and the need to keep voltage drop under 0.02 volt.
Prior to around 2000, most alternators generated 14.2 to 14.7 volts (the latter being adequate for efficient auxiliary battery charging) but many are now only 13.8 volts and post-2014 may be as low 12.7 volts. To cope with this, dc–dc alternator chargers accept whatever the alternator produces and, by juggling volts and amps, optimise the output to best suit the charging regime of the auxiliary battery used.
Auto electricians have been hindered by RV electrics and solar not being included in their training (although I understand this is now being considered by several TAFEs).
This article explores the issues with mobile solar and offers some solutions. Despite the above-mentioned issues, adding solar to RVs (and boats) can work well, provided the installer understands what’s required. Most top-grade systems are by owners who have really done their homework or by a few specialists who do excellent work in this area.
Read the full article in ReNew 126
Can pedal power be used to replace a car? Adam Peck says yes, with his household replacing one car with two electric cargo bikes. He discusses the options.
Cargo bikes are becoming more and more popular these days. This article explains what they are and how to go about choosing one for your needs. It also highlights my family’s journey from a two-car family with two garage-bound pushies to our new one-car status with two well-used electric cargo bikes.READ MORE »
Cargo bikes have become very popular in Holland and Denmark. They are often used as a family transport vehicle in these countries’ bike-friendly cities—and also just for lugging bulky items around. Most of these are pedal-powered pushies due to the mainly flat roads and short distances.
The case for electric
In Australia, cargo bikes are becoming a more common sight around the roads, carrying kids and cargo. At least here in Perth, it seems that these are often electric cargo bikes. With our more hilly roads and longer distances, an electric cargo bike is more practical, making it more likely that it will be used frequently, and as a car replacement.
Cargo bikes are pretty heavy and the loads they carry can be even heavier, another reason why electric assistance is an attractive option. Most box-style cargo bikes (bakfiets, or box bikes) weigh 30+ kg, and can carry 80+ kg in the box, 40 kg on the back rack plus the weight of the rider—over 250 kg in total! With those sorts of loads, unless you have legs of steel, you might have to get off and push that bike uphill if it doesn’t provide some assistance.
Cargo bike styles
There are a couple of different styles of cargo bikes. I nominally split them into three categories: bikes, trikes and utilities.
Read the full article in ReNew 126
Cooking with the sun
Australia’s abundant sunshine should inspire more solar cooking, writes Stephen Williams.
I suspect cooking, unlike, say, water heating, is usually regarded as one of those energy uses that we can’t do much about. But most of us cook something every day and we often do it at times of peak demand, so this aspect of our lives deserves more attention if we want to reduce our fossil-fuel dependence and greenhouse gas emissions. With more people moving to time-of-use electricity tariffs, it is also worth looking at our options from a financial point of view.READ MORE »
So what are the options? Gas is not the benign fuel many once considered it to be and who wants to shell out thousands for an efficient induction cooktop. And even an induction cooktop (assuming you have the required type of pots and pans) doesn’t help when it comes to cooking in an oven. Could solar cookers come to the rescue?
Cooking with solar radiation
With Australia’s abundant sunshine, it seems we could easily use direct solar radiation more for cooking.
There are two main ways to cook using direct solar radiation. Parabolic mirrors concentrate heat to a focal point and are good for relatively quick cooking like frying or barbecuing. Solar ovens, on the other hand, are better for slower cooking and baking. This article focuses on solar ovens.
How they work
A solar oven is essentially a well-insulated box with a glass top (sometimes double-glazed) to let solar radiation in. Reflective panels direct the sun’s rays into the box. You place the food to be cooked in a thin, dark-coloured metal container, and place that in the oven. You then angle the oven to take best advantage of the sun’s position; you can move it during the day to track the sun, but this is not always necessary.
Read the full article in ReNew 126
Off-grid living: 10 years on solar
Rob Burlington and his wife Liz have been living off-grid for over ten years. He describes their self-sufficient solar and water setup, and the lessons learnt along the way.
My wife Liz and I live on 100 acres in the Capertee Valley between Lithgow and Mudgee, west of Sydney. We bought the block 17 years ago and would visit on most weekends, escaping from the outskirts of Sydney while we waited for our two kids to finish their education and run away from home and/or get married.READ MORE »
Our first semi-permanent structure was a cabin we built from a donated garage. On this we installed two 30 watt solar panels charging a 12 volt, 300 Ah battery through a 4 amp regulator to successfully run our lights. We had no hot water but a gas Consul fridge (these are excellent), a small two-burner gas stove and slow-combustion wood heater. The cabin became our full-time residence for the initial 18 months while we built what is now our home.
A modular and self-sufficient home
Our ‘new’ (now 11-year-old) house is worthy of a comment or two. After looking at various alternatives we decided on a RAL modular home. It’s a little different and creates some local discussion but is very practical and comfortable. The RAL factory is located in Ararat in Victoria and we cannot speak too highly of the quality of the workmanship or the support provided by owner-managers Reiny and Lorraine Loeliger and their staff. In fact, we still occasionally keep in touch even now.
We made the decision to go totally solar for two reasons. Firstly, we had always wanted to be as self-sufficient as practicable and secondly, even though at the time the cost of the panels was three times their current price, it was going to cost us at least $15,000 more to connect to the grid, by the time we paid for a transformer and three poles to connect to the high-voltage line that runs across one corner of our block.
Read the full article in ReNew 126
DC appliances buyers guide
You don’t need an inverter to run appliances off a battery-based renewable energy system—many AC appliances have DC-powered counterparts. Lance Turner looks at what’s available and why you might want to use them over AC versions.
Most homes have quite a few appliances, most of which run from 230 V AC mains power. However, if you live off-grid and use a battery bank and inverter for your electricity supply, then AC appliances running from the inverter are not always the best option. Even on-grid homes that have a battery backup power supply (which is becoming more common as users seek to shift loads to cheaper off-peak rates) can run DC appliances if desired.READ MORE »
While the thought of having no AC appliances might seem impossible for a modern home, for small homes, weekenders, caravans and those wishing to eliminate mains voltages, it is possible to have an all-DC home, albeit with some limits to the type and size of appliance that can be operated.
Many appliances actually run on DC, usually via an external or internal power supply. To do this, you are converting battery DC power into AC via your inverter, then back to DC via the device’s power supply—a double-level conversion that can waste quite a lot of energy. Further, just one small device will mean a large inverter needs to keep running, making that energy conversion process even more inefficient. It’s not uncommon for a two watt load to keep an inverter pulling 20 watts or more from the batteries.
Even if you have a large home with all the mod-cons, it is worth considering running some devices directly on DC, allowing you to eliminate some of the power supplies and plugpacks that litter the average home. This is especially the case if you are building or renovating, as it is the ideal time to run extra-low-voltage (ELV) cables without much added cost.
The main reason for using DC appliances is the independence of not relying on an inverter. Although modern inverters, especially the Australian and European-made ones, can be very reliable, all inverters inevitably fail, and they often do so at the worst times, such as during a heatwave when refrigeration is critical, or just before a long weekend, when replacements are unavailable.
Read the full article in ReNew 126
Know your renewables: electrical terms
There are many technical terms associated with electrical systems, but what do they mean? In the first of a two-parter, Lance Turner explains the most common terms you are likely to come across.
You don’t need to have a working knowledge of electrical systems to own a renewable energy system, but knowing the basic terms can help you understand your system—as well as enable you to explain problems to installers in a more cogent manner.READ MORE »
Electricity and electron flow
Electricity in a circuit is the movement of electrons (a subatomic particle with a negative electrical charge) through a conductor. A conductor is any material, often a metal, that allows electrons and hence electricity to flow easily through it.
Electricity in conductors (electrons) flows from negative to positive (called electron flow), but most people talk about current flowing from positive to negative (called conventional current). Electricity may also be a flow of positive ions (an ion is a charged atom; a positive ion is an atom with one or more electrons missing), usually inside batteries, where ions flow through the electrolyte. For most purposes, especially when talking about electrical circuits with appliances attached to power supplies by cables, we are talking about a movement of electrons.
Another two terms often used (and confused) when talking about electricity use and generation are power and energy.
Power is the rate at which energy is generated or used to do work, and is measured in joules per second (see box Joules and coulombs). Power has been assigned its own unit, the watt (W), but it’s important to remember that it is a rate, a bit like measuring your travelling speed in km/h. It’s an instantaneous measurement, at a particular point in time.
Energy measures the total amount of work done by a particular level of power over a period of time. The work may be producing heat or illuminating a light bulb or turning a motor. Energy is calculated as power multiplied by the duration of use, a bit like calculating distance as speed multiplied by time.
Read the full article in ReNew 126
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.READ MORE »
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
The Pears Report: Desperately seeking policy
Along with climate policy and energy market messes, a fridge purchase makes Alan Pears ask: are we condemned to waste energy because we live in Australia?
We seem to be on track to shift from the well-proven ‘polluter pays’ approach to carbon emissions (and other forms of pollution) to a ‘pay the polluter’ approach, using public funds. The government will limit how much will be spent, so we may not even meet our international emission reduction obligations, let alone our equitable share of abatement as estimated based on science.READ MORE »
Luckily the combination of grassroots action, technology change and the structural changes being driven by our over-valued Australian dollar is damping emission growth to some extent. And, under international and local pressure, the government may become desperate enough to reform energy markets to promote energy efficiency and even stop its attacks on renewable energy.
There are some potential positives from the shift away from using the carbon price as the ‘silver bullet’ to fix everything. As I explained in my last column, this led to serious cuts in energy efficiency programs, failed to confront our deeply flawed electricity market and disempowered voluntary local action by households, businesses and local and state governments.
However, a carbon price is a basic element of any effective climate response. It provides a (fairly imperfect) signal to emitters and investors, while also generating revenue to support adaptation, innovation and stronger abatement—forms of ‘direct action’.
Developing countries and energy
I recently came across a very interesting paper published by the World Academy of Sciences for the Advancement of Science in Developing Countries (Sustainable Energy for Developing Countries 2008, twas.ictp.it/publications/twas-reports). Two points really stood out.
First, the $137 billion increase in developing country oil import costs in 2005 exceeded the value of all official aid ($84 billion) to those countries. So if we can help them to reduce oil dependence through sustainable energy strategies, we can improve their wellbeing while also reducing pressure on oil prices and cutting greenhouse gas emissions.
Second, to provide access to the 1.5 billion people currently without basic electricity services would increase global electricity consumption by only around half a percent.
Since most of these people are in rural areas, small-scale renewable energy systems and energy efficiency are the most sensible solutions. A major sustainable energy transition could transform their lives and help to reduce sustainable energy costs for the rest of humanity.
Australia could also do with a strategy to reduce oil dependence. The Bureau of Resources and Energy Economic’s latest estimate is that by 2035 our net oil import bill would be over $40 billion and, by 2050, over $50 billion each year (assuming $100/barrel).
Some personal experiences and their implications for policy
I finally decided to replace my early 1990s fridge and old (but still comparatively efficient) TV in recent months.
The TV replacement was easy. I used the energyrating.gov.au website, then tweaked the brightness of the display to cut energy use to 25 watts for an 80 cm TV. My old 51 cm TV (by far the most efficient available when I bought it) used 55 watts.
The fridge was a different matter. I have been waiting since 2004 to buy the European A++ fridge I’d discovered being made in Turkey. I finally gave up and chose the most efficient 320 litre fridge available in Australia, rated at 300 kWh per year after finding I could not buy a similarly sized A+++ fridge made by the same manufacturer that’s available in Europe (see www.topten.eu). It is rated at 172 kWh per annum (around 210 kWh for Australian test conditions). The manufacturer’s Australian representative told me they had no plans to sell that more efficient unit (with a bigger freezer) here.
My new fridge is still quite impressive. It has a variable-speed compressor, hydrocarbon refrigerant and eutectic panels in the freezer that stabilise its temperature. But why am I condemned to waste energy because I live in Australia?
In comparing my new fridge’s performance with the old one, I have found that its efficiency and variable-speed compressor cut my peak demand by around 100 watts. Using the Productivity Commission’s recent estimates, this saves my electricity suppliers around $30 each year in infrastructure investment. It’s saving me around $75. Since I had to buy a new fridge anyway, and I paid no more than I would have for a less efficient one, I’m avoiding CO2 emissions at a cost of minus $300/tonne!
My old fridge went off to the Phoenix Fridge recycling program, where its refrigerant CFCs can be recovered and its components recycled.
But I have reduced my utilisation of the existing electricity supply assets, depriving their owners of revenue. Should I be charged more for this? See below.
AEMC contempt for 2 million voters
The Australian Energy Markets Commission has released a new report. In the introduction, the report states: “Effective consumer participation can contribute to more efficient markets…” AEMC should check its economics text books. Informed, empowered consumers are fundamental to the efficient operation of markets. Yet after 15 years, it’s still not happening.
The report argues that owners of rooftop PV should be charged more for reducing utilisation of energy supply assets. Can it point to any other market where this happens? Do gas suppliers compensate the electricity industry when people install a gas heater to replace an electric one?
Those who install and use large air conditioners and halogen lights have benefited from large subsidies for many years, yet no action has been taken to make them pay.
The AEMC is taking on over two million PV-owning voters on behalf of the incumbent businesses. When will our political leaders in COAG and the Standing Committee on Energy and Resources step in to sort them out?
Will a ‘thin pipe’ approach help electricity networks to survive?
The latest idea to help electricity network owners adjust to our rapidly changing technologies is to use low-capacity wires combined with distributed energy storage, generation and smart controls—instead of building capacity to supply peak demand.
This is similar to the ‘green grid’ approach that was proposed by solar identity Dale Butler at the 1993 Australian Solar Conference for fringe-of-grid electricity.
It sounded really sensible to me when I originally heard it. It still does, especially given cost reductions and technology improvements.
A typical all-electric home might use 10,000 kWh a year—if it could smooth its demand perfectly over time, it would only need supply capacity of 1.2 kilowatts: most homes have supply cables with capacity of 10 to 20 kilowatts. My latest calculations suggest a three-person best-practice all-electric home with all ‘mod cons’ could now use around 2000–2500 kWh per year. That’s a ‘smoothed’ demand of under 300 watts.
But is this the salvation of network owners? The answer depends on many variables. If a cluster of consumers can share back-up generation and storage, they may not need the grid at all. This back-up generation could be a small cogeneration unit, a fuel cell or output from hybrid cars.
So the challenge for network owners is to diversify their activities. Their market position will be sensitive to policy on whether non-networks can transfer power across property boundaries, or the capacity of smart businesses to find ways of getting around such limits by, for example, moving fully charged batteries to where electricity is needed.
In low-density areas on the fringe of networks, the ‘thin pipe’ will compete with stand-alone energy solutions. In existing areas, it may not be a lot cheaper to maintain a thin-pipe solution instead of a higher capacity one. But changes such as increasing development density and depreciation of network asset values may allow network owners to develop viable business models.
Apartment buildings, offices, retail and small-to-medium industry may provide ongoing markets for network owners. But they are also potential competitors if they gain the right to sell power to neighbours.
Nothing is clear cut in today’s rapidly changing situation.
Alan Pears has worked on sustainable energy issues since the late 1970s. He is one of Australia’s best recognised and most highly awarded commentators on sustainable energy and climate issues. He teaches part time at RMIT University and is co-director of Sustainable Solutions, a small consultancy.
This article appears in ReNew 126. You can buy it here.
Q&A: Instantaneous hot water
We live in bayside Brisbane in a four-bedroom, two-bathroom house with an old-style 250-litre electric hot water system. We are investigating which way to go if or when the system needs replacing. It is on the south side of the house and it does not appear to me to be a straightforward job to change to a solar hot water system. It is also near the main bedroom and I understand there can be noise issues with a heat pump system.READ MORE »
We installed a 1.5 kW PV system three years ago and have happily paid no electricity bills for that period and are $700 in credit. I have looked at Stiebel instantaneous electric hot water systems which, at the top of the range, seem to be appropriate for two-bathroom apartments and can cost around $1500.
The technology looks smart and I cannot see any regulatory objection to this option in Queensland. Are there any practical or plumbing issues in making this replacement? I am not a tech tragic—I would just like an opinion as to the appropriateness of instantaneous electric hot water for a house.
The main issue with a whole-house electric instantaneous system is that it needs a 3-phase power supply, as power draw may be up to 20 kW. Many houses have these now but many don’t. So whether you can install one depends on that. Bear in mind that, while energy use will be less than with an electric resistive storage system as there are almost no standing losses, it will still use a lot more energy than a heat pump or solar unit.
There’s no reason why you can’t install a solar unit. You would use a split system with the tank in the same place as the current tank and the panels on the roof on a tilt frame to overcome the south-tilted roof.
As for heat pumps, most are pretty quiet but noise ratings are given in the specs. You can also put them on a timer so that they don’t run overnight, instead kicking in at, say, 7 am. The most efficient domestic unit on the market seems to be the Sanden, which uses CO2 as the refrigerant. See www.sanden-hot-water.com.au
To read more questions and answers, buy ReNew 126.
Product profile: A very portable solar oven
We have looked at a lot of solar cookers over the years, but the GoSun Stove is the first to be based on an evacuated tube.READ MORE »
The oven consists of a 610 mm long evacuated tube with a 58 mm internal diameter and 76 mm external diameter. Inside this you slide a cooking tray which holds the food to be cooked or liquid to be heated. The tube is mounted between a pair of folding parabolic reflectors that concentrate the sunlight onto the tube, but also fold up to protect the tube when not in use. A carrying handle also doubles as support legs for adjusting the oven to face the sun.
The GoSun can accommodate up to 1.4 kg of food or 1.6 litres of hot beverage. It has an estimated heating capacity of 230 watts and can reach temperatures as high as 371 °C. Meals can be ready to eat in as little as 10 minutes.
There will also be a GoSun Mini, a more compact version for camping and similar uses.
The GoSun Stove comes with a two-year warranty on the tube which covers the cost of a replacement tube regardless of how it gets broken! The other components are guaranteed from manufacturing defects for one year.
RRP: US$279, $129 for the Mini. The GoSun Stoves will be released early 2014, but are available for pre-order now. For more information and to order go to
Product profile: Portable power without the fumes
The need for a portable power source for off-grid, intermittent use is quite common, but most people resort to a petrol or diesel generator. Aside from the fumes, noise and hassle, gensets are about the most expensive way to generate electricity there is.READ MORE »
The Yeti1250 portable solar-powered generator from Goal Zero is designed to provide power for temporary low-demand applications such as caravans, motorhomes, camping, sheds and shacks.
It consists of an enclosure housing a 100 Ah sealed lead-acid battery, a 12 V 20 A MPPT charge controller and a 1200 W inverter. Included in the package is a roll cart for easy portability, two 30 W solar panels, carry bag and cables. Also available is a second battery kit (including connectors) to double the storage capacity, a solar add-on kit that includes two 30 W panels, carry bag and cables, and a tripod for mounting four panels. Maximum solar array size is 240 watts.
There are two 10 A solar charging ports and a 20 A power socket charging port. Outputs include two 220 VAC power sockets, several different 12 V port options and three USB ports.
RRP: $2200 for the Yeti1250 kit, $620 for the additional solar kit, $417 for the battery kit and $170 for the solar tripod. Available in Australia from Off-grid Energy, ph: 1300 334 839, firstname.lastname@example.org, www.offgridenergy.com.au