Buyers Guides

Independent advice on sustainable products at home.

heating buyers guide

Heating buyers guide 2016

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Heating can be a large proportion of energy use in the home. Lance Turner looks at what efficient options are available, including hydronic and reverse-cycle air conditioners.

OUR previous heating buyers guide looked at heat pumps (commonly called reverse-cycle air conditioners) due to their high efficiency, low cost and simple installation. Later in this guide we take another look at reverse-cycle air conditioners and their advantages, and list the most efficient units currently available.

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However, there is another form of heating that not only lets you choose a heat pump as the heat source, but other energy sources as well if they are more appropriate. That system is hydronics.

Hydronic heating
THE BASICS

Hydronic systems consist of a heat source (commonly called the boiler) to heat water, and one or more pipe circuits which have the heated water flowing through them. Each circuit incorporates one or more radiators, which emit warmth into the room.

Most hydronic systems have multiple circuits, so you can heat all or only part of a home, allowing you to leave unused, closed- off rooms unheated to reduce energy use.

Water is circulated through the system using low-pressure pumps, and circuits are turned on/off by electrically operated valves, usually controlled by an electronic controller. The controller enables a system to be programmed to heat certain parts of a home at particular times—for example, heating the living areas during the evening and the bedrooms just before bedtime.

Hydronic systems are recognised to have a number of advantages over other forms of heating. The heat being either underfoot or close to it (through the use of skirting radiators or panel radiators mounted at floor level) means that you get the feeling of warmth with lower ambient room temperatures than with space heating. Also, there is generally very little air movement with hydronic heating, reducing the potential cooling effect of airflows produced by convective heating such as reverse-cycle air conditioners or ducted gas systems.

Read the full article in ReNew 135

Click here to download the full buyers guide tables in PDF format.

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Solar panel buyers guide 2016

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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.

Large-scale manufacturing of solar photovoltaic (PV) panels has led to significant price reductions in recent years, to the point where they have become a common sight in the Australia urban landscape. From powering domestic dwellings to providing power for camping or even hot water, PV panels are everywhere.

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Or almost everywhere. While there are well over a million homes in Australia sporting solar arrays of various sizes, there are still many homes without solar.

This article aims to provide up-to-date guidance for those people looking at purchasing a solar installation, whether that’s a new system or an upgrade. It includes types of solar panels and factors to consider when buying them. The guide focuses on PV panels only. For information on other components that may be used in a solar installation (e.g. inverters), system sizing and economic returns, see ‘More info’ at the end of the article.

Types of solar panels: monocrystalline, polycrystalline and thin film
Solar panels are made from many solar cells connected together, with each solar cell producing DC (direct current) electricity when sunlight hits it. There are three common types of solar cells: monocrystalline, polycrystalline and thin film.

Both monocrystalline and polycrystalline cells are made from slices, or wafers, cut from blocks of silicon. Monocrystalline cells start life as a single large crystal known as a boule, which is ‘grown’ in a slow and energy-intensive process. Polycrystalline cells are cut from blocks of cast silicon rather than single large crystals.

Thin-film technology uses a different technique that involves the deposition of layers of different semiconducting and conducting materials directly onto metal, glass or even plastic. The most common thin-film panels use amorphous (non-crystalline)silicon and are found everywhere from watches and calculators right through to large grid-connected PV arrays.

Other types of thin-film materials include CIGS (copper indium gallium di-selenide) and CdTe (cadmium telluride). These tend to have higher efficiencies than amorphous silicon cells, with CIGS cells rivalling crystalline cells for efficiency. However, the materials used in some of these alternatives are more toxic than silicon—cadmium, particularly, is a quite toxic metal.

Read the full article in ReNew 134

Click here to download the full buyers guide tables in PDF format.

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New choices in lighting: An LED buyers guide

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The move to LED lighting has become mainstream, with more options appearing constantly. Lance Turner takes a look at what’s available.

For many homes, lighting is one of the most overlooked aspects. Incorrect lighting can make a room unpleasant to be in, or make it more difficult to perform tasks such as reading or cooking. Getting it right can take a bit of effort, and though this guide won’t answer all your questions about lighting design, hopefully it will give you a headstart when thinking about the types of lighting to use and the questions to ask.

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With almost all lighting technology moving towards LEDs, this guide focuses on LED bulbs. Even the reasonably efficient technologies such as fluorescent tubes and compact fluorescent lamps are rapidly being replaced by LED lighting. It’s likely that within 10 years, most other light sources will have disappeared in favour of the robustness, longevity and energy efficiency of LEDs.

What is an LED?
LEDs (light emitting diodes) are unlike any other lighting system. They contain no glass tubes or heating filaments, instead using a small piece of semiconductor material (as used in computer chips) that emits light directly when a current is passed through it.

LEDs produce light in a range of colours, without the need for coloured filters; thus, to get white light, a phosphor is used over a blue or UV LED chip, similar to what’s used in a fluorescent tube.

Note that the LED is actually the small light producing element(s) in a light bulb or fitting, but most people now erroneously refer to LEDs as the entire bulb or fitting.

LED specs
There are a number of specifications that are useful to consider when buying LED lights.

Bulb wattage
All light bulbs have a wattage rating, which measures how much power they consume. This is where LEDs have a shining advantage over older, more inefficient technologies. For domestic LED lights, the rating is usually between one and 20 watts, compared to a typical incandescent rating of 25 to 100 watts.

Light output: lumens, LUX and beam angle
Many LED bulbs include an ‘equivalent-to’ wattage rating, showing the wattage of the incandescent bulb that the LED bulb is equivalent to in terms of light output. For example, a six watt LED bulb might be rated as putting out the same amount of light as a 50 watt incandescent.

This ‘equivalent-to’ rating is based on the light output in lumens. The lumen rating of an LED bulb, usually included on the packaging, measures the total light output, relative to the response of the human eye.

For bulbs that are suitable for general room lighting—those with wide beam angles, above 60 degrees, but preferably 90 degrees or more—matching lumens for lumens should give you the result you need. Thus, for these types of lights (these are generally found in the common Edison screw, bayonet or ‘oyster’ fittings), the ‘equivalent-to’ rating should be all you need to determine if the bulb is a suitable replacement.

For directional lights, often known as spot lights, it’s a bit different. These are lights with a smaller beam angle, up to around 60 degrees. Such lights are generally used for task lighting, directed onto a desk or work area. Halogen downlights are an example of these—it’s because of their small beam angle that so many of them were needed to light a room! For these spot lights, small differences in the beam angle can make a big difference in how bright the light appears. Many people have had the experience of buying an LED bulb which was meant to be equivalent to a 50 watt halogen, but found that it appears much less bright. The lumens may have been lower, but more likely the beam angle was narrower, creating a bright light directly under the light but darker patches around it.

Read the full article in ReNew 133.

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A micro-hydro buyers guide

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A micro-hydro turbine can be one of the cheapest sources of reliable electricity—if you have the right site. Lance Turner looks at what’s available.

Solar panels are the energy generators of choice for most domestic renewable energy systems, but there are other forms of renewable energy generation that can provide supplementary or even primary power generation if you have the right site.

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One possibility is a micro-hydro system: the production of energy from water, with domestic-scale systems sized up to 100 kW. If you have a rural property with a suitable water source, then micro-hydro may be a good option, particularly if a high tree canopy precludes the use of solar panels or wind turbines.

The kinetic energy stored in flowing water can be considerable. You just need to look at the deep pools often found below large waterfalls or how the rocks in a creek are worn smooth by the flow of water. To get an idea of the forces involved, try aiming the jet from an ordinary garden hose at your hand. You will feel the force of the water striking your hand and being deflected. This is basically how many hydro turbines work.

Run-of-river versus dammed
Hydro systems fall into two broad designs—run-of-river and dammed systems.

Run-of-river systems simply take water from a high point of the river or creek, pass it through the hydro turbine and return it to the river or creek at a lower point. Only a portion of the water in the water source is diverted through the system.

In a dammed system, the water source is dammed, producing a water reservoir. The height of the water behind the dam produces the required head for the hydro turbine (the head is the term commonly used to describe the vertical height of the water column that is producing the pressure to run the turbine).

Most domestic systems are run-of-river types, as these produce the least environmental impact and are the cheapest to install. They are also the type your council and/or water authority is most likely to approve. After all, damming a water source can cause considerable environmental disruption and should be avoided.

Some run-of-river systems do use a small dam, known as pondage, to ensure an adequate flow into the intake pipe. The amount of pondage can be small or may be increased to provide more reliable energy output from the turbine during times of lower water flows in the water source. It is possible to use pondage that is separated from the water source completely, to prevent any negative effects on the water source.

Read the full article in ReNew 132.

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A battery buyers guide

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The battery bank in a stand-alone or backup power system can make or break the system. Lance Turner examines what to look for in a battery bank and how to get the right battery for your needs.

An extract of the article is below, or read the full article in ReNew 131.

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You can also download the full table of manufacturers, suppliers and their batteries.

Article extract:

As more people look to go off-grid due to the ever-increasing cost of electricity bills and the unreliability of the grid in some areas, the market for energy storage systems is set to expand massively in the next few years. That’s not to say there aren’t options available already—there are plenty, for both off-grid and on-grid use.

There are two main approaches to energy storage: you can buy the required number of individual batteries or cells and have them installed and connected together on-site, or you can buy an integrated ‘storage system in a box’, containing batteries, safety equipment such as fuses and disconnects, and possibly a charge controller or other equipment.

As we looked at integrated storage systems in ReNew 128, this guide looks mainly at the first of these options: buying batteries or cells for assembly into a large battery bank. We also don’t cover batteries for electric vehicles (EVs); see our All About EVs article on p. 38, for a discussion of batteries for EVs.

Battery selection is critical

Arguably the most important part of any renewable energy system involving energy storage is the battery bank. All other parts of a system can be upgraded or added to quite easily, but if you select too small a battery or one not suited to your needs then your system performance, and the battery’s usable life, will suffer. Unfortunately, the battery is the component most likely to be specified incorrectly, either due to a lack of understanding of how batteries perform, or budgetary constraints—the battery bank is now the most expensive single component in the average stand-alone power system (SAPS).

Battery requirements

Batteries are designed for specific applications. In this article, we look at batteries suitable for use in renewable energy systems, either off-grid, in stand-alone power systems (SAPS), or on-grid, in a grid-connected system with storage for either load shifting or backup power.

Over time, and with changes in technology, the requirements for domestic energy storage systems have changed quite considerably. Once common, 12 volt DC systems are now mainly found in caravan and camping situations, though small SAPS systems may still run at this voltage.

Current homes instead usually run AC-based systems. They have 24 or 48 volt (or even 120 volt) DC power systems with inverters to convert the power to 240 volts AC, and use efficient AC appliances.

Such systems need large capacity battery storage to cope with the high surges required to start the motors in appliances such as water pumps and vacuum cleaners, and ensure long battery life through shallow discharge of the batteries. Generally speaking, the deeper a battery is regularly discharged, the shorter its lifespan will be.

Useful characteristics for batteries in renewable energy systems are:

  • long life under a continual charge/discharge regime
  • ability to withstand numerous deep discharges over the life of the battery (e.g. in winter when it may need to be discharged more deeply)
  • low maintenance requirements
  • high charging efficiency; some energy will be lost when the batteries are charged, but the lower this is, the better
    ability to perform over a wide temperature range.
  • low self-discharge; all batteries slowly discharge themselves over time, but the lower this is, the better.

Common renewable energy system battery types

The most common chemistry used in household energy storage systems is still the lead-acid battery. These have been around for more than a century and work well provided that the appropriate size and type are selected, and they are used and maintained appropriately.

As demand for more advanced energy storage grows, there has been much focus recently on lithium-based batteries. For household energy systems this generally means lithium iron phosphate (often called LiFePO4 or even just LFP) chemistry, which has seen considerable advancements in the last few years, with a steady decrease in cost as the scale of manufacturing has increased.

Nickel-cadmium batteries were used for a period in stand-alone power systems. However, their high cost and relatively high toxicity means they have all but disappeared. A related but much safer chemistry is the nickel-iron battery.

Other battery types found in commercial systems, though generally not used in domestic-scale systems, include flow batteries, sodium-sulphur batteries and even flywheel batteries.

Lead-acid batteries
Lead-acid batteries consist of lead and lead-sulphate plates suspended in a sulphuric acid electrolyte. They are a reliable and well-understood chemistry that is relatively forgiving to mild overcharging, although over-discharging can impact lifespan considerably.

In years past, the most common type of lead-acid batteries in household power systems were flooded cell types. At the time, these offered the longest life and best value for money over their lifetime.

However, in more recent times there has been a trend towards prioritising lower maintenance requirements, resulting in an increasing number of systems being installed with sealed lead-acid battery banks. With these, you no longer need to check cell electrolyte levels, and the corrosion by acid that occurs with flooded cells is virtually eliminated.

Sealed lead-acid batteries come in two main designs—AGM (absorbent glass mat) and gel cell. Gel cells have their electrolyte as a gel to prevent spillage and stratification (where the acid density of the electrolyte varies from the bottom to the top of the cells), while AGM batteries have liquid electrolyte, like flooded-cell batteries, but it is absorbed into fibreglass separators between the cells to provide the same benefits as the gel type. Either type can usually be mounted in either an upright or sideways orientation.

Lithium batteries
While lead-acid chemistry is still the mainstay of the renewable energy storage industry, this is steadily changing, with other battery chemistries such as lithium potentially offering considerable advantages over lead-acid batteries.

Lithium iron phosphate (LiFePO4) batteries have higher storage densities (more energy can be stored in a battery of a given volume), greater power densities (smaller batteries can produce greater instantaneous power outputs), much better charging efficiency and longer lifespans than any lead-acid formats.

They can be more expensive to purchase initially, but this is rapidly changing as the push for lower cost batteries for electric vehicles as well as domestic energy storage systems has spurred on many manufacturers to reduce prices and increase availability.

In addition, due to the longer life and higher efficiency of lithium cells, and the fact that their capacity is not affected by discharge rate like lead-acid cells, enabling lower capacity banks to be used compared to lead-acid, lithium batteries are already a cost-effective option when total cost of ownership is considered. While lithium batteries are still a relatively small segment of the domestic energy storage market, this is set to change in the next few years.

Lithium batteries must have an effective battery management system (BMS). This enables each cell in the battery bank to be individually monitored when charging and discharging. Overcharged cells and cells discharged below the minimum voltage point can fail, so a good BMS is a must.

Buy ReNew 131 to read the full article which includes:

  • other battery technologies
  • battery specifications (capacity, battery formats, voltage, battery charging efficiency, battery life)
  • sizing the battery bank for a stand-alone system
  • maintenance
  • battery sustainability
  • safety and a home for your batteries
  • battery bank do’s and don’ts
  • secondhand batteries.

 

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Greywater system buyers guide

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Although many regions no longer have water restrictions, water is still a very precious resource in a country as dry as Australia. Greywater systems let you use water at least twice, which makes good environmental sense. Here, we look at what systems are available.

The advantage of greywater is that we produce it on a daily basis. In many cases it can be diverted to the garden with minimal effort and cost in a number of different ways. You can opt for a low-cost DIY system using something as simple as a greywater diversion hose attached to your washing machine outlet. Or you might be considering installing a full commercial greywater system. Whichever way you go, there are a number of things you need to consider.

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This guide highlights the main issues associated with greywater reuse. There are many choices available and there is no single solution for all circumstances. Therefore, the more research you do, the more suitable your system will be for your particular situation.
There can be many restrictions as to where systems can be installed. In some cases, especially for retrofits, installing a greywater system will require major works—this can make the system cost-prohibitive.

Greywater sources

Greywater is any wastewater generated from your laundry (sinks and appliances), bathroom (baths, showers, basins) and kitchen (sinks and dishwashers), before it has come into contact with the sewer. It does not include toilet wastewater, which is classed as blackwater.
However, while kitchen and dishwasher water is technically greywater, unless you are treating it, it is recommended that you don’t use this water source. Kitchen water only makes up around five percent of total water consumed in the average home, yet it is considered the most contaminated. This is partly due to high sodium levels from some dishwashing detergents, particularly from dishwashers, solid matter such as food waste from rinsing dishes, as well as fats, grease and oils from cooking and cleaning, which can all damage soil structure if allowed to build up.

What’s in the greywater?

The chemical and physical quality of greywater varies enormously, as greywater is essentially made up of the elements that you put into it.
Generally speaking, pathogen and bacteria content is low in most greywater sources (unless you are washing contaminated items, such as nappies) and, provided you take steps to minimise potential contact, such as using subsurface delivery of the greywater, it is of minimal concern.
Choosing the right cleaning products is perhaps one of the most important elements in reducing the risks associated with greywater reuse. The elements phosphorus and nitrogen are nutrients necessary for plant growth. If these elements are kept to a suitable level by choosing cleaning products with low phosphorus and nitrogen content, they can replace the need for fertilisers for gardens and lawns—the nutrients can actually be utilised by plants and soils.
The main concerns with greywater are salt build-up from cleaning products and increased pH levels in the soil. Both can have a detrimental effect on your soil and plants. However, they can both be mitigated by monitoring, conditioning your soils for optimum health and taking care to choose cleaning products with little or no salt.

Salt

Salt build-up in soils, particularly sodium salts, poses perhaps the greatest risk associated with untreated greywater reuse. The accumulation of salts in the soil can damage soil structure and lead to a loss of permeability, causing problems for soil and plant health. The main source of sodium is powdered washing detergents and fabric softeners that use sodium salts as bulking agents.
Concentrated powders and liquid detergents generally have fewer salts than the average powdered detergent. There are many powdered detergents on the market that now have low or no sodium content.
For more information and a list of products that are greywater friendly, go to www.greysmart.com.au (see the resources section for information on this site).

pH levels

Generally speaking, pH levels outside the optimum range of between six and seven affect the solubility of soils and hence plants’ ability to absorb essential nutrients. As most gardeners know, pH values range from one (acidic) to 14 (alkaline), with seven being neutral.
As untreated greywater is generally alkaline, if you have an acid-loving garden, you will need to consider the types of cleaning products you use—washing powders generally make greywater very alkaline, as do solid soaps, while liquid soaps tend to be more pH neutral. The pH of greywater can vary depending on the source—shower water is often fairly neutral compared to washing machine water, for instance.
Before you’ve even applied greywater, pH levels can vary from acidic to alkaline from one part of the garden to another. Given this variability and the likelihood of greywater raising the pH of your soil, it is advisable to regularly monitor the pH and condition of your soil. Acidic soils can be made more basic with calcium carbonate and basic soils can be made more acidic with sulphur. To monitor this, pH test kits and soil conditioners are available from most nurseries.

Other issues

Although salt build-up and pH are of particular concern, there are other greywater components that can have an impact on your soil and plants. They include fats and oils from soaps and shampoos, disinfectants (including eucalyptus and tea tree oil), bleaches, toothpaste, hot water and sheer volume of water—leading to over watering.
For more detailed information on greywater composition, see section 2.4 Composition of Greywater in NSW Guidelines for Greywater Reuse in Sewered, Single Household Residential Premises (www.bit.ly/NSWGreywater) and Oasis Design’s Fecal Coliform Bacteria Counts: What They Really Mean About Water Quality (www.oasisdesign.net/water/quality/coliform.htm).

The complete article looks at greywater system types, use of greywater, greywater regulations and more.

Read the full Greywater Systems Buyers Guide in ReNew 130.

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

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Renewable energy courses guide

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

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

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

TAFE qualifications

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

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

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

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

Universities

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

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

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

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

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Efficient hot water buyers guide

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

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

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

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

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

How they work

SOLAR HOT WATER SYSTEMS 

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

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

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

HEAT PUMPS 

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

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

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

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

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

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

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Energy storage buyers guide

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

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

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

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

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

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

Pros and cons

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

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

Read the full article in ReNew 128

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Remote pumping buyers guide

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

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

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

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

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

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

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

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

Earthwool insulation

Insulation buyers guide

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Is your home hot in summer and freezing in winter? It probably has little or no insulation. Lance Turner takes a look at how insulation can help fix these problems.

BY reducing heat flows into and out of your home, insulation can dramatically improve comfort levels during weather extremes.

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In winter, once the home has been heated to a comfortable level, it will stay that way with far less energy input than an uninsulated home would require.

The same applies in summer. A properly insulated home will take longer to heat up and if an air conditioner is used it will use less energy than one cooling an uninsulated house. Note though, that any windows with high solar heat gains need to be shaded, particularly west windows, as in hot weather, insulation can slow down the ability of the house to cool down if there are large heat gains from windows.

Heat transfer and insulation

There are three ways in which heat transfers to or from a house: conduction, radiation and convection.

Conduction means the transfer of heat through a substance, in this case the walls, floor and ceiling of the house. The type of insulation used to reduce conductive heat transfer is known as ‘bulk’ insulation.

This is the most common home insulation and may be in the form of fluffy ‘batts’ made of many materials, including polyester fibre, glass fibre and sheep’s wool. Bulk insulation may also be in the form of loose-fill material, such as treated cellulose fibre (usually made from recycled paper), which is simply pumped into the roof or wall cavities and sealed with a spray-on ‘cap’. All these materials are poor conductors of heat and so reduce the rate of heat flow, provided they are installed properly.

Radiation is a different form of heat transfer. All warm objects radiate heat in the form of infrared radiation. If this heat can be reflected back from where it has come from using reflective foil insulation, then heat loss or gain through radiation can be greatly reduced.

Reflective surfaces such as foil don’t just reflect, they also have low emissivity (the ability to emit radiation, or heat in this case), meaning heat that has entered the material from the non-reflective side is not emitted from the reflective side easily. This means that foils can work reducing heat flows in both directions, even if only one side of the material is reflective.

Convection heat transfer (heat transferred through the circulation of air) is often the undoing of many insulation jobs. Circulating air can pass between poorly installed insulation materials and thus transfer heat into or out of the house, vastly reducing the effectiveness of the insulation. Minimising convective heat transfer is discussed later in this article.

Read the full article in ReNew 127.

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Solar panel buyers guide 2014

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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.

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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

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DC appliances buyers guide

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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.

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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.

Why DC?

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

RhinoTank

A rainwater tank buyers guide

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A rainwater tank is one of the best ways to become more water self-sufficient, but which tank is right for your home? Lance Turner looks at the options.

Rainwater tanks come in almost any size, shape and colour you can imagine, with a variety of materials to suit different preferences or usage requirements. So what should you look for when buying a tank?

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The first decision you have to make is where the tank will be located. Where you place the tank will determine its size and shape, and possibly even its colour if it needs to blend into the surrounding vegetation or dwelling walls. A large yard offers a number of options. You could place it next to the house or shed, or even under the house.

You also need to consider how the water will get from the roof into the tank, as well as overflow piping. However, there are a number of different systems for plumbing a tank to a home’s gutters that allow a tank to be situated some distance from the home, so this should probably not be an overriding consideration.

Tank materials

The six most common rainwater tank materials are concrete, fibreglass, plastic (usually polyethylene, often just called ‘poly’, or PVC, used in flexible bladder tanks), Aquaplate Colorbond (thin sheet steel with a colour coating on the outside and a waterproof coating on the inside), galvanised steel and stainless steel. Each of these materials has advantages and disadvantages, so let’s look at a few of those.

Durability

A water tank can be a considerable expense, even after a rebate, so you want it to last as long as possible. The expected lifetime of any tank should be at least 20 years, and indeed, many tanks come with a 20 or even 25 year warranty. However, a number of factors will determine just how long the tank actually lasts, and that includes water quality, maintenance and positioning of the tank.

For example, plastic tanks are relatively immune to damage from salty water, so if your tank is regularly topped up from a bore or dam, then a plastic tank might be the best solution. However, if your tank only needs to hold rainwater, then any tank material should be suitable.

The tank’s location can affect the lifetime of the materials. Ideally, the tank should be located in shade if possible, not just to keep the water temperature low and reduce evaporation, but also because some materials are degraded more rapidly by direct sunlight.

Most poly tanks will slowly degrade over time with exposure to the sun, despite having UV inhibitors added to the plastic. Because the plastic is being used to hold water, there are limits to how much UV inhibitor and other chemicals can be added to the polyethylene, so eventually the tanks will suffer some degradation.

Metal tanks come in three common materials. Corrugated galvanised steel tanks have been popular in both rural and urban situations for a long time.

Another steel tank type, Aquaplate, is a derivative of Colorbond steel. It has the colour coating on one side and a waterproof coating designed specifically for tank manufacture on the other. Provided the coating is not damaged during the tank manufacturing process and seams are correctly formed and sealed, the tank should last a great many years.

Stainless steel tanks are known for their durability and strength. They are generally small modular tanks for urban use, but large stainless steel tanks are also available. These are made from corrugated stainless steel that looks much like corrugated iron, just a lot shinier. While stainless steel tanks can be more expensive than other types, they have a number of advantages which we will look at later.

Concrete tanks can be quite durable, but they do tend to sweat if they don’t have a plastic or rubber liner. If you look at a concrete tank that has been around for a while, it is not uncommon to see white powdery ‘salt’ residue on the outside.

Read the full article in ReNew 125

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A window and film buyers guide

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Poorly performing windows can drag down the thermal performance of your home. Lance Turner looks at some solutions.

The importance of reducing heat flows through windows and doors should not be overlooked. A great deal of heat can flow through single-pane glass and an otherwise well-insulated house can suffer considerable unwanted heat loss or heat gain. In fact, a single-pane plain glass window has almost no insulating ability—around R0.2.

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The Australian Window Association (AWA) estimates up to 40 per cent of a home’s heating energy can be lost through windows and up to 87 per cent of its heat gained through them. Choosing high-performing windows and placing them appropriately can reduce energy costs significantly and improve thermal comfort. The art is in knowing how different windows will interact with the design of your home.

Heat transfer

There are three main ways heat transfers through windows: radiation, conduction and air infiltration.

Firstly, heat is lost by indirect radiation. Warm objects inside the room radiate heat at long wavelengths (between 5 and 40 micrometres). This energy cannot pass directly through plain glass as it is opaque to such long-wavelength radiation. However, some radiant energy is absorbed by the glass and this is conducted through the glass to the outside. In summer, the reverse occurs, with longwave radiant heat (radiated by hot air and hot surfaces outside) passing indirectly through the glass into the room.

Still greater is the transmission of radiant shortwave solar energy—consisting of visible sunlight plus near-infrared radiation—which is largely transmitted directly through clear glass.
Secondly, heat is lost through conduction—direct transfer of heat from the warm side of the window to the cool side. In aluminium frames with no thermal break, heat is conducted up to six times more readily through the frame than the glass.

In winter, conduction from inside to outside also drives a convection current on the inside of the window, accelerating the rate of heat loss. Warm indoor air cools when it comes in contact with cold glass and falls to the floor, drawing in more warm air above it.

If your heating system has outlets directly under or above the windows, this will increase heat loss by increasing the temperature differential at the glass and breaking up the air layer on the inside of the window. Deflecting the warm air away from the window can thus save on heating costs.

A final method of heat transfer is air infiltration. This occurs when air leaks through the gaps between the inner frame (that holds the glass) and the outer frame (head, jambs and sill). Poorly sealed windows result in a high air infiltration rate and poor thermal efficiency due to the transfer of warm air.

But the main problem is plain glass. Standard unshaded single-pane, untreated glass windows are an energy efficiency disaster, but there are lots of alternatives. These include double and triple glazing, factory-applied glass coatings, add-on (secondary) glazing systems, stick-on window films and a myriad of window coverings.

But how do you know which glazing system or treatment is the best solution for you? It’s a complex task for the average homeowner, but the Australian Window Association has sought to address this problem and make things easier with the Window Energy Rating Scheme (WERS). First though, it’s worth looking at the window performance measures used in rating windows.

Read the full article in ReNew 124

Eon composite

An electric bike buyers guide

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Cleaner transport options like cycling are not for everyone. But what if the bike could do a lot of the work? Lance Turner looks at the current options in electric bikes in ReNew 123.

Electric bikes (commonly called e-bikes) give the average person another option when it comes to mobility. While a regular human-powered bike is not seen as an option by many due to the need to be the only source of motive power, an e-bike looks a lot more attractive.

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Firstly, we should start by looking at what an electric bike actually is. E-bikes come in a vast array of shapes and sizes, but there are two main categories—road-going and off-road bikes. These both consist of a bike or bike-like frame fitted with an electric motor (either frame-mounted or in one of the wheel hubs) which is powered by a battery (usually a lithium-based battery for low weight) via an electronic speed controller. There are many variations and many suppliers allow you to mix and match components or have a range of different models with different combinations, so finding an e-bike that suits your needs is no longer the problem it used to be.

Road bike power limit

Road-going bicycles are limited in motor power to just 250 watts in Australia, and 300 watts in New Zealand. In Australia, the limit was previously 200 watts but this was recently changed to 250 watts for ‘pedelecs’—bikes that only provide power assistance when you pedal. This reflects the global market, with adoption of the current European standard (EN 15194). Victoria was the first state to enact the change in September 2012; information on the new rules can be found at www.bit.ly/XUJNXY.

So in Australia there are now two categories of road-going bikes—bikes that can run on motor power only, which can be up to 200 watts, and pedelecs, which can be up to 250 watts. There’s nothing like making legislation consistent!

Still, 250 watts is not a lot better than 200 watts. In some countries, such as the USA, there is no power limit, simply a maximum motor-only speed limit—a much more sensible limit as it enables the bike to better handle varying conditions such as steep hills.

Any bike with motor power over 250 watts, whether it has pedals or not, is not technically legal for use on-road under the current laws and should only be used off-road. Some designs, such as ‘step-through’ designs, may be registerable as motor scooters, or it may be better to buy a real electric moped which has passed ADR certification. It will be more expensive but it will be legal.

If you are looking at a road-going bike, then you should ask the supplier to confirm that it is legal for use on the road in your state. If they are not sure, you might be best to look elsewhere.

Buying the wrong bike, one that is technically not legal on the roads, can be a problem—or not. Some people ride without problems, others have been pulled over and been told they can no longer ride their bike. This can be a rather expensive problem as you are then left with a bike that is designed purely for on-road use, yet can no longer be used on the road.

Read the full article in ReNew 123

Photo: Vic Brincat, Keswick, Ontario, Canada

A pool pump buyers guide

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As pool owners soon discover, pool pumps can be big energy users. But some pool pumps are more efficient than others. Lance Turner examines the options.

Environmentally, there are issues with pools. Pools contain high embodied energy materials such as concrete, tile and fibreglass, and they use large quantities of water and toxic materials such as chlorine. In addition, the pool pumps needed to keep them clean use a great deal of electricity.

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Pools can be the largest user of electricity in the home, accounting for up to 30% of household energy consumption—that’s more than a clothes washer, clothes dryer and dishwasher combined, or about two and a half refrigerators. And the pump can contribute up to 76% of that figure—that’s a big chunk of your electricity bill. In Australia, with the predominance of coal-fired electricity, this also means the average pool has a large CO2 footprint.

Despite the costs, more than 12% of Australian households have a pool, with that number likely to rise in the future. So what can be done to reduce some of these impacts? A good place to start reducing your pool’s carbon footprint is to reduce the energy used by the pumping and filtration system.

Voluntary energy labelling standard

At the moment there are no mandatory energy efficiency requirements for pool pumps. However, there is a voluntary minimum energy performance standard (MEPS), with participating suppliers required to test and label their pumps as per the Australian Standard AS5102–2009—Performance for household electrical appliances—Swimming Pool Pump units.

To date, around 30 pumps have been tested and labelled to the standard, and these appear in the table accompanying this guide.

Read the full article in ReNew 122

CMS inverter

An inverter buyers guide

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Whether you live off grid or have a grid-interactive generation system, the right inverter can make all the difference. We check out what’s available, where to get them and which one is right for you.

One of the most important components in a 240 volt renewable energy system is the inverter. In stand-alone systems, this is the device that converts the DC electricity from the battery bank into 240 volt AC mains power* to run standard appliances. In grid-interactive systems, this device converts the energy from solar panels into mains power and feeds it into the house’s electrical wiring.

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It is important to have a good inverter—if your home relies solely on 240 volt power from a stand-alone inverter and the inverter fails, you will have no power, even though it is still being generated and stored.

Inverters are divided into two main types depending on the type of power they provide—modified squarewave and sinewave.

Modified squarewave inverters (sometimes referred to as modified sinewave to make them sound better!) are the cheaper of the two, but some appliances (such as VCRs, TVs and computers) may not run as efficiently using this type of power, and some may not run at all.

Sinewave inverters, on the other hand, provide the same type of power as the mains grid. Indeed, the power from a good quality sinewave inverter will usually be of higher quality and have better voltage stability than power from the grid.

Modified squarewave inverters are becoming rare in renewable energy systems as the difference in price between the two types steadily reduces, so in this guide we only look at sinewave inverters.

Independent or grid-interactive?

Sinewave inverters themselves can be divided into three broad groups—grid-interactive inverters, stand-alone units, and inverter-chargers. There is also a fourth type—sometimes called a hybrid inverter—that combines both grid-interactivity with the ability to take energy from and put charge into a battery bank.

Grid-interactive inverters are connected to both the power source (usually a solar array but sometimes a wind or hydro turbine) and the mains power grid. Power generated by the energy source is converted to AC mains power of the correct voltage and frequency, and fed directly into the grid. This supplements the power drawn from the grid by the home’s appliances. At times there will be more energy generated than being used and the excess is fed into the mains grid. At these times the power meter may actually run backwards (this will depend on the agreement with your power company and the types of meters they use). In effect, the system is using the mains grid as a battery bank.

Read the full article in ReNew 122

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A regulator buyers guide

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Using the right regulator in an independent power system is very important if you want your batteries to live a long and healthy life. We take a look at the types available, what they cost and where to get them.

While most solar photovoltaic energy systems are grid-interactive, many people live away from the mains grid and need to generate their own electricity. Also, as energy companies shift more of their charges to fixed charges (such as the supply charge), thus making energy efficiency measures less cost-effective, more and more grid-connected homeowners are likely to disconnect from the grid and go it alone with energy generation.

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All independent systems require a suitably large battery bank and other equipment. One of the most important, but often overlooked, components is the charge regulator, also called a charge controller.

The choice of regulator is an important one as the regulator can have a significant effect on the correct operation of your system and the lifespan of your batteries. In order to select the right regulator, you need to understand a bit about them and the choices that are available.
A charge regulator controls the amount of energy flowing from your solar panels, wind turbine or micro-hydro system into the batteries, in order to prevent the battery bank from being overcharged.

Regulation methods

There are several ways in which energy flow to the batteries is controlled, including high-frequency series switching, open-circuit series switching, shunt power dissipation and the more recent DC to DC conversion employed by maximum power point tracking (MPPT) regulators. The method used varies between manufacturers and often depends on the energy source the regulator is designed for.

Read the full article in ReNew 121

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Renewable energy courses guide

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Short courses, TAFE and university courses can all provide skills and knowledge in renewable technologies.

Around Australia there are many options to choose from. In each state except Tasmania there’s at least one TAFE offering accredited qualifications in renewable energy. There are also 11 universities providing coursework-based degrees in renewable or sustainable energy, and there are many short industry or TAFE courses providing specific industry accreditation.

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Download the ReNew 2012 guide to Australia’s renewable energy courses (267KB).