Independent advice on sustainable products at home.
Efficient hot water buyers guide
If your old hot water system has seen better days, maybe it’s time for an efficient replacement. We show you how solar and heat pump hot water systems work, what’s available and how to choose one to best suit your needs.
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), at a considerable financial cost each year. Water-efficient appliances are one way you can reduce energy use—for example, you could replace an inefficient showerhead (e.g. some use 20 litres per minute) with the most efficient, which uses less than 5 litres per minute, saving water and water heating energy each time you shower. But far greater energy reductions are possible if you replace a conventional water heater with a heat pump, solar thermal or solar electric system.READ MORE »
Such systems have the added advantage of reducing your greenhouse gas 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!
What we do and don’t cover
From an efficiency and environmental point of view the future of household energy is electric. The rise of rooftop solar and the availability of GreenPower means that households can use 100% renewable energy to run their appliances, including hot water systems.
This means we don’t cover efficient gas hot water options such as gas instantaneous in this guide, although the solar thermal hot water systems listed do have gas boost options. Gas used to be seen as the cleaner energy choice, at least when compared with burning coal, but there are better non-gas appliances available to households now. And changes in the gas market mean gas prices are on the rise. Replacing a hot water system with a modern solar thermal or electric one is often the first step in disconnecting from the gas grid, and the associated costs and greenhouse gas emissions.
We cover systems designed for household hot water that can run from renewable energy, including electricity, and ambient and solar thermal heat. These include heat pump, solar thermal, electric instantaneous and the newer kids on the block, PV diversion and direct PV water heating systems. Heat pump systems can be designed for other purposes in the home such as pool heating or hydronic heating, but these are out of the scope of this guide.
Read the full article in ReNew 139.
Download the full tables from the guide here.
See an energy use comparison between heat pump water heaters and resistive element water heaters here.
Read a list of questions to ask your hot water system installer before giving them the job here.
Keep your cool: External shading buyers guide
With summers getting hotter in many parts of Australia, keeping the sun off your windows and out of your home is becoming even more important. Anna Cumming looks at the options for external shading, for both new builds and retrofits.
THERE’S been quite a shift from pre-industrial times when glass was an artisan-crafted luxury item, and homeowners were taxed according to the number of panes they had. These days, our houses are getting bigger and so are our windows—often to the point of comprising entire walls. Windows and glazed doors frame views, admit natural light and breezes, and allow a connection with the outdoors. In a well-designed house, they also admit the sun’s warmth in winter to assist passive thermal performance.READ MORE »
However, from a thermal efficiency point of view, windows are the weak link in a home’s building envelope: Your Home notes that up to 40% of a home’s heating energy can be lost and up to 87% of its heat gained through windows. Efficient double-glazed windows with thermally broken frames (preventing heat conduction through the frame) perform considerably better—advanced glazing solutions can exclude up to 60% of heat compared to plain single glazing—but will still allow more heat to enter in summer and escape in winter than the adjacent wall.
Internal thermal blinds or curtains can help a lot in preventing heat loss through windows in winter, but to tackle unwanted radiant heat gain in the hotter months, it’s far more efficient to stop the sun hitting the glass in the first place with appropriate external shading.
Location and orientation
There is a huge variety of options for keeping the sun at bay, from carefully chosen deciduous plantings and simple solutions like a piece of shadecloth on a frame, to awnings, shutters, blinds, and even pergolas with sensor-operated louvre roofs. To choose the best solution, firstly it’s important to consider your location and the orientation of your windows.
In most of Australia, shading is needed on windows on the north, and also the east (to prevent summer sun heating the house from early in the morning) and west (to block hot late afternoon sun). North of the Tropic of Capricorn, thought should also be given to shading windows on the south side of your house, as the sun’s steeply angled path in summer means these windows will also receive direct sun. Helpfully, the Geoscience Australia website (www.ga.gov.au) allows you to find your latitude and calculate the sun angle at any time of the day, on any day of the year.
Find the table of suppliers here.
Read the full article in ReNew 138.
An inverter buyers guide
Whether you live off-grid or have a grid-connected 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.
Choosing an inverter may not be the first thing that comes to mind when you’re thinking about installing a solar or solar + battery system. But every one of the 1.5 million solar systems already installed in Australia includes an inverter and, in fact, it can be thought of as the ‘heart’ of the system—if it’s not working, your solar generation is wasted or, if you’re off-grid, you’ll be without power (or at least without mains-equivalent 240 volt power*).READ MORE »
But what is an inverter and why is it so important? In a nutshell, an inverter takes electricity from a power source that produces DC electricity, such as solar panels or a battery bank, and converts it into mains-equivalent power (240 volt AC), ready to be used in your house.
It is important to have a good inverter. In off-grid systems, 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. In grid-connected systems, an inverter failure means your solar panels are doing nothing until the inverter is repaired or replaced.
Which inverter for your needs?
The majority of currently installed grid-connected solar systems will be using a grid-interactive inverter. A grid-interactive inverter converts the energy from solar panels into mains power and feeds it into the house’s electrical wiring—no storage is involved. As indicated by the name grid-interactive, these inverters can export energy into the grid, and require a grid connection (or an equivalent 240 volt AC supply) to operate; they can’t operate in a stand-alone capacity.
When you bring energy storage into the equation it gets a little more complex, as the inverter needs to deal with both a generation source (like solar panels) and batteries; and possibly also the grid.
In off-grid systems, a stand-alone inverter can be used to convert the DC electricity from the battery bank into mains-equivalent power to run standard appliances. An inverter-charger is like a stand-alone inverter except that it has a mains voltage level input, which can be used to charge the batteries from the mains or a generator—it is not, however, grid-interactive, so can’t export energy to the grid.
The most complex inverter type is the hybrid inverter, which can feed energy into the grid from either the solar array or the battery bank. Many hybrid inverters can also power the house from the batteries during a power failure, in effect becoming a large UPS (uninterruptible power supply). They can also charge the batteries from the grid.
This makes many hybrid inverters true bi-directional devices, and many, if not most, can handle all of the energy flows in a home energy system. Some can even divert the excess solar energy to a particular load, such as a water heater, replacing the need for a separate device, known as a solar diverter (the SunMate is one example), for this purpose.
Let’s now look at the features of each type of inverter in a bit more detail.
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. Energy generated by the power source is converted to AC mains power of the correct voltage and frequency and 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 you will accumulate export credits, although how much you get paid for those depends on your feed-in tariff.
Grid-interactive inverters vary enormously in size, from 10 kW or larger units for big domestic and small commercial systems, down to tiny 200 watt models. Some, known as microinverters, are even designed to be mounted on the back of a solar panel to make the panel itself a grid-interactive module. These are ideal for those who want to start small and increase their system over time, or for systems where the array may be partially shaded—in a solar system using microinverters, each panel is independent of the others and not affected if other panels are shaded.
Read the full article in ReNew 137
For the full tables from this guide in PDF format, click here
Renewable energy courses guide
We’ve updated our renewable energy courses guide ready for enrolment time. You’ll find the table of courses—from TAFE certificates to postgraduate degrees—here. In the article, Anna Cumming has a look at what’s new in the industry.
IN the two years since we last published a review of the renewable energy courses available in Australia, things haven’t all been rosy for the renewable energy (RE) industry. Months of uncertainty at federal level over the national Renewable Energy Target, funding cuts to climate-related science, and the scaling back of feed-in tariffs for solar generation have all contributed to a reduction in the size of the industry.READ MORE »
The latest available Clean Energy Council (CEC) figures put the number of people employed in the wider RE industry at 14,020 for the financial year 2014–15, down a big 27% from the peak of 19,120 in 2011–121. However, the CEC puts some of this contraction down to a consolidation of the small-scale solar industry to more stable and sustainable levels. It also notes that RET legislation was passed right at the end of the reporting period, and since then confidence has grown: “The mood across the industry is upbeat in 2016, and it is expected that job figures will begin to grow once project development begins in earnest again under the RET in the coming years.”
David Tolliday, Renewable Energy Training Coordinator at Holmesglen in Victoria, shares this feeling. “The initial RE boom [homeowners taking advantage of rebates and premium feed-in tariffs to install solar PV] has passed, and the solar install industry has settled to around 4200 accredited installers—a good sustainable number,” he says. “The big opportunities now are in bigger-scale stuff like commercial solar, and battery storage on grid-connected systems.”
So, how to get involved? For those wanting to get into the industry or upskill, there is a wide variety of training and courses to choose from, from undergraduate and postgraduate university courses in engineering or focused on broader energy strategy, to hands-on solar design and install certificates offered by TAFEs and private registered training organisations (RTOs), and even free online MOOCs (massive online open courses). See our previous RE courses guide in ReNew 129 for a comprehensive look at the types of courses available, prerequisites and typical training pathways; here, we look at what’s new since 2014.
Read the full article in ReNew 137.
The greening of paint – an eco-paint buyers guide
Paints have become more eco-friendly in recent years, but there are still traps to look out for. Daniel Wurm explains the advantages of using environmentally friendly paints.
The painting industry has undergone a tremendous transformation over the last 10 years. Back in 2006, I was the only painter in Melbourne to have phased out toxic solvent-based paints. The rest of the industry looked at me as some kind of tree-hugging hippie when I spoke about the dangers of VOCs (volatile organic compounds) to human health and the environment. The last time I wrote for ReNew it was still difficult to find low- and zero-VOC paints, and recycling of waste was a massive issue.READ MORE »
Fast forward to 2016, and I am pleased to say that my industry has taken huge strides down the path of sustainability. It’s a good news story that I am happy to tell. Green is not just a fashion statement: it’s becoming standard practice. Let’s look at some of the developments and see how far we’ve come.
First of all, low-VOC paints now make up the majority of paint sold. Almost all painters have at least tried them and all manufacturers have introduced low-VOC versions of their paints. In many cases, even their cheaper trade lines are now low-VOC. This means that low-VOC paints are available from all paint stores.
In addition, over 500 painters across Australia have been trained to identify and use low-VOC paints, and even apprentices are being taught about them as standard practice. No one argues about the health risks of solvent paints anymore; we all know there are issues and we all want to protect our health.
If any painter tries to tell you that low-VOC or zero-VOC paints will cost more or won’t last, simply walk away and find another painter. If they haven’t got the message yet, they probably never will! Almost all major projects including schools and hospitals now have low-VOC paints specified.
Low-VOC paints are categorised according to their use. For example, the Australian Paint Approval Scheme classes low-VOC low-sheen paints as having less than 5 g per litre of VOCs. We could argue about which standard to use when measuring VOCs, but that is about as interesting as watching paint dry, and VOCs are only part of the issue.
More than VOCs
I prefer to look at the whole-of-life cycle perspective. For example, some manufacturers now offer zero-VOC paints across their range and are independently certified by a recognised eco-label. Why not support these manufacturers, who have shown transparency in their manufacturing process? GECA certification (www.geca.org.au) looks at where the raw materials were sourced and what effect the manufacturing process has on the environment. To me, there is little point in choosing a low-VOC paint if the manufacturer is still producing toxic paint; true sustainability can only be achieved when manufacturers look at it holistically.
Natural paints are paints that are manufactured using the least amount of processing. All paints are made from chemicals, but we now know that the more humans alter raw materials, the higher risk there is of those chemicals affecting our health and the environment. I like to think of natural paints as the ‘bio-dynamic’ products of the painting industry; not everyone wants to use them, they cost more, but they minimise exposure to toxic chemicals. Natural paints are made from ingredients such as linseed oil, minerals, earth pigments, lime and beeswax. They may be a good choice for people with allergies. See the table at the end of this article for a condensed list of suppliers of natural and low-toxicity paints.
Read the full article in ReNew 136
Click here to download the full buyers guide tables in PDF format.
Heating buyers guide 2016
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.READ MORE »
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 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.
Solar panel buyers guide 2016
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.READ MORE »
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.
New choices in lighting: An LED buyers guide
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.READ MORE »
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.
There are a number of specifications that are useful to consider when buying LED lights.
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.
A micro-hydro buyers guide
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.READ MORE »
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.
A battery buyers guide
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.READ MORE »
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).
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 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.
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
- battery sustainability
- safety and a home for your batteries
- battery bank do’s and don’ts
- secondhand batteries.
Greywater system buyers guide
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.READ MORE »
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 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 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).
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.
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.
Renewable energy courses guide
With enrolment time for next year approaching, we’ve updated our renewable energy courses guide. Mischa Vickas investigates what’s on offer and the opportunities available.
“Things will keep happening, almost regardless of what happens on the political stage,” says Associate Professor Alistair Sproul from the School of Photovoltaic and Renewable Energy Engineering at the University of NSW; a promising remark at a time of great uncertainty for the renewable energy industry in Australia.READ MORE »
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.
At the front line of the industry are those who directly handle RE technologies. According to the Clean Energy Council, 21,000 people were directly employed by the industry in Australia in construction, installation, operation and maintenance roles at the end of 20131. As a comparison, 27,600 people were employed in oil and gas extraction as of May 20142.
David Tolliday, Renewable Energy Training Coordinator at Holmesglen Institute in Victoria, says the greatest opportunities are for licensed electricians looking to be trained in the design and installation of photovoltaic (PV) systems (both grid-connected and stand-alone) and small wind systems. David says the motivation for undertaking such study is often the prospect of new employment or business development, but at the core of this can be a personal drive to see RE developed in Australia; “I’ve got a passion for it,” he says. David, who has also worked as an electrician for 35 years, undertook training in RE about 10 years ago, and has since benefitted from opportunities to work and teach in RE both in Australia and overseas.
Importantly, RE training is additional to a basic electricians qualification, meaning electricians can diversify into RE while continuing to offer standard products and services.
These courses are offered at over 15 training schools across Australia. If you are not a qualified electrician, a small handful of schools also offer courses in related areas, such as solar sales, carbon accounting and energy auditing, and wind energy site assessment, as well as generalist RE courses that are most suited to architects, engineers and project managers in the construction industry.
An engineering qualification at the undergraduate or postgraduate level can also enable a career in RE research and project management, particularly for emerging large-scale solar and wind technologies. “Renewable energy and energy efficiency is going to be very disruptive to what we are doing now and we need people who can figure it out,” says Alistair.
Whilst a mechanical or electrical engineering degree can provide you with the general skills relevant to RE, students can also undertake engineering degrees majoring in RE, PV and solar, sustainable systems, as well as environmental engineering.
Although the majority of students at university are school leavers, Alistair says that some students are already professionals in engineering or the physical sciences looking to update their qualifications, and some of these go on to start up their own businesses in RE and energy efficiency.
Read the full article in ReNew 129, or download our extensive renewable energy courses table.
Efficient hot water buyers guide
If your old hot water system has seen better days, maybe it’s time for an efficient replacement. We show you how solar and heat pump hot water systems work, what’s available and how to choose one to best suit your needs.
As the price of energy keeps escalating, the idea of being able to reduce energy use has never been more attractive. One of the biggest energy users in any home is water heating—it can account for around 21% of total energy use (on average, according to YourHome). Water-efficient appliances are one way you can reduce energy use, but far greater energy reductions are possible if you replace a conventional water heater with a solar or heat pump system.READ MORE »
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.
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.
Energy storage buyers guide
There has been a steady increase in the number of ready-to-use energy storage systems available. In this mini-guide, we take a look at the options so far.
Providing electricity to off-grid homes has always required the use of a suitably sized battery bank for energy storage.READ MORE »
In recent months, there has also been a lot of interest in energy storage for homes with a grid-connected solar system—whether for avoiding export at times of excess solar generation, load shifting (buying energy when cheap, storing it and then using it to offset energy use at more expensive peak times) or for supply backup, for times of mains power grid failure. The latter is especially important for users with critical needs, such as telecommuters, people with medical appliances and the like.
Both on- and off-grid storage systems need a battery bank sized to suit the requirements. This is coupled with energy generation equipment such as solar panels, a charge controller, an inverter and various other components.
There has been a move in recent years towards storage systems that contain the batteries and other components in a pre-configured ‘storage in a box’ module that is simply connected to a generator such as a PV array. These sorts of pre-configured energy storage systems are the focus of this buyers guide. We have included any unit that contains a battery bank and associated safety gear, as well as at least one other system component such as the charge controller or inverter.
We do not cover individual batteries/cells, as they have their own buyers guide, the most recent of which appeared in ReNew 113.
Pros and cons
There are several advantages to this sort of ‘storage in a box’ system. Firstly, installation is usually quick as much of the wiring between components has been done. Secondly, it often makes for a neater system as many components and their associated wiring are enclosed in a single cabinet.
There are some disadvantages too, including less flexible system sizing—most suppliers have a few standard battery bank sizes that they offer. However, storage units may be modular so that multiple units can be used to make up the required capacity.
Read the full article in ReNew 128
Remote pumping buyers guide
Moving water is a requirement on nearly every remote and rural property. We take a look at the different types of pumping systems and what pumps are available.
On many rural properties, pumping water is critical, whether it be for watering stock, irrigating crops or providing potable water for household use. Mains power may not be available on the property or the pump may be far removed from the house, so these pumps often require an alternative energy source, such as solar panels or wind power.
For both rural and non-rural off-grid properties, off-grid pumps are also often used for circulating water, for example in a remote-coupled solar hot water system.
These pumping requirements may also be critical to the operation of a farm business. Such off-grid pumps thus need to be reliable, easy to maintain, long-lived and cost-effective.
So what are some of the features of pumps that need to be considered? Firstly, different tasks require different pumps: for example, the pump for drawing water from a well or bore will be different from a pump to circulate water through a hot water system. Secondly, the amount of water and the height it needs to be pumped to (the ‘head’) also vary from site to site, and the pump needs to cater for these requirements.
To meet these variations in pumping requirements, there are many different types of pump on the market. These include the well-known windmill-powered bore pumps, solar bore pumps, reticulation pumps and pressure pumps. There are also numerous types in each of these categories, adding to the confusion in choosing a pump.
This guide looks at pumps designed to be powered from renewable energy sources—solar, wind and water. It includes DC electric pumps as well as pumps directly driven by wind or water power.
To read the pumping guide in full (PDF format), click here
Insulation buyers guide
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.READ MORE »
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.
Solar panel buyers guide 2014
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
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
A rainwater tank buyers guide
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?READ MORE »
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.
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.
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
A window and film buyers guide
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.READ MORE »
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.
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