In ‘Q & A’ Category
Q&A: The end of gross metering
I am a long-term member of the ATA and I wonder if you could advise me. Did ATA promote an electricity supplier last year as an alternative to the main ones which are so coal-dependent, and if so which one?READ MORE »
I am with Energy Australia and 10 years ago I put in solar cells and they paid me what I paid them. A few years back when the feed-in-tariff (FiT) was introduced I was given a time-of-day meter for free and have been on a 60c/kWh FiT and gross metering ever since.
Now from 1 January 2017 they offer two plans: buy a smart meter and get 6c FiT and pay $120 per annum or buy a smart meter and get 12c FiT and pay $240 per annum plus a panel wash once a year! I also understand that the smart meter they propose cannot be read remotely from my living room. Would you have more information? I am actively looking for alternatives (I live in Artarmon, NSW).
In 2015, we worked with Total Environment Centre to produce the following online green retailer’s guide available at www.greenelectricityguide.org.au.
However, the end of the NSW gross FiT and the need for net metering to be established has changed the ball game somewhat. While the greenest and dirtiest retailers won’t have changed much, who is offering the best deal to transition you to a net metering arrangement with the most competitive feed-in and consumption tariffs can only really be ascertained by shopping around. We have prepared general advice on what to look for; find the report at www.ata.org.au/ata-research/life-after-feed-in-tariffs-report. Retail offers are changing regularly so the Australian Energy Regulator’s tariff comparator site may be the best place to compare them, as it’s location/network specific: www.energymadeeasy.gov.au
—Damien Moyse, ATA
Q&A: Wicking beds
I was very interested in your article on wicking beds in ReNew 135. I have had good success with the Gardening Australia wicking boxes made from polystyrene broccoli boxes. These have PVC tubes filled with soil which go right down to the bottom of the water reservoir. Even if the water level is very low, they are still wicking up through the tube of soil.READ MORE »
My question concerns the beds you showed that had gravel in the bottom. I can’t see how the water would wick up through gravel unless the water level was right up against the geotech. If it only wicks when the water level is near the top, it kind of defeats the purpose of having a wicking bed that is self-watering!
Maybe I’m missing something here. Can you clarify this for me please?
To the best of our knowledge it is undesirable to submerge soil in water—even though it will wick very nicely. Organic matter (such as that found in healthy soil) is food for microbes, both good and bad. When submerged in water, the balance of microbes changes from mostly healthy ones that require oxygen (aerobic), to smelly unhealthy types that don’t (anaerobic—the same goes for your compost/worm farm!).
So by refining the wicking concept, or the materials involved, we’ve found a way to provide the soil with a good balance of moisture and air for healthy soil and happy plants, but prevent organic matter from being submerged in water. You’re right to say when the water reservoir is full, the water touches the geo-textile and is sucked up into the soil via capillary action.
And yes we do use a specific kind of gravel—7 mm bluestone screenings or ¼” minus in the old tongue—for three reasons: it is inert or close enough to it so won’t decompose, therefore it will hold up the soil (!) and still have enough room between the pieces for lots of water.
The screenings themselves actually wick water upward to a certain extent, thus contacting the geotextile fabric and wetting the blanket, even after the water level has dropped below full. In our research we have observed the wicking effect up the screenings themselves to be up to 10 cm.
To round it all out, the enclosed nature of the wicking reservoir, regardless of how much or how little water is retained, creates conditions for humidity and condensation to occur (especially in warm weather when the plants most need that moisture). We don’t know if this has been studied or not, but it does explain why the plants in our wicking beds remain happy even as the water level drops below the extent to which the screenings may wick water up to the geotextile fabric. We think water, even from the lower reaches of the reservoir, condenses on the underside of the geotextile fabric, then wicks up the standard height (30-40 cm) into soil. Hence the fact that the many beds we build in this way all work so well.
Hopefully some university or more scientific types from the ATA membership will set up clear-walled wicking beds and start quantifying this phenomenon so everyone can have a better understanding of what is and isn’t going on.
—Carey Priest, Very Edible Gardens
Q&A: DIY double glazing effectiveness
It was an interesting article about double glazing by Alan Cotterill in ReNew 135. However, I am led to believe that double glazing relies on a vacuum between both sheets to be effective. How did Alan achieve this? Was his objective to cut down sound only? Double glazing is certainly a good idea, particularly where I live in the Blue Mountains, but I don’t have it because of cost.This is why the article interested me, but I doubt its effectiveness for retaining warmth.
AREAD MORE »
Double glazing doesn’t rely on a vacuum, it uses an air gap of a particular width that is wide enough to provide a level of insulation and narrow enough to prevent convective currents in the air between the two panes which would transfer heat from one pane to the other. Many double-glazing units use inert gases such as argon between the panes, as it is a better insulator, but there’s not that much difference between argon and air, so DIY double glazing can work quite well compared to single-pane windows.
There are vacuum window units, although I don’t know of anyone making them here in Australia; possibly Pilkington has their Spacia units available. You can’t produce a vacuum between two unsupported flat panes of glass as external air pressure would press the panes together and possibly shatter them. In vacuum-insulated windows they use many tiny posts between the panes to provide the support for the glass, but obviously this sort of window will not be perfectly clear although it comes close. The space between the panes is much smaller for vacuum glazing than with gas-filled double glazing. For example, Pilkington’s Spacia units have a 0.2 mm gap compared to at least a 6 mm for gas-filled units.
Q&A: Single-slice toaster
I read your article on household appliances ‘It’s in the Stars’, but what about the humble toaster? Every morning in households across Australia and worldwide, power is wasted because, if you only want to toast one slice of bread, both elements fire up if you are using a two-slice toaster. If you are using a four-slice toaster and want to cook one or three slices, again an unneeded side of the element will switch on.READ MORE »
It shouldn’t be too hard for toaster manufacturers to design a more energy-efficient unit with independent elements. Small individual savings like this can add up to significant savings in energy use. There must be lots of ways savings can be achieved. It just needs someone to develop the ideas.
We can’t rely on our governments to make all the right decisions on the important subject of climate change and carbon footprints. I believe that it is up to the individual as well to make an effort to keep their energy use down to a minimum if we are going to make a difference and survive this crisis.
Very few toasters are designed for just one slice. There are single-slot toasters designed for two slices side by side, but, of course, when toasting one slice, the elements are effectively larger than needed and so there is still wasted energy.
There was a toaster designed in Japan that just does one slice, but it is only available for 100V supplies and it doesn’t get good reviews. However, Dualit’s two-slice classic toaster (www.dualit.com/products/2-slice-newgen) has the ability to turn off one slot for toasting just one piece, so that would be the best option. They are also designed to be repairable, another plus.
The downside is price; they are around $400, although they can be found cheaper if you look around. The energy saving would never pay for the difference between these and a cheap toaster, but given the Dualit is designed to last a lifetime (although there are reviews to the effect that they have early failures as well), then it might be worth the investment. There may be other, lower cost toasters with a single-piece capability but I couldn’t find them after about 10 minutes of searching and checking reviews.
Overall, the energy wasted by a toaster is pretty small as it only runs for a few minutes at a time. While it does add up to a lot across the whole country (or planet), other inefficient appliances can waste a great deal more. For example, if a toaster is running an unnecessary 500 watts of element for three minutes, that equates to 25 watt-hours, or the same amount of energy wasted by a small plugpack drawing just one watt or so continuously—not much in the scheme of things. Indeed, a 3 kW solar power system would produce this much energy in just 30 seconds.
So, while all energy savings are important, there needs to be enough to provide an incentive to actually manufacture a more energy-efficient device, and I suspect that in this case, there just isn’t enough incentive to do so for most manufacturers.
Read more Q&A in ReNew 135.
Q&A: Understanding solar
I love the magazine and have been subscribing for a number of years. I would like to get some very basic information on solar from you. Although your articles about going off-grid are really interesting, I can’t follow the detail, and I suspect a lot of readers of my generation (70s) are in the same boat. I would eventually like to go off the grid and therefore would like you to answer a few very basic questions.READ MORE »
I live in the Canberra region which is really sunny, with an average yearly total of 246 sunny days. My average electric use is 19 kWh/day and I currently have a 2.025 kW PV system.
If we receive eight hours of sunshine in a day does this mean I would get 16.2 kWh? Regarding storage, what would be the optimum amount of battery storage required to go off the grid without having a diesel or petrol generator, in my area? Is there any course that would cover the sort of basic knowledge I require?
Yes, solar can be confusing, and there is a lot of jargon around! Your solar panels are rated at a total of 2 kW which is the power they will generate at standard test conditions which include:
- strong sunlight directly shining at the panel
- panel temperature of 25 degrees.
These conditions don’t often occur in the real world. The sun moves around, and as panels heat up their output reduces. Then there are additional losses in cables, inverter and other components.
To estimate how many kilowatt-hours (kWh) of energy the system will generate in a day, we can’t rely on whether a day is described as sunny, or the number of hours of sunshine. A better measure is the average number of kWh a 1 kW solar system will generate over a whole year.
Check out the table at www.bit.ly/1NpXb5h.
Over a whole year, a 2 kW solar system in Canberra should average about 8.6 kWh of generation per day. Of course, generation will be higher in summer and lower in winter.
So if you wanted to offset your yearly electricity consumption, you would need to add many more panels.
As for going off-grid, what is your motivation to do this? Off-grid systems are expensive. We’ve analysed the economics previously and even with high grid tariffs, going off-grid isn’t attractive on a purely economic basis. As a rough rule of thumb, to supply an electricity usage of 19 kWh per day, a reliable off-grid system might cost between $57,000 and $95,000. We expect this to come down over time as batteries get cheaper, but on the other hand, the Aussie dollar is low!
There are many ATA members off-grid, but they generally are very frugal users of electricity, typically around 5 kWh per day. It’s difficult to go off-grid without a generator. The big issue is getting through a cloudy winter week. Space heating and water heating are big factors too.
Here’s a great course to learn about this: www.bit.ly/1RQBeeE. I wrote a review of this course in ReNew 132. Another information resource is Sunulator, including the user guide: www.ata.org.au/ata-research/sunulator.
And here’s a useful article to explain some important terms: www.bit.ly/1l6RQ83.
—Andrew Reddaway, ATA
Q&A: Polystyrene foam alternatives
I found out from a friend that most of the expanded polystyrene used in building in Australia probably contains a brominated flame retardant—likely HBCD or DBDE—and that these are being banned in Europe because they are persistent, toxic chemicals.READ MORE »
We are about to build a sustainable house but don’t want to use something that’s both toxic to people and persistent in the environment.
Apparently these flame retardants are not used in polystyrene used in food packaging (phew!) but a flame retardant is required in all commercial building polystyrene.
I’ve called a few companies and they have trouble telling me what the exact chemical is. I’ve found that they import their beads from China already coated in the retardant, and then expand them here. Apparently the flame retardant is just a coating on the beads and not part of the chemical structure, so it can come away once installed, and end up in dust or in the air.
Are you able to tell me if anyone at ATA has looked into this and could you recommend a supplier that doesn’t use a brominated flame retardant? I’d be a willing customer!
We are not aware of any polystyrene foams for building that use fire retardants that are not brominated. According to the US EPA publication 740R14001, Flame Retardant Alternatives For Hexabromocyclododecane (HBCD—Final Report, June 2014 (www.bit.ly/FRAFH14), “No non-brominated flame retardants are known to be compatible in polystyrene manufacturing and associated flame tests.”
There are other products that are naturally fire-resistant and so don’t have added fire retardants, such as hempcrete, timbercrete, AAC (Hebel) and similar naturally derived building materials. Insulation materials such as glass and mineral fibres are naturally flame retardant. I used Knauf Earthwool insulation in our home here; it is naturally non-flammable and the fibre binder is based on plant starches.
To read more questions and answers, buy ReNew 133.
Q&A: Point-of-use water heaters
I’m looking for information on instantaneous electric water heater taps for sinks. I’m considering them to address the water and energy inefficiencies associated with the long pipe runs from my current water heater to kitchen, bathroom and laundry sinks.
I’m aware of instantaneous tap water heaters without storage and with integrated lever taps for this application, and these are what I’m most interested in hearing from people about.
With the shower, similar issues and savings opportunities arise, but the much less frequent use (typically once a day per person) make showers a much smaller opportunity to save water and energy by this means.
However, shower-specific instantaneous water heaters are available (which differ from sink units), so I’m happy to hear any ATA views on those as well.
For example, has there been a ReNew article reviewing any of these in relatively recent times? I remember seeing adverts for these in ReNew at some time in the past.
We haven’t reviewed such units, although several have appeared in the Products section of ReNew. These include units from www.rezi.com.au, www.stiebel.com.au, www.heyprestohotwater.com.au, www.gleamoushotwater.com.au, www.microheat.com.au and www.zipindustries.com.
They are all of similar efficiency (i.e. 100%); the main issue is the electrical circuit. The tap-integrated units generally work with a regular 10A power point or standard wiring, whereas the 15A and greater units (shower models seem to be rated around 5000 to 6000 W, or 20 to 25 A) need a dedicated circuit. The larger units are all three-phase and are not usually suitable for domestic installations unless three-phase power is available in the home.
These units can vary enormously in price and some are more repairable than others. Make sure you get one with an easily replaceable element if possible, and ensure spare elements are available.
The other thing to be aware of is the level of heating provided. Most of the single-phase units, especially the tap-integrated units, will only raise the water temperature by 10 to 20 °C for a reasonable flow rate, which might be fine in warmer climates, but if you have colder water temperatures they may not do the job. Check the specifications for each unit at the maximum flow rate required.
To read more questions and answers, buy ReNew 132.
Q&A: Battery and solar developments
Q: I HAVE read and heard that the next generation solar batteries superseding lithium will be available and ready for market in two years time. That being the case, can you please indicate whether a hybrid solar system currently working on lead-acid batteries can be retrofitted with the upgrade?READ MORE »
Also, are you aware of any developments whereby solar panels can be wirelessly connected to the inverter/batteries i.e. the solar equivalent of wireless internet connectivity on a laptop?
Lastly, are you aware of any double-glazed, aluminium or wood-framed window systems with integrated solar panels, either already available or coming to market? Would ReNew be able to run a feature on this subject at some stage?
A: THERE IS a lot going on in battery development at the moment, but most of it is focused on modifications to lithium chemistries, such as using silicon nano-wires in the electrodes to reduce degradation and improve lifespan and energy density. There are some other chemistries around, such as the Aquion Energy sodium ion battery, as well as rechargeable zinc-air batteries, flow batteries and a few others. However, for the moment the two industry workhorses are lead-acid and lithium chemistry units, in particular lithium iron phosphate (LiFePO4) for larger storage requirements.
The cost of lithium batteries is steadily decreasing and with the commissioning of Tesla’s Gigafactory next year, the price is expected to go below US$150/kWh by 2020, possibly as low as US$100/kWh. So, for the next decade or so, lithium batteries are most likely to be the best bet. All of the other chemistries are really in their infancy as far as development is concerned.
Whether you can upgrade to a newer battery type will depend on the other system components and the proposed battery system. For example, a battery system with similar voltage range during charge/discharge will probably be able to be used, provided that the solar charge controller in the system can meet the charge requirements. Some charge controllers have fully programmable voltage setpoints, so that sort of controller is more likely to be able to handle a new battery chemistry. However, most battery chemistries in development have their own management systems, so they may not need a charge controller at all: the management system will control charge and discharge of the battery.
The other issue will be your inverter and whether it can handle a possibly wider voltage range of a new battery chemistry. Many inverters also have programmable minimum and maximum voltages, so there’s no way to know without knowing your current inverter model and the new proposed battery chemistry.
Wireless data transfer and wireless energy transfer are very different things. Data transfer only takes milliwatts of power, whereas energy transfer for a typical domestic solar power system would need to be in the kilowatts—a million times more power at least. There are prototype energy transfer systems being developed and some have reached the stage where 100 watts or more of usable power can be transmitted over a short distance (inside the same room, for example), but these have relatively low efficiency compared to running cables, as well as much greater cost and complexity. They also require the room to be filled with an alternating magnetic field of considerable strength—something that many people might find disconcerting. So far, all domestic-scale wireless energy transfer devices have been aimed at the gadget market—charging mobile phones and the like.
Regarding solar windows, there have been a number of companies working on these, and we have covered some installations in the past, such as in ReNew 101 where we looked at windows at Ballarat University, Schott Solar’s ASI transparent thin-film panels. However, it appears they no longer make them. Most of the manufacturers that were using their glass modules also seem to have disappeared, except one, although they don’t appear to be using the Schott modules: www.ertex-solar.at/en/products.
Kaneka still make transparent PVs, but in the last PV buyers guide (ReNew 126, just over a year ago), we found no transparent PVs available here.
There are several companies working on new transparent glazing materials, including Oxford Photovoltaics (www.oxfordpv.com), New Energy Technologies (www.newenergytechnologiesinc.com) and SOLPROCEL (www.solprocel.eu).
When interesting products hit the market we always try to include them in the Products section, so that’s the best place to keep an eye out for them.
To read more questions and answers, buy ReNew 131.
Q&A: Using solar first
The solar feed-in tariff being offered by most companies is the minimum 8 c/kWh. However, if you are home during daylight hours and are using electricity at the same time that your solar panels are producing, does your household use that solar power (in effect) and so save you being charged at 29 c/kWh?READ MORE »
Yes, at each instant your solar generation will take the path of least resistance. Your household appliances are supplied first (offsetting 29 c/kWh as per your tariff), then any excess is pushed to the electricity grid in your street (feed-in or export).
Electricity can flow in only one direction at a time down the cable between the street and your house. Your meter has two registers. Whenever electricity is flowing from the street into your house, the import register is accumulating, costing you 29 c/kWh. When electricity is flowing from your house to the street (feed-in), the export register is accumulating, earning you 8 c/kWh (expected to drop to 6 cents or so next year).
If you got onto a premium feed-in or transitional feed-in contract several years ago, your feed-in tariff would be higher, eg 66 c or 25 c/kWh. With current low feed-in tariffs, your solar generation gives best value when consumed within the house. We wrote an article on this last year: www.ata.org.au/news/latest-solar-payback-times.
You might find our solar electricity booklet useful: shop.ata.org.au/shop/solar-electricity
And if you’re looking to do a detailed analysis, we have developed a free tool called Sunulator. Please see www.sunulator.org.au.
To read more questions and answers, buy ReNew 130.
Q&A: Taking grid-connected system off grid
I was very interested in the off-grid issue but it didn’t answer my question about converting from a grid-connected system to off-grid. What would I need to do if I want to convert my existing grid-interactive solar system to off-grid?READ MORE »
You could just sell the grid-interactive inverter and use the solar array as-is to charge an appropriately sized battery bank via an MPPT (maximum power point tracking) charge controller. This controller will match the high voltage output of the array to the lower voltage battery bank. You then add a standalone inverter and anything else required for the stand-alone system. Sometimes the array is reconfigured to produce a lower voltage and higher current, but it’s not necessary nowadays with MPPT charge controllers, some of which can handle very high array voltages, such as the MorningStar Tristar (www.morningstarcorp.com/products/tristarmppt- 600v/). This is called a DC-coupled system and is how most off-grid systems were traditionally done until recent times.
The other method is called AC coupling. You keep the current system and add the battery bank and a suitable inverter/charger. This new inverter creates a microgrid that the grid-interactive inverter can feed into. When there is more energy coming from the panels than the house is using, the inverter/ charger feeds it back into the battery bank. AC-coupled systems seem to be becoming the norm for larger domestic off-grid systems, not just those that have been converted.
There are pros and cons to either method. Personally I prefer the DC-coupled system as it doesn’t all hinge on the inverter/charger—if that fails, you have no energy available at all. With DC-coupled systems, if the inverter fails you still have the array keeping the batteries charged and you can use a low-cost backup inverter for mains power until the main inverter is repaired, or you can use DC power directly. Of course, you can do the latter on an AC-coupled system as well, but AC-coupled homes almost never have any provision for direct DC use, whereas DC-coupled systems often do, even if just for lighting.
We will be looking more closely at how AC-coupled systems work in a future issue of ReNew.
Q&A: Battery advice
I need to replace my 12 volt batteries. My power comes from a few solar cells and the load is relatively light and not every day—a studio with 60 watts of lights (currently old quartz halogen. which are easy to now replace with more efficient LEDs) and probably a 12 volt CD/radio. Would you recommend the Jaycar SLA deep-cycle battery SB1699—or indeed what else?READ MORE »
Also, perhaps you may have ideas about inexpensive basic 12 volt CD or DVD players that could hook into existing speakers. I have been scrolling websites without much luck; portables seem to have their own lithium batteries which rather defeats my needs. Car stereos are too fancy, with Blu-ray etc.
Jaycar’s SB1699 might be a bit small for your use, but their next size up is 100 Ah, which is probably too large. There are a lot of battery suppliers that may have a larger range, such as www.batteriesdirect.com.au, www.batteriesplus.com.au and www.batteryworld.com.au (stores only, no online shop).
I have had a few problems with lead-acid batteries in the past being a tad flat when purchased (not good for lead-acids), although with a dozen or so cycles they usually come up okay.
But, given the falling price of lithium batteries and the fact that many are drop-in replacements for lead-acid nowadays, you might want to consider them. Examples are the 12 volt models at www.ev-power.com.au and www.evworks.com.au.
Re the CD player, you can reuse a computer CD/DVD drive (one with play and stop buttons on the front) for this sort of thing. There is an adaptor kit that lets you do this but you need electronics experience to build it; see Jaycar part number KC5459.
But if you want just simple play functions then you don’t need an adapter, just supply it with 12 V from the battery and 5 V via a small regulator, and connect the headphone output to the speakers. If they are powered speakers then you will get good volume; if not then you might need a small amplifier between the two, such as www.ebay.com/itm/140808997786 or Jaycar’s AA0487 or AA0473 (single channel only).
Of course, this is all very DIY and if that doesn’t appeal then a low-cost car stereo is probably going to be the best option.
To read more questions and answers, buy ReNew 127.
Q&A: Instantaneous hot water
We live in bayside Brisbane in a four-bedroom, two-bathroom house with an old-style 250-litre electric hot water system. We are investigating which way to go if or when the system needs replacing. It is on the south side of the house and it does not appear to me to be a straightforward job to change to a solar hot water system. It is also near the main bedroom and I understand there can be noise issues with a heat pump system.READ MORE »
We installed a 1.5 kW PV system three years ago and have happily paid no electricity bills for that period and are $700 in credit. I have looked at Stiebel instantaneous electric hot water systems which, at the top of the range, seem to be appropriate for two-bathroom apartments and can cost around $1500.
The technology looks smart and I cannot see any regulatory objection to this option in Queensland. Are there any practical or plumbing issues in making this replacement? I am not a tech tragic—I would just like an opinion as to the appropriateness of instantaneous electric hot water for a house.
The main issue with a whole-house electric instantaneous system is that it needs a 3-phase power supply, as power draw may be up to 20 kW. Many houses have these now but many don’t. So whether you can install one depends on that. Bear in mind that, while energy use will be less than with an electric resistive storage system as there are almost no standing losses, it will still use a lot more energy than a heat pump or solar unit.
There’s no reason why you can’t install a solar unit. You would use a split system with the tank in the same place as the current tank and the panels on the roof on a tilt frame to overcome the south-tilted roof.
As for heat pumps, most are pretty quiet but noise ratings are given in the specs. You can also put them on a timer so that they don’t run overnight, instead kicking in at, say, 7 am. The most efficient domestic unit on the market seems to be the Sanden, which uses CO2 as the refrigerant. See www.sanden-hot-water.com.au
To read more questions and answers, buy ReNew 126.
Q&A: Increasing system load
Since my household increased from one to three members I am finding my 1500 W renewable energy system, which was more than adequate for a frugal me, is not coping with the extra residents even though we use energy sparingly, only do washing etc on sunny days and have purchased low-energy computers and fridge.READ MORE »
Our system was only designed to take up to 2000 W of solar panels, so after I put on two new panels the system is still short on energy when we have two cloudy days in a row.
My battery charger will be getting regular use from now on, but only puts 10 A (300 W) into the batteries. I am looking for a battery charger that can deliver 30 amps and reduce the time I need to run my 3000 W generator.
Longer term, I may have to buy a second system, but can you suggest a suitable charger that is not too expensive please?
There are plenty of chargers around that will do that sort of current, and more, but the maximum current rate depends on the battery bank size. See www.baintech.com.au/chargers and www.inverter.com.au/category5_1.htm for examples, and there are a lot of other suppliers, but high-powered chargers like this are never really low cost. There are some cheap ones on eBay, but bear in mind that some are not well regulated and can overcharge the battery bank, and many are direct from China, so if they fail, there’s no real recourse.
Generally, if you are finding that your battery bank is struggling after the second day then you are cycling it way too deeply and it is too small for what you are drawing from it. The use of a charger will help but it is still adding cycles to the bank and the bank will degrade faster than it otherwise would.
Something to note regarding generators, they are usually rated in VA (volt-amps), not watts. They are not the same thing unless the load on the generator (battery charger or whatever) has a power factor of 1. Very few electronic loads do, especially battery chargers, so a genset rated at 3000 VA won’t be able to power a 3000 watt charger. Obviously, a 30 V, 30 A output is only 900 W and probably needs around 1200 W input at most, but it’s surprising how much some gensets struggle with battery chargers.
To read more questions and answers, buy ReNew 125.
Q&A: LED bulbs and radio buzz
I recently bought four LED lights to replace CFLs in the kitchen. I’m very happy with the light output and colour, but unfortunately there is one side effect—when they are turned on they make my clock radio in the bedroom buzz. What is this caused by and is there anything I can do to stop it? I would just put these globes in a spot where I don’t need to use them in the morning, except that they are the only screw fittings in the house. Another LED in the pantry has no effect.
This is a common problem: many LED bulbs produce electrical noise as they have switchmode drivers inside them to convert the power supply voltage down to whatever voltage and current is needed for the LEDs. The electrical noise can be radiated as radio waves from the house wiring, causing interference, or it can travel back through the wiring as electrical noise, causing the same problem. I suspect your problem is the former.
There are a number of solutions, of which several are quite simple. The first is to get some clip-on ferrite beads, these are the sort of thing you see at the end of some computer leads, basically a lump in the cable, but in clip-on form rather than moulded in. Examples can be seen at www.bit.ly/ferrite1 and www.bit.ly/ferrite2. You simply clip them over the cable as close to the light fitting as possible.
If that doesn’t fix it entirely, using a larger ferrite and winding two or three turns of the cable through it will increase the effectiveness of the ferrite.
You can also put small value capacitors directly across the socket, but this involves electrical wiring, so you’ll need to find an electrician experienced at mains wiring, and you must also use the correct capacitors (X2 types of appropriate voltage rating). A simpler and more electrician friendly option would be to have mains filters connected at the fittings. A typical example of a suitable unit (which could be fitted inside a junction box) is Jaycar Electronics part number MS4001.
But definitely start with the clip-on ferrites, they are simple to install and no electrician needed, assuming the wiring is accessible from inside the ceiling. Just be careful if installing them that you ensure the wiring is in good condition – old wiring can have degraded insulation and be very dangerous. If in doubt, contact an electrician.
To read more questions and answers, buy ReNew 125.
Q&A: LED downlights and power problems
I have been told by a sparkie that dimmable LED lights cope better with power fluctuations than non-dimmable ones. Is there any truth in this? Also, I was told by a salesperson that if a fairly expensive LED four-light track failed I would have to replace the whole fitting. This doesn’t seem right to me. Presumably you could replace globes with most fittings, or replace the driver or driver parts if this were the problem, rather than throwing away the entire fitting?
How well a fitting copes with power problems depends on the quality and design of the driver. Dimmable fittings will be designed to handle a range of voltages and ‘chopped’ waveforms, so they handle spikes well, but a properly designed fixed-output driver should work just as well. It also depends on what you mean by fluctuations, such as long-term (minutes to hours) variations in mains voltage, or short-term spikes caused by motors etc, or both.
The advantage with a dimmable driver is that it does give you the option to add dimming later should you want or need to.
Regarding the track light, that depends on how it is designed. If it has replaceable bulbs, then no, you wouldn’t have to replace the whole unit. Many suppliers are selling standard halogen track lights with LED retrofit bulbs, so the combination is fairly common.
If the fitting is designed from the ground up as a LED fitting then it will have one or more drivers driving the embedded LED arrays, so if you get a LED failure, you will have to live with that light being out unless you can get a replacement array and find someone to install it. If the unit uses a single driver to drive four arrays (unlikely, but I’ve seen poor designs like that) and the driver fails then, again, you would need to find an equivalent driver and have it fitted by a technician (with LED experience—all electronics techs are not created equal).
As it depends on the fitting design, you’ll need to get technical details or have a close look at the fitting you are proposing to use so that you can see how it’s configured.
This is one of the aspects that is working against LED lighting at the moment—there are so many variations and you need to understand what you are buying.
To read more questions and answers, buy ReNew 124.
Q&A: Energy sucking pump
I got a rude shock the other day when I purchased a new water pump to supply my house with tank water. I put my energy meter on it for few days to get an idea of how much energy I would use on an average daily basis. When I went to disconnect it, I noticed that it was drawing 17 watts while it was doing nothing. I called the company that sold me the pump and they assured me that a pump should draw no power unless a tap was on and it was running, so I dismantled the whole thing and brought it in.READ MORE »
They plugged it in to their ammeter which said it was drawing nothing. Fortunately, I had brought my meter with me and showed them that it was drawing 17 watts. Then they noticed that it has a couple of LEDs on it that show power on etc and said that it has to draw some power for the LEDs. I would consider trying to break into the box and get rid of the LEDs, but 17 watts seems like more than needed for one LED.
Then they told me I was going to have to buy a pump with a pressure tank instead (the very pump they had previously told me I didn’t want to buy because it would cut in and out while having a shower). They then fitted this new pump with a pressure tank they had ‘sitting out the back’ and sent me on my way.
I am not overly excited about the outcome, not the least because I now have to build a whole new pump house as the pressure tank doesn’t fit under the previous one.
I did the calculations and given that I am getting 66 cents for PV power I put into the grid, it would cost me $63/year to have the first pump connected as purchased. The pump I had before this neither had a pressure tank nor drew power when it wasn’t running, but the same company that said it wouldn’t draw power when it wasn’t running, now say that all pumps either draw power when not running or have a pressure tank. Is this true? Is this power doing anything more than powering an LED power indicator? Do you know of pumps that don’t do this and if so, which ones?
If the pump has an electronic controller then it will draw some power even when off. The only pumps that won’t are those with simple electromechanical pressure switches. Some pumps are variable speed and are designed to eliminate the need for a pressure tank, but if it’s a simple on-off type controller then it should still have a tank.
The problem with many mobs selling pumps is they tend to undersize tanks for pumps that need them. If a tank is sized correctly, the pump won’t need to kick in during an average shower, unless it was almost empty (close to the pump’s cut-in pressure) anyway. For a whole house system, the minimum tank size you should look at to reduce pump cycling is around 100 litres, but with pressure tanks, the larger the better.
My personal preference with pumps is a simple electromechanical pressure switch and a decent-sized pressure tank. It’s simple, robust and effective.
Q&A: Basement living space
I am currently considering the possibilities of converting a sizeable basement area into a future ‘granny flat’ for my wife and myself, and handing over the home above it to one of our children. Leaving the social issues alone, the more I consider the virtues of doing this, the more it seems like a viable option.READ MORE »
Apart from the opportunity to design a space more suited to us in our twilight years, I see massive benefits in the area of energy efficiency. On the downside, there are technical issues of the structural, plumbing, drainage and electrical kind as well as those related to ventilation and natural light.
It is no doubt likely that all of these issues have been dealt with countless times before my engagement with them. In considering the best strategy to become better informed about the proposal, it came to mind that as a long time ATA member, I could do no better than start there.
My search in the ATA articles database has been unfruitful. Is it possible that in your library of things technical you have come across references on the subject and/or stories from others who have taken up this challenge?
I would start with posting the request on the ATA and other forums, but there’s a lot of info out there on this already. I did a google for basement living and a lot came up, including companies that do conversions such as www.basement-living.co.uk (in the UK but there’s bound to be others), sites like www.bit.ly/YRJ8YC and www.bit.ly/XA04Tx and safety tips like www.bit.ly/YRJj64.
For individual problems, there are lots of ways to solve each one. For example, with lighting you can use regular fluoros or LEDs (my preference), you can pipe sunlight in from outside (can be expensive) or you can install false skylights (a solar panel outside that’s wired to a LED panel inside), so that the light indoors follows what’s happening outside—like a skylight, just simpler to install. After dark, the LED panel can also be powered from the mains as primary lighting.
For ventilation, you need a decent rate of air change as there will be few air leaks in a basement and you want to reduce moisture accumulation, so a proper HRV system (see www.bit.ly/UZnKnH) would be a good option, although they can also be expensive.
But there’s lots more to consider. Your first step might be to find an architect who has done this before, or you can take the DIY approach and just do a heap of research.
Q&A: Small wind considerations
In the article on small wind power in ReNew 122, I found it odd that there is no mention of the possibility of lightning strikes nor maintenance considerations, especially when we are told that tower heights of 36 to 42 m are the norm in some countries.READ MORE »
I had a grid-feed PV system installed in Grafton and a stand-alone system in Coonabarabran. Both companies advised against wind, claiming that the electrical surge from a lightning strike could flow to the inverter and other equipment and damage the whole system.
Pending sale of the Coonabarabran property, I hope to install a stand-alone system at a different site that lacks neither sun nor wind and where the only turbulence would be created by the house itself which, though small, is two storeys at the rear, with the ridge being just under 6 m. Of the two installers I have spoken to in this district, one said the same as the two companies mentioned above and the other more or less said that by the time anything happened to the turbine it would probably have paid for itself, which to me is a completely unsatisfactory attitude.
I am probably better to stick to PVs but, as the article says, you do see numerous small turbines around the countryside apparently in good order. For that matter, what happens with the old Southern Cross mills or the commercial wind turbines? I find it very puzzling that, at this relatively late stage, there seems to be no consensus view as to what does or does not work with small wind, and would suggest that it merits an article in itself.
Lightning protection is a complex area. In my experience, there are loosely three schools of thought for tall objects including wind turbines. The first two cost money. They are:
- Divert the lightning, e.g. using a finial and earthing (not very practical for small wind turbines) and/or MOV surge protectors (effective but have limited lifespan).
- Insulate/isolate the turbine and electrical installation from earth as much as possible so the lighting naturally takes another route.
- Do nothing—which costs nothing up front obviously but of course carries far higher risk of expensive damage later.
Neither options one nor two are guaranteed to work; in locations not prone to lightning some argue neither are guaranteed to be necessary either, hence school of thought number three.
Because lightning is not predictable and the level of risk is location-specific, there is no clear ‘best’ approach for lightning protection of turbines. I’ve known of one wind turbine on a 20 m tower on a coastal hill to get struck almost annually, but many other turbines that have never been hit. I’ve worked on 80 m wind monitoring towers and found that, on average, these seem to get struck once every five to ten years.
Lightning risk is only one of a long list of environmental considerations you would make when assessing a site, and the point of Katie’s article is about avoiding the main pitfalls of choosing a wind site. So, while clearly lighnting protection is a consideration for designing a turbine system, I would only consider the highest risk locations to be absolute showstoppers for wind, and only where there are clearly other energy options.
Most people do find solar to be the best option, given how much cheaper it has become in recent years and the fact of it being solid state and therefore lower maintenance, quieter etc—but wind energy can still be the best choice for some locations.
Craig Memery, ATA Policy Team
Q&A: Water pump counter
I wonder if you’ve ever seen something that would measure when and if my greywater system pumps to the header tank, perhaps some kind of tank or pipe flow counter? The system is connected to a drip system and the overflow goes to sewerage so it’s possible that it’s not even working.READ MORE »
If you are trying to measure flow volume, there are many sensors for measuring flow, it just depends on the pipe diameter. For example, see those at www.futurlec.com/Flow_Sensor.shtml but there are others made for larger pipes, such as those at www.watermeters.com.au.
If you are wanting to count the number of operations or the running hours, then that depends on the pump voltage, but assuming it is a mains-powered pump, then something like Rockby Electronics (www.rockby.com.au) part number 32442 or 40601 will do those jobs; just power them from a suitable plugpack whenever the pump is turned on. You could also use them for a DC pump with a suitable small DC-DC converter.
Q&A: 230 V, 240 V, whatever…
I’m an avid ReNew reader, member and past contributor. We had a recent experience that we thought wouldn’t be uncommon amongst your readers and thought it would make an interesting story.READ MORE »
We’ve been living off-grid for the past five years. During this time we’ve had issues with electrical appliances breaking down, and each time as soon as the technician discovers we’re off-grid they blame the system. It’s a real fight to get them to consider other options.
The most recent example was today which prompted this letter. We purchased a new electronic fridge, and had a problem with it as soon as it was plugged in. I won’t bore you with the details, except to say that before even looking at or hearing the problem the technician had decided the problem was caused by our power, his rationale being that electronic fridges needed a constant 240 V supply.
When he tested our system is was only providing 230 V. Of course, in the end he finally admitted there was a problem with the fridge and a replacement is being sent.
What would have been really helpful was a fact sheet, written by a qualified person, to give to the tech explaining why the power system is not the problem.
You really have to wonder how up-to-date some technicians are, given that Australia officially shifted to 230 volts over a decade ago. This is why current inverters have 230 volt outputs, not 240.
The Australian Standard AS 60038 states the nominal mains voltage as 230 V +10%, – 6%, giving a range of 216.2 to 253 V. The ESAA Customer Guide to Electricity Supply gives more details on page 27 and indeed is a useful document to read for anyone interested in electricity supply in Australia. It can be found at www.bit.ly/WYBb66. Other similarly useful documents are ENA’s Customer guide to Electricity Supply at www.bit.ly/XInUhr and the Electricity Networks Operation Standards 2011 at www.bit.ly/Trfoor.
Even so, most appliances have a wide input voltage range, often from 200 volts up to 265 or so, depending on the brand, model and the markets the model is sold into. Indeed, most modern electronic devices use ‘universal voltage’ power supplies that handle 85 to 265 volts, although the fridge motor will be designed for a narrower voltage range. But, the motor doesn’t seem to be the problem, the electronic controls do, so the technician blaming the power supply on a voltage basis shows considerable lack of knowledge.
Having said that, if you are having a lot of electronic device failures then you might want to have the output waveform of the inverter checked in case it is producing a non-sinusoidal waveform or is producing a lot of electrical noise on the waveform. Any technician with an oscilloscope can check the waveform for any oddities. There might also be another appliance that is producing electrical noise that is damaging other appliances.
Read more Q&A in ReNew 122.