Q & A « Renew Magazine

In ‘Q & A’ Category

Low VOC materials

We are completely renovating a period home at Newstead near Castlemaine, Victoria. Our architect and cabinet maker haven’t been able to find a green product for use on the inside of kitchen cabinets that hasn’t been glued together with nasties. I want a low VOC product which isn’t solid wood if possible.

There’s a few options, such as E0 MDF, which is a virtually zero offgassing MDF. If you google ‘E0 MDF’ you will find suppliers. The other option is X-board, a building board made from recycled cardboard and other fibre. It is available as a plain board or as X-board plus, which has E0 MDF laminated onto it for strength. See www.xanita.com for the manufacturer and www.sharpplywood.com.au for an Australian supplier. There may be other suppliers carrying it too.
Lance Turner

Wood heater emissions

I visited an eco-village where the burning of wood, such as in a pot-bellied stove for space heating, is not permitted.

The problem might be that fallen timber was scarce in the area that this village was situated. On the other hand it might be an emissions issue. But what if there is a forest nearby with a plentiful supply of fallen, and thus decomposing timber?

My understanding is that rotting timber generates CO2 in its decomposition process. If this is the case, doesn’t it make sense to generate roughly the same amount of CO2 by burning the timber to warm a house? Or does burning timber generate more CO2 than in its natural decomposition process?
Mike Belfield

There’s a number of issues here.

The first is that most people with wood heaters don’t know how to use them properly. They often overload the firebox, turn down the airflow and let it run at a slow burn. This produces not only CO2 but plenty of methane, soot and creosote, so wood heaters, the way most people use them, are shockingly polluting.

Another issue is that the collection of timber removes habitat from forests. There’s myriad tiny critters that rely on the cover it provides to survive, and some also eat the timber as it decomposes, so removing too much can stress an ecosystem to some degree.

Generally, due to the wood heater issues above, most environment centres have worked out that wood fires are not the eco-friendly heat source many used to think they were, and are now discouraging their use. Sure, most heaters are built to burn very cleanly when used properly, but very few are used properly, and that’s the problem.

There are better solutions, such as pellet heaters, which don’t control airflow, but rather fuel flow, so they always burn the fuel in plenty of air to ensure clean burning. The pellets are usually made from agricultural waste that would otherwise have been burned or landfilled anyway. The only issue is that the pellets are not sourced locally and so there’s transport emissions, which could be considerable.
If you want to go down the wood heating path, monitor your wood collection and also how you use it, making sure it is properly dried and burned with the air damper fully open.
Lance Turner

Solar panel lifespans

I was hoping you might be able to help with a query I have received from one of our engineers about solar panels. What is the usage life of a solar panel, he understands it to be 15 years. And once they are retired are they recyclable, and do we have the infrastructure to recycle them or are we preparing for the boom in disposal?
Karen Freidin

The minimum life expectancy of a solar panel is around 20 years but most manufacturers give 25-years warranties now. Most rate their panels for at least a 25 year life and some rate them to 30 years. Uni-Solar rate theirs for a 40 year life.

As far as I know there’s no one recycling solar panels in Australia, although there are schemes elsewhere. There have been a few articles on these schemes, such as this Treehugger article http://bit.ly/solar-recycling and this on The Daily Green bit.ly/dg-solar

There’s even a company that’s collecting them in preparation for recycling schemes, see pvrecycling.com

Solar panels contain some valuable materials, including trace rare metals, silicon and aluminium. Therefore they do have recycling value and it’s only a matter of time before someone starts doing it here. However, as the PV industry has only geared up here in the last decade or so, it will probably be another 10 years at least before large quantities of panels become available for recycling.
Lance Turner

A double duty fire pump

I am building a new house and will install a large water tank for combined domestic and fire fighting purposes. We will need an electric pump for the house water, and the Rural Fire Service require a minimum of 3kW (5hp) petrol or diesel powered pump and a 38mm or 65mm storz fitting for fire fighting. Is it feasible, technically and financially, to do away with the petrol pump and instead install just the one pump for domestic and fire, powered by mains electricity with a battery backup? I assume 30-60 minutes of pumping through the 38mm outlet would be needed in a fire.
Nick Manning

While it is technically possible, it’s not something I would do as the two tasks are very different. A house pressure pump needs to flow a few tens of litres of water a minute at fairly high pressure, while a fire fighting pump needs to flow a great deal more. So, if you were to use a pump capable of being a fire fighting pump as a home pressure pump it would run inefficiently most of the time. The only way to avoid that would be to use a very large pressure tank for the home, at least 200 litres or more. Personally, I think all home mains pressure systems should have a tank this size anyway to greatly reduce pump stop/start cycles, but most homes don’t.

The other issue is that fire fighting pumps are often more useful if they are portable. Being able to move the pump if needed can reduce the length of hose required and the flow losses associated with it. Also, if a pump is fixed and tethered to a power system there’s always the chance that the system could fail at the most critical time. Fuses and circuit breakers can trip, or you could get caught when your batteries are at a particularly low level.

Personally, I would use a pump for the home that is optimised for that purpose and have a separate fire fighting pump. After all, they are only used very occasionally so there’s minimal running costs. If you did want to use an electric pump for fire fighting, you could put together a setup where there’s a separate battery bank for the pump which is kept on float charge by the main system via a DC-DC converter. If going down this path I would use a DC pump motor, not an AC one, which eliminates the need for an extra inverter and the associated cost and complexity. Really, anything is doable if you want to spend the money on it, but considering how often a fire fighting pump is used, you are better off keeping it a separate system rather than designing the main house system to include those capabilities.
Lance Turner

Replacing air conditioner controls

Our Bonaire evaporative air conditioner is suffering from a deceased control circuit which is instructed via a remote hard-wired handpiece. According to the manufacturer, as my appliance is over 10 years old they no longer make a replacement board.

They claim that they can fit a more modern board, operated by radio, however, the quoted cost really cannot be justified.

In addition, a neighbour has replaced their old 2-speed motor air conditioner with the latest technology and seem to have swapped reliability for uncertainty as to whether the new machine is going to operate or not.

Technicians advise that problems are due to ‘local radio interference’ such as remote garage door openers and they are unable to rectify the faults.

It seems to me that these air conditioners are not really fit for purpose, hence my reluctance to venture down this path.

Looking further ahead, the time will come when our unit will be beyond economic help. With this in mind, I would appreciate your thoughts on the viability of using a modern industrial inverter speed control. The other functions performed by the current circuit board, i.e. water valve solenoid, water pump etc. can be easily bypassed and operated manually.

If this proposal is viable and in the interests of conservation, when the machine ultimately dies, I intend salvaging the motor/control unit for a new life in my workshop. In fact, I have two of these motors and sending them to a disposal site seems a real waste. The motors are made by Webster Manufacturing in South Australia, are rated at 800W and have four connection terminals on one end.
Jim Crawford

Without knowing what type of speed control the system uses I can’t really say, but many smaller devices use capacitive or inductive control, i.e. they just put a capacitor or inductor in series with the motor for the lower speed. You could do this just with a double throw switch if you were happy to do it manually. If it had variable control, you could use an off-the-shelf speed controller, some of those will handle up to 2000 watts. The rest of the functions, as you say, can be manually controlled. You could also remote control them using aftermarket remote units such as those sold on eBay. The store at stores.ebay.com/ColdfusionX-Electronics/ has a good range and I’ve used their remotes before and they work well.

The other option would be to use a small microcontroller board and program the operation into it. There’s a number of cheap options, the most popular now being the arduino boards as they are low cost, and the programming software is free and easy to use. There’s various interface boards available for them including relay and isolated triac control boards, so the interfacing shouldn’t be too hard.

It’s interesting that others are having problems with their air conditioner remotes; most modern remote controls are digitally encoded so that other radio sources don’t interfere, as the radio bands allocated for this sort of work have tended to become quite crowded with all the remotes out there now. It seems some companies are still not using properly encoded remotes—just cheaper to use the old technology I expect!
Lance Turner

Panels not facing north

I live in a lifestyle retirement village at Seaford, South Australia, and we have recently been given permission to install a 1.5kW solar electricity system. I am looking at two options—monocrystalline and thin film.

What is the difference in efficiency between a six by 260 watt panel monocrystalline system and a 15 (or maybe 16) panel thin film system? I can only fit the thin film on the east-facing roof. The monocrystalline system will fit on either the east or west roof but installers prefer to put it on the west-facing roof. There is no possibility of installing on the north-facing roof—there’s no room for either system.

I am interested in which system will produce the most electricity and any other pros and cons there might be.
Chaye Oliver

Panels really should face north, but if you can’t do this, try and get all panels facing the one direction. However, this depends on the array configuration and the type of inverter used.

For instance, you might have an array where all the panels are wired in one series string. If you face half east and half west, then the whole string will only perform as well as the side with the lowest insolation. In other words, in the morning you won’t get full power from the east facing panels as the west facing panels are getting almost no sun, so the whole array will put out very little. In the afternoon, the same thing happens.

If the east and west arrays are separate and are wired to separate inputs on the inverter (some inverters have multiple separate inputs), then each array half will perform as well as it can, so there’s no issue splitting it across roofs that face different directions.

Don’t worry about efficiency of the panels, this isn’t the issue really, all it determines is the physical size of a panel for its rated output—a 60 watt crystalline panel will have a smaller size than a 60 watt thin film because the thin film is less efficient, but they both are still rated at 60 watts. However, thin film panels are less prone to reduced power output as they heat up (known as the temperature coefficient) and so generally, given two equivalently rated arrays, the thin film array will produce more energy over the course of a year as it performs better when hot (the usual condition for panels in Australia). Some crystalline panels have improved considerably in this way in the last couple of years, but you need to look at the specs for each panel. The coefficient is given as a figure of percentage per °C above 25°C, the smaller this figure, the better. For instance, a panel with a temp coefficient of -0.5% per °C running at 60°C will actually put out 0.5 x (60-25) or 17.5% less power than its rating.
Lance Turner

Flow batteries

I am an ATA member in the process of building a new house and installing stand-alone solar power. We have been advised by one company to wait for the RedFlow batteries to appear on the market as they are better batteries. As we have never heard of them could you please provide us with the pros and cons of these batteries?
Kristine Woodd

The standard workhorse in the stand-alone power system industry is still the lead-acid battery, but there are several newer technologies starting to make inroads. Flow batteries are one type and the RedFlow batteries are included in this category, as are Vanadium redox batteries.

The other technology that is now being used to replace lead-acid batteries is lithium iron phosphate and similar chemistries. A couple of examples of suppliers of these are ThunderSky (Winston battery, see http://en.winston-battery.com/) and Sky Energy (now China Aviation Lithium Battery Co (CALB), http://en.calb.cn/). Both of these batteries are available in Australia. While these are expensive initially, they have vastly longer lifespans than lead-acid and because they can be deep cycled with little effect on lifespan, you can often use a smaller battery capacity compared to a lead-acid battery bank.
Lance Turner

LED lighting for the home

I have been an ATA member for about 12 years and we are currently preparing to build our new home in the Perth hills. I was hoping to use LED lighting when we build and have read most of the ReNew articles, particularly in issue 90. I am not up to date with the technology and was wondering if you may know of any products off-the-shelf and where I would find them, and if you had any system design advice for a novice. Internet searching has left me with more questions than answers.

We are also considering going stand alone with the power supply in the future, what impacts would this have on the light system?
Dwayne Scook

My first suggestion would be to avoid downlights if at all possible. They cause all manner of problems, the main one being that they compromise ceiling insulation and the most common ones (narrow angle replacements for halogens) are not a suitable light design for general room lighting. There are LED downlights with wide beam angles designed for ambient lighting but they still require holes in the ceiling and insulation. There are some insulating covers designed to overcome this problem but they add to the cost and complexity of installation.

If you are looking at having the whole house running 240 volts (i.e. using an inverter for everything when you eventually go off-grid) then I would use light fittings designed to take standard GLS globes and fit them with LED bulbs—there’s quite a few good ones including those from EarthLED and Viribright, but there’s many others, some even have Australian approvals. Switch lighting (www.switchlightbulbs.com) is due to release a 240 volt version of their bulbs early next year and Philips is extending their LED bulb range in Australia later this year, so the options are growing.

Another option is LED strips and ribbons. The prices of these materials have dropped enormously of late. While most of it is Chinese sourced (the ‘brand name’ ribbon can cost up to $200 a metre), the quality is still not bad and you could expect up to a decade of use from it, depending on how long it’s used for each day. Most ribbon runs from 12 or 24 volts DC, so you power it from a suitable power supply, which are readily available and cheap. However, this also allows you to wire the fittings to a compatible battery bank at a later stage. Even if you have a 24 or 48 volt battery bank, you can simply use a DC-DC converter to supply 12 volts to the ribbon. The advantage of doing it this way is that you are not relying on your inverter for lighting, so should your inverter fail, you still have lights. Also, when running a house-sized inverter at low loads, the inverter runs very inefficiently. Indeed, at very low load levels an inverter can waste a great deal of energy, negating the use of efficient lighting altogether.

There are also rigid lightbars that are similar to the LED ribbons but are contained in aluminium casings. I have recently found one that comes in a 15mm x 10mm case with a clear cover and has an inbuilt switchmode driver and rectifier, so it runs from any voltage up to 30 volts, AC or DC. It doesn’t get much simpler to implement than that.

So, yes, LED lighting is complex, but that’s because there are so many options. And that’s a good thing, as you don’t have to stick with the same type of light in each room. You can mix and match and find the most suitable type for each room of the house. But, the simplest solution is standard GLS type light fittings and suitable LED bulbs. It’s a fast, simple and cheap option and gives you the opportunity to try all manner of LED bulbs.
Lance Turner

Halogen transformer failure

Have you ever heard of plug-and-play MR16 LED downlights causing the failure of switchmode electronic transformers? I have been using some 6 watt LED downlights to replace 50 watt halogens and they seemed to work fine upon initial installation. In one recent instance, four lamps were installed and within a few days, three of the electronic transformers failed. If it was one, I would say the transformer was already on its way out, but a 75% failure rate seems to indicate that the LED lamps may have had something to do with it.
Ethan Burns

Standard transformers are designed to drive into a simple resistive load whereas the drivers inside the LED bulb would be drawing current in a non-linear fashion. This would affect some electronic transformers and not others, it just depends on the quality and/or design of the unit.

Generally, when doing LED upgrades, I try to encourage people to ditch the transformers altogether and fit GU10 fittings (the bulbs run directly from mains voltage), they look the same as an MR16 fitting just without the transformer hassles.

To solve your problem you should replace the transformers with proper LED transformers, which usually have a regulated 12 volt DC output. ATA has some in the ATA webshop and there are many other sources. If your transformers are plugged into power points up in the ceiling, then you could even replace them with standard 12 volt DC switchmode plugpacks of a suitable current rating.
Lance Turner

Mini maximiser not a MPPT

Can you please tell me the input voltage rating of ATA’s mini-maximiser kit? I am thinking of driving 12 volt fans off a solar panel and I am wondering whether I could use amorphous silicon panels (which have an output voltage of around 40-60V and output power of 50W) as direct input or whether I’d have to level-shift the panel voltage first.
Dirk Fiedler

The kit is not a maximum power point tracking (MPPT) maximiser but rather just works off a fixed setpoint voltage. It allows the panel to charge the capacitors and when they reach that setpoint it connects them to the motor to dump a pulse of current into it. This causes the cap voltage to drop a bit and the motor is then disconnected from the caps and the cycle repeats. However, if the current from the panels is greater than the motor needs then the maximiser effectively leaves the caps and hence the panel connected directly to the motor. This causes two problems with such a large panel to motor mismatch.

The first is the motor is overdriven until it reaches a point where the voltage across it is high enough to cause it to draw the full current available from the panels. This means it could be running at a very high voltage and hence considerable overspeed.

The second problem is that the maximiser circuitry itself is not designed to handle such input voltages. For the 24 volt version it has a voltage regulator on board but not for the 12 volt version. You would have to adjust some component values in order to keep the regulator function but run it as a 12 volt output unit.

When running a 12 volt motor you should use a nominal 12 volt panel, and a 24 volt panel for a 24 volt motor.
Lance Turner

Welders and gen-sets

I have a PV-run home and use a 6.25kVA gen-set for high demand work. I recently acquired a CIG 170 inverter welder and found that it wouldn’t run off the gen-set. I made enquiries and was told that I needed more than 6.25kVA to run it, and since the gen-set was about 16 years old and has done an enormous amount of work I decided to buy a Chinese made unit advertised as a 10kVA.

On checking the specifications on the internet it turned out to be 9kVA. I bought it and on reading the manual it is actually rated at 8kVA. Still, I thought it would run the welder, but it won’t on a regular basis. It did once and worked fine but it just switches itself off since then and prior to then. Could the problem be that the get-set is making dirty power? If so, can I buy any device to clean up the power. Any advice or suggestions appreciated, thanks. The welder works fine on mains power.
John Carroll

The problem is that welder has a kVA rating that’s exceeding the generator’s capacity. With AC, kVA is not the same as kW, you have to allow for power factor (which is a ratio of the real power to apparent power). What this means is that as the power factor of the load gets worse, the kVA capacity needed to run the load increases, even if the actual power in kW stays the same.

Your inverter welder uses a switchmode power supply and these can have poor power factors as they will usually draw their current in short, sharp spikes near the peak of the waveform. There’s a great example of this at http://bit.ly/gensetpf where you can see the current waveform distortion caused by a computer power supply. Even though the voltage and current are in phase, the waveform distortion reduces the power factor considerably.

To calculate the kVA capacity needed to run a particular load, you divide the rated power by the power factor. For instance, a 5kW load with a PF of 0.6 would need a gen-set rated at least 8.3kVA, but in practice it would need to be higher.

What you need to do is to find the power factor and kW rating of your welder. It should be listed on the specs plate somewhere, although power factor may not be listed. If not, then the only way to find out what it is (if the manufacturer can’t tell you) is to measure it with a suitably rated energy meter. Also, the power factor of a load can change depending on the power being drawn by that load. For example, when using the welder on a light setting it might have a PF of 0.8 but on a higher setting that might drop to 0.7.

If this is all too difficult then your only real option is to trade up to a heavier duty gen-set. I would buy something with a kVA rating of at least twice the kW rating of the welder.

I couldn’t find PF specs on the CIG 170 but the similar (in specs at least) BOC MMA 170 has a rated PF of 0.73. Judging by its output of 170 amps and voltage of 20 or so volts I would expect its input to be somewhere in the range of 4.5-5kW, meaning it could need at least 7kVA to run it. Assuming yours is similar then your gen-set is borderline as cheaper gen-sets rarely live up to their ratings. I would just upsize the generator or find one that can handle loads with poor power factors.
Lance Turner

Tanks and solar hot water

We are in the final stages of having our farm resumed by the state government to build a cargo railway line. We have been thinking of going solar for a few years but the uncertainty of our situation has caused us to put it off. However, the new farm will give us the opportunity to set things up right from the start and we would like to generate enough electricity to meet our own needs whilst still being connected to the power grid.

We will not have town water and will be dependent on rainwater tanks. This means whether we get a passive or an active solar hot water system we will need to use electricity to pump the water to the roof or off the roof respectively. As much as we like the idea of solar hot water could there be disadvantages without mains water pressure?

Would it be easier, environmentally friendly and in the long run more economical for us to have an ordinary electric hot water system with a larger photovoltaic panel array rather than a solar hot water system with a smaller PV array? The house already has an ordinary electric hot water system in good condition.
Bill Parke

There’s a few solutions, but generally people on tank water will usually have a pressure pump coupled with a large pressure cylinder to simulate mains pressure. This is the simplest solution and lets you run any mains pressure system you wish. Provided you go for a big pressure tank (at least 200 litres), the pump won’t have to run too often and you can use a smaller, lower powered pump. Many plumbers will specify a large, high powered pump and a small tank, but this is inefficient as it results in many stop-starts for the pump each day, which loads up the inverter and wastes energy.

If you are happy running everything on low pressure, then just pumping to a good-sized header tank will also work and it eliminates the need for a pressure-rated cylinder.

If you decide to go for an electric-only water heater, don’t get a purely electric unit as they waste a lot of energy; a heat pump system will produce the same amount of hot water for a third of the energy use (they work like a fridge in reverse, gathering heat from the air and concentrating it in the tank). This is especially the case if you want to power it from solar‑you need to make everything as efficient as possible.
Lance Turner

12 volt washing machine

Some years ago I was given part of your book Build your own green technology. On page 89 there was an article by Chris Harkin on converting a Hoovermatic twin tub to 12 volt operation.

Unhappily I only have page 89 of this article and I am now in desperate need of the rest as I live on a farm without electricity so am totally dependent upon my wind/solar system.

Please would you be so kind as to send me the rest of this article so that I can get someone to convert my twin tub. I am based in South Africa.
Rev. Angora van Doorn

That’s an old article that first appeared in our magazine Soft Technology (now known as ReNew!) I’m not sure how relevant it will be for your machine.

I take it you don’t have an inverter, but instead everything runs from 12 or 24 volts DC? There are some very low powered washing machines around that can run on small inverters, but that depends on your budget of course and I’m not sure what sort of range of machines you have access to over there.

If you already have the machine and want to convert it, I don’t recommend rewinding the motor as they did in the article, it’s a great deal of work. 12 volt DC motors are readily available from car wrecking yards as they are used for fan motors, wiper motors, window winders etc. More powerful units can be found in trucks and buses. They are also used for electric wheelchairs and various other small electric vehicles and can often be found for low cost but it can take some searching. Ebay has a new global search site at global.ebay.com that can help you find suitable parts if you can’t find them locally.
Lance Turner

A solar cellar

I’m interested in putting some solar heating into my cellar. What I was thinking of was building a greenhouse and then blowing warm air from the greenhouse into the cellar.

So what I need, ideally, is a solar powered fan that could blow warm air through a duct into the cellar. Some sort of thermostatic control would probably also be needed.
Can you suggest where I might get it?
Dave Clarke

Great idea. A solar greenhouse to heat the cellar…simple, cheap and you can do it yourself. For the fan(s) you could use a large 12 volt computer fan—Jaycar has a good range (have a look online and you may find a 12 volt fan and duct combination). Match the fan up with an appropriate solar panel. Choose one with a similar power rating to the fan.

You don’t really need a thermostat as the solar panel will only operate the fan when there is enough sun, and therefore heat, to make the greenhouse and hence the cellar warmer.

So there you are—a nice, simple, cheap cellar heating system. If you really want to use a thermostat there are some good ones available online such as the unit at http://bit.ly/pdnNAN.

However, you really don’t need a differential thermostat as the temperature in the cellar is likely to be constant and almost always cooler than the greenhouse. A simple temperature based thermostat would do. But I would try the simple way first and just use the solar panel to switch the fan on and off.

Ducting is available for central heating and airconditioning companies.
Mick Harris

Extending a solar system

We have twelve 180 watt solar panels installed (2.16kW) and a Fronius IG30 inverter, which is listed as a 3kW inverter on the invoice.

The Fronius booklet states under input data the recommended PV power is 2500 to 3600Wp and under output data, nominal output power is 2.5kW and maximum output power as 2.65kW.

We are looking at increasing the power we generate so my questions are:

1) Is the Fronius IG30 a 3kW inverter and/or can it accept up to 3.6kW?

2) We currently have two rows of six 180 watt panels, can we add a row of four 180 watt panels, making the system 2.88kW, or do we have to add six panels, making it a 3.24kW system, and if so is this okay for the Fronius IG30?
Judy Tulloch

Adding small numbers of additional panels to your system can be tricky. First you need panels which are compatible. This means you need panels with the same electrical characteristics—the same voltages and power output. The power outputs of solar panels have been creeping up recently. A few years ago, 165 and 175 watt panels were common. Now most panels are 185 or 190 watts. Finding panels with the same wattages can be difficult.

The next problem is to do with the way the panels are wired. Panels are wired together in strings (in series). The voltages of the panels are added when wired together. So eight 24 volt panels wired in series would give 192 volts. These voltages are required as most inverters require high voltages to operate. A typical 3kW solar array could have two strings of eight panels each. If you try to add another string of four panels this does not give you enough voltage for the inverter and also does not match the voltages of the other strings. So it may be necessary to rewire the existing strings so that you have two strings of 10 panels.

However, this depends on the inverter’s input voltage range. It may only be possible to have three strings of six panels or three strings of seven panels. This is where an accredited designer is required to make sure the string configuration will suit the inverter’s characteristics.

Now, looking at your specific situation, your inverter currently only has 2160 watts of solar PV input so you could certainly add more panels. How many depends on the inverter voltage characteristics and the string configurations as explained above. The power input you quote of “2500 to 3600 Wp” is still dependent on the way the panels are wired. However, if the manufacturers are marketing the inverter as a 3kW unit you would not want to go too far over that total power.

Really, you need to consult an accredited designer to get an appropriate upgrade design.
Mick Harris

Cheap genset backup

I was interested in your view on LPG generators. I know the preference would be for a solar back-up solution, however I am not sure if I want to invest the upfront capital for a system that would only be used once every couple of months. Elgas currently have a special on LPG generators and I know everyone says, ‘don’t buy anything from China’, but for an emergency back-up it is a cost effective solution. The only concern I have is the quality of the power and I would probably just have my fridge/lighting on this as I would be concerned that the quality of power may damage my plasma TV over time.
Gavin Gordon

Some gensets have regulated output, some don’t. The simpler ones are just an engine hooked directly to an AC alternator probably won’t be regulated and output voltage will vary somewhat with load, as will the frequency. However, this isn’t much of a problem nowadays as most electronic devices have universal power supplies with wide input voltage and frequency ranges. For instance, a typical power supply might have a voltage range of 100-250 volts and frequency range of 47 to 63Hz.

The only possible issue I would expect is that if the genset is very lightly loaded, the output voltage might be a bit high, but that’s easy to test with a multimeter and if you are concerned, just connect a simple load like a lightbulb to bring the voltage down a bit. So long as you stay inside the ratings of the TV’s power supply you should be fine.

Much of the Chinese stuff is much better than it used to be, I certainly don’t discount as an option Chinese made goods any more, I have a mains pressure pump which is a Chinese cheapie and it’s great, as are a number of other devices I have, the average quality of Chinese goods has improved enormously in the last few years. Besides, almost everything you buy is made in China, including the PC you are typing on most likely!
Lance Turner

Solar power credits

I live in country Victoria and have just had a 2kW PV solar system (with a 4kW inverter for later expansion) installed as I have always wanted to go a bit greener and like the idea of something for nothing after the initial cost.

I plan to have the second 2kW of panels installed soon and have had a site inspection and am currently waiting for the written quote.

I was wondering what happens tax-wise if we are always in credit on our power bills and have the money paid out? As of our last bill we were $200 in credit with out solar hot water which I have just installed.
Andrew Bristow

At this stage, feed-in tariff revenue does not affect personal tax liabilities. The only consumers that can get caught are pensioners or other social security beneficiaries who may have their entitlements adjusted based on FiT revenue.

Of course, this is not to say that the ATO may make a ruling in the future to count FiT revenue against taxable income, but this is not the case at the moment.
Damien Moyse
ATA Energy Projects & Policy Manager

Pumped energy storage

I am an ATA member with a keen interest in renewable energy and associated technologies. Recently, a friend with similar interests approached me for some advice concerning an alternative energy idea he has come up with for his rural property.

He has installed 1.2kW of grid-connected solar PV and is also considering some small-scale wind power for his property. In addition to this he has a 9 megalitre dam and potential for storage about 60 metres above this on the top of a hill. He now wants to determine whether he could install a small-scale pumped storage system using micro hydro.

Do you know to whom we should speak to about working out whether the proposal is sensible or not and secondly, if it is sensible then whether we could apply for a grant for its installation? I am not aware of any small-scale, renewable energy powered pumped storage systems anywhere and I think it might provide a useful test project for such a system.
Mike Horne

The problem with pumped energy storage systems is that there are considerable energy losses. You lose energy due to inefficiencies in the pump caused by friction, cavitation etc, as well as frictional losses in the pipes. At the generation end you also have pipe friction losses, generator losses etc. In short, a pumped storage system wastes a lot more of the originally generated energy than does a large battery storage system.

As he has a grid-connected inverter, it’s not clear why he wants to store energy in a pumped storage system. In a GI system the grid effectively acts as your energy storage, and it’s a lot more efficient at doing so.

His wind power system should also be able to be connected to the grid. It might need a different grid-interactive inverter to the one installed but there should not be any reason (technically at least) why he can’t have two parallel systems.
Lance Turner

Solar car battery charging

If one wished to connect a low current 12 volt solar panel to one’s car battery to keep it charged whilst parked in the garage for three months unattended, would a regulator unit be necessary? The PV has an isolating diode in it to prevent leakage when there’s no sun.

With some late model cars I have been told that the disconnection of the battery will cause the loss of some settings in computer circuits of the car and when a battery needs changing they put jumper leads on to prevent this.

Any helpful comments appreciated.
Brian Jones

You should put a regulator on any battery not being monitored regularly. Car batteries have a fairly high internal discharge and will probably be okay if the panel is sized to just replenish this with not a lot of extra input, but there’s no way to know what this leakage actually is without letting the battery go flat and seeing how long it takes. The leakage increases as the battery ages too, so you are better off getting a slightly bigger panel that will cope with keeping the battery charged as it gets older. I would use at least a 5 watt panel for this use, some of the small ‘battery keeper’ panels are too small for long term use.

You are only looking at $20 or so for a small regulator so it’s not worth damaging a good battery for the sake of a small amount of protection.

The Regulator buyers guide in ReNew 100 will give you a place to start. Note that Futurlec (www.futurlec.com) now have a range of prebuilt regs that seem to work well, I’ve got one on a system at my place and it’s been perfect for around a year now. There’s a number of other low cost basic units available from online sellers, as well as ebay.

That is indeed true about settings being lost, and not just on newer cars, my ’94 Liberty forgets if I disconnect the battery. The engine has to relearn its correct idle speed which takes a few days, which is quite bizarre actually. I have a small spare 12 volt lead-acid battery that I clip across the battery terminals before I remove them from the main battery. There are battery keepers that consist of a 9 volt battery clip connected to a cigarette plug via a diode but these are pretty useless as most cigarette lighter sockets seem to be switched by the ignition nowadays. A small battery with clip leads and a diode for protection is the simplest solution.
Lance Turner

Solar power increases bills

I want to install a solar power system but one of my friends has installed a 1.5kW system and their bill has gone up three-fold. Their usage before is about $800 per bill with AGL. After the solar installation the bill has gone up to $2400.
Is that because the solar system is too small and once you have installed the solar system the electricity company started to charge use based on off- and on-peak usage?
If my usage is about 4.2kWh each day should I install a 1.5 or 3kW system to avoid such a huge jump in the bill?
Joseph Choy

This is not the fault of the solar power system, it is caused by the new power meter and new tariff structure that go with it. Putting in a solar power system will result in the early installation of a new smart meter (we will all get these meters eventually). These meters have a dual electricity rate.

During the day electricity costs more and at night and on the weekend it costs less. In my case I pay 26 cents daytime and 11 cents at night. The average cost should be about the same, but if you use a lot of energy during the day your bill will go up. If you have a small solar power system (say 1 or 1.5kW) then this system will not produce enough electricity to significantly reduce your energy use and the higher electricity price will push up your power bill. But if you have a bigger system that produces more than you use during the day the exported energy can dramatically reduce your bill.

Start by doing everything you can to reduce your daytime energy use. You could also put in a larger solar power system.

Solar can work well for you if you get the numbers right. My feed-in tariff is about 66 cents per kWh. I have a 2kW system and small energy consumption. I have not paid a power bill since I installed the system and have a $126 credit.
Mick Harris

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