E-News Issue #21
Well, the big news this month is the Goods and Services Tax (GST). Someone said they heard that renewable energy products were to be GST free. I've been scanning the media etc and have been unable to confirm or deny this position. We've also written to the Democrats and to SEIAA seeking to lobby and clarify the situation. However, there does appear to be some good news in the Democrat "green" package:- $4M per year (rising to $6M and $9M in subsequent years) for up to half the capital cost of household PV systems and a big $66M per year to convert rural diesel generation to renewable energy. Personally, I don't like the GST but maybe there is some good news in it for our industry.
Plasmatronics PL40 Regulators
We are very pleased to see these roll off the production line. We've filled your back orders and by the time you receive this, they should be in stock.
The 20W unit has become unavailable (we are not certain for how long). We do have a 35W one available for $6 wholesale.
There are a lot of high level talks and planning going on. The merger will take effect from 1 July as previously announced. However, we are still pretty much in the dark as to what will happen in terms of affecting us, our competition and our product range. Stay tuned for some interesting times ahead!
Flat Batteries in Winter - by Peter Padels
The problem of having plenty of power to spare in the summer months and battery troubles due to lack of solar input in the winter months is a common one for most 'stand alone' solar folk in the Australian southern states or anywhere in the world in the temperate zones.
With 'stand-alone' I am not referring to the fact that you are alone and capable of standing on your own two feet, but that you have a power system which is not grid-interactive (ie capable of buying and selling power to the national grid) or grid-tied as they call it in USA. This problem may not be an easy one to find a solution for and a bit of lateral thinking may provide a different solution in each scenario. There are a number of possible solutions worth considering.
One being the purchase of more solar panels to see you through the winter months. The other being the purchase of an inverter that is capable of turning a diesel generator on and off as required.
For your first solution you will need a lot more solar panels, but not necessarily a lot more battery storage. Batteries use power to function, some of the energy used to charge batteries is used up in the making and breaking of chemical bonds and some of the energy being 'wasted' by the battery in what is referred to as self-discharge rate. Despite what many people believe, batteries do not store electricity.
A battery converts electrical energy into chemical energy when the battery is charging and then converts the chemical energy back into electrical energy when the battery is discharging. Any lead-acid battery will discharge at a rate of 1% per day or greater, depending on the type of battery it is and its age. As the battery gets older, its self discharge rate increases, to the point where eventually you may have to scrap the battery if it becomes too wasteful of power if it hasn't died from other causes in the meantime.
It is not just age in terms of years that causes this kind of deterioration, but the kind of use and abuse that the batteries get in their life. Just like certain levels of self-abuse such as smoking, excessive drinking, poor diet etc will cause more rapid physical aging in humans, the use of contaminated water (as opposed to distilled or demineralised water), excessive charging and discharging, frequent and deep discharges will all cause premature aging in batteries.
Some people may come up with the solution for lack of power by simply just adding more battery storage. But if you get the gist of what I have just been saying, doing so may in fact be a step backwards.
There needs to be an optimum relationship between the size of the loads, the amount of energy capable of being delivered by the charging source and the battery bank size. Because your system works quite adequately in the summer months, I would suggest that the battery bank may already be of a suitable size unless your loads increase dramatically in the winter months. In the winter months it is your charging source that reduces in output and it is this that needs to be increased in order to save your batteries in the present scenario.
Hence solution number one, buy more solar panels.
Solution #1, Buy More Solar Panels
Buying more solar may be a solution, but if you are talking about a lot of cloud cover in winter, I would again agree with Alan T Gray's assessment of it not being the solution that "... I'd rush into because you'll be burning off power in summer ... like crazy."
When I design a solar power system I base it on average solar radiation figures for each month of the year for the location for which the system is being designed. I usually design for 4 or 5 days autonomy to a maximum discharge of between 50% and 70%. It is not a very good idea to totally discharge a lead-acid battery.
Not having your particular load data, I cannot carry out such an assessment, but I would not be at all surprised if you would need perhaps three or four times as many solar panels for the winter months, as the days are shorter, your loads have probably increased and solar panels produce considerably less power in overcast conditions. I would hope to find a more palatable solution than this.
Solution #2, Interactive Inverter Charger
Many of the more expensive and fancier inverters are based around computer components, both to determine the actual sine wave shape as well as a host of other functions such as degree of sensitivity to small loads to switch on from standby mode, turning specific appliances on and off at predetermined times and turning a generator on and off, based on time of day, battery voltage or calculated battery amp-hour capacity.
The up-front cost that you quoted may be similar to the real cost of solution #1. One difference being that you have a constant on going cost of buying fuel, as well as having a noisy, polluting and inefficient solution. On a more positive note it certainly is an excellent way of looking after your battery bank without having to increase your personal workload much beyond needing to guarantee a constant supply of fuel to the generator.
The cost does not have to be as great as you indicated in your letter. A Selectronic SA21 sinewave inverter in combination with a Woods 24 volt 80 amp charger would be able to do most of what the Trace can do for less (about $4000).
The Selectronic Inverter can turn the generator on when a predefined voltage or a predefined Low Amp-Hours reading is reached, but then the generator would stay on for a predetermined duration rather than when the appropriate voltage or amp-hours is achieved. If you are quite happy with the inverter that you already have, then the same generator control can be achieved with a fancy solar regulator.
These regulators can keep a record of battery volts, maximum and minimum volts for the day or week, incoming amps, accumulated amp-hours for the day and much more. The inverters I discussed in the previous paragraph can also provide a lot of this kind of information.
The new Plasmatronics PL regulators now also have generator control functions, being able to turn the generator on at a predefined Low Amp-Hours reading and to then turn it off again when the Amp-Hours reaches a preset value. The 20 amp Plasmatronics regulator sells for $290 and the 40 amp version sells for $380.
Solution #3, Other Energy Sources
With sufficient solar panels to meet your summer loads, it may make a lot of sense to look for another energy source, preferably one that is more readily available over the winter months.
When you mention lots of cloud cover through winter, the question arises whether this cloudcover is associated with windy conditions or plenty of rain. You may find that by adding a wind turbine or a micro hydro turbine to your existing power system that this could get you through the winter months without having to rely on fossil fuels. A reasonable size wind turbine may cost you a similar amount to solution #2, but the micro hydro option will probably cost you less than the diesel generator, assuming that you have access to a creek or spring with sufficient head.
For the micro hydro to be worthwhile you would only need sufficient water flow through the winter months when the solar doesn't keep up.
Another possible energy source could be a woodfired steam engine, which could also be used to heat water using the waste steam and to warm the air in the house by connecting the house to the steam shed with air ducts. The biggest problem with steam engines is that I don't know of anyone who has ever managed to automate them and they tend to be a bit labour intensive.
Solution #4, Reducing Power Consumption
I am not talking about living in the dark and not using any appliances every winter, but improving on energy efficiency and reducing power consumption without affecting lifestyle.
With most household appliances, energy efficiency appears to be of the least concern to the manufacturer, whereas user convenience tends to get priority treatment. Hence putting a heating element into the walls of a fridge so that they don't accumulate frost is considered a good selling feature even though it is counterproductive to the operation of the fridge to keep things cool and causes the fridge to consume more energy to achieve the same result.
Many solar households have everything dependant on an inverter to provide the power. This means that if you wish to do something that doesn't require very much power in itself, such as listening to the radio or just having one reading light on in order to read a book, the inverter maybe using many times as much power as the radio or the light requires just to stay in the on mode.
The closer the continuous inverter rating is compared to the actual load requirement the more efficient it will be. With both the radio and reading light situation the most energy efficient option would be to have them powered directly by the battery which would require having to have a 24V reading light instead of a 240V light and having a portable battery powered radio connected to the battery supply via an appropriate voltage converter.
We sell a voltage converter that will supply 12V from a 24 volt supply and at a very high level of efficiency.
Similarly, you would not use a 240V clock radio as that would require the inverter to stay on and consume power 24 hours per day. You can buy a range of portable stereos that can be connected to the battery supply that have a programmable timer with an LCD clock built-in and can turn on the radio, CD player or tape deck at any pre-programmed time.
If you like to be able to record TV shows to watch at a later date, it would be worthwhile considering buying a TEAC model MV-1414P 34cm AC/DC TV & VCR combination which is able to keep the time and record a program at the chosen time without requiring a 240V supply. If you were to do the same with a standard 240V TV & VCR combination, the inverter would have to stay on the entire time that you weren't going to be there in order to record the program, which can add up to quite a considerable amount of power.
If you wish to use a computer, you may argue that a desktop computer is less cost than a laptop or notebook computer. Considering that the laptop computer uses one tenth of the amount of power that the desktop computer uses, this cost comparison is suddenly weighted very much in favour of the laptop computer.
As a rule of thumb, the desktop computer would require something in the order of 60W to 80W worth of solar panel for each hour of the day that you use it for, whereas the laptop computer could run all day long on one single solar panel.
The desktop computer would need an inverter costing between $500 and $850 to supply sufficient power whereas the laptop would need an inverter costing only $100 if you are not able to run it directly from a DC supply. So if you need to provide your own power to run the computer, the laptop computer will work out considerably cheaper.
Your average 240V washing machine consumes about 600 watts whereas the Fisher & Paykel Smart Drive washing machine consumes 80 watts when washing and 165 watts when spinning, giving an average power consumption of only 100 watts.
An hour wash cycle per day will then only consume as much electricity as a 20 watt light bulb being used for 2 hours or as much power as an 80 watt solar panel will put into the battery in about 1 hour.
A Hoover Breeze model U1432 upright vacuum cleaner consumes 410 watts and does a better job of sucking up dust from the floor than any other vacuum cleaner rated up to 1200 watts according to a recent Choice Magazine report.
There are probably many more examples of selecting appliances specifically with the goal of reducing power consumption and very often this can work out cheaper than staying with existing appliances and having to buy extra solar panels to cope.
Solution #5, Changing the Angle of Your Solar Array
You didn't indicate in your letter at what angle from the horizontal (presumably pointing due north) your solar array is mounted.
If, for example, your solar array is angled at 30° from the horizontal, by increasing that angle to 60°, you may increase your solar input in mid-winter by as much as 16%. If you had a solar tracker you may get up to 30% gain in mid-winter compared to the solar array mounted at 30° whereas the solar tracker would only give you 13% gain compared to the solar array mounted at 60°.
If you consider that a solar tracker may cost you $1000 and you have eight 64W solar panels giving you a total of 512 watts, you may find that buying an extra panel (eg an 80W solar panel for $670) is more cost effective.
The expected gain from the solar tracker in mid-winter in your case would be 13% of 512 watts which will yield an extra 66 watts, presuming that the solar tracker doesn't malfunction.
A solar tracker facing the wrong way is worse than having no tracker at all.
Please note that all these figures I am quoting are for Victoria and the situation may be entirely different in a different location.
I hope that out of all these options you find a reasonably cost effective solution to your problem.
Cheers from Dave and all the RPC crew.
Dave Lambert (Director)
- Issue #92 - 06/12/2005
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- Issue #79 - 05/01/2005