Saving money using solar
We have installed a 1.5kWh system at our home which was purchased through our local sustainablity group for $2500 (after rebate) and are finally receiving a 60c p/kwh feed-in tariff from our supplier. We also have a stand-alone system connected to our shed.
We wash our clothes at night when the rate’s at 20c per kilowatt-hour, we don’t have a dryer so use the clothes line or, if it’s wet, the clothes horse in front of the fire. We turn everything off at the power point (including microwave) except the fridge and freezer. We don’t usually have the TV on until after 6pm, unless babysitting, but usually have the radio on.
We also power whatever we can using 12 volts from the stand-alone system. This includes 12 volt hand drills (converted cordless drills), fluoros over workbenches, charging cordless phones, charging cordless headphones, charging our Coleman camping lamp, running the CD/tuner, two 12 volt LED downlights and the media player and hard drive (they have voltage regulators built in and will operate from 11.8 to 14.5 volts). We also have a 12 volt to USB adaptor, with various leads to charge ipods and mobile phones.
I have also run a 12 volt feed from the batteries to our patio which powers our patio lights (I’ve removed the transformer) and a CD/tuner, which was a freebie from a mate. We also have a 12 volt pump for watering the garden.
My wife has finally sorted out all the paperwork with our supplier, after they buggered up the last couple of bills, so soon we will be able to see how much we are really saving.
Lee Saville
Panel orientation makes a difference!
I suspect a lot of people overestimate solar PV output for east and west facing panels. I recently recorded some figures when I stayed with friends near Coonabarabran in NSW (latitude 31°S).
On the property are two systems. Both have the same monocrystalline panels, with six panels in each system and no shading from buildings or trees. One system faces north with a 30° panel tilt and the other faces east with the same tilt. Both were connected to the grid in July 2011.
In 72 days, the north-facing panels produced 427kWh while the east-facing panels produced 310kWh, so the output from the east-facing panels was around 27% less.
I plan to compare the figures after they have been feeding into the grid for one year.
Ashley Campbell
Getting the units right
As a subscriber of a few years now, I’d like to congratulate you on the continuing excellence of the magazine. I look forward to its arrival every quarter.
As an engineer, I am continually irritated by people’s misuse of and misunderstanding of symbols and terminology related to energy—but not in your publication I hasten to add. I don’t think I have ever seen such misuse in ReNew except perhaps in readers’ letters.
Things like watts/hr instead of Watt-hours and the like are plentiful in the media, and especially so on the internet. Battery capacity is a particularly badly understood area. While it’s irritating, it is also understandable given that only people who followed the maths/science stream in high school are likely to have been formally taught such things. Unless you really understand the relationships between force, work, power and time it’s difficult to fully engage in discussions about energy.
My suggestion therefore is for an article or perhaps a series of articles explaining the basics of force, pressure, work and power in physical and electrical terms. I think there’s a real need for some basic knowledge to be disseminated. After all, knowledge is power (pun intended).
Anyhow, that’s my ten cents’ worth.
Neil Biggar
Thanks for the suggestion Neil, if other readers would like to see articles like this email us at renew@ata.org.au
Ed
High cost abatement PVs
I read with interest Alan Pears’ report on the concept of high cost abatement PVs (ReNew 116). I have to agree with everything he said.
What he did not cover was the fiscal side of the matter—money for greenPower is a finite resource so should be spent wisely.
Why should we as consumers pay 60c/kWh for domestic PV-generated electricity when we can get the same energy from (for example) large-scale wind for 9c/kWh? Put another way, we can pay a fixed amount per time frame (say $10 a week) and get 17kWh from PVs or 111kWh from wind. Which would you choose?
Productivity commission findings are that the abatement cost for domestic PV systems ranges from $400 to $1000 per tonne, which is very high on a global scale.
From a broad perspective, if as a society we put the same amount of dollars that have been put into domestic PV into large-scale wind, the green energy sent to the grid would have been seven-fold what we have, to say nothing of the night and winter time generation.
I am all for people having their own domestic PV systems, but why should the rest of us pay for this most expensive form of green energy?
Disclosure: I have grid-connected PV systems, for the generous feed-in tariff which all consumers are paying for.
Bruce Jeffery
Renewables better than underground cables
During the 2010 state election campaign in Victoria, the now-Baillieu government promised to implement all 67 Bushfire Royal Commission recommendations. The article in The Age on 12/09/11, Call for underground wires to cut fire risk, identifies issues being considered in relation to Recommendation 27. Instead of 20 tonne excavators digging through the bush and severely impacting fragile environments, a far better approach is to install alternate systems on properties, rather than incredibly expensive underground cabling. The cost of alternate systems could be borne by the government and the electrical transmission companies creating the rarest of outcomes: a win-win-win-win for the government, households, the electrical transmission companies and the environment.
Properties should be supplied with the appropriate systems, such as stand-alone photovoltaic (PV) systems, while others might need hybrid systems of PVs and wind, depending on the geographic location and the needs of each individual property. Residents should be fully supported to learn and manage these systems and not be lumped with a system they can’t manage. These systems should be maintained by an appropriate body for five years before becoming the responsibility of the property owner.
This approach is a far more sensible option, especially in rural/remote areas where the thousands of kilometres of underground cabling to only a few properties seems an outrageous undertaking.
Leon Trembath
We could not agree more. The ATA has been a contributing member of the Bushfire Powerline Safety Taskforce over the last 12 months, which has been considering bushfire mitigation approaches in fringe of electricity grid locations. The ATA has made the case that it will often be far cheaper for households to be provided with a stand-alone power system, under a properly managed service contract, than to pay for undergrounding or insulating of powerlines lines at hundreds of thousands or even millions of dollars per kilometre.
Damien Moyse
ATA Energy Policy Manager
Reducing fridge startup current
I recently converted a freezer to a fridge; the conversion was successful, with at least a 60% reduction in energy consumed, although I would expect this to be less during summer months. When I measured the starting current it was a whopping 180 amps from my 12 volt system and at times would drop the battery voltage too low for the inverter to cope. Upon measuring the phase angle between the starting and running currents, they were only displaced by about 15°. I expect this is standard for most small fridge compressor motors, as manufacturers do not consider correcting the phase angle as most of these units are plugged into a 10 amp grid powered outlet.
After doing a bit of research and reading I found that the best angle of displacement to provide maximum torque for the motor to start is 90°. I placed a 500 volt, 6uF capacitor bank in series with the starting winding. This required breaking into the three-pin starting relay attached to the motor, breaking the circuit and drilling a hole in the mechanism to bring out a wire to connect to the capacitor bank. The other end of the capacitor I was able to attach to an external terminal on the starting unit.
This modification reduced the starting current down to 60 amps and gave a far smoother startup in less time. At the moment of starting, my 600 watt inverter did not have any trouble starting the fridge, as the shorter starting time and lower current allowed the battery voltage to remain steady.
I believe this conversion will allow people with small to medium solar energy systems and inverters to be able to use standard off-the-shelf fridges. I would be happy to forward a schematic diagram to any ReNew readers who may need to reduce the starting current and increase the torque of any induction motor which has a start-run winding.
Out of interest, my system is a 720 watt capacity photovoltaic system with a 12 volt, 800Ah (C/10) battery bank and 600 watt continuous, 1200 watt surge capacity inverter.
Peter Rusanow, electenergy@yahoo.com.au
Peter’s modification is a good example of adapting off-the-shelf equipment to be a bit more efficient and much easier to run on smaller renewable energy systems. Unfortunately, most manufacturers don’t consider the use of their equipment on renewable energy systems when they design it, preferring to keep designs simple to keep costs down (which is fair enough, as most devices will never be used on small renewable energy systems).
We should state here though that this sort of modification can be dangerous if done incorrectly and that you absolutely must have a good understanding of electrical theory and practical applications before attempting any such modifications. These modifications will, of course, void any warranty on your fridge and should such modifications cause a fire, don’t expect your insurance company to pay up!
Lance Turner
This entry was posted on Monday, December 12th, 2011 at 10:53 am