Our Sydney home solar power generation system
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Wanting to reduce (or ideally eliminate) our electricity bill, we took advantage of the current Federal and NSW Government rebates and incentives to purchase a solar power system. We have a system designed to generate approximately 50% of our power needs annually. As our annual electricity usage is under 6000kW/h, the system is capable of producing approximately 3000kW/h per year. Along with the environmental benefits, with the rebates on offer at the moment, that means that we should be earning $2000 per year. With a bill of around $1200/year, we will be about $800/year in front! That income is also deemed to be non-taxable income by the ATO, in recognition that people are not only trying to reduce their power bills, but do their bit for the environment. Very simply, an array of solar panels is installed on the roof. The solar array converts light into electrical energy. This is fed to an inverter, which converts the solar power array's energy into the mains grid voltage. A new, additional power meter is installed into our electricity meter box. This new meter measures the solar power generated and feeds this into the electrical grid. Nothing changes with regard to the existing meter. Due to there being only a limited time during the day where a fixed solar array would be at its peak generating level, a rating based on geographic locations has been determined. Along with the size of the generation system, an annual figure in kW/h is given for a generation system. This helps determine the size of the solar array if you wish to generate all or some of your energy needs. Alternatively, you can determine how much of your energy needs can be met by installing a predetermined size solar array system. Limiting factors such as the available roof space, direction of available roof space and shadows by surrounding buildings or trees need to be considered. In our case, a 2kW system was purchased to generate approximately 3000kW/h per year. The government rebates also had a bearing on the decision - the payback period will be 2 to 3 years for our particular situation. Government rebates: There are 2 parts to the government rebates. When you install a renewable power generation system, you become entitled to "Renewable Energy Certificates" or RECs. RECs are tradeable and have a varying value determined by trading on the markets. Depending upon where you live (the daily useable sunlight changes depending upon your geographic location and is factored in to the REC system) and the size of your solar array, you create a number of RECs. The Federal Government rebate multiplies your REC value by 3 up to the first 1.5kW of your generation system. So in our case, we gained a 3x bonus for the first 1.5kW, then gained a standard REC for the remaining 500W in our 2kW array. Generally, the RECs you create by your system are calculated and sold back to the installation company for their going rate. This offsets the initial installation cost. In our case, that was about $5000. The second part is the feed-in tariff, or the money you will be paid for generating electricity. In NSW, all power generated is purchased by your local electricity supplier. The going rate is 60c/kW/H in NSW. (STOP PRESS: from 28 October 2010, this is now 20c/kWh for new systems installed after this date.) AGL has an 8c/kW/h incentive. As we are already with AGL, we will be paid 68c/kW/h. We currently buy electricity for 20c/kW/H in round figures. So there is roughly a 3 to 1 incentive to produce renewable electricity. Therefore, our 2kW system producing 3000kW/h/year will pay us just over $2000/year. As we use roughly 6000kW/h/year, that bill is $1200. So future electricity bills for use will be credits! We are yet to see how this will be funded to us at this point in time. Our system: Australian made "Silex Solar" panels. 12 x panels, each is rated at 170W. (2040W, or 2kW in round figures). I paid a slightly higher price to keep my money in Australia, than cheaper panels from off-shore. The panels are made in Sydney and are also made to our local conditions. 2kW inverter - this is mounted on the wall next to the meter box. Interestingly, it makes a bit of noise that we were not expecting. It is high pitch and varies according to the amount of sun shining. Brighter light is higher pitch/louder. It is not so loud to be a problem, but is audible and shouldn't be a problem. At night, it seems to shut-down on its own accord (after a period of no generation from the solar array). Meter - this is "free" from the electrical supplier, but an exorbitant cost is charged to have it installed. Only a special class of electricians can install the system. I won't be recommending the company that installed our system to anyone. Their customer service skills were very poor, and went down-hill after having signed up and paying the deposit. It took 2 weeks from start to finish of the installation process. The electrician who did the initial work wasn't really knowledgeable about the DC or solar side of things. I had to question his work twice - he wasn't aware of some of the more technical aspects in connecting the array to the inverter. He was going to wire it in such a way that we would not have obtained maximum benefit from the system components we purchased. As they did not have all the required materials on the day to wire it up, subsequent visits had to be arranged. At the end of it, anther electrician had to correct another problem to get it all working. 6 October 2010: our 2kW photo voltaic array was "commissioned" 7 October 2010: at the end of day 2, 11kW/h had been generated (under 2 cloudy sky days.) 8 October 2010: 9.7kw/h had been generated. Interestingly, our system is supposed to supply an average of 8.2kW/h/day. Being a partially cloudy day, this was a good result. The inverter is very informative, showing the number of hours the unit has been in operation since day 1 and also the current day. Likewise for kW/h generated. Instantaneous power being produced is also shown every few seconds. Quite interesting to watch as the clouds were moving quickly and the light intensity changed from full sun to bright light under cloud to overcast. Even without direct sun, under overcast skies with drizzly rain, we were producing a small measurable amount of energy. I look forward to full sunny days, no more power bills and a warm-fuzzy feeling! Photos of our solar power system:
This is a general photo of the roof mounted array. There are 12 panels, mounted in a group of 8 and 4. Electrically, they are wired into 2 strings of 6 panels. As a bonus, the panels shade part of the roof which will also help in summer to reduce cooling costs.
This shows how the panels are mounted to the roof. The tiles are removed where the brackets are to be installed, with the bracket attached directly to the timber rafters. The tile is cut to allow the bracket to protrude. A rail is attached to the brackets, which in turn has the panels attached to the rail.
The overall view of the inverter (on the right hand side) next to the meter box. An additional "DC" circuit breaker housing was also installed.
This is the additional meter installed in the existing meter box. It simply measures all the solar power produced. The circuit breaker next to it is also new. The meter shows 18kW/h.
A close-up of the screen on the inverter. At the time of the photo, it shows energy produced since the beginning of the day (7.4kW/h) and the energy the inverter has produced since it was installed (18kW/h). There are also a running total of hours in use, the instantaneous power being produced, array voltages, temperature of the inverter and other useful information. A short video clip of the inverter's display screen. If you listen carefully, you can hear the high pitch of the internal electronics.
Update on its generating capacity after 10 days (18 October 2010):
Usage over the last 10 days
has been 118kw/h. (Costing $21.24 + connection cost portion)
Power generated over the last
10 days has been 83kW/h. 7 of the last 10 days have been overcast to very
cloudy. Only 2 full sunny days, 1 mainly sunny day. The best days have each
generated over 12kW/h. The worst was less than 3kW/h. (Earned $56.44 in
feed-in tariff over the last 10 days, in front by about $30 for this period)
On average, 8.3kW/h per day
has been generated. This is what it has been expected to generate, although
we have had 7/10 days of overcast to very cloudy days. The peak instantaneous
power that was noted was 2138W, in between passing clouds.
Based on usage and what has
been generated over this period, we have generated 70% of our power. Very
impressive. As the days are still getting longer, that should improve further,
although usage is also expected to increase as the days get hotter.
It powers itself up between
0630 and 0700 in the morning and shuts itself down between 1800 and 1900.
October 2010 - NSW Government feed-in tariff update:
As expected, the Government reviewed the feed-in tariff after their goals were reached earlier than expected. As a result, the feed-in tariff is now 20c/kWh, reduced from 60c/kWh for systems installed from now on. Existing installations up and running prior to 27 October 2010 will not be affected. We just made it! It is not all bad news for new installations - at best the increasing engergy costs will be reduced depending upon the size of the system installed, but with a much longer pay-back period. 1 December 2010 - our first bill I eagerly opened the first bill after having the solar system operational. Good news, but not exactly as expected. The total bill was $1.11. A credit of $257.04 was not quite able to cover the $258.15 expense. Interestingly, of the $1.11 bill, there is "GST included of $23.47".
What I wasn't aware of during the billing period was an increase in our energy cost by nearly 2c per kW/h. That doesn't seem much, but for 800kW/h, it adds up. If the meter had been read just 24hours after it actually was, we would have been in credit. As I have been monitoring the stats every few days, I estimated a credit but wasn't aware of the rise in charges that quietly occured. Considering that of the 89 day billing period, we have had solar operating for 55 days, we have done well. Our usage for the same period is also lower (around 11.3kW/h per day). The running daily average power generated is 8.2kW/h for those 55 days. This has been constant throughout the entire period. The maximum power generated in any one day that I have witnessed has been over 13kW/h. On the wetest, overcast day (today), 3kW/h was generated. 26 February 2011 - our second bill Now that one full billing cycle has passed, the results are in. Although the prices to buy electricity have again increased, the total bill was a credit of nearly $140. This was as expected. Now that summer is on its way to winter, things will be interesting with less daylight hours. I have been keeping an irregular log of readings and the daily solar power average is also at its lowest since installation. This corresponds to an increase in more cloudy days than normal for this particular summer in Sydney. 18 May 2011 - things are changing Almost time for the next bill. Closely monitoring the system over the last few weeks, the performance is improving with clear skies. Over the last couple of 100% cloudless sky days, the system has produced 8.3kW/h for each day. The running average generation since installation is 7.51kW/h per day. The days are still getting shorter, but is better than the 1kW/h for the worst rainy day. At this stage, the solar rebates will just cover the usage and connection charges for this period. But if the new NSW Government has their way, there will be retrospective legislation put through that will change the 60c rebate scheme to 40c. That isn't good news for the 160,000 or so NSW premises that will be affected. My system was installed with good intentions and calculations that would have us energy-bill free at least up until the scheme ended in 2016. That would also be enough time to fully pay back our initial outlay and allow a buffer zone for periods of less than average clear skies, and some increases in energy cost. I have expressed my concerns to the relevant people. Also the Solar Energy Industries Australia web site is worth visiting for up-to-date information and details of various state rebate scheme information. 5 July 2011 - update Belated good news - the crazy idea to retrospectively introduce a 40c/kW/h rebate in lieu of the 60c rebate has been canned. The weather has been generally gloomy, with very few 100% cloud-free days. Combine that with the shortest days of the year, and the solar output hasn't been too exciting. What I can confirm is that just before the shortest day of the year, there was a 100% cloud-free day. The solar output was 8kW/h. That is encouraging, as the system was supposedly meant to produce an average of 8kW/h each day over the year. Since day 1, the solar output has averaged 7.13kW/h per day. A little short of the designed average, but considering the general weather since Christmas, not a bad output. Also of note, the maximum instantaneous output I have noted over winter is around 1400W (I did see 100% overload on one occasion in summer. >2100W output). Due to the geographical positioning of my system, the output springs to life with nearly full sun quite early in the day in winter. The peak seems to be around mid-late morning, with a really low output for the last couple of hours of the day and often shut down by 1700. The worst winter day noted had an out put of less than 1kW/h (wet and overcast). I am unable to check the output each day. Although my inverter has ability to output lots of statistics, that component is an optional extra. I wasn't aware of that until it was too late. But back to statistics, I have a complex excel spreadsheet that I monitor my system with. Every so often I take note of the cumulative solar and usage readings, and feed them into the spreadsheet. Since day 1 (270 days ago), 47.53% of our electrical energy use has been off-set by the solar system. Therefore, I'm happy that the system is doing what it was designed to - produce 50% of our electrical energy needs (slightly less, but the weather is blamed for the shortfall). If we had more sunny days, there would obviously have been an increase in output, likely well over the 50% design amount. 21 October 2011 - one year of solar power The weather has improved somewhat and the inverter has been working hard lately. That is good news and better than the same time last year. Today, the system produced just under 12kW/h with the maximum instantaneous output noted around 1500W. I didn't watch it all day, so it may have gone about that level at some point. The system has been operating for just over 12 months, so the results to date are as follows: 2655kW/h produced over 376 days. That averages out at 7.06kW/h per day since installation. Slightly under the designed average of 8kW/h, but that can be put down to more than average number of cloudy days. Average daily usage since the solar system was commissioned is 14.75kW/h per day. That is also slightly down on the 16kW/h for the same period last year. Therefore, 47.88% of our electricity consumption has been generated by our solar system over the last 376 days. Not too bad since the designed 50% average has almost been met, under less than ideal or average weather conditions over the same period. Terminology explained: Voltage: is the potential difference or electrical force (Using a water tank as an analogy: Think of the height of water in a tank as a measure of voltage - a higher tank will have a higher voltage) Ampere (amp): is the unit of measure of electrical current (Think of the diameter of a water hose connected to the tank - smaller diameter = less current, larger diameter = higher current) Watt: is the product of voltage and current (ie: volts multiplied by amps) Kilowatt hour (kW-h): - unit of energy. For example, a 1000W heater running for 1 hour will use 1kW hour of energy. A 15W compact fluorescent light running for 10 hours, will use 0.15kW hour of energy.
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