Solar PV: Research and installation
|8 x 188W panels installed giving a total of 1.5kW, more than enough for our needs|
I know a little about solar systems, having installed a very small system on my VW Kombi about 12 years ago. Gearing up for a home system has been a much more complicated process, especially with all of the changes to rebates along with the hundreds of different types of systems available and **FANTASTIC OFFERS** that flash brightly before your eyes.
Justifying the purchase of a photovoltaic system has been difficult, hours of research, contimplation and discussion are behind the image that you now see.
In Australia solar systems are subsidised by the issuing Small-scale Technology Certificates (STCs - previously called RECs). These certificates represent the polution that they save from going into the atmosphere, they are a 'tradable commodity' and are purchased by big polluting business to allow them to continue to pollute. So by selling your STCs (and getting a cheaper system) you are negating the 'clean energy' that you are creating.
There are other options available such as GreenPower. While you can get 100% green power, sourced from mainly wind farms and hydro power plants there are some draw backs. The first one is the loss in transmission, which can be significant. There are no wind farms or hydro systems anywhere near us. What you are actually buying is primarily coal power with a greater allowance of green power being fed into the grid. Also, there is no direct connection between how much power you use and what is required to generate it. I believe that if you understand what is involved in producing electricity then you will be more conservative in how you use it.
While using renewable energy sources is a vast improvement on using fossil fuels, there needs to be a reduction in energy usage too. Why? Fossil fuels are an amazing source of concentrated energy that have been created over millions of years, we are using this energy much faster that the earth can replace it. By setting up renewable energy systems on a more appropriate scale that reflects the power that is required we can significantly cut back on our demand for precious fossil fuels, saving them for times of real need.
We have designed this house with energy use as a key design issue. In our home we consume, on average, 3kW per day. The average Australian home consumes more than 5 times this. This means that we require a much smaller solar system to provide for our needs, in fact with a 1.5kW solar system that would normally supply about 30% of a homes power, we could become a net exporter of power and generate an income in the process - which could in turn pay for the system.
People often look at payback time as a way of justifying the purchase of a solar system.When people purchase a spa or a larger TV do they consider this? No, not usually. In most cases payback on a solar system is not a good way to measure the benefit. In our case, however, this is different. Why? Because of the way the Premium Feed in Tariff works, along with our our energy efficient household.
Premium feed in tariff for Victoria is 66c per kWh exportedThe peak time that the panels generate power is between 9am and 3pm (varies considerably between summer and winter). The energy that we use during this time will reduce the amount of power that we export to the grid, and hence get paid for. So reducing power usage during this time will increase our income. This can be done by doing our clothes washing early in the morning or at night for instance. I'm estimating that we will use about 1.2kWh per day while the panels generate power, so we should export about 4kWh per day.
Current power cost is 25c per kWh peak, 15c per kWh off-peak
Estimated average production in Melbourne is about 5.4kWh per day for panels facing true north with a 20° tilt angle (according to the Clean Energy Council). Since our panels will have a less than perfect tilt angle I will assume that we will generate 5.2kWh per day.
Solar power exported: 4kWh x 365 days x 66c* per kWh = about $960Estimated revenue from 1.5kW solar power system is $638 per year (decreasing as power costs and service costs increase). The system cost us $3390 plus ?? connection fee. If prices don't change and we don't increase our power usage then the system will pay for itself in 6 years. Knowing that prices will increase dramatically in the next few years we can assume that it will take longer, although we still wont have to pay for power regardless of price increases. After that, any money generated by the system will be a profit. In the process we will be exporting an estimated 1460kW of electricity during peak use times over the year. We will become a mini power station for our community.
Peak power (weekday) not paid for: 1.2kWh x 261 days x 25c per kWh = $78
Off-peak power (weekend) not paid for: 1.2kWh x 104 days x 15c per kWh = about $19
Estimated income from panels = $1057
Estimated bill from power company (2011 prices)
Service fees: $70 per quarter = $280
*I estimate that 60% of our power usage is peak and %40 off peak
Peak power imported: 1.8kWh x 365 days x 60% x 25c = $99
Off-peak power imported: 1.8kWh x 365 days x 40% x 15c = $40
Total power expenditure = $419
*Note In NSW the premium feed in tariff (which is no longer available) is looking like it could be retrospectively reduced from 60c per kWh to 40c per kWh - update - NSW gov't backed down on this issue. This could happen in Victoria (where I live) too. New systems in NSW only get 20c per kWh as a gross feed in tariff (all power generated by the system). State and Federal number juggling is causing huge uncertainty in the industry and for consumers. As if it wasn't confusing enough as it is!
For grid connect systems the ideal angle of of the panels should be the latitude (Seymour is 37°) minus 10° to maximise the amount of energy produced annually. If I was installing a stand alone power system the ideal angle would be the latitude plus 15°, because I would want to be maximising solar input during winter. (info and image source: Your Home)
* Update 28th June - I recently discovered a great solar calculator that can estimate the power generated at different tilt angles. According to this calculator the power generated at the ideal angle of 27º (due north) is 1911kW per year / 5.24kW per day, at 12º is 1848kW per year / 5.06kW per day, a 3.4% / 63kW per year / 170W per day loss.
|Variation of solar module output with orientation and tilt angle for latitude 35°S. (image: Your Home)|
I have investigated getting a hybrid system that is both a grid feed and grid back-up system, which would mean that the system would continue to run, even during a black out. Straight grid interactive systems cut out when the grid fails, as a safety precaution. While the grid is very reliable at present where we live, that might not be the case down the track. The inverter is quite a bit more expensive and the system would require batteries (which need maintenance and replacing). This type of system could be used to maximise the feed in tariff by using off-peak electricity at night to charge the batteries, which would then power the house during the day. Thereby allowing you to export all of the electricity that the panels generated at the premium rate. While I like the idea of this system, the numbers don't add up. The system would cost about three times more and the payback would not be significantly greater than a grid only system, because we use such a small amount of electricity during peak energy production times.
The system we chose
I've chosen to install a Sharp system, both panels and inverter after considerable research, for a number of reasons.
Sharp are a trusted brand, in the solar business since 1959 (they claim to be the world's leading manufacturer of solar panels)I requested eight 188W mono crystalline panels, rather that the option of seven 220w or 215W polycrystalline panels, not because they are significantly better, but because by using eight panels (an even number) I could more easily convert the system to stand alone or hybrid system (using batteries) at a later date if I so desired.
The panels are made in Japan (usually a sign of good quality, and my partner is Japanese)
The inverter is made in China, but under strict quality control from Sharp
Sharp make other products, so the company should be around for many years to come
The system is a mid-range system, not the best of the best, so not outrageously expensive.
Origin Energy were offering, what I think, was a great deal on these systems. About $400 more than a standard system. Total cost was A$3390, which was about what we were prepared to spend.
Origin were also offering the ability to pay it off interest free over a year. The price for this system has increase significantly since I ordered it, as the rebate has reduced more than originally anticipated. We got in just in the nic of time, with a rebate of nearly $5000.
|Panels being mounted onto a raised railing, allowing for airflow that helps keep the panels cooler during summer. The pitch of 12 degrees is less than ideal, but probably wont significantly affect the amount of power that we can generate.|
|Grid interactive inverter being installed|
|Sharp grid interactive inverter and DC isolator installed, allowing for the system to be shut down easily|
"Aero-Sharp has a longer warranty :) 10yrs vs 5yrs for the Sharp."Summing up
"Very clever marketing trick. Makes an illusion of quality... There is plenty of products on the market with the same or even longer warranty than prestigious brands. The truth is the business case for those products take into account (in some cases) up to two full replacements of the item during the warranty period! They are so cheap to make that the manufacturer will still make a profit after two full replacements. The probable number of replacements is determined statistically. An owner of Aerosharp will get through 10 years without out of pocket expenses albeit with disruptions. But they have to conceive the fact that after 10 years they are up for a new inverter."
My advice is to be very careful when choosing a PV system. Read up on solar, the Clean Energy Council consumer guide and the Your Home technical manual are a great start, so that you can understand some of the terms, have an idea what to look out for and what you are talking about.
There are plenty of shonky operators out there, if the deal is "too good to be true", it could well be just that.
We originally signed up with another installer who offered us a 'great deal' that was heavily discounted - in exchange for using our project as a case study and to promote their business, but I found the pressure selling techniques that were employed disconcerting - and so I would find it difficult to recommend that company to other people. I pulled out of the deal during the 10 day cooling off period, as was not impressed by the manner in which the company handled the situation.
Even dealing with a recognised company can be dodgy, especially at the lower end of the market. It's important to ensure that quality components are installed and that the system is going to be installed by experienced technicians - backed-up by a warranty from a company that should still be around to address any issues before the warranty runs out.
If you don't want to do the vast legwork to save a few dollars (and risk an expensive mistake), then deal with a reputable and experienced installer like Sun Real or Going Solar, that have been in the game a long time. Suppliers like these only deal in quality components and ensure that you will get the system that you need, rather than one that someone wants to sell.