Key solar questions for professionals
In 2013 the renewable energy celebrated the one millionth solar system installed in Australia. It is estimated that over the next 5 -10 years a further 1 million solar power systems will be installed in Australia.
|Year||Number of solar systems installed in Australia|
* Data provided by the Clean Energy Council & Solar Business Services 2013.
Delamination occurs when the bond between the plastics (on the back) and the glass (on the front) separate. This is problematic for a solar panel because it allows air and moisture to creep inside which will cause corrosion and imminent failure.
Delamination will occur if:
- Inferior plastics are used or
- If the thermal properties of the plastics are poorly understood so it doesn’t melt to exactly the right point or
- The plastics or the glass are not perfectly clean and compatible or
- The laminating machine is inferior and poorly regulated for pressure and temperature
Bubbles, creases or imperfections on the plastic rear surface are an indication of the workmanship in lamination and can be an early sign of delamination.
Predicting how solar technology will evolve in the future is difficult but we can look at history and the factors that are driving energy demand around the world as a guide.
Historically, solar costs have fallen by 20% for each doubling of manufacturing volume and roughly followed Moore’s Law which was first identified by an Intel executive in the mid 1960’s. Given that semiconductors and solar cells share the same base material (silicon), the evolution and cost reduction trajectories could considered to be quite similar.
If the industry’s growth and cost reductions continue along the same trajectory, solar energy will be cheaper than today’s lowest wholesale energy cost (typically coal fired) within the next 10 to 20 years (perhaps even sooner) which is likely to create even more growth.While the introduction of electricity storage solutions in the next 2-5 years will change the distribution model fundamentally.
We have also seen efficiency, reliability and performance of solar systems increase steadily which increases the future use of solar across many applications.
For example, LG's innovative NeON solar panels use double sided wafers to harness even the light reflecting in the backing sheet of the panel. While these panels created 270W per panel in February 2013, only 9 months later 300W panel were being produced. This represents a 10% increase of output in a relative short timeframe.
There are also a wide variety of as yet experimental ways to produce electricity from the sun using new materials such as Nano technology films, that can be applied to regular building materials. Since 2009 LG has secured over 200 patents in solar technology, the highest of any solar panel manufacturer. These patents will shape the technological advances of solar power systems in future years.
A 2 kW system will very rarely produce 2 kW/h of electricity in one hour. There are clouds and variance in the sun intensity, as well as inverter efficiency percentage and cable loss to take into consideration. Even in good sunlight conditions expect a 10% loss on average.
Generally a 2kW quality solar power system with a quality inverter generates between around 1.7 and 1.8 kW generation in sunny bright conditions. LG Electronics rate our panel output under standard temperature of 25 degree celsius and consistent conditions. Through tests, called flash test we are able to compare the output of a batch of solar modules.
It is the amount of light, together with the operating temperature that determines the electricity output generation of a solar cell. Solar cells, being usually dark in colour do heat up in sunny conditions and on the roof your panel could easily be heated from 40 degrees to as much as 90 degrees depending on the season. That’s why using quality backing sheets and long life sealants is so vital for the longevity of your panel.
At around 40 degrees solar cells in general produce around 5-8% less power than they generate at just 15 degrees lower – at 25 degrees. Heated up at 75 degree Celsius one can experience a loss of 15% or more. Therefore the best day for solar output is a clear bright day, with moderate temperature. Because of Australia’s overall high sun irradiation, solar systems here produce comparatively higher electricity output, when compared for example with northern parts of Europe.
For brief periods given the right conditions peak power could be gained or exceeded. For example if there was a short rain shower that cooled the panels, followed by a crisp clean sunlight, the 2kW system could for a period thereafter produce 2,1 kW, till the panels heat up. So in contrast to popular belief, solar panels do not love very hot days, but produce the best result in clear, medium temperature days.
Finally dirt does accumulate over time on the panels, and while most of it is washed off during rain, this can also lead to a small loss of potential output. For the most likely output of electricity generated by your LG system please try our output calculator given in the calculators section.
All solar modules do loose efficiency over the years. The efficiency loss in case of LG Mono-X panels is just 0.7% per year, after the 1st year. The maximum efficiency loss a LG panel should have is 19.8% over a 25 years period for LG Mono-X.
Solar cells within solar panels are interconnected using a flat, conductive ribbon in series and parallel connection. Most use a tin coated copper ribbon although the number of connections, width and thickness varies by manufacturer.
An issue increasingly well understood by quality manufacturers is how these interconnectors are connected (soldered) to the silicon solar cell and how the connection method maximizes conductivity without placing undue stress on the solar cell. In cheaper panels these solders are often undertaken by hand via manual labour. Therefore the consistency of the soldering varies. In automated manufacturing the solders connectors are uniform. LG’s panels are made with very low tolerances, meaning each panel must match each other to a fraction of a mm.
Poor hand soldered interconnections can cause micro cracking in the solar cells through thermal expansion and contraction stress or the interconnector can break. In the worst case, a poor solder connection which opens and closes with thermal movement can cause an arc and potentially damage the panels.
For example, some manufacturers solder the entire length of the interconnector, and some only solder every few millimetres, theoretically reducing stress caused by thermal expansion and contraction. Some use thinner interconnectors which may stretch more, avoiding stress.
When you are assessing a solar panel, observe the neatness, alignment, size and quantity of the interconnectors.
PID is an undesirable effect on of some solar modules. The factors that can cause PID include voltage, heat and humidity and most solar modules are exposed to the combination of these factors during their working life. Nevertheless the PID effect does not occur on all or even a majority of solar modules.
Potential Induced Degradation, as the name implies, can occur when the module’s voltage potential and leakage current drive ion mobility within the module between the semiconductor material and other elements of the module (e.g. glass, mount and frame), thus causing the module’s power output capacity to degrade, in some cases significantly. PID reduces both the module’s maximum power point (MPP) and its open circuit voltage (Voc) along with a reduction in shunt resistance.
The solar electric power system and surrounding install environment interact to cause PID. As the install environment cannot be changed, the easiest way to avoid PID damage to the panel is to chose a solar panel who via manufacturing quality has inbuilt PID resistance. The choice of glass, encapsulation, and diffusion barriers have all been shown to have an impact on PID. For the front glass several studies have shown sodium to exhibit a causative factor.
So in short quality panels with solid encapsulation and diffusion barriers seem to offer a better long term protection against PID damage. LG panels such as our new NEON module in past PID tests via Fraunhofer Institute and TUV have had minimal degradation after extreme PID tests and achieved a PASS ranking.
Suburban homes in Australia are connected to the electricity grid (power lines). Our electricity system uses 240Volt and alternating current electricity (AC). But the electricity generated by solar panel is direct current (DC). That means grid-connected solar PV systems use micro inverters or a central inverter to transform the DC electricity into AC electricity suitable for ordinary household use.Houses with grid connect solar systems consume the solar electricity first and then if more electricity is required than the solar system creates - at that point in time - the rest of the household's electricity need is sourced directly from the electricity grid.
Solar industry is well regulated in Australia with Australian Standards regulating the product as well as installation and maintenance. Below is a list of the major Australian Standards:
PV & Inverter Standards
Grid Connected Solar Electric Systems
Standalone Solar Power Systems
Quality solar installation companies follow these standards.
Solar panels are tested at 25 degrees Celsius for rated outputs. The efficiency of the panels is based on irradiance and not temperature. As the temperature increases the efficiency falls. Have a look at the efficiency chart below.
If we jump ahead here is what we are likely to see:
- Solar power will be a strong contributor to the energy generation mix;
- Solar technologies which are significantly more efficient and thus able to be fitted to more locations, more tolerant of shading and easily integrated into the fabric of buildings;
- Advanced solar technologies which allow the integration of solar into materials such as fabrics and paints;
- The increased storage of solar energy in compact batteries to be released during days with low sun light or during the night;
- Solar will be used to store energy in batteries and these batteries will be used for vehicles and many other applications.
Although this may seem far-fetched, many examples of these applications and scenario’s are actually being trialed today in laboratories or in applications where cost is no barrier.
From history, one thing that it is proven is that despite some bumps and glitches, solar panel costs have fallen from $6 per watt in 2007 to around $1 per watt, which drives further costs reductions and it has happened far faster than most analysts projected.
LG is committed to solar research and solar panel cost reduction with a high number of solar patents.
The amount of electricity being generated is directly related to the amount of sunlight shining on to your home solar system. The more your solar modules are covered in shade, the less electricity your system will generate.
Even a single antenna or a chimney shadow on your panels can affect performance and electricity output. Depending where you reside in some areas of Australia such as the Blue Mountains near Sydney over 10% of homes are less suitable for solar due to tree coverage close to the home.
The new technology of micro-inverters on each panel instead of one large string inverter can help with shadow issues as the losses associated with shade can be reduced by as much as 25% with each individual panel being managed to achieve maximum electricity output. Talk to your LG dealer if your shadow issue is a serious one and check if power optimisers or micro-inverters are a potential solution for you.
Silicon solar cells are made of very thin wafers, usually around 0.20mm thick. Although they have some ability to flex, they can suffer from pressure/stress induced cracks which are so small they are impossible to see with the naked eye. These are called micro cracks. The long term effect of micro cracks on panel life expectancy and performance are still being researched.
Micro cracks can be caused by poor handling of the solar cells during assembly (usually through non automated systems), or transport/ installation damage from vibration or shock if improperly handled or dropped.
It is not possible to see micro cracks during manufacture by the naked eye, but LG uses Infra-Red scanning cameras which can detect and isolate micro cracked cells during processing. Our modules are EL tested both before and after lamination. LG tests its panels for micro-cracks before leaving the factory and we keep an EL spectrum photo of every panel before it is shipped. Should a panel be detected with a micro crack by the quality control process before leaving the factory it will not be sold.
When you are assessing a solar panel, look for quality packaging and careful transportaional handling by your installer, so that micro-cracks can be avoided.