The concept behind the creation of a micro inverter (or solar micro inverter) has been going around in the solar industry for quite some time already before the first prototype was introduced to the world.
The design of the micro inverter we know today can be traced back from Werner Kleinkauf concept in the late 1980s at the Institut fur Solare Energieversorgungstechnik. Recent development in micro inverters includes devices that accept DC input from not just one solar panel, but two.
Ascension Technology, an American company, started working on micro inverter in 1991. They came up with a shrunken version of the original inverter that they market as something that can easily be attached on a panel to make an AC panel. The micro inverter prototype wasn’t as efficient as expected since it overheats. Then, in 1994, they delivered another prototype for testing to Sandia Labs. Ascension Technology partnered with ASE Americas in 1997 to launch the 300 W SunSine panel (solar panel).
Applied Power Corporation (APC) subsequently purchased Ascension Technology after projects involving micro inverters eventually ended. However, by 2002, APC was then bought by Schott AG, a German manufacturer of top-quality industrial glass products in markets such as household appliances, solar energy, electronics, optics, pharmaceutical industries and automotive. The production of SunSine was cancelled and Schott AG’s existing designs were produced in favor of the micro inverter.
A micro inverter is a relatively small power inverter used to convert direct current (or DC) form of electricity to a solar panel or a solar cell and then onto an alternating current (or AC) form of electricity. Electricity generated from several micro inverters are then fed to the electrical grid.
Solar panels produce DC at a voltage that is dependent on the module’s design as well lighting conditions. In converting DC to AC using string inverters, the solar panels are connected one after another in a series to produce one huge burst with a nominal rating of about 300 to 600 VDC. The accumulated power will then pass through the inverter and will consequently be converted to regular AC voltage (240 VDC/60 Hz for the U.S. and Canada and 220 VDC/50 Hz in Europe). The big challenge for using this type of inverter is the limited and often unreliable selection of power ratings.
In comparison, micro inverters are connected to many solar panels. They obtain optimum power that even small amounts of debris, snow or shading in a solar panel wouldn’t affect the electrical output unlike central inverters. They perform in maximum power point tracking to a connected solar panel. Using multiple panels reduce the cost of equipment used and using micro inverters in making photovoltaic systems (PV) cost less than if string inverters are used.
Micro inverters are used to handle the output from a single solar panel. They usually rated an electrical output of 190 and 220 watts. With the use of micro inverters, large transformers and large electrolytic capacitors are not needed anymore. They are replaced by more dependable ultra thin capacitors. No fans are needed since cooling loads are reduced. A micro inverter connected to one panel allows it to segregate and adjust the output of that panel and a dual micro inverter can do this for two panels.
Any solar panel that is otherwise not working well will not affect or put the other panels around it offline if micro inverters are used. The array can still produce more power than in a string inverter. If weather conditions, like shadowing, are taken into consideration, these gains can become significant. Makers of micro inverters claim that the device can still source out 5% output at a minimum and can rise up to 25% more in some cases.
Because micro inverters have lower heat and power load, they have greater reliability than other inverters. Warranties given are usually fifteen to twenty-five years. Expected failure of a micro inverter would be a hundred years from the moment of its use. Fault isolation is possible when using a micro inverter. Problems can be spotted easily – may it be a major or minor problem.
The only downside of using micro inverters is the cost of electricity it produces per watt. Manufacturers also limit the number of products they produce because of economic problems.
The Enphase M175 model released in 2008 by Mastervolt was considered as the first commercially successful micro inverter version sold in the market. It has integrated a design that can use the 120 in a system which can support over 600 watts of panels.
As of 2009, several manufacturing companies from China and Europe have launched new and improved micro inverter models, hailing it as one of the most important technological advancement in the PV industry. By September 2011, one million units have been shipped and approximately 30% are in use in the PV residential market in California. By 2011, manufacturers have introduced dual micro inverters that can utilize DC input from two solar cells that consequently reduces the equipment cost and can match up to PV module outputs.
The newer models have tackled the differences in problems concerning price-per-watt. The recent versions of the micro inverter have minimized the cost because it was balanced out by the small number of panels used. The recent models have improved its energy collection based on a fixed size array of solar cells that avertedly high equipment cost as well.
Micro inverter sales have been a success in the residential market since they are small and don’t take a lot of space. Its size can still perform at optimum capacity. However, shading problems from trees or other neighboring homes can still pose as a challenge.
Micro inverter and solar electronics companies can be found all over the world. There are eight companies in the United States alone. They are: SolarBridge Technologies, Phobos Energy, Direct Grid, eIQ Energy, Azuray Technologies and Petra Solar. Micro inverter manufacturers in other countries include: Solar Edge in Israel, Involar in China, Enecsys in England, NUCA Enerji in turkey and Sparq Systems in Canada.
With energy crisis deepening in all parts of the world and governments realizing the danger of fast rate of depletion of fossil fuels in the form of petroleum and CNG, solar energy remains one bright hope for alternative form of energy to fulfill the requirements of shortfall to be met. Despite there being bright sunshine in many parts of the country, number of people getting installed solar panels on their rooftops is still not too high. This is in part due to high cost of solar panels and inverters and in part due to loss of power due to shading.
Knowing the shade factor before
installation can be beneficial
For any house to be considered an ideal for solar energy output through solar panels it must have a south facing roof with the roof not very old or otherwise reroofing might be required. The house must have minimum number of trees in the surroundings as shading is a number one enemy of solar energy conversion. The shade factor of your house is determined by solar installers. This is necessary because shading reduces energy production in a considerable manner. Even a single panel receiving shade becomes a big problem for energy production in the case of ordinary inverters. This is where microinverters scores over ordinary ones and have come as a revolution in the field of solar energy.
In case your house is positioned in such a manner that it receives shading in one or two of the solar panels only, you have nothing to worry as microinverters installed in solar panels ensure that solar energy production from other panels is not affected in any way. Another advantage of microinverters is that they allows the user to see what each panel is generating and know in time if a panel is about to break down so that your installer can do troubleshooting in time.
Microinverters have eliminated the
problem of shading faced earlier
If you remember your Christmas tree and its lighting a few years ago, you must remember how one string went out and the entire lighting went out. This is what shading does to solar energy production in case of shading of one or more panels. But these days, this problem has been taken care of with installation of microinverters in solar panels. Getting done an energy assessment before solar installation helps an owner cut down on his consumption by nearly 10% which cuts down on the amount of solar energy your home needs by almost 20% thus saving money by reducing the amount of money in solar panels.
If you do not know, a solar panel is made up of silicon based material that is known for absorbing solar energy. This stored sunlight activates electrons present in a solar cell to produce electricity in the form of direct current. But all our appliances run on Ac and this is why solar energy needs to be converted into AC using inverters to make it ready for use in homes. Installing solar panels is a onetime investment as the panels have a long 25 year warranty while the inverters of today are also very long life, lasting for 10-15 years.
Till now, inverters that were an integral part of all PV systems were the biggest hurdles in making people go in for solar systems for houses as they were prone to early failures. The invention of microinverters and their use in solar panels has meant that home owners can now rest peace as these microinverters carry warranties of 15-20 years just as they get similar warranties in the case of solar panels. The reason why microinverters of toady come with so long warranties is the use of thin film capacitors in place of electrolytic capacitors. Nearly all companies have begun replacing electrolytic capacitors with thin film capacitors thereby giving long guaranties and warranties. However, the thing to note with these microinverters is their higher cost of installation per watt of energy production in comparison to central inverters and string inverters. While string inverters cost between 0.25-0.5 USD/watt and central inverters cost less than 0.3 USD/watt, microinverters can cost anything in excess of 0.5 USD/watt to nearly a dollar/watt. This is really bad for the marketing of these devices that already fare badly in comparison to conventional energy sources. Lower efficiency of microinverters than central and string inverters is another factor hampering in success of these new devices. It is required to raise awareness about these products and to let consumers know more about their benefits to become familiar and ask for these pro