The inverter
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The inverter is the electronic heart of the PV installation. An inverter is an electronic device which converts the DC electricity from the PV panels into 230V AC current or electricity that exactly matches the stuff that you get from your wall outlet. The plug of the inverter cable is simply plugged into a wall outlet. This means that PV electricity in your home (export) competes with electricity from the electric public utility (import). Which one wins depends on the time of the day, the amount of sunshine and the number of electricity-guzzlers switched-on in your home. If it is hard for you to grasp the concept, think of an inverter as an electric device that, for a change, does not consume electricity but produces electricity instead. |
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are discussing here grid-connected PV-systems. A solar panel
does not necessarily have to be grid connected. On off-grid locations
like ships, caravans, motor homes, garden sheds, whatever, you can mount
as many PV panels as you need and via a battery charger/controller charge
batteries and power lamps, electronic gear and machines. In a grandiose
way this so-called autonomous PV is achieved for instance by the monks
of the Monastery
of Christ in the Desert
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There are numerous types of inverters for sale in the world of grid-connected PV. Every need, taste and scale is being served by the industry. Here are a few inverters, but this is only a handful of the enormous supply. My advice: always mount the inverter on a dry and well-ventilated place inside the home. Shield the inverter from direct sunlight. The electronics inside these devices generate some heat and cause the inverter to become warm (especially on hot sunny days!).It is essential that the inverter is placed such that an engineer can check or service the wires and electronics if necessary. |
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This inverter is a Soladin 120 manufactured by Mastervolt. I have two of these mini-inverters ( dimensions 12 x 6 x 6 cm) serving as many PV panels. The DC current from the PV panel arrives via the black (-) and red(+) DC wires that plug via the green connector into the inverter. The inverter itself is simply plugged into a wall outlet. The green LED flashes in sync with the amount of power generated.The maximum size PV panel that can be attached to this device is a 120 Wp panel. Maximum output is 95W, no more whatever size PV panel. | ||
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This extremely good-looking device was revealed in the spring of 2005 by Mastervolt: the Soladin 600 grid-tied string inverter. In contrast to most inverters, the Soladin 600 is not a plain industrial design but instead something you want to show in your living room. Because this device is a string inverter it needs only two DC cables from the PV installation to the living room. The technology is the proven stuff Mastervolt has so much experience with. Its PV-capacity is 600 Wp, which may be good for the Dutch market where the utility companies allow only a tiny PV system installed on a single electricity group. Since the Soladin 600 is not a scalable unit, if used in the big German grid-connected PV systems (e.g. a 3 kWp system) one would need several of these slick Soladins (in this example 5 units, or one of the bigger yet 'industrial design' Mastervolt units). Output is limited at 600 Watts, so connecting more PV panels than a total of 600 Wp would not make sense. A LED indicates whether electrical power is being generated. This LED blinks proportionally with production. Own consumption: 7-9%, depending on the load. At night, power consumption is nearly zero (<0.05W). A small, powerful box: 25 cm high, 16 cm wide. The device has a RS485 port which makes it possible to read performance via an adapter connected to a PC. Picture submitted by Michiel Klees (Mastervolt). | ||
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SMA Germany is a leading company in inverter design and manufacturing. The Sunny Boy series belong to the class of central inverters. The company philosophy is that one big inverter for all PV panels is much more efficient and economical than the situation in which every PV panel has its own mini-inverter (and as a consequence summation of mini-losses and mini-efficiencies). This Sunny Boy is equipped with a Sunny Display. Software for the PC is free available on the internet (www.sma.de) although the interface is optional (and expensive). A very efficient, reliable and robust design. | ||
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The Prosine 1800i inverter produces 1800 W AC with, as claimed by the manufacturer, 'a sinus so clean that it is better than that delivered by the local power utility'. A good-looking design of the German manufacturer, Prosine (www.prosine.de). This picture was submitted by the Dutch representative, Statpower Technologies Europe, and this picture is courtesy by myself on request of this company | ||
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The electronics giant Philips made a short excursion into the solar PV business in 2003-2005. The company manufactured an entire range of inverters. The smallest (shown here) are were ministring central inverters, that is they serve four to six PV panels. The inverters shown here were named EVO-500 (500 Wp load maximum). They were cleverly designed, and they look sexy. A blinking LED indicates that the inverters are working properly. The only way to measure output is to place an output meter in between the inverter's cable plug and the wall outlet. In July 2005 Philips sold its inverter division to Steca (Germany). | ||
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Another "submitted" inverter, a picture of a Philips EVO 2000. The owner is mr. Peters. The EVO 2000 has an efficiency of 95%. It has two separate DC entries, making it possible to connect two strings of 1000 Wp each. This concept is called multi-string. As a result, Philips claims their EVO 2000 inverters deliver maximum performance and short pay-back times. EVO 2000 inverters offer a constant capacity of guaranteed 2000 Watts, independent of the ambient temperature. Cooling is via natural ventilation (cooling ribs) making sure that the device performs without producing noise. The inverter is equipped with a display and on-board logging. There is also a PC/network interface. EVO Connect provides a web server that can be opened with Internet Explorer with which you can see actual performancer and energy yield. Extended EVO Connect software is available both in an end-user/powerplant version and an installer version. Clearly this manufacturer has good expectance of its product. The guarantee period is 5 years!
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The ugly duckling among inverters is this Exendis Gridfit 250. Would you proudly show a thing like this to your mother-in-law? The Gridfit can be used as standalone inverter serving one big PV panel (rated at 250Wp) or as a ministring central inverter two to four PV panels. The PV panels on the left and right of my solar thermal collector are connected with this device. It has a yellow LED that flashes in proportion with power performance, but the LED is located in the wrong spot. The Gridfit is considered as one of the most reliable small inverters available, and I am quite satisfied with it.
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