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HERIC Topology: How a Brilliant Idea Brought 99% Efficiency For Solar Panel Inverters


Brilliant ideas usually don’t need years of hard labor, or at least so it happens most of the time. For example, by implementing a switching trick into a DC to AC current converter used in solar panels, Heribert Schmidt, an electrical engineer (with a doctorate), from the Fraunhofer Institute for Solar Energy Systems has managed to halve inverter losses, bringing the efficiency to 98 percent.

Well, it’s not much in absolute numbers, if you think the previous efficiency figure was 96, but applied to solar panel inverters worldwide, this change really makes a difference. He invented the trick back in 2002, and since he has been getting many awards for it.

For the ones who didn’t get much so far, here’s the explanation in as-lay-as-possible terms. Solar panels produce direct current (DC). To connect the solar panels with the electricity grid, direct current has to be transformed in alternating current (AC), which, in time and amplitude has a sine shape. Alternating current has the advantage that it can be transmitted through wires over long distances, with far less losses than direct current (Nikola Tesla showed that a hundred years ago).

To be made alternating, direct current has to pass through a device called an “inverter.” What the inverter basically does is it takes the current directly from the solar panel, stores it into a buffer capacitor, passes it through an inveter bridge consisting of four semiconductor switches that “chop up” the direct current through rapid on/off switching. So far, the alternating current’s wave has a square-like shape. To transform it into a sine shape it is then passed through an inductor.

More or less, this is the logical schematic. Now, what Schmidt did first was realizing that losses in this circuit are caused by the return of current between the output inductor and the input capacitor. To prevent this, he decoupled the two through a switch at certain intervals, so that the current wasn’t able to return.

Schmidt patented his idea under the name of HERIC topology and started developing this type of inverters with SUNWAYS, a company located in Konstanz, Germany. In 2009 he set a record efficiency of more than 99 percent for solar panel inverters and won the Fraunhofer Prize.

[via physorg]

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