Inverters and Converters

This is a short post about the cost of DC convertes and Inverters. If you buy a solar panel these days you pay about 30ct/Wp, which is cheap (and 10ct of that is tax!). Then you are supposed to buy an inverter, which cost about 20 ct/Wp, so that doubles the price. The inverter pumps the 40 Volt output power to 110 or 220 AC. This is done with buck converters these days.

The trick is to release the energy to the 220 AC so that it flows. Because AC goes positive and negative, so if you add 220 Volt positive to the AC grid while the AC itself is -220 Volt, you lose it all and you weaken the AC. Makes sense, but at the same time it’s not rocket science.

Another trick inverters do is to track the MPP or maximum power point of the panel. This is the voltage at which the new electrons the sun dislodges are taken away at optimal speed. It shifts with the strenght of the sunlight. If you draw to much current from the panel or too little you lose power conversion. MPP tracking inverters are way more expensive than non MPP tracking.

So the cost of this kind of device for a 400 Wp panel is 80 Euro.

Now if you just want to convert 40 volt to 12 volt or something like that, you can use a DC/DC boost converter wich costs about 5 Euro (on Alibaba). You don’t get MPPT tracking and you don’t get AC synchronization.

So 80 Euro vs 5 Euro. That is waay to large a difference.

Now of course inverters have been developed over years, so they are sophisticated, and they last a lifetime. The certification is expensive etc. etc.

Just adding MPPT and 220 AC output is not 80 Euro expensive.

But this adds to the case of home batteries and a separate home grid vs outside grid. It makes you think why do you need power from outside all the time. You could cut the cost of your solar installation by 1/3th if you run a home system with 24 Volt DC or even a 220 AC system that is not synchronied. With enough buffering batteries you can top those up with 220 from the grid if needs be. You lose 5% but who cares.

Of course batteries are still way to expensive. We really need those potassium ion batteries, or Zink Bromine ones, which you can make at home. We feel like we should do a DIY demo. TBC..