Inverter losses for solar power system?

Question

I have been searching quite a lot on this over the internet but i am really confused. :(

I want to set up a solar power system for a small office. What I am really confused about is taking into account the inverter losses. I have come across various calculators over the internet which ask separately for wattage AC loads and DC loads. They then ask to multiply AC load wattage by 1.15 to account for the inverter losses.

So here are my questions:

1) Multiplying by 1.15 gives me the DC wattage? Is that dependent on the efficiency of the inverter? If an inverter has efficiency of inverter is 85%, then would i multiply AC wattage with 1/0.85 ?

2) I want to replace my grid-connection with this system. That means, all my appliances will be powered through the inverter (INCLUDING THE DC APPLIANCES). Should I multiply the wattage of DC appliances with 1.15 as well to account for the inverter losses (because they are also getting power from inverter, like the AC appliances) ??

3) Over the internet, I have seen that the losses for modified sine-wave inverters are 20% more than what is stated. Is that true? and how should I account for that in my calculations? Btw what about pure-sine wave inverters; is their efficiency the same as what is quoted on them?

4) Does the efficiency of inverter differ for appliance to appliance (e.g. a motor working on inverter will have lesser efficiency than a light? )? How do i account for it in my calculation if this is true?


Any help is appreciated... I want to make a complete table for power consumption and the required inverters...please provide me help!!!

Answer 1

Inverter losses vary from design to design, but typically, losses are pretty close to a fixed amount for a particular inverter. It's the power the inverter uses just by being turned on. As a general rule you can figure 15% of maximum. If your inverter is 2000 watts max, a typical loss might be 300 watts. It doesn't matter how much or even if you are using equipment that's plugged in. If the inverter is turned on, it's using 300 watts and is "lost".



Inverter loss is usually only important when you're running off a battery and want to calculate how long a battery or battery bank with a certain amp hour rating will last. If you're on a solar system, it doesn't really matter, until you swiitch to battery backup.



Personally, I'd try to work from the equipment to be powered back to the solar panel. Let's say for example you need 2000 watts of power for a maximum. At 120v that's just under 17 amps. Not wanting to run at absolute maximum anyway, I'd ignore inverter loss for now and opt for something about 25% more than I needed just to be easy on the electronics in the inverter. I'd be looking for an inverter or combination of inverters that could provide 22 amps or more... , or 2500 watts or more.



Assuming 12 v, you're talking 12 volts at 170 amps from your solar system. (2000 watts / 12v)



So... now it's dark and you need to run on battery...



Lets suppose your battery bank is 12v and 1,000 amp hours, and your more typical usage is 1200 watts. NOW add the 300 watts the inverter uses, for a total of 1500 watts. 12v * 1000 Ah / 1500 watts = 8 hours on battery. Only have a few light's on? Three 100 watt bulbs = 300 watts

300 w for lights + 300 w for the inverter = 600 watts. 12 * 1000 / 600 = 20 hours.

Using those energy efficient bulbs?

3 * 26w for the lights + 300w inverter loss = 380

12 * 1000 / 380 = 31.5 hours



Clear as mud?

Hope that helped.

Answer 2

Inverter Losses

Answer 3

Now solar inverters have efficient more than 95%. And not only inverter but you have to consider battery capacity and efficiency. Also Panel efficiency.



Here you will get an idea about selection of inverter battery and panels after considering losses.



http://www.scienceinfusion.com/sizing-a-solar-power-system/



http://www.scienceinfusion.com/solar-battery/

Answer 4

My Inverters have about a 93% efficiency, as in 93% of the power going in goes out the AC socket, at least that is what I measured by by the current x voltage going in, and the rated watts of the load.



Those are smaller inverters, one 75W, the other 400W.

Answer 5

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