question on rating inverters

[nigel76]

Hello everyone,

My first question on here after trying to find the answer somewhere on the internet.

I'm currently working out the pricing to see if it is worthwhile to build a 5mw solar park.

If I have a connection to the grid for 5 MW. I want to make sure I get as close to that in regards to what comes out of the inverters.
My question is this, being that the max currents and voltage are worked out at STC of irradiation 1000w/m2. So using a panel that gives 250 watt I need to use 20,000 panels to get my 5MW output not taking into account about 20% for losses. however what happens if the irradiation goes higher than 1000w/m2? will I blow my inverters? do I need to look into the maximum irradiance in the area?

Some pointers would be greatly appreciated.

[Mike90250]

... what happens if the irradiation goes higher than 1000w/m2?

We all get a sunburn, and starve in a year. That means the sun has gone bonkers

..will I blow my inverters? .....

No, the inverters throttle back to stay within safe operating limits.

[nigel76]

Thanks Mike.

[Sunking]

Hello everyone,

My first question on here after trying to find the answer somewhere on the internet.

I'm currently working out the pricing to see if it is worthwhile to build a 5mw solar park.

If I have a connection to the grid for 5 MW. I want to make sure I get as close to that in regards to what comes out of the inverters.
My question is this, being that the max currents and voltage are worked out at STC of irradiation 1000w/m2. So using a panel that gives 250 watt I need to use 20,000 panels to get my 5MW output not taking into account about 20% for losses. however what happens if the irradiation goes higher than 1000w/m2? will I blow my inverters? do I need to look into the maximum irradiance in the area?

Some pointers would be greatly appreciated.

Your are dreaming. Wake up and pinch yourself.

But to answer your question nothing happens except you generate more power than expected. Irradiance is measured over a period of a day which is a measure of energy expressed as watt hours with respect to electricity.

Panels are rated in watts which is a moment in time, and a 100 watt panel will never generate more than 100 watts. In reality a 100 watt panel wil never generate more than 90 watts at any given point in time. So if you only have 4 Sun Hours in theory it will generate 400 watt hours. If you have 5 Sun Hours it will generate 500 watt hours.

To pull off your dream you will need a team of engineers, lawyers, and investors plus several years of court battles. You do not even know the difference between energy or power is. aka watts and watt hours. So wake up and pinch yourself.

There are only 2 or 3 people in the USA that have enough money to throw away and enough political influence to do something like this and they would not likely live to see it completed. So see if you can get Boone T Pickets or Warren Buffet to help you out.

[nigel76]

Your are dreaming. Wake up and pinch yourself.

We'll see.

[nigel76]

Thanks Sunking,

I didn't see the rest of your reply there,

In answer to your points, I'm building in romania we have the land and permit for 5 MW connection to the grid. It is very different here to where you are in terms of what is needed.
I do understand the basics of energy and power it may not have come across that way but such is life.

Just to clarify, the peak output of a panel say a 240w one is what the panel puts out at stc or 1000wm2. However the (what is the term I am looking for then if i want the power hitting the earth at any moment if irradiance is for a 24 hr period) theoretical max is more (if you times the Voc by the Isc) but this is not possible to reach in real life unless as mike says the sun moves closer to the earth allowing for more than 1000wm2 a any given time.

[Sunking]

this is not possible to reach in real life unless as mike says the sun moves closer to the earth allowing for more than 1000wm2 a any given time.

Well first you will never receive 1000 watts/m2 at any given moment in time. That is the lab STC rating.

However all that is accounted for in calculations using your areas solar insolation tables. If you look say in July the monthly average is say 6200 wh/m2. That translates directly to 6.2 Sun Hours. So for a 1000 watt panel means it would generate 1000 watts x 6.2 hour = 6.2 Kwh. But that is an average through the month collected of many years. July 5th it maybe cloudy and you only receive say 2 Sun Hours, and the next day bright and sunny and you receive 7 hours. The daily target moves each day.

[nigel76]

Well first you will never receive 1000 watts/m2 at any given moment in time. That is the lab STC rating.

Thanks for the answer I had rung a couple of panel makers today and couldn't get a clear answer on that,

[Sunking]

Look at manufactures that post 2 rating, STC and PTC.

PTC is the real life application. STC is just a meaningless lab condition manufactures use to test with. PTC will be about 80 to 95% of STC

[vinniethePVtech]

Unless you have a tracking system it isn't expected to hit a total of 5mega watts with 5 mega watts of panels, even if its a perfect day at peak hours.
Fixed systems if at the proper degree of slope to the equator will probably hit max roughly at peak hours between 12:30~2:30 depending on the season.
When I build systems on a commercial level there is usually 5.5mega watts of PV panels for 5 mega watts of inverters, there are several challenges to meet the criteria for 5 mega watt out put. With 5.5 mega watts of panels the system if built right should perform roughly to cec AC of 4.7mega watts on average.
There is voltage drop from conductors, length of conductors, size of conductors, and heat losses; temperature that associates lowered amperage, tilt of panel, and of course the one that people typically don't account for which is soil coverage over panel surface area.

People assume systems make the most power in the summer which isn't entirely true. Summer temperatures lower amperage which in effect reduce wattage output. Inverters harvest less dc current the higher the temperature becomes. End of spring weather typically yields better numbers than the summer. If people want good harvest numbers in the summer time shading or a cooled room help provide better efficiency.

I have built commercial systems in colder condition climates such as colorado, and alaska which has blown fuses because the cold environment in effect has the pv and inverters producing power above STC conditions. DC calculations for fuses is 1.35 X Imp. AC calculations for fuses is 1.25 Imp.

[russ]

For an introduction to solar panel terminology try this - PV module comparison http://homepower.com/view/?file=HP134_pg50_Sanchez