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Get Powered Up! Certified Energy Manager Jeff Yago answers your alternative energy questions

Wondering about a great new energy-saving device
you found on the Internet? Then CLICK HERE!

Sorry. Jeff no longer answers questions online.
This will remain as a searchable
resource for all BHM website visitors.



 

Cross check my design

Saturday, November 15th, 2008

Hi Jeff,

I am impressed on your publications and answers you do give to questions on Energy problem.

It will do me good if you attend to mine own question/solution to my need.

I have the need to have a back up power for my data center active devices, servers and other equipments and in the addition to the provision of a generator I still need a Battery Power back up that will take over on emergency.

By my load evaluation on the equipments running for 12 hours per day and working for two days with out charging, an average total watt-hour per day of 49,964.57wh/d.

I have in mind of using a 48v, 200Ah battery for my battery bank. Taking this into consideration I have an average amp-hour/d of 1,040.93 Ah/d.

The sum of all the power ratings of the equipments is approximately 16KW, and I intend deploying a single 20Kw inverter with thirty 48v,200Ah battery or in other have have six 3kw inverters with six same battery for each inverter and balance-distribute the loads among them.

This is exactly what I have in mind and I want to know your view to it. Also which brand of inverter and battery will you recommend? In each situation, how long will take to charge the bank?

Thanks

Chekwube Kamah

Chekwube:

Based on your description of system capacity, this is a very large and very expensive backup power system. Any casual review of your plans with the limited information you have provided is not possible to address on a “free advice” web site.

Since just the inverter alone will cost as much as $35,000.00, not to mention thousands of dollars for batteries, I am quite sure you can spend a few thousand dollars more for the assistance of a solar system designer which you clearly will need.

If you thought you could do all this for a few hundred dollars and free design services you are going to be in for a real surprise.

Good Luck,

Jeff Yago

 

Simulating a grid on a grid-tied system

Wednesday, August 6th, 2008

Jeff,

I have a Fronius 5100 inverter on a grid tied solar system. When the grid goes down, I lose all power to my house even though the solar panels are working.

Is there a way to simulate the grid so that when power goes down I can still utilize my solar energy?

Thanks

Mike Emmons

Mike:

I can’t believe this was a surprise to you, and I sincerely hope the installer made it very clear that ALL grid-tie solar inverters are designed to shut down in the event of the loss of grid power.

If they continued to operate after a power outage, they could be energizing a downed power line that the utility crew would not realize power was being supplied from the wrong end of the line which they may not check. Keep in mind that any power you are sending back to the grid at 240 volts AC goes through the transformer on the power pole in reverse and will go out onto the power lines at 480 or higher voltage which is deadly.

All inverters must pass a very strict testing process to make sure their design will not allow this to happen, and proof of meeting this safety requirement must be provided to the local utility before they will allow you to install the inverter on their grid. The equipment label will note – “UL 1741″ and “IEEE 929″ to indicate this.

Yes, there is a way to make a grid-tie inverter “think” the grid is still operating and not shut down, but this requires a second inverter with battery backup. In addition, since the first inverter is now being fooled and continues to operate, your system must isolate the output from the utility grid, and include enough electrical loads in your home that are operating to consume this excess power being generated or you will have a system error in the inverter that will shut the system down.

I do not want to give out too much information on this subject as you really need to work with an experienced solar installer to make this conversion due to several safety concerns, but it can be done.

Good Luck,

Jeff Yago

 
 


 
 

 
 
 
 
 
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