Solar power research and development project

[Crom1111]

Hello all,

I would like to develop a device which can take the variable energy input from a string of solar panels and convert it in real time to a usable power supply in the form of a standard US 110 household outlet that can carry at least 15 amps. Having energy storage batteries incorporated into the system is not an option. I recognize that with the nature of solar, the input power will surge and decline rapidly and erratically. To overcome this the system would be powered by a string of panels that would greatly exceed the 1800 Watts that are needed to reach 15 amps. I am rough estimating around 5000 Watts of potential input. So the device would need to be able to dump the excess energy to avoid burning out the outlet on particularly sunny days and it would need to be able to provide less than 15 Amps of 120AC on days where the energy generated is low. The device would need to produce a clean sine wave under all these condition so electronics and other sensitive devices could be used without damage. I assume it would also need a shut off that would prevent a load from exceeding what the panels are currently providing. Is such a device technologically possible and if so what components would be needed to make it a reality?
At this point I am not so concerned about the financial viability or other more pragmatic solutions. I want to find out if the power from solar panels be used in real time without batteries and if so how would you make that happen. I also want to state that I am not an electrical engineer. I am a tinkerer and I am skilled at a number of trades but I do lack the technical expertise that I am sure most of you have, That being said I wish to apologize if I use improper terminology or lack critical understanding of a point. I will do my best to keep up as the conversation progresses. Thanks all for your help and feel free to correct or guide me if my proposal is in some way flawed or incomplete. I am always willing to learn.

All the best,

-Crom

 

[IRstuff]

I don't see that you've mentioned anything that isn't already off the shelf. Obviously, you can readily buy an inverter. I'm unclear why you wouldn't simply grid-tie the inverter and allow the utility company to buy your excess capacity, rather than just dumping the power. Dumping 3.2 kW is going to create a huge heat source that'll need to be cooled.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[Skogsgurra]

My first reaction to your questions were the same as IR above.
Then I started thinking. Why do you want to dump excess energy? Why not sell it to the utility? Why do you not want batteries?

First question is still difficult to find an answer to. It is true that solar panels deliver current in proportion to irradiance. But that does not mean that they go to kilovolts when the current isn't used. So I see no need to dump excess energy.
Second question. You may be in a location where there is no land lines and no Connection to the utility. Is that so? Then I can understand why you have not chosen to sell energy to the utility.
Third question. Batteries need maintenance. Not much, but still. An alternative are supercapacitors. Not infinite Life, but quite good nowadays.

Your humble tone reflects some lack of fundamental understanding and there may be a reaction to that (EngTips is for PE:s) but I hope that your posting remains. It started an interesting chain of "if:s".


Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

You need dump nothing, rather you use only what is needed. The solar power is simply PWM'd onto the inverter's input capacitor bank to keep the cap bank at the appropriate peak voltage for the designed inverter output voltage, (169Vdc for a 120Vac output or 339Vdc for 240Vac). The panels will just bump their voltage up and down by the PWMing.

If the voltage starts dropping, either individual loads need to be dropped or the entire load needs to be dropped. But if the entire load is dropped you need a way to determine if the array can support the re-pending load. This would require either an insolation sensor calibrated in array output power or some sort of dummy load to provide array loading to allow an assessment of the array's immediate power potential.

Alternatively, just get a standard off-the-shelf solar inverter designed for off-grid operation and add the smallest battery possible to allow it to do it's normal function, just with a very low capacity bank.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[OperaHouse]

I have an off grid system somewhat similar to that. There is only a car battery to provide surge current, could possibly get away with a SLA. Some have used super caps for very temporary storage. I dump excess power to heat water because I have no real battery storage. They have three phase pumping systems that have no batteries. While not common, this is all being done now. The only trick is to know when to shut down. These systems have to be really smart. If you don't have great computer skills, move on to the next experiment.

 

[itsmoked]

Opera is this your main residence or a vacation residence?

Keith Cress
kcress -

http://www.flaminsystems.com