need help going green and willing to pay for help! solar / relay / timer control

[henry barbera]

i live on a caribbean island and clouds are expensive!!! believe it or not a kwh of electric at 120v is US$.50 because of the laws here i have hooked up pv solar arrays to inverters and have run directly to the compressor of a/c units. no batteries and i'm still on grid. all of the electric i produce is consumed by the ac unit cause they use more then the panels produce ( i leave the unit at the lowest setting and the compressor never stops running) and the solar/inverter circuit is not complete unless the ac unit is on. i tie the solar power into the compressor and the circuit is only complete when the a/c contactor is closed and the compressor is running. i only run the ac during the day and the house gets nice and cold and retains it will into the next morning. i manually turn my ac off late in the day, my ac bill has been reduced in a major fashion!!! every time a cloud goes when the ac is running i'm pulling loads from the grid. that costs me$3 / hour and adds up fast. the house actually gets to cold but when the sun is out it's almost free - so what the heck. if i'm home and the big black cloud goes over i manually turn the a/c off and back on when the sun comes out. what a nuisance!!!! i was hoping i could hire to do some work for me. i need a design and build. read amps from a pv solar array and if the circuit is producing above a preset level of amps then keep the relay for the ac circuit closed. if the amps fall below that preset level then open the relay. then with a timer delay check the amps again in 3 minutes and close if we have enough or open if it’s below the preset level of amps

the timer will always be 3 minutes after each opening or closing. i’m running a compressor and don’t want start / stops all the time. the timer could continuously read after the 3 minutes has elapsed.

the preset level amps (120v 60hz) has to be adjustable. i may want to run it if i’m getting 5 amps or perhaps 10 amps. i want the ability to choose that level.

i have more details but i think you get the general idea of what i’m looking for. in the beginning i need one then i’ll need six more and then who knows how many. i'm sure there will be a few issues we need to work through.

to make matters worse i have three guest houses which i have identical systems and a few friends already have similar systems installed. those clouds are expensive!!!!

i understand electric in a basic way and have no education in electricity but i can do 90% of any wiring i need. this is well above me.

thanks,
henry barbera

 

[Fish4Fun]

Hey Henry! Welcome to EP!

Hrmmm, I think this is something that could be "designed" fairly easily....as for actually "making it" that might be a different matter, perhaps I can help, but for now, I will think on it....and wait a bit to see what others suggest....

Fish

 

[(*steve*)]

Some inverters ave outputs which can report their current status (mine uses bluetooth). If you monitor this you can keep track of the power produced from minute to minute if you like.

Alternatively you can measure the voltage and current at your mains connection and by looking tat the relationship between these you can determine if you're importing or exporting power and change your load accordingly.

 

[Colin Mitchell]

The simplest idea is to use a smaller solar panel to detect the condition of the sun and use the output to switch the A/C on and off.
This way you don't have to touch the output of the main PV set-up.
All this can be done with a solar panel, battery, a chip and relay.

 

[henry barbera]

Some inverters ave outputs which can report their current status (mine uses bluetooth). If you monitor this you can keep track of the power produced from minute to minute if you like.

Alternatively you can measure the voltage and current at your mains connection and by looking tat the relationship between these you can determine if you're importing or exporting power and change your load accordingly.

I don't have blue tooth capable inverters and i need to only measure what we're getting from the pv solar array and then open / close a relay based on that number relative to the variable preset. i never export power because my panels produce at maximum just a little less then what the compressor draws. the only additional feature which makes sense would to add a timer delay so the system isn't on/off constantly. the a/c manual states - "do not restart within 3 minutes of turning off"- could do with the controller board i'm not really sure but i know it's good to 'not' constantly turn a compressor on and off.

 

[henry barbera]

The simplest idea is to use a smaller solar panel to detect the condition of the sun and use the output to switch the A/C on and off.
This way you don't have to touch the output of the main PV set-up.
All this can be done with a solar panel, battery, a chip and relay.

i think the issue with this idea is that my panels are roof mount - some face south east, some south and some south west so my controlling panel in your scenario won't always give me a good number to work with. the location or the sun during the day and the time of year would make things difficult. but on the surface thats' a GREAT IDEA and thanks for the reply. any other ideas?

 

[Colin Mitchell]

A cloud is a cloud is a cloud.

 

[henry barbera]

A cloud is a cloud is a cloud.

all clouds are not created equal....
your suggesting i control off of another mounted solar panel. the problem is that the new panel has to face in one direction when mine face all over the place. there is a big difference in the south-east vs south west facing panels in the morning and in the evening. it could be a 90% difference. now one might think a cloud is a cloud is a cloud but i've fluked the arrays' with clouds on different days and at different times. you would be amazed at the differences. not all clouds are created equal. it's the 'combination' of the different clouds with the controlling array not really pointed in the same direction in relation to the sun as the existing array that i believe (and i am assuming) would cause a big difference between the two. i agree the method you suggest would work - somewhat to a certain degree, however, if i can measure the amps i am receiving then that would take into consideration everything, time of day, clouds, position of the sun and is the one value which means the most to me because i can directly correlate that to the money being spent. irregardless i have to measure something - a new panel or the array so why not just measure the array. like i said this stuff is above my head but i have to believe if there is a way to do what i want as originally suggested then it would be the best way. so again, good idea but if you have a suggestion for the original concept or even a different one i'll be all ears. thanks colin!!!!!!!!!

 

[Colin Mitchell]

You are talking about peak generating, I am talking about detecting a cloud. Two entirely different things.

 

[Gryd3]

Yes, but depending on the angle of the sun, the panel on the opposite side of the roof may read as if it's behind a cloud.
It sounds as though 'cloud detection' is a simplistic form of what the op needs.
Ideally, the op needs to detect when the power supplied by the panels dips below a certain point so he can turn off the AC unit(s). To do this, the system as a whole should be looked at.

 

[henry barbera]

Yes, but depending on the angle of the sun, the panel on the opposite side of the roof may read as if it's behind a cloud.
It sounds as though 'cloud detection' is a simplistic form of what the op needs.
Ideally, the op needs to detect when the power supplied by the panels dips below a certain point so he can turn off the AC unit(s). To do this, the system as a whole should be looked at.

Exactly, dead on and thats' what i'm proposing. if the system is generating enough amps (variable - i set the amount) at 120v 60hz on the out side of the inverter then complete the other circuit with a relay. Again - it would also be necessary to have a 3 minute time delay between an off and an on.

I think of it like this - i fluke the power out from the inverter and if i have enough then i flip the switch.

 

[Gryd3]

Exactly, dead on and thats' what i'm proposing. if the system is generating enough amps (variable - i set the amount) at 120v 60hz on the out side of the inverter then complete the other circuit with a relay. Again - it would also be necessary to have a 3 minute time delay between an off and an on.

I think of it like this - i fluke the power out from the inverter and if i have enough then i flip the switch.

How is the inverter connected to the AC...?
Here is my most immediate concern:
-Current is drawn, not pushed.
So if you monitor the current, and one of the AC units turns off, or down. (Say when the compressor shuts off) the current will drop, and the circuit may assume it's due to a cloud.)

I am under the impression that the AC units are connected to the grid, and your panels. Is this correct?
If you turn off an AC unit, will the panels provide power for anything else in the building?

 

[Arouse1973]

Hi Henry
Could you use two current transformers to measure the difference between the two feeds or arrange the wiring so you did have two feeds. Then switch them out when the imbalance is a certain amount? It would be nice to see a wiring diagram of what you have.
Adam

 

[henry barbera]

How is the inverter connected to the AC...?
Here is my most immediate concern:
-Current is drawn, not pushed.
So if you monitor the current, and one of the AC units turns off, or down. (Say when the compressor shuts off) the current will drop, and the circuit may assume it's due to a cloud.)

I am under the impression that the AC units are connected to the grid, and your panels. Is this correct?
If you turn off an AC unit, will the panels provide power for anything else in the building?

your right on it. the panels are connected to the AC unit and when the AC unit is on then the power from the inverters can be drawn and consumed. YES the AC unit is also tied to the grid. if the AC unit is turned off then the power from the array does not feed the house / grid - it won't feed anything.

the inverter is tied into the compressor and the contactor must be closed from grid power. so i can only draw from the solar array when the grid is up and the compressor is on. if the array produced more power then the AC unit would draw then that excess would feed first back into my other household needs and then if it still had more then my house needed it would feed back into the grid. my solar array is sized so that could never happen. on the best day - best time the array will produce 95% of what the AC unit consumes.

as noted in my original post - 'there could be other issues' you hit that dead on the bulls-eye to. i suspected that i won't have anything to read if the circuit wasn't under load. so thats an issue which needs to be addressed. we would be in a catch 22 but i wasn't 100% sure about that. my thoughts are i know i can test a battery under load. i assume it's something simple like a heating element. i'm an idiot thinking out loud here but what if we put a heating element, pump or something else what would draw more power then the AC unit and the relay could feed to either the AC unit or this other thing.

 

[henry barbera]

Hi Henry
Could you use two current transformers to measure the difference between the two feeds or arrange the wiring so you did have two feeds. Then switch them out when the imbalance is a certain amount? It would be nice to see a wiring diagram of what you have.
Adam

you just went over my lay person head. i just replied to another reply which explains how it's wired. i hope that helps you - help me.

 

[Gryd3]

if the array produced more power then the AC unit would draw then that excess would feed first back into my other household needs and then if it still had more then my house needed it would feed back into the grid.

the inverter is tied into the compressor and the contactor must be closed from grid power. so i can only draw from the solar array when the grid is up and the compressor is on.

I would love to see a diagram... I'm a little confused.
One one hand, it sounds like the compressor itself within the AC units is connected to the solar panels, and the control boards and remaining components in the AC units were on mains.
On the other hand, you say that there is a possibility of it feeding back into the home which indicates that the solar panels are connected to mains...
Can you also please send us the make/model number of the inverter you are using?

I want to be certain I understand the setup before I recommend anything..

 

[henry barbera]

I would love to see a diagram... I'm a little confused.
One one hand, it sounds like the compressor itself within the AC units is connected to the solar panels, and the control boards and remaining components in the AC units were on mains.
On the other hand, you say that there is a possibility of it feeding back into the home which indicates that the solar panels are connected to mains...
Can you also please send us the make/model number of the inverter you are using?

I want to be certain I understand the setup before I recommend anything..

i would love to be able to draw you a diagram but the only class i have ever had that dealt with electric was in 5th grade and that was over 45 years ago.

your right the handler is tied to the mains and not the solar. ONLY the compressor is tied to the solar inverter and the compressor is ALSO tied to the grid. the compressor must be on for the solar / inverter circuit to be complete (closed). to start the compressor i must have power from the grid. if i have no grid power i cannot turn my compressor on and my solar circuit is not closed.

you said: 'On the other hand, you say that there is a possibility of it feeding back into the home which indicates that the solar panels are connected to mains...'
i think i said it right - perhaps not. if my solar array was producing more then the compressor draws then the excess could go anywhere - the house or the grid. the thing is - whatever the array is producing the compressor will consume it all. if my array was much bigger AND my compressor was on then i could power other items cause it would go right to the mains.

i mounted the solar panels, ran all of the wiring, hooked up the inverters and ran the wires to the AC unit. actually to five different AC units all with their own solar array / inverters. all stand alone systems. an electrician did the final hook up to the AC units. that step was out of my league and i knew it. he did say that he hooked it to the contactor or other side of the contactor. i know it works like he said it would and it is saving money!!! i know that the grid-compressor circuit must be closed to close the solar-inverter-compressor circuit.

i have china no brand name,mid-priced, true sine wave mini inverters - i bought a couple extra thinking they would be crap but i haven't lost one yet. i have one of nine in my garage - it's super hot and the air is salty but it seems to be a little work horse.

i wish i could draw a diagram the above is the best i can do.

 

[Gryd3]

i would love to be able to draw you a diagram but the only class i have ever had that dealt with electric was in 5th grade and that was over 45 years ago.

your right the handler is tied to the mains and not the solar. ONLY the compressor is tied to the solar inverter and the compressor is ALSO tied to the grid. the compressor must be on for the solar / inverter circuit to be complete (closed). to start the compressor i must have power from the grid. if i have no grid power i cannot turn my compressor on and my solar circuit is not closed.

you said: 'On the other hand, you say that there is a possibility of it feeding back into the home which indicates that the solar panels are connected to mains...'
i think i said it right - perhaps not. if my solar array was producing more then the compressor draws then the excess could go anywhere - the house or the grid. the thing is - whatever the array is producing the compressor will consume it all. if my array was much bigger AND my compressor was on then i could power other items cause it would go right to the mains.

i mounted the solar panels, ran all of the wiring, hooked up the inverters and ran the wires to the AC unit. actually to five different AC units all with their own solar array / inverters. all stand alone systems. an electrician did the final hook up to the AC units. that step was out of my league and i knew it. he did say that he hooked it to the contactor or other side of the contactor. i know it works like he said it would and it is saving money!!! i know that the grid-compressor circuit must be closed to close the solar-inverter-compressor circuit.

i have china no brand name,mid-priced, true sine wave mini inverters - i bought a couple extra thinking they would be crap but i haven't lost one yet. i have one of nine in my garage - it's super hot and the air is salty but it seems to be a little work horse.

i wish i could draw a diagram the above is the best i can do.

Well, this is where I think we will get stuck without adding additional outdoor sensors.
In order for the compressor to use the solar panels or mains (if the panels were low), there would need to be:
A - Switching components somewhere to switch back and forth between mains and Solar.
B - Matched phases so that the AC compressor can draw 95% from Solar and 5% from mains.

Measuring current from the inverter would not work unless it was providing power in parallel with mains. Measuring DC voltage across the panels would give you some funny results, as the voltage would drop considerable under load.


You may need to reconsider Colin's suggestion, perhaps by using either small calculator sized panels on each major face of solar panels you have constructed, or photoresistor/diodes.

 

[Fish4Fun]

Henry,

I can think of several scenarios that might "work", but at the end of the day what you want is very close to an existing product.....a UPS (Uninterruptible Power Supply)....Except one small caveat, you want the UPS to use the mains for "back-up" and your solar panels as the primary power source....if there is a "brief" interruption of power because of clouds, you would like to supply your air conditioners from the mains supply, but if the "cloud cover persists" you would like the system to simply shut-down.....does this accurately describe one possible way to view "solving" your problem? Before I go any further in my thinking I want to clarify that something along these lines is what you actually want....


Fish

 

[(*steve*)]

If you have multiple panel orientations, does that mean you have multiple inverters (or inverter(s) with multiple independent inputs?)

grid connected inverters typically use high voltage arrays and thus measuring the voltage is potentially dangerous (and measuring the current -- even with a hall effect sensor) has some risks.

One solution is to measure the voltage/current for each array and then convert this to an instantaneous generated power. To do this safely you need to ensure that your array is grounded, and I'm not sure that these arrays are.