# Efficient energy savings

1. ## Efficient energy savings

Hey,
Where I live solar panels are very effective. Because of this, every year, more and more houses switched to solar. The electric company here makes insane profit charging people 29 cents a kw. When someone goes solar with grid tie net metering, they make enough power for two house holds. With 16% of the houses having solar, the electric company put the program to a crashing halt. Net metering is permanently closed. The company used the excuse of their infrastructure unable to keep up with the new power being dumped into the system. However I suspect they only stopped it so they can force everyone to buy their power at .29 kw.

Anyway, why the long explanation? I have a rare case where grid tie isn't an option. I keep dreaming of this amazing project I want to build, but I don't know enough about this to even begin to get the parts.

The idea is to save as much money as possible of the utility bill.

Let's say we have 5 kw of solar panels, with a battery bank, and connected to the grid.

The idea is to use the solar panels for energy to power the house, but what happens if we start using 6kw and only have 5 kw in solar panels, well then use 5kw from solar panels and 1kw from the batteries. What happens if we are using 6 kw and the batteries are empty? Use 5kw from solar 1 kw from grid.

The problem with most inverters, they don't even come with an ac input. Then the inverters that do come with an ac input, cost like 2 grand and switch to grid power or generator power entirely when solar isnt enough. If we make the switch entirely, were wasting power on electricity, the idea is to only use what you need.

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2. ## Re: Efficient energy savings

Hi,

What you need is a "controllable inverter" and a measurement unit for the grid power.

Then control the inverter for zero back_to_the_grid_power.
* if the solar power is higher than the consumed power: energy is stored in the batteries
* if the solar power is less than the consumed power: energy is drawn from the batteries
* if consumed power is higher than inverter_power: difference power is drawn from the grid

I assume there are ready to buy intelligent inverters that can be configured for this.

Klaus

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3. ## Re: Efficient energy savings

Combining the power sources on the DC bus is the most simple option. Have a AC/DC converter (battery charger) that's proving the missing power from the grid.

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4. ## Re: Efficient energy savings

The dream of converting to PV panels is on a scale with building your own power plant. You need to be aware of every detail of your system, load usage day and night, battery condition and state of charge, sky conditions, Amperes available from your panels, charge rate, wiring size and condition, etc.

Consider available roof space for PV panels, or tank of water. Avoid mounting valuable equipment in reach of thieves.
Look into the recreational vehicle market to see what equipment is available for low VDC.
Consider which loads could be 12V (low VDC) versus high VAC.

5. ## Re: Efficient energy savings

The dream of converting to PV panels is on a scale with building your own power plant. You need to be aware of every detail of your system, load usage day and night, battery condition and state of charge, sky conditions, Amperes available from your panels, charge rate, wiring size and condition, etc.

Consider available roof space for PV panels, or tank of water. Avoid mounting valuable equipment in reach of thieves.
Look into the recreational vehicle market to see what equipment is available for low VDC.
Consider which loads could be 12V (low VDC) versus high VAC.
Yeah, I'm considering all of this of course. Again the obstacle at hand is how to do this. I could convert ac to dc, then combine dc from solar with dc from power outlet, but whos to say where the amps are going to come from? What if all the power comes from the grid and the solar panels aren't doing any work?

I've been trying to look into "ac coupling" https://www.homepower.com/articles/s...upling-methods
and set up like an off grid system like the one shown. But I can't really find ac coupling inverters, and in general it seems to be a term used for syncing sine waves or something like that.
sigh again I don't know what I'm doing .

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6. ## Re: Efficient energy savings

Originally Posted by FvM
Combining the power sources on the DC bus is the most simple option. Have a AC/DC converter (battery charger) that's proving the missing power from the grid.
But how can I dictate where the wattage is coming from? The grid can provide infinite wattage, I don't see why the solar power won't just be randomly ignored. Sorry my knowledge of electronics is moderearly limited. Also turning ac into dc and dc back into ac causes like 10% losses. So then I need 10% more batteries. Also, What happens if i build this system with no batteries, at night time it's just going to waste power converting 15kw from ac to dc and back from dc to ac?

7. ## Re: Efficient energy savings

But how can I dictate where the wattage is coming from? The grid can provide infinite wattage, I don't see why the solar power won't just be randomly ignored. Sorry my knowledge of electronics is moderearly limited.
It's no electronic problem, rather basic electrical properties: voltage, current, power.

The idea behind DC coupling is to avoid grid-tied inverters and related problems with admissions by the utility company, energy metering and billing. Priority of solar panel source can be easily achieved by setting the battery charger parameters respectively.

The solution can be reasonable if you are mainly using solar power but want a grid backup supply, which seemed to be the objective stated in your initial post.
Also turning ac into dc and dc back into ac causes like 10% losses. So then I need 10% more batteries.
Yes, more losses for the backup supply, but why "need more batteries"?

Also, What happens if i build this system with no batteries, at night time it's just going to waste power converting 15kw from ac to dc and back from dc to ac?
Why should an unloaded inverter "convert 15 kW"? It consumes a certain amount of no-load losses.

If you want to keep a grid connected power supply, there might be an option to control grid tied solar inverters so that the meter never runs backwards.

8. ## Re: Efficient energy savings

Id like to try that last option, but can you link me an inverter that is capable of doing this? my own ebay, google, and amazon searches are not so fruitful.

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