Any power left for the house

Farmer

Some of you are having a great time with my posts so I have another:D The meter and grid tie disconnect are side by side. Main power runs to main 200A panel through 250ALU 30' and disconnect junction is also beside main panel and goes out to greenhouses in ground 3x250ALU 660 Feet at greenhouse sub panel full load is 35-40 amps for 3 weeks in summer when all exhaust fans are on during hot days. The Solar grid (24 235W 5.5kW panels) is 20' from this sub-panel this location has the inverter and connects this panel. I would like as much as I can get to the house or will the house feed off the grid due to loss in the distance? Can I install anything to help? The distance from the meter to the pole transformer is 80' if that is useful.

BB.

Re: Any power left for the house

Guess at your power needs:

40 amps * 240 VAC * 1 kW/1,000W * $0.15 per kWH * 21 days * 12 hours per day = $362.88 per season

So ~$400 per season--Sound about right?

I know of nothing that would offer a return on investment that could supply ~8 HP worth of loads for less than 1 month a year.

Options would include:

Look at replacing fans with more cost effective drive units (DC PM motors + VFD's)... Both more efficient and allow you to trim motor speeds to need--instead of full on or full off.

Review your billing plan... Many commercial plans can include "power factor" penalties--You may be using (40 amps * 240 volts 9,600 VA but only using ~0.67 (67%) of that as actual work (9.6kVA*0.67PF=6.4kWatts)--Uncorrected Induction motors (depending on design, loading, etc.) can have poor Power Factor which the utility will charge you for (basically the utility may charge you for "worst case" PF in any 15 minute period--And use that against your whole bill for the month or even the year).

Changing to VFD's or even just adding correction capacitors (see electrician) may save you some money on your bills--With no too much outlay in cash.

Also review billing--In California commercial billing, very roughly 1/2 of the bill is actual kWH (or kVA) used, and the other 1/2 is a "reservation charge" which is your 15 minute peak usage in the last year--If you can cut your peak usage, you may save a bunch of cash over the entire year.

Look at other needs (say water pumping) that could spread out that load over ~9 months so you can "divert" power to green houses in summer heat, otherwise pump to pump/cisterns/etc.

Other than the last suggestion, none of my observations include spending money on solar panels just yet.

-Bill

Cariboocoot

Re: Any power left for the house


I thought he was saying he has a GT system already and wants most of the power to go to the main house rather than the greenhouse. There's no way to do that I can think of other than separate service for each.

Then again I've just been shoveling snow out of my shed for an hour and am having trouble breathing, much less thinking.

inetdog

Re: Any power left for the house

Cariboocoot wrote: »

I thought he was saying he has a GT system already and wants most of the power to go to the main house rather than the greenhouse. There's no way to do that I can think of other than separate service for each.

Then again I've just been shoveling snow out of my shed for an hour and am having trouble breathing, much less thinking.

It looks that way to me too (not the having trouble thinking part....).
Just as we get questions about wanting an inverter to draw power from the panels instead of from the battery when the panels are producing enough output, some people have a concern about whether the output of a GTI inverter goes preferentially to local loads rather then "being sold to the grid and bought back again".
In this case, the question of which of several loads the GTI output goes to does not really make sense, since the loads are all being served by the same meter at the same price.

If the goal is to say that the house is net-zero while the greenhouses are not, or vice-versa, that is just an exercise in meaningless numbers.

Farmer

Re: Any power left for the house

Cariboocoot wrote: »

I thought he was saying he has a GT system already and wants most of the power to go to the main house rather than the greenhouse. There's no way to do that I can think of other than separate service for each.

Then again I've just been shoveling snow out of my shed for an hour and am having trouble breathing, much less thinking.

At least you will live longer with all that exercise:D You almost had it, it must be the English language there is too many meanings for each word. Now the greenhouses run all year long with pumps small fans to keep some of them inflated and lights here and there but the max power they consume is in the summer and with everything on 240 35-40Amps only 4Hrs a day and only when temps get over 35C. I cannot separate them at night the greenhouses draw off the main house panel. I just would like to use 1/2 of the GT system output and sell the rest to the grid and buy it back at night but it is so far away that my concerns are it will be lost in distance. I do have a good running creek that I could drop in some Aquair Submersible Generators to help with consumption.

Cariboocoot

Re: Any power left for the house

Unfortunately AC is not directional (or it is bidirectional). As far as the GTI is concerned the greenhouse, house, and grid are all part of one circuit (albeit a complex one). The power it produces will simply go to wherever the resistance is least, i.e. the point of greatest load, whether that be the greenhouse, house, or grid.

The only way to "time shift" load consumption is to store the power (in batteries for example) when it can be purchased for cheap and then feed off it when purchase is dear. It is doubtful that the expense and complexity of such a system would be worth investing in unless there is a huge price difference between day and night.

inetdog

Re: Any power left for the house

Farmer wrote: »

At least you will live longer with all that exercise:D You almost had it, it must be the English language there is too many meanings for each word. Now the greenhouses run all year long with pumps small fans to keep some of them inflated and lights here and there but the max power they consume is in the summer and with everything on 240 35-40Amps only 4Hrs a day and only when temps get over 35C. I cannot separate them at night the greenhouses draw off the main house panel. I just would like to use 1/2 of the GT system output and sell the rest to the grid and buy it back at night but it is so far away that my concerns are it will be lost in distance. I do have a good running creek that I could drop in some Aquair Submersible Generators to help with consumption.

Using just half of the GT output is just the same as selling all of that GT output to the grid and buying half of it back. If in addition you have a separate meter that measures your PV output and part of your incentive is based on the power produced whether it is sold back or used locally, nothing will change either.
As a practical matter, if the run of wire from the mains connection point to the GTI is low enough resistance the the inverter will start, it will not have a significant effect on how much power gets from the GTI to the grid. Exactly which source the greenhouse and house loads get their power from (tracking the individual electrons, as it were) is not important as it will not have any effect on either the POCO meter reading of the PV output meter reading.

The only place where this discussion becomes important is for the UK case where the owner is paid more for PV power that they use locally than for PV power that they sell back. And once again, even in that case, as long as the greenhouse load plus the house load is more than your PV output you will get the higher rate, and if the greenhouse load plus the house load is less than your PV output it will not matter where you use the load power, you will still be selling back.

Now in the somewhat unlikely situation that there are two meters at the greenhouse, one for net usage and one for production, and your incentive is based ONLY on those two meters, then the load in the greenhouse is what is important for the super high incentive. The solution to that is to get the usage calculated only by the output meter at the greenhouse and a single meter feeding both the greenhouse and the house.

inetdog

Re: Any power left for the house

Cariboocoot wrote: »

The only way to "time shift" load consumption is to store the power (in batteries for example) when it can be purchased for cheap and then feed off it when purchase is dear. It is doubtful that the expense and complexity of such a system would be worth investing in unless there is a huge price difference between day and night.

And if that were the case, you would be best off just charging your batteries at night and using the power during the day while selling all of your PV output back during the day. Or leaving PV out of it altogether.

Farmer

Re: Any power left for the house

inetdog wrote: »

It looks that way to me too (not the having trouble thinking part....).
Just as we get questions about wanting an inverter to draw power from the panels instead of from the battery when the panels are producing enough output, some people have a concern about whether the output of a GTI inverter goes preferentially to local loads rather then "being sold to the grid and bought back again".
In this case, the question of which of several loads the GTI output goes to does not really make sense, since the loads are all being served by the same meter at the same price.

If the goal is to say that the house is net-zero while the greenhouses are not, or vice-versa, that is just an exercise in meaningless numbers.

I asked my wholesaler months ago about switching they did let me know of a place in Vancouver that made programmable switches that can go between 2 power selections. My problem was I needed a 200A switch that micro fed the grid and held back full load but they could not help me but they would see if the could make one.