Large system

[Roqm]

The ptac units are all 1 phase cooling is Rated 778 watts heating 3.5kW voltage is 208-230 according to the spec sheet

Your looking at 320a just to run the heaters thats not the initial surge when starting or your other items in the units...the best thing to do would be consult a pv engineer in your area to get an inept idea on what would be needed....based on what you want your system to do.

 

[Coolthings]

517kWh per day
Assuming 5 hrs solar, thats 517,000Wh / 5h = 103,400W of solar.

If you have 350W panels, that would take 295 solar panels. How much room do you have for panels?

>>google search
Modern solar panels are around 15% efficient, so that works out to approximately 150 watts per square meter, or 15 watts per square foot.

103,400W / 15W / sqft = 6893sqft if densely packed.

Just messing with numbers.

Thank you that helps put in perspective. The energy cost for the past year was $24,000 for the 186,000kWh any reduction will help. The location is Kentucky USA. I have 4900sq feet of south and east facing roof if needed I can reduce by installing on demand water heater other than that I am stuck with the heating and air con units

 

[mrzed001]

The ptac units are all 1 phase cooling is Rated 778 watts heating 3.5kW voltage is 208-230 according to the spec sheet

So the units are heated by AC? And if it needs 3,5kW then this are older types where heating is done with a heating wire ?
If so then this could be the reason for your very big power consumption.
The newer AC units are heatpumps and use the same amount of power for heating and cooling. Like a 12000BTU unit runs under 1kW.

The 25 kWh/day is a lot of consumption for a flat. My 2 floor + under garage house uses 12kWh/day and we use electric cooking plates and have 2 servers run all the time. Even with an AC running (cooling or heating) all day it is under 20kWh.

On-grid hybrid is a good solution if you want to have some power in a blackout.
But it has several subtypes (I put in some schematic pics before).

If you really want everything to be able to run on a blackout then you need to prepare for a very BIG bill.
500kWh you need for a day. So at least that much of battery.
The cheapest is the DiY battery pack like $3.000 per 14 kWh (with BMS and 100kg 220lbs), so for 500kWh you need 36 of these $108.600 (that is 3,6 tons = 2 smaller car).
With any company made battery it is x2 - x5
Except the new one @Will Prowse tested and cost $3.900 / 10kWh and plug-and-play and can parallel 16 in a stack.

For inverters a single stronger (15kW) Victron Quattro costs like $10.000 and you would need a bunch of them (do not know how big can be the stable consumption in kW and how big the inrush ?)

And a badass big relay to disconnect the hotel main in a blackout to go off-grid.

To lower your power bill needs a lot of solar panels and MPPT. Like one 420Wp 2 m2 (21 square feet) solar panel costs $200 and you need like 200 from it.

So to go in all would cost a lot.
But you can start small with the possibility to expansion.
One Victron inverter, small battery (like 50kWh), 40-60 solar panels. With this you can reduce the grid consumption by the amount the PV produces. Also have some equipment on constant UPS power from Victron.

 

[wattmatters]

IMO work should first be done on the demand side of the equation. 25kWh/day/unit is nuts. Get this down first.

Going straight to the supply side of the equation is putting the cart before the horse.

Install much more efficient heating/cooling, sort out the insulation, better sealing/draft proofing and other thermal properties of the units, double glazing of windows/doors, strategic seasonal shading, change the nature of appliances in units to be more energy efficient options (e.g. clothes dryers should be heat pumps). Swap lighting over to LED. Sort out hot water supply options. There is a whole raft of things to be done with energy efficiency.

By sorting out the requirements of the demand side it means the supply side (solar PV, storage etc) can be significantly reduced in scale and complexity and cost.

If outage backup is required, then make a clear call on what is really essential to operate during backup periods. It's an outage, backup isn't a permanent state of affairs, it's meant to get you though. By putting a focus on what really needs to operate for such periods rather than assuming everything must run as normal then this also significantly reduces the size and complexity of the backup supply side equation.

And don't forget that backup can also be provided by or supplemented with a standard diesel generator. It's not like everything has to be UPS cut over via a monster battery system.

I have a 25 unit complex near me. Large restaurant as well. They have a 40kW PV array, no batteries and use a big diesel generator for outage coverage and have done a big renovation of all units to significantly improve their energy efficiency.

 

[12VoltInstalls]

For inverters a single stronger (15kW) Victron Quattro costs like $10.000 and you would need a bunch of them (do not know how big can be the stable consumption in kW and how big the inrush

In this circumstance, engineers that are familiar with equipment to the gigawatt level are probably the least costly solution. There’s inverters basically the size of a minivan: There IS equipment that will do this project. I just don’t think monetarily it will be cost effective.

 

[MisterSandals]

I usually like to show numbers but even with unrealistically low estimates for equipment and labor, you're looking $200,000 outlay and at least 10 year break even if you have very good luck with equipment (low maintenance and replacement).

As others have stated, focusing on reducing energy use will pay back immediately. If you give financial incentives to your tenants, where you share part of the savings for example, it will reduce your costs.
Or even putting the burden of the energy costs on your tenants, this will change energy use patterns.

 

[12VoltInstalls]

Since in many areas propane is roughly the same cost per btu as gridelectrons I’d probably think about propane hot water

second I’d do a cost/life/return analysis of the electric wall heaters VS rannai propane heaters.
add option “B” for split delivery AC
May not be the greenest approach, but at least it makes the solar a reasonable possibility.

Oddly, gridtie as a peak load buffer/battery/backup can actually leverage savings- the grid can enable an affordable solar program while not requiring the great investment into failsafe capacity under full occupancy if you stay all electric
And the advantage of the rannai’s for heating is that in a grid-down situation you theoretically could sustain a month or however big your propane storage is if some neoteotwaki situation occurs.

 

[mrzed001]

In this circumstance, engineers that are familiar with equipment to the gigawatt level are probably the least costly solution. There’s inverters basically the size of a minivan: There IS equipment that will do this project. I just don’t think monetarily it will be cost effective.

This is far from a gigawatt level
Here I saw a single container solution that has 1,2MWh battery and can give 0,5MW out. Also substation works as an UPS.
It was needed because a lot of 0,5MW solar farms are in the area (and already installed I think two of them).




This was about 3 million dollar

 

[12VoltInstalls]

This is far from a gigawatt level

Ya, I was just saying the truly “big” setups aren’t exactly made of the stuff that’s going retail.

 

[mrzed001]

Ya, I was just saying the truly “big” setups aren’t exactly made of the stuff that’s going retail.

There are industrial sized inverters, true. But the batteries are made from the same cells as we use.
The Tesla Megapack is made from the same cells as the EVs.
BYD makes megapacks from the same LFP cells there use on EV and solar batteries.
48V batteries like Pylontech is made from the the same prismatic cells.

In the first page is a video I put up with a Victron container solution.
That has
- 6pcs 15kW inverters = 90kW
- 102kWh battery
- 130kW solar panel and MPPT.
And it is enough to power a smaller factory with cutting lasers and everything.

 

[wattmatters]

And the advantage of the rannai’s for heating is that in a grid-down situation

Provided you also supply them with backup electric power - they'll still need an electrical supply to operate the ignition and control system.

 

[12VoltInstalls]

Provided you also supply them with backup electric power

Of course! I assumed that would be inferred. Sorry.