35,000 SF Commercial Office Building

[mciholas]

And those peaks are due to multiple AC units turning on at once so a few ESP devices set up to make sure that cannot happen via the thermostats would mitigate that.

I have so much excess HVAC capacity (despite being less than half the office building guidelines) that it would be reasonable to install a control system to peak shift thermostat demands. Basically, avoid a random event where too many are on at once.

The top end idea is to monitor my total building demand from the grid and set a threshold that prevents more HVAC units from operating until we are under that threshold. Basically use the HVAC units as load shed. I would need some timeout on this to keep from starving the building for HVAC if we have other demands, but it would trim my peaks and save demand charges.

This sort of system is a bit of development, but relatively low cost.

Shaving my peaks helps in all possible systems, no solar (reduces demand charges), only panels (lowers times of grid import), and with battery storage (keeps inverter and battery load down). So this is an idea that works for all possible futures.

Battery backup is very nice in a hurricane area and not relying on FPL is cool even though their rates are very reasonable.

My parents in Sarasota, FL on FPL definitely want power backup. They suffer multiple days of outages with hurricanes. They cannot move or evacuate during these events. They are also driven mad by nuisance outages from FPL, brief outages that are just enough to drop every clock and computer. My mother has at least a dozen UPS all over the house and keeping them happy is a pain (the batteries age out all the time). So they are very interested in some sort of backup system that can power the house for at least a day or two on a critical panel. If we add solar panels to that, then they get economic benefits as well as extended off grid run time. They can still get 100% net metering, so they can easily reach economic viability.

These issues do not afflict my building, however. That would be purely an economic play, and without 100% net metering, the payback period is lengthy.

My minimum monthly meter charge is $15 which has me considering what it would look like if I went "off grid". What I mean by that is try to meet my energy needs entirely through solar, but keep the grid as the backup "generator". If I have a string of cloudy days, draw from the grid. This would require a hefty battery bank, like 500 KWH or so, to approach off grid reliability. That's $100K in batteries alone.

I have not yet factored in the tax credit to all this, so that helps. A business gets 30% for the system total cost, another 10% if you meet a domestic content threshold, and another 10% if you build at certain sites. I get the first, maybe the second (depends on equipment choices and costs), and won't get the third, so 30% for sure, maybe 40% if I can find enough domestic sourced materials to reach the threshold.

Mike C.

 

[12VoltInstalls]

This sort of system is a bit of development, but relatively low cost.

Virtually any hvac RTU-integrated system installed in the last ~15 years can be controlled with predictive software on the low-voltage side.
15 years ago the internet accessible control add-on optioned for a 40kSF med office building (originally built 1969) when all the a/c was upgraded was only ~$1000.
In your case it will cost more because it’s 2024, AND I’m guessing you’re gonna need electricians pulling wire for a few days to do it since your building is new enough that you’re likely not needing to replace everything except the ducts like the building I oversaw.
Probably these days there is some software or another that actually uses CT’s to monitor loads. The software we had merely ‘knew’ numbers- somebody recorded what the running loads were and the central controller balanced it that way and as clunky as it was it worked. Your building sounds much more tech ready

 

[mciholas]

In your case it will cost more because it’s 2024, AND I’m guessing you’re gonna need electricians pulling wire for a few days to do it since your building is new enough that you’re likely not needing to replace everything except the ducts like the building I oversaw.

All 9 of my HVAC units are in one mechanical mezzanine centrally located in the building, so easy to get to and wire however I want. I chose to make long supply and return ducts to do this, but it shortens everything else such as loop piping, electric power, drains, and control wiring. Net cost is about the same, but having all the units together is a long term savings.

This is the HVAC mezzanine showing the well header system:



And here are some of the units in the room:



The entire floor is a corrugated steel drain deck, pitched to a gutter in the center (visible in the first photo if you look carefully), so if there are any leaks, it all drains away harmlessly. The drain also deals with air conditioning condensate and with humidifier drains.

The HVAC techs working on my system think it is a dream compared to the stuff they have to do under crawl spaces, in attics, and above ceiling tiles. They can do all their work without bothering anybody in the rest of the building, with ample built in lighting. In particular, no ceiling tiles are disturbed which eliminates debris raining down on people's desks.

Nobody in the building notices when the HVAC units are on, you can't hear them at all due to being far away, and the geothermal output is so smooth, the temperature never varies more than a degree. The system has been in operation for 10 years, no leaks or issues, works wonderfully.

I might put the inverters and other solar kit there, too since it is in the center of the building just under the roof. If I have a large array, then attaching to the inverters in the central part of the roof makes sense, and the array wires would be short. There is plenty of space.

Mike C.

 

[shadowmaker]

This would require a hefty battery bank, like 500 KWH or so, to approach off grid reliability. That's $100K in batteries alone.

Sunsynk has 1MWh fully lined battery container with build-in climate control, fire suppression system, EMS and alarm with 400kW hybrid inverter and I think I saw it ~98K$. Don't know if that was just one time offer, but that was almost a year ago and LFP prices are lower now. They have smaller 0,25MWh and 0,5MWh sets also.

 

[frasere2]

I think you can look at this a different way. Let's say you want to plan a 5 year payback. Multiply you annual cost and get the most value you can for that price (so 5*17.5k ~ $85k). You should be able to put a 100kw system together for that price and eliminate your bills. You should be able to get equipment cost down to $0.5/watt, and then find a firm locally to do the install, should be able to get that done for $30-35k, which would keep you below the $85k. Now as far as the incentives, they are many for businesses. First, you get the 30% tax credit from IRS. Then you get use MACRS to depreciate the entire thing in 5 years, but this year you can take 60% of the whole cost in depreciation in year 1 (40% if you complete the install next year, 20% the year after. then none). Plus you get to use 85% of the cost as the depreciable base (not 70% even though you already took 30% off). So lets assume instead you spend $100k (for easy math).

Purchase prices - $100k
Year 1 30% = -$30k tax credit
Bonus depreciation in year 1= 60% of 85k = $51k in depreciation
MACRS depreciation: 40% of 85k = 34k*20% (yr 1 Macrs) = 6.8k
Value of year 1 depreciation = 51k*21% (tax rate) + 6.8k*21%= $12,138
Depreciation year 2: 32% of 34%= 10.88k in depreciation = value = $2.28k
So in the first 2 years, your net cost of the 100k system is
100k
-30k
-12.138k
-2.28k
= $55,582 and you still have about $3.4k in tax benefits in the following years, so a net cost of about $52k. Payback is now actually 3 years (less with any increases from utility). But of course, you can have your accountant double check to make sure. Any state taxes would be on top of this amount.

You should produce 500-600 kwh per day with this system. It's too bad you can't be paid for excess solar generated. If you could, then I'd try to put a 300-400kw system on that roof.

 

[mciholas]

You should produce 500-600 kwh per day with this system.

When I use the PVWatts Calculator:

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

I get about 121 MWH per year from a 100 KW panel array. That works out to an average of 332 KWH per day, so not quite as productive as you expect. One issue is that my roof is ridged north/south so the panels are flat (equal numbers on east slope and west slope). The extra cost of some sort of tilt scheme is more than just putting in more panels, though one has to consider the apportioned cost of the wiring, mounts, and inverters, too.

Would require 250 panels of 400 watt size, which is a lot! Getting all that installed for $1/watt seems optimistic, but perhaps doable.

Due to the flat mounting, I get 4.77 MWH in December and 14.84 MWH in June, so the output is not very uniform over the year.

My usage is about 300 KWH per day, so the 100 KW array does do the trick to zero out my usage, but that does not zero out my utility bill. My export credit is only a fraction of the import cost.

The rules allow me to generate MORE power than I use overall and get credit for it, but only up to the amount of my bill. if I generate more than that, it builds a credit balance that accumulates and doesn't ever seem to expire. The best I can do it get to the minimum monthly payment each month.

My metering charges:

During the Month, Company shall measure the total kWh amount of Inflow and the total kWh amount of Outflow.

The Inflow kWh for the Month shall be billed in accordance with the Customer’s standard Rate Schedule, with all applicable rates and charges (heretofore defined as Standard Charges).

The Excess DG kWh (Outflow) for the Month shall be multiplied by the Marginal DG Price to determine the Rider EDG Billing Credit.

For each Month, the Customer will be billed the Minimum Monthly Charge as defined in the Customer’s applicable Rate Schedule. If the portion of the Customer’s bill for the Month attributed to the Rider EDG Billing Credit is in excess of the amount attributed to Standard Charges less the Minimum Monthly Charge, the amount in excess will be accumulated in a Rider EDG Billing Credit Balance for use in a subsequent period.

If the portion of the Customer’s bill for the Month attributed to the Standard Charges is in excess of the Rider EDG Billing Credit, any remaining Rider EDG Billing Credit Balance will be applied until the bill becomes the Minimum Monthly Charge or until the Rider EDG Billing Credit Balance becomes zero.

In accordance with IC 8-1-40-18, when Customer discontinues Rider EDG service and no longer receives retail electric service from the Company at the Premises, any unused and remaining Rider EDG Billing Credit Balance will revert to Company.

In short, I can't make money, but I can zero my bill by making more power than I use. If I build a large credit, I carry it forward. So I will build a credit in June and then use much of it in December. But I need a larger array to do this than 100 KW.

Presently, my import costs are about $0.15 per KWH, my export is $0.038 per KWH. Basically, about 25% effective value of export.

I appreciate the computations regarding tax benefits. It is useful to consider it in those terms.

Mike C.

 

[12VoltInstalls]

Would require 250 panels of 400 watt size

And 20,000lbs of weight