Go Big Or Go Home – Taking a Commercial Bldg Geothermal
I own a large historic commercial office building – 200,000 square feet.
My goal is to convert it into 180 apartments.
The positive is I have 2 surface parking lots on 2 sides of the building, 130 parking spaces each. This gives me space for drilling wells, then cover them with the repaved parking spaces. With the new tax code passed, I believe I can get 50% of the costs of a geothermal system in tax credits (30% green energy + 10% economic zone + 10% US made). So now the higher costs of geothermal may be an acceptable issue.
Can someone recommend a URL or source for large commercial buildings looking to implement HVAC geothermal projects, e.g. larger and/or deeper wells for a community/building system, then split into individual apartments? What I need to know going forth is a very very rough can it be done and the costs.
If geothermal costs + tax credits for an apartment high rise can be done anywhere near conventional electrical HVAC for an apartment high rise, I would love the opportunity to take the building green with geothermal.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
It’s common on college campuses, so it’s certainly possible. Costs vary widely. Some ways to bring down costs include under sizing it and using something else for peak heating demand.
You can go green without it though.
The question I have to ask is, who pays the heating and cooling bills? Because that will be decisive in the economics of this project.
Bingo. Individual heat metering is possible but then you’re responsible for two bills a month. Or include it in rent and hope for the best. Plus if something breaks, you have 180 cold apartments.
Geo or not, the building usually takes care of part of the load and infrastructure. Usually this means a boiler and chiller providing a water loop inside the building. This then supplies individual heat pumps in each unit. The rent/condo fees pay for the building side costs and the tenant/owner pays for the electricity for the heat pump.
In some ways geo does makes this simpler as you don't need a building chiller/boiler but then you do need low temp heat pumps for each unit as the standard ones don't work with near 0C water.
This sounds about where my thinking is.
The attraction of going ground source is I can eliminate the sea of HVAC units on my roof. Instead I would have to provide a building water loop from the 50 degree ground for the individual tenant HVAC units to tap into. Each unit already has its own electric meter, so it would require each unit to have a tenant HVAC to be wired to the tenant's electric.
Makes sense to me! Maybe explore air to water too - a mix of ground and air source might work out to be more efficient and cheaper.
The heating and cooling of the units would be their individual utilities.
I'm not trying to create units that are inclusive with utilities.
The current design is HVAC on the various floor roofs, so a sea of roof top units.
There is plenty out there, I would search for a similar local association for assistance:
https://ontariogeothermal.ca/downloads/22-04-27-collecdevgeothermalfilessizereduction.pdf
Thank you for the link.
It's certainly technically feasible. The University of the District of Columbia just built a new student center with a 200-ton geothermal system: https://www.setty.com/portfolio-of-experience/udc-new-student-center
The question is whether it will make financial sense. And that depends upon a lot of factors. It seems like there are two ways you can organize it. Either the landlord (and I use that term to mean whoever manages the building) is responsible for all heating and cooling. Alternately, the landlord provides each unit with a stream of water from below ground, and a return for water, and each tenant is responsible for operating and maintaining a heat pump using that stream. The second configuration is how a lot of commercial buildings are operated, where the building has a cooling tower on the roof that all tenants share, and each tenant is responsible for the HVAC equipment within their space.
We would be moving to the second version with the building providing only a central loop that individual units tap into. I don't want the obligation of having to make the entire building utility payment monthly. I'd rather that cost be an issue with the tenants-utility company directly. We would focus only on HVAC for the common areas of the building.
Since I have 2 parking lots (128 slots each) I'm interested in trying to use the space to drill the wells and then repave the lots. Not sure what the well configuration and depth would be though.
HistDev, you may have a problem with density of #wells per unit area. If the wells are too close together, you end up having the wells compete with each other for the heat available in the surrounding ground. This can result in cooling the ground to the point where you have freezing problems and lowered COP.