Industrial Engineering

Redefining District Energy

PME Magazine June 2020
By Max Rohr

Imagine if every building in an urban neighborhood has a gasoline-powered generator running to produce electricity instead of relying on an electrical grid from the local utility company. Maybe every balcony in a high-rise building has a little generator churning away to charge cell phones and power TVs. Would that seem odd? Why are so many heating systems single-unit sized?

When thinking of district energy applications and energy transfer pipe, normally a large city comes to mind. District steam systems in New York City and Denver are two examples. Typically, enormous steel pipes under streets feed a block of buildings with water or steam, but district energy doesn’t have to be that big.

For the sake of this article, I’ll loosely define a district system as anything outside of the normal approach of every independent building having a boiler or furnace in a room of the building that could have otherwise been used as a closet. District energy could be a single-boiler plant in the parking lot between a few buildings.

When I worked as a manufacturer’s rep in the swanky resort towns of Colorado, I would go to a lot of mega homes and commercial building campuses. I would bring my tool bag, park outside and the property manager or butler would take me to the ballroom for a cup of tea. Just kidding: They would normally escort me through the massive compounds to the least accessible, deepest, darkest corner of the structure. We would brush away the spider webs and make our way to the mechanical “room.” I put room in quotes, because sometimes these spaces required crawling to enter and seemed to be afterthought closets more than full rooms.

Small-scale district energy systems

There is a major architectural desire to maximize usable space in a building, so mechanical rooms are shrinking further into the shadows. Instead of shoehorning mechanical equipment into these tight spaces, could they be moved outside of the building all together?

Here are some advantages of small-scale district energy systems, using energy transfer pipe:

  • Get that noisy machine out of the building! Few people enjoy hearing a boiler come to life behind their walls; it is usually considered a necessary evil to stay warm. A district energy system may mean that the noisiest component inside the occupied space of a building is a small circulator or zone valve, because the boiler is under a different roof. Back in 2012, Fort Lewis College in Durango, Colorado, centralized 12 boilers to one new location. In a mechanical upgrade to student residence buildings, they went with a central boiler plant and use pre-insulated PEXa pipe to connect each building to the hot-water source.
  • No need to worry about finding a path to vent a new appliance in the basement of a building. Many boiler upgrades hit a snag when existing atmospheric vents are set to house new condensing appliances. While there are many ways to get plastic vent materials through an old chase, it is a tough task and may involve a plan-B; a sidewall vent. Instead of pumping products of combustion out the side of a building, like a leaky water balloon, move the whole boiler plant out of the basement.
  • Safety is a factor any time you run a combustible gas line into a building. When installed properly, there isn’t much cause for concern, but there are always cases when someone damages a gas line in a building and an emergency is created. In a district energy system with energy transfer pipe, the only part of the boiler system that comes into the building is the supply and return piping.; no combustible gas and no products of combustion.
  • Maintenance access is a concern in some secure locations. Privacy concerns can complicate the simplest of maintenance tasks. In some buildings, the annual task of cleaning and checking every unit becomes a monumental effort of scheduling a visit to each residence. If your boiler is in a separate building, you can back a service truck up to the equipment and not disturb a single resident.
  • Speed is of the essence when changing out a boiler. When moving the a new boiler plant, the existing plant does not have to be disturbed until the new system is ready to be hooked up to the load. Flexible energy transfer pipe can help quickly pull new supply and return lines into the existing mechanical space with few connections. This is a great strategy to minimize inconvenience for residents.
  • Pick the best energy source for the region, not the one that will fit most easily in the basement. If the system is in the country and can to use wood as fuel, tie a few buildings together and create a small energy district.
  • One of my favorite district energy projects combines single-family houses with a large geoexchange system. The Whisper Valley community near Austin, Texas, uses an enormous geo field as an energy battery and circulates the fluid to all the buildings in the neighborhood. This community will eventually have 7,500 homes, so it is no small project. Their district energy solution is helping them deliver new, net-zero-ready homes.

District energy isn’t a fit for every project, but it is an underutilized concept. When working on a project with multiple structures in a cluster and bending over backward to figure out how to wedge a boiler into a small area without negelcting code compliance for clearances, give district a look. Two eventual problems could be solved with one desicion: No. 1, the occupant has more usable space to store yard tools or a vacuum. No. 2, the installing and service contractors can back their trucks right up to the boiler plant and get to work.

Reference: https://www.pmengineer.com/articles/94837-redefining-district-energy