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Uncle Bob and Aunt Betty's two-story farmhouse was a haven for my brother and me during our childhood. While it didn't boast modern amenities, the old-fashioned radiators under each window ensured a cozy warmth throughout the house. These radiators were a blessing during cold winters, providing a spot to dry our snow-soaked gloves.

This Ain’t Your Great Aunt Betty’s Room Radiator!

Steve Maurer, IME
Uncle Bob and Aunt Betty's two-story farmhouse was a haven for my brother and me during our childhood. While it didn't boast modern amenities, the old-fashioned radiators under each window ensured a cozy warmth throughout the house. These radiators were a blessing during cold winters, providing a spot to dry our snow-soaked gloves.

Today, building climate control for heating is far more complex than Aunt Betty’s radiators. But radiant heat still plays a huge part in commercial and industrial heating.

The benefits of radiant heat
So, let's chat about radiant heating systems in general. They're pretty cool, actually.

Radiant heating systems offer several advantages over traditional forced air systems. They can be up to 30% more energy-efficient, translating to significant savings on energy bills.

These systems deliver a uniform warmth, eliminating hot and cold spots in a room. They operate silently, devoid of fan or blower noises, creating an ambiance similar to a silent, invisible fireplace. Directly warming the body, the heat feels natural and comfortable.

Health benefits are notable too; without ductwork, these systems don't circulate dust or allergens, ensuring cleaner air quality.

Of course, newer models can run a little cooler, are easily adjusted for temperature control, and have safety guards to shield from accidental burns.

Radiant heat for climate control in industrial and commercial applications
While I was researching radiators and radiant heating, I came across a term I wasn’t as familiar with: district energy heating.

District energy heating, also known as district heating, is a system that produces heat at a centralized location and distributes it to residential, commercial, or industrial users. This system offers an efficient and environmentally friendly alternative to traditional heating methods.

The primary components of a district energy heating system include a central plant where the heat is produced, a distribution network of insulated pipes that transport the hot water or steam, and heat exchangers in each building that convert the heat into a usable form.

Typically, the heat is transferred to the distribution network by hot water or steam, which is then pumped to buildings via underground insulated pipes. The heat exchanger converts the heat into a usable form for space heating and domestic hot water once it reaches a building.

District energy heating systems are beneficial in scenarios where there is a high density of buildings, such as in cities or large campuses.

District heating looped systems
A district heating system typically consists of two loops: the primary and secondary loops. These loops are integral to the operation of the system and work together to efficiently deliver heat to individual buildings.

The primary loop, also known as the main or network loop, starts at the central heating plant where heat is produced. This loop contains a network of insulated pipes that transport hot water or steam from the central plant to different areas of the district.

The water or steam in the primary loop remains separate from the water used in individual buildings. It circulates continuously between the heating plant and the district, transferring its heat to the secondary loop through heat exchangers located at each building.

The secondary loop, also known as the building or customer loop, begins at the heat exchanger in each building. Here, the heat from the primary loop is transferred to the water in the secondary loop. This heated water is then distributed within the building to provide space heating and domestic hot water.

Once the heat has been extracted, the cooled water returns to the heat exchanger to collect more heat from the primary loop, and the cycle repeats.

Both loops are closed systems, meaning the water or steam inside them does not mix with the water in the other loop or enter the building's internal plumbing. This design ensures that the quality of the heat source is maintained, enhances the efficiency of heat transfer, and minimizes the risk of contamination.

Electrical and other components in a district heating system
A district heating system relies on various electrical components to function efficiently and effectively. These components play crucial roles in heat generation, transfer, control, and distribution.

  • Boilers: Boilers are the heart of a district heating system. They generate heat by burning fuel (like biomass, coal, or gas), or through electrical resistance heating, or by harnessing geothermal energy. The heat produced is used to boil water, producing steam or hot water that is then circulated through the system. Modern boilers are equipped with advanced controls and sensors to optimize efficiency and safety.
  • Pumps: Pumps are used in both the primary and secondary loops of a district heating system. In the primary loop, they circulate the hot water or steam from the central heating plant to the district. In the secondary loop, they distribute the heated water within individual buildings. Pumps must be powerful enough to overcome the resistance of the system and ensure a constant flow of heat.
  • Heat Exchangers: Heat exchangers are where the heat from the primary loop is transferred to the secondary loop. They consist of a series of plates or tubes that allow the hot water or steam and the building's water to pass closely without mixing. The heat is transferred through the walls of these plates or tubes from the primary to the secondary loop.
  • Valves and Controls: Valves regulate the flow of hot water or steam in the system, while controls monitor and adjust the system's operation to maintain desired temperature levels. Thermostatic controls in individual buildings can adjust the heat output based on the building's needs. Advanced systems may have automated controls that respond to external factors like weather conditions or electricity prices.
  • Meters: Meters measure the amount of heat delivered to each building, which is essential for billing purposes. They typically measure the volume of hot water supplied and the temperature difference between the supply and return lines to calculate the amount of heat used.
  • Electrical Wiring and Components: All these components require electricity to operate, so a district heating system also includes electrical wiring, circuit breakers, transformers, and other electrical components. These ensure the safe and efficient operation of the system and protect it from electrical faults.

Each of these components plays a vital role in the operation of a district heating system. Together, they enable the efficient generation, transfer, and use of heat across a district.

As you can clearly see, this is way more complex than Uncle Bob’s and Aunt Betty’s farmhouse radiators.

And safer, too.
Photo courtesy of Danfoss
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