PIPING NETWORK

The distribution network in a district energy system is of critical importance. Transmitting energy generated by the thermal source efficiently to the buildings in the network is a key factor in achieving success.

The Piping Loop

Pipes for district energy systems are buried underground — an expensive endeavour. Trenching costs a lot of money and it makes economic sense to install all the pipes at the same time instead of having to dig trenches to bury some of the pipes at a later stage. This requires a fair amount of planning ahead while designing the piping loops. For example, if the district energy system is responsible for supplying heating and cooling using steam and chilled water, the piping loops have to be designed taking into consideration the number of pipes that will be needed and the contents of the pipes.

Insulation

In any energy transfer process, the insulation of pipes is a critical consideration since the temperature at the outlet is directly dependent on the effectiveness of pipe insulation. The key is to find the optimal insulation thickness without hemorrhaging capital costs, while keeping heat loss to a minimum. District energy systems commonly use steel pipes insulated with polyurethane wrapped in protective high-density polyethylene (HDPE) casing.

Optimal pipe diameter

The amount of thermal energy delivered is a function of water temperature and flow volume. Smaller pipes transferring fluids at higher velocities, or larger pipes transferring fluids at lower velocities are ideal for maintaining given flow volume. Lower velocity in larger pipes reduces friction, thereby reducing the pumping energy required. That being said, the larger pipes are more expensive to install. These considerations should be weighed carefully to determine the optimal pipe diameter for the district energy system.

Pipefitting and connectors

Since district energy systems often cater to a sizeable number of buildings, the piping network should be laid out in a way to efficiently transfer energy with minimal losses. This requires good pipefitting and high quality joints and connections between the pipes (for example, metal pipes are usually welded or soldered). In some cases, use of additional HDPE jacketing may be required. The connections between the pipes should ensure that no leakages take place or have checks, like embedded wires, to monitor breaks in the pipelines and leaks.