Q.  Are Williams steam lines “leaky” causing us to waste energy? 

Williams central heating system, comprised of the co-generation heating plant and underground steam lines, is a very efficient part of our campus utility infrastructure.

The heating plant operates at 83% efficiency, meaning that for every BTU (british thermal unit)  of energy input, 0.83 BTUs of high pressure steam are generated. The high pressure steam then runs through a turbine to generate electricity.  About 5,000,000 kWh of electricity are produced during the winter months, in addition to the steam heat produced.   Once the steam leaves the plant, it travels through steam tunnels to reach our campus buildings.

Converting steam to building heat: In the buildings the steam then travels through coils in heat exchangers to transfer the energy from the steam to water that subsequently circulates throughout the buildings.  As the steam loses heat in the exchangers it condenses and returns to liquid state. 

One way to evaluate the efficacy of this system is to determine the amount of condensate, condensed steam, that comes back to the heating plant.   At Williams, we recover about 92% of the steam that has been sent out through the system. Therefore, we only have to “make up” or add about 8% water to the system.   As a point of reference, EPA noted a steam improvement project in a large specialty plant that reduced its boiler make up water rate from 35% to 14-20%. Currently Williams is operating at a much better rate.

Melting snow: You may notice in a couple of spots on campus that the snow melts first where there are steam lines buried underground. While this does indicate that the ground is a little warmer in those areas, it is not an indication that the steam lines are leaking. Even well insulated steam lines will be warmer than typical ground temperature in the winter.   Our maintenance practises also ensure that our system operates at maximum efficiency.   Much of the steam system is housed in tunnels large enough for our maintenance personnel to enter.  

Keeping things working: Several times per year, we go through the tunnels to ensure that steam traps are not leaking and that insulation is adequate and performing well. Insulated steam lines should not be too hot to touch by hand.  At the steam plant, we evaluate both the amount of condensate returned, we do this by measuring the amount of ‘make-up’ water we need to add to the boilers, as mentioned earlier; and the hardness of the water.  

The hardness of the water can indicate that some of the municipal water has entered the system.   Hard water has a high mineral content usually due to dissolved calcium (Ca2+) or magnesium (Mg2+) .   Whenever we detect elevated levels of water hardness our maintenance personnel are dispatched to determine the source of this infiltration and correct the problem.  We have a regular program of repairing and up-grading our steam line and related infrastructure in order to maintain high performance levels.  

All of this work helps minimize the amount of energy necessary to keep our buildings at a comfortable temperature during the cold winter months.

Get more info: If you a have comment about Williams heating ,or want more information, post a comment below or send an email to Stephanie Boyd ( sboyd@williams.edu).

Thoughts? Go to the Sustainability Blog or send an email to Stephanie Boyd (sboyd@williams.edu) to comment.