There are still a dozen or so cooling towers on campus, and ISTC staff are meeting with related building representatives later this month to review the options for reducing water consumption in these towers.
The Illini Union has demolished its old cooling towers for HVAC in the past 15 years, and recently demolished the old evaporator cooling system for the refrigeration chilling water in 2017. Almost all of our HVAC is now on DDC, with the exception of AHU’s 1, 2, & 3 in the South Building attic, and AHU-21 in the North Building NW subbasement.
Water Station Foreman, Shawn Young, indicated today that there are two remaining stand-alone cooling towers on campus buildings maintained by F&S: Temple Buell Hall and the Personnel Services Building. One of these (Personnel) is scheduled to be added to the central chilled water loop in 2020, according to the Utilities Energy Production and Distribution Master Plan. Base on that discussion, Morgan Johnston will be following up with the Water SWATeam to let them know that because there are so few remaining stand-alone cooling towers, this is not a high-priority item to pursue.
Morgan Johnston and Chenxi Jiang have requested a meeting with Dave Boehm and other Building Maintenance representatives to discuss the options for implementing a new water conservation strategy for stand-alone building rooftop cooling towers.
We set COC = 5 for pilot studies.
Updates and discussion of greywater meter, greywater design standards, cooling tower cycles of concentration, water use dashboard, and student outreach.
Below is information provided by Jeremy Overmann, B.S. Ch. E., Water Treatment Specialist, on the water use and cycles of concentration (COC) in a cooling tower, as requested after a Land and Water SWAT meeting.
"
Water SWAT members,
Here is some more information regarding the cooling tower discussion at today’s meeting.
This first graph shows how much water a typical 100 ton Cooling Tower uses per hour, and how this changes when the tower is operated at various Cycles of Concentration (COC)
NOTE: a 1 ton cooling tower can remove 15,000 BTU/hr of heat.
Most standard chemically treated Cooling Towers use unsoftened water and operate between 4 – 6 COC, depending on the source water quality (also called Make-Up water) and the efficacy of the chemical treatment program.
As COC increases, the potential for formation of calcium scale (and possibly other types of scale) increases. Scale deposits reduce the energy efficiency of the chiller and the cooling tower, and result in the need for labor intensive cleaning to remove the scale.
The following table shows the relationship between volume of Cooling Tower blowdown (bleed), blowdown rate (% bleed), COC, and total water usage.
Cycles of Concentration is controlled by choosing the rate of blowdown. This is done by controlling the blowdown (bleed) valve at the bottom of the tower.
|
COC |
BLOWDOWN |
TOTAL USAGE (Makeup) |
||
|
Gallons |
Percent |
Gallons |
Percent |
|
|
1.5 |
10,000 |
100% |
15,000 |
100% |
|
2 |
5000 |
50% |
10,000 |
66% |
|
3 |
2500 |
25% |
7500 |
50% |
|
4 |
1667 |
17% |
6667 |
44% |
|
5 |
1250 |
13% |
6250 |
42% |
|
6 |
1000 |
10% |
6000 |
40% |
|
7 |
833 |
8% |
5833 |
39% |
|
8 |
714 |
7% |
5714 |
38% |
|
Note: Evaporation = 5000 Gallons |
||||
In a “Zero” blowdown cooling tower, softened water is used, and cycles of concentration ranges from 20 – 100 or higher. To achieve proper water chemistry to provide corrosion protection, usually need to operate at > 20 COC.
During the Champaign Regional Office Building study, the highest COC achieved was 51. The blowdown valve is turned off, however some water is lost from leaks in the tower, and from droplets of water that escape with the air that is drawn through the tower.
|
COC |
BLOWDOWN |
TOTAL USAGE (Makeup) |
||
|
Gallons |
Percent |
Gallons |
Percent |
|
|
1.5 |
10,000 |
100% |
15,000 |
100% |
|
5 |
1250 |
13% |
6250 |
42% |
|
10 |
555 |
6% |
5550 |
37% |
|
25 |
208 |
2% |
5208 |
35% |
|
50 |
102 |
1% |
5102 |
34% |
|
75 |
66 |
0.7% |
5066 |
34% |
|
100 |
51 |
0.5% |
5051 |
34% |
|
200 |
25 |
0.3% |
5025 |
34% |
|
Note: Evaporation = 5000 Gallons |
||||
"
Updates on BIF Greywater Meter application. Discussion on Cooling Tower COC and "Zero" blowdown systems.
The iCAP Working Group met and discussed the following agenda items. Meeting notes are attached.
1. Brief iCAP Portal overview by Morgan
2. Discuss any updates to Water002, Cooling Tower Increase COC
3. Discuss Trans008, Bike Parking in Ramps
4. Discuss updates to Econs004, Green Labs Coordinator
5. Consider issues with recommendation process and view recommendation tracker
Review of pending recommendations: BIF Greywater, Increase Cooling Tower COC, Design Center Greywater Piping. Discussion on possible edits to the SWAT/iWG process. Student members will submit proposal to Student Sustainability Commision for apermanent meter to measure BIF greywater use. The Water SWATeam will meet every other week and will have a joint meeting with the Agriculture, Land Use, Food, and Sequestration (ALUFS) SWATeam this semester.
Discussion focused on finalizing information for Poster for the Campus Sustainability Celebration in October of 2016.
