Document ID: EPA-HQ-OW-2008-0667-3639
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2014-08-15T04:00Z

MEMORANDUM

Tetra Tech, Inc.
10306 Eaton Place, Suite 340
Fairfax, VA 22030
Phone	703-385-6000
Fax	703-385-6007

TO:			Paul Shriner and Lisa Biddle, EPA
FROM:		John Sunda, Tetra Tech
DATE: 		November 13, 2013

SUBJECT: 	Analysis of Manufacturing Facility Cooling Water Use for Electricity Generation

Tetra Tech was tasked with identifying the proportion of manufacturing facilities that use cooling water predominantly for generating electricity similar to generating facilities. A review of the flow data analysis used to estimate the proportion of non-contact cooling water used at manufacturing facilities revealed that this data was not suitable for this analysis since the analysis focused on data from larger facilities (DIF >100 mgd). This analysis includes all facilities that completed a detailed survey and focuses only on the reported percent electric generation data.

Question 4 in Section 2 of the detailed technical survey requested data for each cooling water intake structure (CWIS) regarding the percentage of cooling water used for each of the following purposes:

   1. Electricity generation using steam turbines;
   2. Electricity generation using prime movers other than steam;
   3. Air conditioning;
   4. Production line (or process) contact and/or non-contact cooling (other than electricity generation or air conditioning);
   5. Other.

Since this data was reported on an intake basis, the results of this analysis are reported on an intake basis since reporting this data on a facility basis would require a much more in-depth flow-weighted analysis. All results are weighted using DQ facility weights.

Data from in-scope facilities listed in the master database were sorted into manufacturers and generators. The percent reported for responses 1 and 2 from the list above were then added to represent percent cooling water used for electricity generation.

Table 1 below shows the percentage of generating and manufacturing facility intakes (weighted) that reported a percent of cooling water used for electricity generation (EG) that was greater than the percentage thresholds shown. For example, 8% of manufacturing intakes used >95% of intake cooling water for electricity generation. Table 1 shows that a threshold of 90% EG included the majority (94%) of generating facility intakes and therefore is a good indicator for identifying an intake that is predominantly used for EG cooling water and is similar to intakes at generating facilities.

                                    Table 1
Proportion of Intakes Based on Percent Use of Cooling Water for Electricity Generation
              Percentage Electricity Generation (EG) Threshold[a]
                          Generating Facility Intakes
                        Manufacturing Facility Intakes 
Manufacturing Facility  Intakes at Facilities Where Total Plant Cooling Water Use was Predominantly for EG[b]
                                    >99%
                                      71%
                                      6%
                                      3%
                                    >95%
                                      89%
                                      8%
                                      4%
                                    >90%
                                      94%
                                      9%
                                      5%
                                    >75%
                                      96%
                                      12%
                                       
                                    >50%
                                      96%
                                      17%
                                       
                                    >10%
                                      97%
                                      29%
                                       
                                    >0%
                                      97%
                                      46%
                                       
[a] Includes sum of items 1 and 2 listed above ("electricity generation using steam turbines" and "electricity generation using prime movers other than steam").
[b] Excludes intakes where other uses were >10% or those at facilities with other intakes with <90% electricity generation.

One inconsistency with the manufacturing facility intake data was that some intakes reported percentages for each category that when summed together exceeded 100%. In some cases, an intake would report that a high percentage was used for EG and also a high percentage was used for production line or process purposes. This was particularly notable for paper manufacturing intakes, suggesting that these data represented situations where water was being reused for multiple purposes. Also, many manufacturing facilities had multiple intakes with some intakes used for EG and other intakes used for process or other purposes. In order to get an idea of how many intakes were associated with facilities where total plant cooling water was used predominantly for EG purposes, manufacturing intakes with a percent EG >90% were examined to see if:

    1. There was a significant portion (>10%) of cooling water reported as being used for non-EG purposes (Items 3 through 5 above) or; 
    2. If there was another intake at the same facility with percent EG being much less than 90%.

The column on the right shows the percentage of intakes where both types of intakes were excluded. Note that this column stops at >90% cooling water used for EG since this evaluation was intended to identify the proportion of manufacturing facilities that use cooling water predominantly for generating electricity similar to generating facilities and the exclusion criteria were based on 90% threshold.

This analysis indicates that an estimated 5% of intakes at manufacturing facilities are associated with facilities where cooling water was predominantly used for EG. The analysis also indicates that an estimated 46% of intakes at manufacturing facilities use at least a portion of their cooling water for EG purposes. As reported in TDD Section 5.3, the results of separate survey question indicated that 60% of manufacturing facilities had generated electricity during 1996, 1997, or 1998. Factors that may contribute to this apparent inconsistency include:

   * This analysis measures "percent intakes (47%)" while the other measures "percent facilities (60%)." Since many manufacturing facilities may use only one of several intakes for EG purposes, the total number of EG intakes and facilities may be similar in value but the total number of intakes will be higher than the total number of facilities resulting in a lower proportion of the total.
   * Some facilities may generate electricity without using cooling water (e.g., a cogeneration system is used where all of the turbine exhaust steam is used for process purposes).