Athletic Club Operations Data

Description and Monthly Utility Usage History

Table 5-1: Health Club Appliances

The data will show that approximately 900 members use the facility and about 20,000 gallons of water are consumed there each day. In order to heat 20,000 gallons of water, each water heater must run for approximately 6.7 hours per day. The water heaters are capable of producing 50.2 gallons of hot water per minute (see Appendix A).

This health club is a relatively large facility. It has a gymnasium, with a running track, an indoor pool, an outdoor pool, an aerobics room, a cardio-vascular exercise room, a weight training room, two locker rooms with showers, spas and whirlpools, as well as a children’s day care center. ACN’s annual utility budget is of the order of $220,000. Their electrical budget was approximately $150,000 in a period of one year⁷. Approximately $50,000 was spent on natural gas² in a year, and $20,000 on water and sewage⁴. Notice that roughly 23% of their utility budget was spent on natural gas², which is used both for water and space heating. In addition to their large thermal demand, ACN’s electricity usage⁷ comprised about 68% of their utility budget in the past year.

Figures 5-1 show the club’s monthly water, gas and electric usage respectively, throughout a period of a year, with their respective costs shown. Figures 5-2 show the trends of the utility usages with the concurrent ambient temperatures¹⁰. In these figures, the monthly usages and costs were normalized to periods of thirty days. Figure 5-2b shows that much less gas is used in the summer than in the winter. This is because a large percentage of their gas use is for building space heat, of which very little is needed during the hot summer months. However, some heat is still required for the spas and the outdoor pool. During those summer months, instead of heating the building, it is air-conditioned. Figure 5-2c shows a significant increase in electrical usage during the summer months. This increase is very costly to ACN. Georgia Power uses a complex rate structure to calculate the cost of ACN's electricity usage⁷ (see Appendix C). The rate depends on a billing demand that is the greatest of the current month's actual peak kW demand, 95% of the peak kW demand during the summer (which they define as June through September), or 60% of the peak kW demand during the winter (October through May). For any facility that uses gas to heat their space and electricity to cool it, clearly the winter demand calculation is not going to be the largest of the three possible billing demands. The large peak demand due to air-conditioning during the summer, combined with the large amount of electricity used throughout the month, results in a high electric cost for ACN.

Using the gas usage history² demonstrated in Figures 5-1b and 5-2b, a distribution of gas use was estimated (see Appendix A). Summer was taken to be June through October for this calculation because ACN’s gas history shows those months have a base gas load compared to May and November. Therefore, November through May were taken as the winter months. Approximating that 20,000 gallons per day of water were used, and 900 members per day use the club, and knowing the heat rates input to the washers and dryers, Figures 5-3 were created. In Figure 5-3a, the Summer Gas Distribution, it was assumed that the only space heat used was in the spas and pools. Figure 5-3b, the Winter Gas Distribution, shows that during the winter 45% of the natural gas the club used was for building space heat. Figure 5-3c shows the Overall Gas Distribution throughout an entire year. Water heating comprises 41% of ACN’s natural gas needs, most of which is for the showers.

Daily and Hourly Data and Observations

Hourly Data

The dramatic decrease in gas usage at 4:00 PM (1600 hours) is partly due to some lack of resolution in the meter, which reads in ccf or 100 ft³. That hour could also represent a time when many people are exercising and very few are showering. This idea somewhat correlates with the decrease in the Hourly Water Usage curve, Figure 5-4b, which occurs an hour earlier than the one in Figure 5-4a. Since such a small amount of water was used during the 3:00 hour, not much water needed heating during the 4:00 hour. This theory harmonizes with Figure 5-4c also. Note the large increase in people that walk through the door at 4:00 PM. They probably exercised during the 4:00 hour and those same people probably did not start using the showers until the 5:00 hour. This phenomenon is further explained in Figure 5-4d, which shows how much water each person used on an hourly basis. This curve only has dramatic changes at the beginning and end of the day. At the beginning of the day, the large change is probably due to a lag period between exercising and showering. Towards closing time, many people do not take showers at the club. They take showers at home. In the ratio of amount of water to number of persons, the numerator is decreasing, but the denominator is decreasing much faster, approaching zero because the facility is closing, resulting in the ratio increasing. Also, the one-hour lag period between the time a person exercises and the time that person showers slows down the rate at which the numerator of the ratio decreases.

Figure 5-4e shows what the average hourly temperature was on that day¹⁰. It correlates with the decrease in gas usage that occurred at 4:00 PM. This may be yet another factor that explains that decrease. The peak temperatures of the day occurred during the 3:00 and 4:00 hours.

Figure 5-4f shows the Hourly Electricity Usage at the club on March 10. The large oscillations are due to the lack of resolution in the meter. It measures 500 kW-hr, i.e., the multiplier on the meter is 500. An attempt was made to estimate the meter readings to the first decimal place. This helped somewhat during the 9:00 and 10:00 AM hours.

Daily Data

Figure 5-5a shows the Daily Gas Usage at ACN. Notice the decrease that occurs during Days 17-22. These are the April data points during which Atlanta was experiencing unseasonably warm weather. The facility required less natural gas for space heating. Figure 5-5b shows the Daily Water Usage, which varies only somewhat throughout the term. Figure 5-5c shows the Daily Attendance. The lowest data points occur on Fridays, Saturdays and Sundays (Days 4-6, 11-13, and 20-22), Sundays being the lowest of all. Similarly, the highest data points in Figure 5-5d, Daily Water Usage per Person, occur on Fridays, Saturdays and Sundays. Compared to weekdays, people are more relaxed on Saturdays and Sundays and can arrive at the club early enough to make sure they have time to take a shower at the club before it closes. On Fridays, the increase probably occurs because people tend to go out on Friday nights instead of going to a health club. Therefore, the persons who would normally go to the club shortly before closing and shower at home, do not go to the club at all, decreasing the denominator of the ratio and thereby increasing the ratio of water used per person. Contrarily, during the week, people who have to work and then exercise after work are likely shower at home, decreasing the numerator and thereby decreasing the ratio. The average daily temperatures¹⁰ are expressly shown in Figure 5-5e. Figure 5-5f, Daily Electricity Usage, shows a generally larger consumption during the warmer April days. It correlates with the decrease in gas usage seen in Figure 5-5a and the increase in temperature seen in Figure 5-5e, although again, due to lack of resolution in the meter, the data has some scatter.

Summary of Observations