Case Study: A Medical Center Boiler Replacement
In 2016, the boilers at a Medical Center in Northern Michigan were replaced. Natural gas consumption information was provided for 2015 and 2017. This report was created to compare the heating performance before and after boiler replacement.
The cost savings of the new boilers was determined by comparing gas consumption (CCF) to the heating degree days (HDD) of that month. A heating degree day shows the number of degrees a day’s average temperature is below a fixed temperature balance point and is used to predict the environmental heating load for an amount of time. In this analysis, a balance set point of 60°F was used. Figure 1 shows the heating degree days per month for year 2015 and 2017. For 2015 and 2017, the total HDD was 7,374 and 6,599, respectively. The CCF for each month is shown in Figure 2.
Even though the heating season of 2017 had more heating degree days than 2015, gas consumption for the building decreased.
Using the two sets of data, gas consumption per heating degree day was calculated. Figure 3 shows a plot of this data and the gas consumed relative to environmental conditions. The months of May through September were excluded in the analysis due to low heating requirements. The heating efficiency for 2015 was 15.7 CCF per HDD and 12.8 CCF per HDD for 2017.
A heating degree day shows the number of degrees a day’s average temperature is below a fixed temperature balance point.
Figure 1 shows a year with fewer heating degree days in 2015 than 2017. Figure 3 shows an increased heating efficiency from 2017 to 2015. The improved system in 2017 results in less natural gas purchased from DTE Energy. Table 2 in the Appendix shows 2015 and 2017 cost $88,491 and $62,919, respectively, resulting in an annual savings of $25,572.
There were difficulties faced in this analysis. One year before and after the boiler replacement is not statistically significant to prove an increase in heating efficiency and the boilers were not the only equipment to consume natural gas. An increase or decrease to the equipment within the building can impact the annual gas consumption.
Even though the heating season of 2017 was greater than 2015, gas consumption for the building decreased. The replacement provided an increased heating efficiency, an energy saving for the building, and a cost savings for the owner.