We have developed an innovative method for accurately tracking fuel oil and propane use by homes that is much more accurate than the current degree-day method. The new method, now called Delivery Cost Reduction, or DCR, is designed to lower fuel oil delivery costs by 25 to 35 percent. It can also become a new equipment sales tool.
It produces an equation for each home that relates fuel use to outdoor air temperature, with a typical measurement error of only about 2 percent compared to 20 to 60 percent uncertainty with K-Factor-based methods. This permits more precise fuel oil consumption and the ability to increase average fuel drops from 160 gallons to more than 200 gallons for a 275-gallon tank while lowering the run-out frequency. The plots that follow compare the accuracy of the DCR and K-Factor methods for predicting fuel use.
These plots demonstrate the improved accuracy with the DCR method. Fuel use predictions with conventional K-Factors vary widely and are not reliable. For example, for a degree-day interval of 1,400 degrees days, the fuel use in gallons per degree-day varies from 6.5 to more than 14.0. Predicted fuel use varies from about 100 gallons to 215 gallons of oil for the same degree-day value. This is an uncertainty range of more than 50 percent. In contrast, the DCR plot on predicts fuel use with an error of only about 2 percent. (See Figures 1a and 1b)
An important application for the new DCR method is its ability to accurately track changes in fuel use after energy efficiency improvements are installed in homes, including new burners, new boilers or furnaces, improved controls and building upgrades such as thermal insulation.
Past fuel-use data are collected before the energy improvement, the equipment or building upgrade is installed and fuel-use data after the upgrade are collected to determine the reduction on fuel use that is produced. The precision of the DCR calculations allows the energy savings to be measured very accurately. The actual cost savings of the improvement can then be compared to its cost so that payback periods and returns on investment can be accurately determined.
Figure 2 shows a house in which thermal insulation was installed and the actual fuel savings were determined by the DCR method. The upper curve was the fuel use before the insulation and the lower curve is after. The actual savings are measured by comparing the slope of the lines that show fuel use as the heat load varies. In this case, the thermal insulation reduced energy use by 28.5 percent a year.
This cost savings calculation is only possible because the DCR method predicts fuel use with accuracy on the order of 2 percent. The K-Factor (degree-day) method cannot be used to measure fuel savings because of its much higher measurement error (20 percent to 60 percent).
The exact same approach that is shown in Figure 2 can also be applied to other energy-savings devices, including new burners, new higher-efficiency boilers and furnaces, and energy-savings controls including night-setback thermostats.
This is particularly important in the case of boilers, because the Annual Fuel Utilization Efficiency program, as mandated by the United States Department of Energy, frequently underestimates the actual savings produced by new high-efficiency boilers. In fact, research that I conducted at Brookhaven National Laboratory showed that AFUE tests underestimated fuel savings with new high-efficiency boilers by as much as a factor of three or four.
The DCR method allows actual fuel savings to be measured to demonstrate the real savings produced by new oilheat equipment. In many cases, we expect actual fuel savings to exceed 25 to 40 percent when an outdated boiler is replaced with a new high-efficiency model. The new method also enables, for the first time, accurate quantitative analysis of state and federal insulation and weatherization programs.
The DCR field tests for homes heated with oil or propane can be a new sales tool that has not been available before. As energy prices are increasing again, the benefit of investing in higher efficiency equipment also increases. The added cost of higher-efficiency equipment often can be justified based on paybacks and life-cycle fuel cost savings.
The increase in sales of flame-retention head burners is a good example. Testing at Brookhaven after the oil price increases in the 1970s clearly showed that retention head oil burners reduced fuel use by 15 percent. This produced paybacks on new burner installations in one or two years. Over the next several years, flame retention burner sales increased to millions of units. l FON
John E. Batey has 30 years of engineering experience, including research and applications related to combustion equipment performance, carbon monoxide, oil and gas burners, oil leaks, soot damage, furnace fires, heating equipment and air emissions. If you have any questions about the information presented in this article, or if you need additional references, call him at (203) 459-0353 or e-mail email@example.com.