 |
 |
 |
faculty students alumni courses major/minor requirements internships study abroad newsletters/journals
Environmental Studies Department |
|
Energy Use at Macalester CollegeBy Lee Dooley and Claudia Sánchez de Lozada
The purpose of our project was to evaluate the current energy consumption on Macalester College Campus and to examine consumption trends, conservation practices, and areas where improvements can be made. The two areas that account for the total energy consumption on campus are heating and electricity. The central steam plants on campus provide heating for all buildings, while the electricity for the campus electrical loop is supplied and monitored by Northern States Power (NSP). Macalester purchases three different types of fuel for heating: natural gas, #2, and #6 fuel oils. NSP is Macalester’s natural gas provider, while Marathon-Ashland and Koch Refining supply the other two fuel types. Natural gas is the fuel source most commonly used (Annual Energy Summary, 1998-99). It is also the cleanest source of fuel available in terms of emissions. The other two types of fuels are used rather sparingly and kept as a backup source of heating in times of limitation from natural gas. We see no conflicting interests when it comes to the reasonable reduction of energy use around campus. As usage decreases so do the costs, making it beneficial for the campus to cut down on any unnecessary consumption. Several steps have been taken by the physical plant department to attain this goal. Lighting retrofit, the switching from halogen bulbs to more energy efficient fluorescent lighting has taken place in several buildings. These bulbs have a longer lifetime and use less wattage to achieve the same desired lighting effect. The library has recently undergone the most thorough retrofit of any building on campus. During the fall and winter of 97/98 new lighting was installed throughout the building. Consumption decreased by approximately 50,000 kWh the following year due to this effort, a savings of about $2,400 dollars. Motion sensors for turning on and off the lights have been placed in buildings also. Many of these are in place in various locations around campus, several of the bathroom facilities as well as hallways in the buildings have been fitted with such devices. A project by David P. Bergstrom, Mechanical Systems Manager, is currently being undertaken to assess the applicability of a similar type of sensor in the Olin-Rice hall. The preliminary work has been done during this semester and the physical plant plans to start installing the Watt-Stopper Light® in Olin-Rice over the summer. The benefits are immediate for decreasing electricity usage and as far as monetary paybacks, the devices have between a year and a half to a two year payback time. The cost per sensor is around $250. Energy Use at Macalester Looking at the available records of energy consumption at Macalester, it can be seen that electrical consumption at Macalester has been increasing dramatically in the past years, while fuel consumption has been decreasing. Energy consumption can be compared for both heating and electricity in terms of BTUs (British thermal units). Total BTU use for both of these areas are compared in the pie charts. Electricity is most easily monitored using kilowatt-hours (kWh) which can be converted to BTUs using the following conversion. 1 kWh = 3.600 MJ = 3600000 J and 1 BTU = 1055 J Because fuel is used for heating purposes, a greater number of heating degree days will probably lead to an increase in total energy consumption. Each heating degree day stands for every degree below 65ºF during the school year. A low temperature that reached 64 degrees F for the day would be counted as 1 heating degree day, in comparison, a low temperature of 0 degrees Fahrenheit for the day would be counted as 65 heating degree days. In order to analyze the trend in energy use, we compared two school years with a similar number of heating days: 1986-87 (with 6238 heating degree days) and 1998-99 (with 6806 heating degree days). In terms of electricity, during the 1986-87 school year 8,767,200 kWh were consumed, while during the 1998-99 period, 12,972,000 kWh were utilized. Interestingly enough, even though both school years had a similar number of heating degree days, fuel accounted for 75% percent of energy consumption in the 1986-87 year, and for 66% in the 1998-99 period. At the same time, the percentage of energy consumed from electricity increased from 25% to 34%. It is a rather interesting trend to note, despite the addition of extra floor space in renovated buildings and additional buildings being added on to the heating system, fuel used for heating has still managed to decline.
Looking at the available energy consumption data, we see that total fuel consumption at Macalester has fluctuated over the past 15 years. However, an increasing trend in kWh consumption is evident.
In order to understand the reasons for the increase in electricity consumption, we tried to correlate the years showing peaks in consumption with different campus events. Several jumps in electricity consumption can be correlated with campus buildings going on-line and the completion of renovations to the older buildings. The first dramatic increase in kWh usage was during the 1988-89 school year, with consumption increasing from 8,894,600 kWh the previous year to 9,900,000 kWh. It was during this year that the construction of the library was concluded and it was connected on-line. Aside from all the electricity required by this new building, the library housed a new computer facility that increased the building’s electricity requirements even further. The next peak in kWh consumption took place during the 1990-91 year, increasing by 844,800 kWh. That year Carnegie Hall was renovated, and an a/c system was added to the building along with an increase in usable space. To equip a building with an a/c system increases the electricity requirements for the building. However, during the 1992-93 year and the 1993-94 year when Humanities and Old Main were equipped with a/c, there was no visible peak in kWh consumption. This might indicate that a/c does not have such a great energy demand as an increase of usable floor space in a building. Additional floor space together with a/c probably are the cause of the 1997-98 peak. During this year the George Draper Dayton Hall was concluded and connected on-line, increasing Macalester’s total square feet by 38,000. This is also the first air-conditioned residence hall. The largest jump in kilowatt usage over the fifteen-year period took place the year that Rice Hall’s renovation was completed and the building became fully functional (1996-97). This year an increase of 1,146,854 kWh consumed from the previous year was experienced. The renovation of this building, where all of the science departments are located, involved the creation and renovation of several computer labs and research laboratories. The addition of extra usable space, computer labs and central air conditioning would contribute to the increase in kilowatt usage. Olin-Rice also has to follow air recirculation guidelines due to its laboratories. Energy Costs at Macalester The increase in electricity consumption has also led to an increase in Macalester’s monetary expenditure on energy. Comparing the same school years as we did previously, we observe almost a doubling in the costs of electricity ($330,664 to $626,697) from 86-87 to 98-99. Because of this constant increase in kWh consumption and a small, $0.01, increase in price per kWh from 86/87 to 98/99, the expenditure on electricity has nearly doubled during this period.
The price per unit of fuel has also increased during this time. During the 1986-87 school year, the price per 100k of BTU was around $0.21, the unit cost was slightly higher in 98/99 school year. The price increased by $0.02, making it $0.23 per unit in 98/99. The almost negligible change in pricing may suggest that a greater reliance on electrical energy is the actual underlying cause for Macalester’s increased energy expense.
Even though most of the energy comes from fuel consumption, the great majority of the money expended on energy is used for electricity. It is clear, also, that the electricity expenditure continues to increase each year. Energy Consumption by Building The information available also allows us to determine which of the buildings are responsible for greater percentages of energy consumption. As it is (hazily) clear from the following graph, Olin-Rice is the main energy consumer of all Macalester’s buildings.
During the 1998-99 school year, Olin-Rice accounted for 22% of the total electrical use on campus. The second highest consumer was the library, using 12% of the electricity consumed. There are several reasons for Olin-Rice’s high electric consumption. The first one being that the floor space of the building is quite large, housing a large number of classrooms, laboratories and offices. Another important source of energy consumption is the HVAC system of a building. This system is composed of large horsepower fans (5 to 30 HP) and is responsible for the heating, ventilation and air conditioning of the building. The HVAC system is normally shut down at night in all non-residential buildings on campus. Because Olin-Rice contains research laboratories, it can not be turned off at night. A few of these research laboratories are equipped with fume hoods in order to remove potentially noxious or toxic fumes. Because of safety requirements, air can not be recirculated through Olin-Rice, so the air replacing the portion expelled through the fume hood system has to be replaced with outside air. This air has to be conditioned to the temperature inside the building. According to safety requirements, when the hood is open the air circulation velocity has to be 100 feet per minute. This velocity requirement decreases when the hood is closed, thus the HVAC system doesn’t work as hard. It has been observed that many times fume hoods are left open, even when no one is working by them. This accounts for a large portion of the energy waste in the building. Steps to Take A continuing cooperative effort with the physical plant in their ongoing projects would be best advised for long term electrical energy consumption reduction. Buildings equipped with current use reduction technology have clearly shown that these measures work. Terry Gorman, head of the security office on campus, was contacted to assess as to what measure of importance is placed on turning off the lights in buildings during rounds at night. He said that it is instituted in the protocol and a topic in several meetings. A greater stress of importance in this area for security guards making rounds would benefit energy savings. The best way to reduce present use would be to raise awareness of this issue around campus for both students and staff. The inability of staff and students to turn off lights in classrooms, offices, laboratories and rooms when they are not in use is evident around campus. Any steps taken to raise awareness of that fact would have immediate benefits. Most of the thermostats for the a/c system are manually controlled. Keeping rooms or buildings a few degrees warmer during times of use could also cut electrical use considerably. |
|
|