Consumption of Thermal Energy
Benchmarks
Total thermal energy consumed in million BTUs
Energy consumed per square foot of campus buildings
Background
Most of the campus is heated by steam and hot water generated from our central boiler plant. The steam is transmitted across campus through a network of underground pipes that eventually feed into the radiators in 18 of our major campus buildings. Three high-pressure steam boilers capable of producing 41,800 pounds of steam per hour are located in the basement of Jonas Clark Hall. The boiler plant primarily uses oil as its fuel source, with the oil stored in large underground tanks. The boiler plant is too small for current needs and additional capacity will be needed in the future.
In addition to the steam-generating boilers, Clark University uses a dual fuel (diesel/natural gas) cogeneration plant to produce 1,600 kW of electricity. Cogeneration is based on the idea of capturing the "waste" heat produced in generating electricity as another source of thermal energy. In the Clark cogeneration plant, the waste heat comes from jacket water used to keep the engine at the correct temperature, much like the radiator cooling system of an automobile. The jacket water is used to supply a hot water loop that heats seven of the major buildings on campus, with the radiators in these buildings removing heat from the loop. In the summer months, the same underground water loop is used for chilled water from a chiller plant on the roof of Goddard Library as a way of air conditioning these buildings. The combustion exhaust from the cogeneration plant engine is also used as energy in the form of a waste-heat boiler positioned between the engine and the exhaust stack and feeds steam into the main power plant.
Performance
During the baseline period, the total thermal energy use reduced each year. We track our progress by measuring total thermal energy usage per calendar year, as well as thermal intensity, or the total thermal energy used per square foot per calendar year. In 2004 the University consumed 84,600 million BTUs of thermal energy. This thermal-energy use was reduced to 78,200 million BTUs in 2005 (a 7.6 percent decrease).
This decrease in thermal energy use occurred even as the total amount of buildings on campus increased. Thus our thermal intensity was reduced by a larger percentage, from 68.7 thousand BTUs per square foot in 2004 to 60.6 in 2005 (an 11.8 percent decrease). In 2006, total thermal energy usage decreased again to 73,000 million BTUs (a 6.6 percent decrease). Because there was no change in square footage, the thermal intensity decreased by the same percentage (6.6 percent).
This progress occurred, in part, a result of deliberate efforts to reduce heat energy consumption on campus. The Lasry Center for Bioscience, which has been awarded Gold LEED certification, is one of the most energy efficient buildings on campus, in large part because of the "heat wheel" utilized in the mechanical design. We also replaced a 40-year-old chiller in the Goddard Library with a more efficient model, made steam-line and trap repairs at several campus locations to reduce steam loss, and installed air-lock doorways in some campus buildings to reduce heat loss. Several of our off campus houses have received new energy efficient boilers, and we have also installed domestic hot-water heaters in Dana Hall, Higgins University Center, and Bullock Hall, thus enabling the University to operate in September and October without starting the main boiler plant. Integration of energy efficiency improvements into all renovation projects on campus has facilitated these improvements. We have benefited significantly from partnering with National Grid in their rebate program that provides cash incentives for these energy efficiency investments.
Goals and Next Steps
Among efforts to further reduce energy consumption on campus, energy improvements to Goddard Library (our largest consumer by far) will be a critical component of the proposed renovation of this building as the new Academic Commons of the University. In the summer of 2007 we will replace single pane glass in two of our least efficient buildings, Geography and Jeppson, thereby improving energy efficiency. Many other buildings have already received energy efficient windows as components of renovation projects. We are exploring ways to capture additional energy from our cogeneration plant, which has for years helped Clark to maintain heat energy costs that are low compared to our peers. Another priority is to replace our aging waste-heat boiler to increase the steam output by approximately 20 percent; longer term we need to add capacity to meet the needs of an expanded campus and increased population.