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Cornell University

Energy Conservation-Supply Side Efforts

District Heating System 

Distributed digital process control

Boiler and plant controls were converted in 1985 to new digital (microprocessor) equipment that provides much higher reliability, accuracy and automation. Boiler dispatch is optimized providing the lowest fuel use for the plant as it provides steam to the campus for heating. The level of information and automation available allows the 24 hour operations staff of the plant to make much better decisions regarding operating costs and efficiency.

Boiler oxygen sensors

Oxygen sensors were added in boilers in 1990 to minimize excess air passing through the boilers beyond that necessary to completely combust the fuel supply. Any deviation from the required values for the boilers can be tracked, and causes identified, maximizing boiler combustion efficiency and minimizing fuel use.

Economizer feedwater pre-heaters

All of the primary boilers for steam generation utilize an extra feature that recovers heat from the combustion gases leaving the boiler to preheat the feedwater coming in. This extra feature scavanges extra heat from the waste gases, leaving the boilers improving overall efficiency and minizing fuel use. In addition, our largest boiler utilizes an air pre-heater to preheat combustion air using waste energy that would otherwise be lost to the environment.

Cogeneration of electric energy

In 1985 the heating plant pressure was doubled to 400 psig and backpressure steam turbine electric generators were added which now generate 30 million kWh per year of electricity (nearly 12% of total campus use) at about twice the thermal efficiency of conventional power plants. Nearly all steam generated to heat the campus is passed through the turbines to generate electricity before it flows to the buildings and is condensed as a heat source. A conventional power plant throws away this "heat of condensation" which is why our "cogenerated" electricity (generated together with steam which is used for heat) requires only half the normal energy input. A typical power plant efficiency is 35-45%, while the Cornell cogenerated electricity is made at about 70% efficiency.

Turbine heat recovery

As part of the design for the turbines, all waste heat from the generators and bearings normally lost to the atmosphere was combined in a centralized heat recovery system with dedicated heat exchangers and piping. This heat is used to preheat boiler feedwater in the plant minimizing fuel use.

Optimized turbine dispatch

The control logic for the turbines was modified in 1995 to allow steam flow through the turbines to control pressure of the distribution system. This complicated control logic change minimizes, to the greatest extent possible, any steam bypassing the turbines, and maximizes the amount of electricity cogenerated.

Boiler 1 variable speed drive induced draft fan and fabric filter

As part of the 1986 installation of a fabric filter that removes fly ash from boiler exhaust gases, a variable speed drive was used to control fan capacity. At the time of its installation, this was one of the first electric variable speed drive boiler fans of its size in the country. The drive minimizes fan energy input for moving exhaust gases from the boiler through the fabric filter to the chimney.

Auxiliary equipment variable speed drives

Nearly 150 horsepower of pumps and 800 horsepower of fans in the plant utilize variable speed drives to minimize energy input and optimize equipment control. The end result is better control of plant operations, reduced maintenance, and minimized electric energy input for auxiliary equipment operation.

Lower plant export pressure initiative

Over a 15 year period from 1985 to 2000 an aggressive program was instituted to lower the steam pressure required in the distribution system and the buildings. This has resulted in significantly lower pressures leaving the heating plant at all hours during the year. This increases the ability of the cogeneration turbines to make electricity and the cooler steam temperatures have reduced heat losses from the piping system to the environment. The lower pressures and temperatures have also minimized wear and tear on all equipment and piping.

Boiler 8 combustion efficiency improvements

From 1990 to 2000 many changes have been made to the largest steam boiler in the plant to improve its combustion efficiency. As the work horse boiler for the plant, these changes have resulted in a significant reduction in fuel use. These changes include replacement of the air pre-heater, grate drive, casing replacements, and reducing boiler air infiltration.

Boiler 6 and 7 replacement

These two primary boilers in the Central Heating Plant were replaced in 1993.  They utilize high efficiency dual fuel (oil and gas) units with state of the art controls and enconomizers to reduce fuel use and add new firm capacity.

Boiler 8 steam turbine drive induced draft fan and fabric filter

As part of the installation of a fabric filter that removes fly ash from boiler exhaust gases, a variable speed steam turbine drive was used to control fan capacity. The variable speed drive minimizes fan energy input for moving exhaust gases from the boiler through the fabric filter to the chimney. All steam leaving the turbine is exhausted to campus where it is utilized for heating after providing work energy to the fan drive.

Steam distribution system leak repair and insulation upgrades

Over the past 15 years, a significant renewal program has replaced large segments of the steam distribution piping, some of which dated back to the 1920's. This program has reduced steam leaks and heat losses through piping insulation on a very large scale. This successful program will continue for at least another five years at which time nearly all of the main system segments will be renewed.

Sonic Soot Blowers

Cornell University pioneered the use of sonic soot blowers in coal boilers in 1983.


District Cooling System

Chiller 7 variable speed drive

The 3500 horsepower (4000 ton) electric motor driven chiller completed in 1987 was designed with a variable speed drive, the first of its kind by Carrier Corporation world wide. This chiller uses 40% less electricity than a standard constant speed motor driven unit.

Chilled water pump variable speed drives

From 1987 to 1990 centrifugal pumps that move chilled water through the chillers and the distribution system piping were converted to infinitely variable flow using variable speed drives from 125 to 350 horsepower. 3300 horsepower pumps in total, significantly reduced pumping energy use and allowed plant flows and pressures to exactly match campus varying needs. Cornell was one of the first campus systems to utilize the large central plant pump drives.

Thermal storage tank

Starting in 1991, a 4.4 million gallon insulated stratified chilled water thermal storage tank allowed shifting of 40,000 ton-hrs of cooling from day to night. The higher efficiencies possible at night and use of off-peak electricity, decreased cooling energy use and electricity costs. Overall campus production efficiency was increased by 10% due to use of cooler night time air for refrigerant cycle heat rejection.

Chilled water plant 3 free cooling

Cooling for the campus chilled water can be provided by a 1,000 ton heat exchanger rejecting heat to a cooling tower installed in 1987. Cold outside air cools the cooling tower below the temperature of the campus chilled water allowing the heat to flow from hot to cold without the need for refrigeration. This project won a national award for energy cost savings.

Chilled water plant 1 free cooling

This 1,500 ton project completed in 1989 supplemented the previous free cooling effort by cooling the campus for much longer each year using Fall Creek water as a natural heat sink through a heat exchanger (non-contact cooling). The elimination of refrigeration and a cooling tower further reduced energy use, and the more constant creek water temperature eliminated four months of refrigeration each year.

Chilled water plant automation and distributed digital controls

Over the course of four years from 1987 to 1991, all three chilled water plants were fully automated with distributed digital controls to allow for best dispatch and highest efficiency operation of seven campus chillers. All auxiliary equipment and chillers energy use was minimized by computer logic and operator decisions each day.

Lake Source Cooling Project

The Cornell University Utilities Department  commissioned an innovative deep water source cooling project using a renewable resource, the deep, cold waters of nearby Cayuga Lake, as a non-contact cooling source for the campus chilled water system. The Lake Source Cooling (LSC) Project began providing 16,000 tons of cooling to the campus in July of 2000 with an 87% reduction in energy use versus conventional cooling alternatives (a savings of over 20 million kWh per year, enough for 2,500 homes). LSC has been described as "a project that supports a sustainable future." All indications to date support this statement. For more information, please visit the LSC website.


Hydropower

Hydroelectric plant on Fall Creek

Cornell restored in 1981, and continues to operate, the hydroelectric plant built in the early 1900's. Some of the flow of Fall Creek enters a buried pipe (penstock) at the north face of the Beebe Lake dam. The water travels underground to the plant located just below the suspension bridge. The facility generates an average 5 million kWh, enough for 600 homes.


Distribution Systems

Energy Distribution System Upgrades

Cornell spends over $1 million a year to replace and re-insulate its energy distribution systems (electric, steam, chilled water and natural gas) to control and reduce energy loss.


Energy Conservation Initiative