By H.H. Angus & Associates
York University Cogeneration PlantEngineering
H.H. Angus & Associates of Toronto designed and oversaw the construction and commissioning of a 10 MW cogeneration facility at York University in northwest Toronto. The new plant was completed in...
H.H. Angus & Associates of Toronto designed and oversaw the construction and commissioning of a 10 MW cogeneration facility at York University in northwest Toronto. The new plant was completed in two phases ending in 2003 and is now saving the university $2 million each year in energy costs. It has also reduced nitrogen oxide emissions by 90%.
The cogeneration plant supplies electricity and steam to the 557,400-m2 Keele campus. Located in a 385-m2 addition to the existing Central Utilities Plant building, the cogeneration plant and existing utilities are operated by a common control system. It was a complicated installation that involved integrating the cogeneration plant with both the existing facilities and with the Toronto Hydro grid.
The university wanted a self-sufficient power source, improved energy efficiency, increased sustainability and lower operating costs. Cogeneration was the answer because it uses what would otherwise be waste heat produced by generating electricity. By combining power sources it can achieve thermal efficiencies approaching 80%.
H.H. Angus has a long history on the York campus, having designed approximately 70% of the existing centralized utilities and done engineering for many of the campus buildings. For this turnkey project, the consulting firm was commissioned by Solar Turbines. H.H. Angus provided all the mechanical and electrical design services, acted as prime consultant for the construction, and oversaw commissioning. Since the manufacturer is based in Texas and California, the Canadian consultants played a pivotal role in organizing contractors and even helped decide the route for transporting the heavy equipment across Canada.
The cogeneration plant is designed to be continuously operating and consists of two Solar Taurus 60 turbine generator sets, twin heat recovery steam generators (HRSGs), and gas-fired duct burners that increase steam production. The twin turbine generators produce more than 9 MW at 13.8kV and, when operated synchronously with the duct burner, produce approximately 130,000 lb/hr of saturated 275 psig steam.
York University traditionally has received electricity from Toronto Hydro via four feeders, two at the Finch transformer station and two at the Bathurst transformer station, at a total 27,600 volts. The distribution voltage on campus is 13,800 volts, which requires two substations, one at Steeles Avenue West and one at Keele Street. This complicated power network required one turbine to be tied to each substation.
Phase 1 involved tying the new systems into the existing campus services (substations, gas lines, steam lines, etc.), constructing the building addition, and installing one 5 MW gas fired turbine and heat recovery steam generator. Also installed were an operational control system, duct burner, air intake cooler and hot water preheat economizer. Phase II, begun several years after the first system had established a solid track record, added a new absorption chiller and a second 5 MW gas fired turbine and associated equipment. The total project was completed in seven years.
The entire campus electrical load cannot be supported by the turbines alone, so a load shedding system was incorporated into the design to protect the campus in the event of an interruption in the Toronto Hydro power source. In the event of a total failure, a “black start” diesel generator allows the cogeneration plant to be restarted and subsequently supply power to the entire campus.
The gas-fired turbine sets were modified to allow them to burn either gas or oil, and to perform with low nitrogen oxide (NOx) emissions. They were upgraded with a duct burner, which increased the steam production and efficiency. The exhaust gases from each gas turbine are rich in oxygen and very hot. By firing supplementary natural gas into this gas stream, an additional 36,000 lb/hr of steam is produced from each cogeneration set, at near 100% efficiency.
Extensive analysis of the process flow led to the installation of inlet air cooling to increase the output of the turbine. The design allows the turbine to run with heat recovery, with boosted heat recovery or with no heat recovery at all, depending on the load requirements. By using an existing chimney stack, the construction costs were reduced and turbine back pressure was minimized.
During the late spring, summer and early fall, absorption chillers use the excess steam to make chilled water for campus cooling, eliminating the need for an electrical chiller. The generator can also operate in VAR control to use better the electrical distribution capacity and lower system losses.
The plant is a good neighbour and has a discreet, unimposing appearance. Noise was a big concern as the plant is close to residential buildings and the university’s Tennis Centre where the Canadian Open is held every year. Following extensive modelling, H.H. Angus engineers incorporated multiple inline ductwork silencers, exceeding the requirements of the community and the Ministry of the Environment. Passers-by would be surprised to know that there are two jet engines bolted to the ground inside the building.
Interfacing with the utility
Dual high speed fibre-optic communication cable connects the plant and the Steeles substation 1.3 kilometres away in order to allow the operators to monitor and control the transmitting conditions and perform load shedding. Normally the turbines operate in parallel with the grid, and the university imports power from Toronto Hydro as necessary. However, if power from the utility is lost, the turbines would overload without these instantaneous, high-speed communications.
Two forms of relay are used to monitor the supply from the grid: traditional under-frequency relays and the new rate of change of frequency relays. Rate of change of frequency (df/dt) is a development that allows load shedding to occur in anticipated knowledge that, given time, the underfrequency tripping setpoint will occur.
Altogether, the system addressed the university’s electrical and steam requirements, and gave them a versatile, reliable and independent source of power that produces electricity at a higher energy efficiency than electricity plants operated by Ontario Power Generation. In comparison to coal fired plants, for example, the York University plant uses less than half the fuel energy to produce the same amount of electricity. The installation has improved the steam plant efficiency by 5% and at the end of the first phase cut annual energy costs by 18 per cent. The University has been awarded carbon credits for the installation.
H.H. Angus wrote operating manuals and trained university staff to operate the system. Throughout its development and operation, they monitored and commissioned the entire project. The work was completed on time and on budget.
Owner: York University, Toronto
Client: Solar Turbines
Prime consultant, mechanical & electrical: H.H. Angus (Paul Doherty, P. Eng.; Paul Isaac, P. Eng.; Karl Annis, P. Eng.; Rod Mons, P. Eng.)
Structural: Carruthers & Wallace, Phase I; Adjeleian Allen Rubeli, Phase 2
Architect: Young + Wright Architects
Environmental consultant: Angus Environmental
Acoustic consultant: HGC Engineering
Energy consultant: J.P. Zanyk & Assoc.
Contractors: Cloke Kirby; Western Mechanical; Nichols Radke/Aecon; Black and McDonald; Ontario Electric