Issue 4, 2015

Combined Heat & Power (CHP): Fuel combustion always produces heat first and then power later.  CHP (also called cogeneration in larger power generation applications) is an efficient thermal energy system that does exactly that; combusting fuel to produce heat first and power second.  Onsite cogeneration, CHP and district energy systems are highly reliable having continued to operate through many storms and regional electrical system outages.   In addition to a 70-80 per cent GHG reduction against coal power, gas fired CHP systems have quantifiable benefits that are not often considered, including very low air pollution, very high system reliability, and low transmission losses, making them ideal to support renewable energy.  In short natural gas based CHP and cogeneration represent both a GHG mitigation system, and a climate adaptation solution for energy resilience.

System Efficiency Boost: Gas turbine cogeneration systems have many innovations, including the use of high O2 content of their exhaust to burn additional fuel in the heat recovery boiler. These duct burners can boost steam production with several benefits:

  • allowing smaller gas turbines for CHP applications;
  • provide good opportunities for aero-derivative gas turbines;
  • increased heat transfer and lower stack temperatures for better efficiency; and
  • provide intermittent cycling flexibility.

Gas Turbines for Cleaner Energy: Stationary gas turbine energy systems have been the most prolific of any energy technology additions over the last two decades. They are used for pipeline compressors, in the electricity sector to drive electrical generators, and in industrial and municipal cogeneration and CHP systems. Over half of the fleet has been added since the year 2000, resulting in 16000 MW of newly installed systems in over 100 locations, which have helped to avoid about 40 Mt/yr of CO2eq and 300 kT/yr of air pollution across Canada.

Hydrogen-based Energy: Hydrogen atoms dominate the composition of the universe. Methane (CH4) is a unique fuel, where the H-atoms have over four times more energy per unit weight than the carbon content. They provide 60 per cent of the energy value of natural gas, making it in reality more a “hydrogen fuel” than a carbon-based fossil fuel. Along with high efficiency, this is the reason for the low CO2 emissions of many natural gas systems.

Reducing Station Blowdowns: Rather than venting methane during necessary compressor unit maintenance shutdowns, Union Gas is using mobile natural gas compressors to transfer the natural gas in the station yard piping back into the main pipeline.   The Lobo and Bright stations each have a 100 kW electric motor driving four small NGV compressors to remove gas and reduce the 5000 kPa yard pressures down to below 400 kPa. This allows the entire site to be drawn down for maintenance projects, with minimal gas releases.

Supporting Wind Power: Combined cycle natural gas-based technology used in today’s electric generation is an excellent choice to support intermittent renewable energy, like solar and wind, because it is able to respond to plant cycling issues and avoid damage to equipment. Flexible gas turbine operations have been optimized for part load and start-up sequences. Newer designs have also increased ramp-up rates from 20 MW/min to 50 MW/min using redesigned steam systems, variable loading rates, and once-through steam generators that result in more moderate NOx emissions levels.

Cleaning the Air

Cleaning the Air: Why are ‘gas turbines’ called that? Well it’s not because they burn natural gas fuel. The ‘gas’ referred to is the high pressure hot air going through the turbine blades. A 30 MW gas turbine will push through a volume of air equivalent to that of a large city’s air (2 billion m3) in its annual power generation. Large, highly advanced, inlet air filters ensure this intake air is very clean to maximize the turbine’s performance. As a result, rather than producing fine particulate pollution, these systems actually remove most sub-micron particulate matter (PM), dust and volatile organic compounds (VOCs) from nearby air.