How to take 1 million tones of CO2 out of the atmosphere

23 Feb 2010Archived News Climate Change Matters

With each edition of Climate Change Matters, Energetics will profile a method by which greenhouse gases can be removed and cost savings achieved.

The potential greenhouse gas abatement of cogeneration

Combined heat and power (CHP), also known as cogeneration, is an efficient, clean, and reliable approach to generating power and thermal energy from a single fuel source. By installing a CHP system designed to meet the thermal and electrical base loads of a facility, CHP can significantly increase the facility's operational efficiency and decrease energy costs. At the same time, CHP reduces the emission of greenhouse gases.

Prime movers (machines that transform energy from thermal, electrical or pressure form to mechanical form) for CHP systems include mature, higher volume technologies like reciprocating engines or gas turbines as well as commercially proven but lower volume technologies such as microturbines and fuel cells.

In this edition of ‘How to take 1 million Tonnes of CO2 out of the atmosphere’, we will explore the potential impact of a trigeneration system (cogeneration system with the addition of an absorption chiller to provide cooling) for a commercial facility in the ACT.

The scenario

The facility owner is considering installing an on-site cogeneration system to generate 80% of their electrical and thermal needs on an annual basis.

Based on a recent economic analysis of the facility, a trigeneration system has the potential to significantly reduce annual greenhouse gas emissions and energy costs for the facility.

The system's characteristics are:

  • The prime mover is a lean-burn natural-gas fired reciprocating engine with an electricity generating capacity of 750 kWe
  • The CHP is expected to operate 15 hours per day, 5 days per week during periods of higher electricity costs
  • The CHP will provide cooling (5 months per year) and heating (7 months per year)
  • Cooling will be provided by a single effect absorption chiller with a co-efficient of performance (COP) of 0.8
  • Generator sets typically operate at a 30-33% electrical efficiency and up to 45% thermal efficiency
  • The proposed trigeneration system presents an emissions intensity of about 600 kg CO2-e/MWh generated.

The estimated average reduction in net annual energy costs over the 20-year lifetime of this new asset would be $250,000 per annum.

By displacing power supplied from the grid, this system at this facility will save annual greenhouse gas emissions of 1,560 tonnes of CO2-e.

In order to save 1 million tonnes of CO2-e, just over 640 cogen units of this size would be needed. As an example; an Energetics' assessment of the ACT indicated that there would be capacity for 40 units in commercial buildings alone.

In addition to reducing emissions by 1 million tonnes per annum, the deployment of this much cogen capacity would save 160 million dollars a year in energy costs.

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Gilles Walgenwitz

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