COMPARATIVE-ANALYSIS OF THE FACTORS AFFECTING SMALL AND MEDIUM-SCALE GAS-TURBINE COGENERATION IN AUSTRALIA THE UK

The viability of gas turbine cogeneration in Australia is affected by technical, economic and 'cultural' factors. A combination of these fac tors must explain why in Australia, and in New South Wales (NSW) in pa rticular, cogeneration is not as widely used as it is in some other co untries. A model has been developed to analyse the economics of retrof itting gas turbine cogeneration to industrial sites with electrical lo ads in the range 3 to 30 MW, and with a wide range of heat loads. The model compares the cost of operating the cogeneration plant with the c ost of generating steam in gas or coal-fired package boilers and purch asing power from the local supply authority. Supplementary firing of t he turbine exhaust gases to increase the inlet temperature to the heat recovery steam generator is considered. This performance modelling of gas turbines is based on analysis of a large number of modern industr ial and aeroderivative machines. For particular heat and power load de tails a range of gas turbines and heat recovery steam generators is tr ialled. The model calculates the simple payback period achievable with each combination. This model provides a quick estimate of the feasibi lity of cogeneration in meeting various heat and power loads. The outp ut from the model for a set of typical NSW input data demonstrates tha t there is a wide range of possible solutions. For a 8 MW(e) (electric al demand) project paybacks range from less than 3 1/2 years to more t han 10, depending on the buyback arrangements and the choice of machin e size. Typical data from the UK result in generally shorter payback p eriods: cogeneration projects in NSW in the size range of interest are not normally able to achieve payback periods as short as similar size d projects in the UK. In order to assess the relative importance of th e technical/economic and 'cultural' factors, a comparison has been mad e between the best paybacks achievable for various load combinations w ith input data from Australia and the UK. Based on the results of this comparison and the previous modelling work, it is concluded that if c ogeneration capacity in NSW is to increase significantly, there must e ither be a fall in the price of natural gas relative to electricity, o r Australian governments will have to enact policies in favour of the smaller cogenerator.