Up to recent times, many Co/Tri-gen systems installed in Australia have either not met expectations in terms of ROI or performance.
Cost and time blowouts were some of the reasons for this, but the main problem has been in the planning and design. In order for such systems to perform in an optimal manner, 24-hour operations at high load factors are critical. The problem has been that the anticipated loads have not eventuated or the right questions were not asked in the first place.
Unfortunately, the result has been that many have been put off going down the multi-gen path. When solutions look difficult, or even have a perception of difficulty, most people run for the hills. However, I believe strongly that, planned correctly, multi-gen (co, tri, quad-gen), can have a huge impact on reducing CO2 emissions while offering return on investment (ROI) in as little as three years.
So how can the risk of sub-optimal outcomes be minimised? First and foremost, during the discovery process, it is crucial to probe deeply and ask all the right questions. Another essential ingredient is to communicate with all relevant stakeholders from finance, to operations, facilities and senior management. This will ensure that at least most of the puzzle is revealed, thus minimizing the risk of failure, certainly from a loading/usage perspective that is.
The city of Sydney has planned and committed to Australia’s first precinct wide trigeneration system with an initial capacity of 60 megawatts with a final capacity when completed of about 477 megawatts. This is an ambitious but worthy project that is projected to lower greenhouse gas emissions by 33 per cent. In terms of payback and economic viability, it is imperative that every ounce of waste is utilized to maximise both ROI and impact on the environment. For example, if cooling is not effectively utilized, or not used at all, then the ROI extends while the effect on the environment is reduced. Like any project, it depends on how it’s packaged, sold and implemented. If any one of these goes wrong, then the risks increase exponentially.
A well-known large Australian company implemented one of the largest cogeneration systems in Australia back in 1997. This system covered a base load of approximately six megawatts. Instead of purchasing backup diesel generators, senior management opted to upgrade to a co-gen system which is now used for primary base load power as well as hot water for heating and the laundry facilities. Even with the very cheap power rates back in the late 90s, this Australian icon managed to achieve an ROI of between seven and nine years. At today's rates, the ROI could be as little as three to five years, and those are good numbers in any person’s language, particularly for renewable power.
Cogen/Trigen systems have come a long way and even quad generation is now available where water vapour can be extruded from a humid external environment with the grey water returned for reuse. In certain cases, it makes much more sense to use adsorption chillers, which convert hot water to chiller water using water as a refrigerant. Unlike traditional absorption chillers which have a coefficient of performance (COP) of one, the newer adsorption chillers have COPs from two to five and cost much less to maintain though their initial capital costs are higher.
The bottom line is that we will see more of these technologies appear and soon many of them will be powered by organic and agricultural waste instead of piped gas. The ROIs are improving and with appropriate planning and engineering, we will see these ROIs improve further, along with greater reliability and lower maintenance costs. All in all, an excellent and bright future awaits this constantly evolving technology.