19 June 2013 — LETTER: I just noticed the news that Sydney has dropped its trigeneration plans.

Last year I was invited to speak at the Asia Pacific District Cooling Forum. I was also asked to find other speakers and I invited a representative of the City of Sydney to come with me to speak on the Sydney trigeneration project. Nobody could come so I thought to say a few words about it myself to give Sydney a plug.

When I sat down to consider the Sydney proposal, it soon became clear to me that the Sydney plan was fatally flawed. I then set down and tried to find a solution.

The solution lies in existing technology called combined cycle generation. The novelty consists in the fact that I have added a heat pump to condense the steam from the second-stage steam turbine. Thus a great feature of the system is that it would make water and not need any cooling water. Also, it would not be necessary to reticulate any hot water through the city to provide heat for low coefficient of performance (about 0.5) absorption cooling and avoid installation of all the absorption systems at individual buildings.

We would simply supply a lot more electricity for the same fuel consumption, thereby reducing emissions very significantly. We would drive chiller sets to provide cooling with the extra electrical energy at COPs of three to four, which is six to eight times more efficient than absorption cooling.

If we then set about retrofitting CO2 or ammonia systems to existing buildings, we would reduce the emissions even further as these total energy systems are much more efficient the present HFC chiller sets with cooling towers.

If Sydney were to implement both schemes over time, Sydney would be the cleanest city in the world in terms of the lowest emissions, and energy and water consumption per square metre of city office building.

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  1. After submitting the material above to the editor, I realized that I was speaking in general terms, whereas I should have included some specifics on the issues raised above. In an attempt to throw some clear light on the matter, some specific key performance indicators are given below, i.e.

    1. nearly 65% reduction in emissions,
    2. a heat rate (gas fuel consumption) of 6 GJ/MWh,
    3. an hourly water production of 7.2 kl/MWh and
    4 a saving in cooling water consumption of about 0.85 kl/MWh.

    About 10% of the generated energy would be used to make water in Multi Effect (ME) evaporation with a heat pump. The above figures are based on a 200 MW Combined Cycle plant. It is much easier to distribute high efficiency electrical energy to a City through an existing electricity distribution grid than to dig up many kilometres of City streets to deliver hot water to provide low efficiency absorption cooling.

    The emissions from a natural gas fired Combined Cycle Generating Plant (CCGP) would be only 0.348 t CO2e/MWh, which is only 35.3% of the Forecast NSW 2012 Pool Coefficient of 0.968 t CO2e/MWh. THIS REPRESENTS A REDUCTION IN EMISSIONS OF NEARLY 65%.

    Furthermore, because 60% of the heat value in the natural gas is available as electrical energy, electricity generating fuel costs of a CCGP are about 1/3 lower than a TriGeneration Plant (TGP) and as such CCGPs are not as sensitive to fluctuations in gas prices as TPGs. If 10% of the energy were used for water production, about 7.2 kl of water would be produced per MWh of generated electrical.

    Therefore a 200 MW plant would deliver 180 MWh plus 1.44 Ml of water every hour for a fuel consumption of 1,200 GJ. A cooling tower would no longer be required and this would save about 0.17 Ml of water. The cooling tower pump and fan energy would also be saved, no cooling tower water treatment would be required and the danger of legionella disease would be entirely

    The next step would be to reduce the energy consumption of the HVAC function in existing buildings by 30 to 65% and more in new buildings retrofitting and using existing technologies respectively and Sydney would be the cleanest City in the world.

    Hoping that the above clarifies the matter somewhat.

    With best wishes and kind regards

    Yours sincerely

    Klaas Visser- Hon,M.IIR, M.IIAR, M.Inst.R, M.ARA, MKNVvK, M-eurammon.
    KAV Consulting