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    Natural Gas Generators

    I have a client in the commercial real estate industry which had the following questions about Natural Gas Generators. I wanted to get people's perspectives and answers on these questions from different offices/markets around the country. Which markets/verticals are Natural Gas Generators used and why? Primarily what sizes and for what purpose (emergency standby or cogen or life safety etc)?
    The pros and cons of using it in the different markets/verticals, compared to diesel?
    Is NG generator (becoming) prevalent in commercial real estate? If yes, why? Is there a size threshold past which it becomes cost-effective?
    How established is the service support for natural gas generators. Are technicians/spares availability the same as diesel to support when there is an emergency?

    #2
    It can only be used for Emergency Systems when the natural gas supply can meet the exception of 700.12(B) or else you need on-premises fuel supply sufficient for not less than 2 hours’ full-demand operation of the system.
    It is often used for cogen since that is not Emergency.
    Natural gas gens cannot pickup large step loads, so you need to have multiple transfer steps or a load that can handle a large swing of voltage / frequency.
    Ron

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      #3
      Originally posted by Shujinko View Post
      I have a client in the commercial real estate industry which had the following questions about Natural Gas Generators. I wanted to get people's perspectives and answers on these questions from different offices/markets around the country. Which markets/verticals are Natural Gas Generators used and why? Primarily what sizes and for what purpose (emergency standby or cogen or life safety etc)?
      The pros and cons of using it in the different markets/verticals, compared to diesel?
      Is NG generator (becoming) prevalent in commercial real estate? If yes, why? Is there a size threshold past which it becomes cost-effective?
      How established is the service support for natural gas generators. Are technicians/spares availability the same as diesel to support when there is an emergency?
      I would guess that there is. I don't know about there but here in UK, CCGT is by far the largest energy supplier right now. Nuclear and wind are in second and third respectively. About 70% of total consumption.

      Just observation. Don't suppose that helps you.

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        #4
        We have around 60 units varying in size from 5kw - 2.5MW, with both natural gas and diesel. We have several NG units under 1MW that were accepted by the AHJ for emergency use. I've witnessed 2 new (in the last year) 750kw NG units perform a full (resistive) load acceptance and rejection without issue.
        For larger NG gas units over 1 MW, we do see the issues described above - longer crank cycles (up to 45 seconds) and complicated load shedding and load restoration controls that are required to mitigate the load acceptance issue.

        We prefer NG for emergency and standby purposes over diesel due to fuel storage requirements and fuel cost. We do not cogenerate with our recip generators. We have several 1.2MW - 2MW diesel and NG units available for peak shaving but we typically run the NG units due to fuel costs and limited diesel fuel.

        For the same kW rating, a NG unit is physically much larger (and more expensive) than its diesel equivalent.

        Service and spare part availability are not distinguishable from the diesels.

        Comment


          #5
          OP does not give any location information.

          If in a seismic area, NG often has an automatic shutoff, either at user meter or supplier mains shutoff. Son's house has a simple earthquake valve that is a heavy ball sitting on pedestal that falls onto orifice for moderate quakes, has to be manually reset. Critical loads thus need to be local storage fuel. They may be out there, but have not seen any big NG bladders on any gensets.

          PS: in costal areas, Senai/Fujiyama (sp) has shown critical emergency diesel needs to be installed higher than worst case predicted Tsunami.

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            #6
            Electric utility likely provides energy at less cost than you can generate your own with NG/LP or diesel. Exception being if you have heavy demand penalties at times it may be cost effective to cogenerate to avoid those penalties, but only during the necessary time periods.
            I live for today, I'm just a day behind.

            Comment


              #7
              NG has advantages over Diesel in the maintenance arena. Diesel units have frequent oil change requirements; NG/propane far less so. Plus, for any volume of stored Diesel fuel, the fuel needs "grooming" i.e. circulation with filtering & biocide as critters grow it it. Furthermore, a Diesel tank will likely have EPA-permitting issue. NG has a point of failure Diesels do not; they need a spark ignition.

              But the big issue is as mentioned above; if you are in an earthshake area, you can't rely on the gas supply. (Outside of that, NG in the US is highly reliable.) It may be possible to get a NG/propane system where you keep some propane on-site but normally use NG.

              Large systems may be on a "shedding" contract; when there is a major cold-snap the NG supplier requires you cease use so they can meet their heating demand. Conversely, large AT&T facilities & others may be on power-shedding tariffs; when the PoCo calls, they go to their backup Diesels. On Sept 17 1991, this went very pearshaped when the rectifiers at 33 Thomas Street NYC failed to switch properly and exhausted the batteries before the alarms were answered. This took down the three airports and impaired much of the FCC air traffic control system nationwide.

              Lastly, don't forget Solar Corp (now owned by Caterpillar) turbines. They are used for backup power systems in many locations. They offer more KW/ft^3 than reciprocating engines.

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