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  • #31
    Originally posted by Logan005 View Post
    Many islands have on again off again reliability, and 3 to 4 times as expensive. so solar power even with batteries makes more sense. You could also just as well pay to maintain those same batteries when the grid is on. Solar would be Auxiliary power unless grid tied.
    Many years ago, late '80's or so, I was part of an engineering group that was tasked with designing/engineering backup diesel powered generating equip. for a bagasse burning plant on the island of Kauai. As I recall, one of the more interesting aspects of the job was the engine silencer (muffler) design which, due to local requirements, had a very severe exhaust noise level to meet, some ridiculous # like 60 Db(a) @1 m, w/more severe low frequency attenuation.

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    • #32
      Originally posted by J.P.M. View Post
      had a very severe exhaust noise level to meet, some ridiculous # like 60 Db(a) @1 m, w/more severe low frequency attenuation.
      I think you meant dB SPL. Regardless it is an impossible requirement in an open environment. 60 dB SPL @ 1 meter is conventional speech. It would take a building with extremely thick walls or buried deep in earth to do that.

      A ported deisel Engine is 150 Db SPL @ 1 meter which is louder than a Jet Engine @ 50 meters away. 150 db SPL is a detonation of small amount of explosives. Example a 12 gauge shotgun 1 meter behind it is 150 Db SPL. If you were to stand in front of someone 3 feet away and shoot a 12 gauge over their head, they will be death. Now imagine that sound repeated 90 times a second on a 12 cylinder diesel engine running at 1800 RPM.
      MSEE, PE

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      • #33
        Originally posted by littleharbor View Post
        in Avalon where there are privately owned residences there are very few rooftop arrays. Don't know why as we have plenty of sun here.
        Speaking of 1MW arrays, I hear the peak load on the Catalina Island grid is 5MW. Tempting to ask if there's a good place on the island, hopefully near the existing power plant, for at least a 1MW array... they've got the battery and diesel (or CNG?) generators already. it'd be neat to see if a 1MW PV array would be cost-effective.

        What do you think -- is there a good four-acre site available for a PV array near Avalon?

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        • #34
          Originally posted by Sunking View Post
          I think you meant dB SPL. Regardless it is an impossible requirement in an open environment. 60 dB SPL @ 1 meter is conventional speech. It would take a building with extremely thick walls or buried deep in earth to do that.

          A ported deisel Engine is 150 Db SPL @ 1 meter which is louder than a Jet Engine @ 50 meters away. 150 db SPL is a detonation of small amount of explosives. Example a 12 gauge shotgun 1 meter behind it is 150 Db SPL. If you were to stand in front of someone 3 feet away and shoot a 12 gauge over their head, they will be death. Now imagine that sound repeated 90 times a second on a 12 cylinder diesel engine running at 1800 RPM.
          You are correct. I apologize for my careless nomenclature references. As best as I recall, the Db "(a)" weighting was used to mask/handle low frequencies. It was/is indeed a S.P.L - Sound Pressure Level, but with the lower (and higher) frequencies basically smeared over/reduced by the "(a)" weighting in ways and for reasons that make some sense, some of those reasons due to perceptions of the human ear, but too complicated and not well understood by me to describe here.

          After ~ 25 years, I seem to remember seeing some testing that showed stack S.P.L. at ~ 60 Db(a)+/- a couple of Db and about the same along the silencer stack @various elevations and 1m distant. I believe the client was satisfied.

          SPL in the absolute sense is an absolute pressure level, independent of frequency. Various weightings are used for different reasons and applications. The measurements were done w/ B & K ( Bruel & Kjaer) sound instrumentation. I think their website has more info on sound pressure level measurement.
          Last edited by J.P.M.; 02-05-2016, 01:33 AM.

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          • #35
            [QUOTE=DanKegel;n302618]

            Speaking of 1MW arrays, I hear the peak load on the Catalina Island grid is 5MW. Tempting to ask if there's a good place on the island, hopefully near the existing power plant, for at least a 1MW array... they've got the battery and diesel (or CNG?) generators already. it'd be neat to see if a 1MW PV array would be cost-effective.

            What do you think -- is there a good four-acre site available for a PV array near Avalon?

            Dan, There are but as I said If it were to come into question the land would need to be "donated" by the Wrigley family. It would be awesome to see our power being created by the sun as opposed to a group of mega sized diesel engines. Our bigger problem over here is water. 100% of our water comes from this island, none from the mainland. El Nino seems to be turning out to be a dud this year and this Island is as dry as a popcorn fart. We have two desalination plants working now but they only make a portion of our water needs and are really expensive to operate.
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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            • #36
              [QUOTE=littleharbor;n302643]
              Originally posted by DanKegel View Post

              Speaking of 1MW arrays, I hear the peak load on the Catalina Island grid is 5MW. Tempting to ask if there's a good place on the island, hopefully near the existing power plant, for at least a 1MW array... they've got the battery and diesel (or CNG?) generators already. it'd be neat to see if a 1MW PV array would be cost-effective.

              What do you think -- is there a good four-acre site available for a PV array near Avalon?

              Dan, There are but as I said If it were to come into question the land would need to be "donated" by the Wrigley family. It would be awesome to see our power being created by the sun as opposed to a group of mega sized diesel engines. Our bigger problem over here is water. 100% of our water comes from this island, none from the mainland. El Nino seems to be turning out to be a dud this year and this Island is as dry as a popcorn fart. We have two desalination plants working now but they only make a portion of our water needs and are really expensive to operate.
              As a "you could just do this " idea, maybe operating one or both of the desal plant w/solar might be a possibility or a starter conversation.
              Last edited by J.P.M.; 02-05-2016, 12:33 PM.

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              • #37
                Originally posted by Sunking View Post
                I think you meant dB SPL. Regardless it is an impossible requirement in an open environment. 60 dB SPL @ 1 meter is conventional speech. It would take a building with extremely thick walls or buried deep in earth to do that.

                A ported deisel Engine is 150 Db SPL @ 1 meter which is louder than a Jet Engine @ 50 meters away. 150 db SPL is a detonation of small amount of explosives. Example a 12 gauge shotgun 1 meter behind it is 150 Db SPL. If you were to stand in front of someone 3 feet away and shoot a 12 gauge over their head, they will be death. Now imagine that sound repeated 90 times a second on a 12 cylinder diesel engine running at 1800 RPM.
                Apparently with the right muffler it can be done. Long ago I was on Long Island (NY) and happened to walk by
                a diesel generating plant, right down town. At the side walk was a muffler, about 6' in dia at the base, and pointed
                straight up some 50'. Standing by it I could hear a "pom pom pom", but it wasn't loud. It would not have interfered
                with a conversation at that spot. I was impressed. Bruce Roe

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                • #38
                  Originally posted by bcroe View Post

                  Apparently with the right muffler it can be done. Long ago I was on Long Island (NY) and happened to walk by
                  a diesel generating plant, right down town. At the side walk was a muffler, about 6' in dia at the base, and pointed
                  straight up some 50'. Standing by it I could hear a "pom pom pom", but it wasn't loud. It would not have interfered
                  with a conversation at that spot. I was impressed. Bruce Roe
                  Someone told me there is a picture of the silencer/stacks I mentioned somewhere on the net. As part of the engineering effort on the project, I did a good part of (but by no means the entire) wind/seismic design. As I recall, they had a total height of about 100 ft. or so in two sections w/strakes on the upper portion. I did not get involved w/engine bases or foundation considerations where different vibration and other design concerns happen.

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                  • #39
                    Originally posted by J.P.M. View Post
                    As a "you could just do this " idea, maybe operating one or both of the desal plant w/solar might be a possibility or a starter conversation.
                    I wonder if adding a solar thermal desalinator (e.g. http://waterfx.co/aqua4/ ) might be an option. No idea what they cost.

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                    • #40
                      I saw a youtube video of a guy trying to silence a small 4 cycle generator and exhaust thru the wall. He managed to completely mitigate the exhaust noise, but the actual engine noise from such small engine, the end product was useless. in excess of 100 db of noise. I also see a lot of people using some really fancy exhaust on Chingens Chinese bicycle engines. trying to quieten them down. still sounds like a chainsaw going down the road.
                      4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrf

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