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3289Re: [hreg] Assistance RESPONSE #3

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  • Bashir Syed
    Sep 3 8:09 AM
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      The approach described in my post was based upon a book by Scott Skar & Kenneth Sheinkopf, "Consumer Guide to Solar Energy: More ways to reduce your energy bills and save the environment," New Expanded Edition & Doreword by Dennis Weaver, Bonus Books, Inc. Chicago, IL 1995. ISBN  1-56625-050-1.
      As far as losses are concerned the rule of thumb for quick calculations is to assume the syystem efficiency as about !0 % rather than the Mono/Poly-Crystalline Solar Panel's advertised efficiency of 16%. This technique shown by the two authors is simple and for quick look up. Of course there are many other variables based on individual needs, installation fees. The price $6 per Watt is what is advertised in the current literature of ISES or ASES, which may increase due to rising cost of Silicon feed stock - aka Grey Gold.  
      The most efficient use of PV-Stand alone systems is for pulling water out of tube wells for livestock and farms in agriculture, being used in many not so well off countries where the cost o electricity is becoming prohibitive.
      The Insolation maps prepared by NREL provide approximate estimates of sunshine in a generalized manner, like the Isotherms on the weather maps provided by meteorological/weather agencies. 
      Recalling an article in one of the previous issue of Solar Today, even folks in New York City are installing PV Systems on the rooftops of many sky-scraper buildings in Manhattan. The solar energy is converted to AC via Inverters, and fed to the grid, which reduces the bills of the utility customers and the extra energy received by the utility company is sold to other customers for their use. 
      Thus, it is looking at a glass half filled with water, which to some appears half filled and to others half empty. No matter how one looks at it, the energy costs provided by the utility companies are going to increase at a faster rate than they had projected due to many factors (War , Katerina hurricane, etc.) and the only solution is to use an alternate source for which the cost of fuel is ZERO. Just look at any electric bill from your Utility company and you will find approx. more than half the cost for FUEL embedded in that bill. 
      To answer the question of another member about using CNG in cars and buses. I visit Pakistan for our RE projects, and find that the cost of Petroleum (Gasoline) is becoming out of reach for an average person in that part of the world. Thus, Japanes/Koreans were ingenious and invented conversion kits for autos and buses which when installed let the vehicle run on both fuels (Petrol/Gasoline and CNG), cuting the cost of fuel to almost half. And now literally majority of folks have their vehicles fitted with these conversion kits to cut down the cost of fossil fuels , which people can at least afford. Oner drawback is that the CNG tanks are smaller in size, for which one has to have some Petrol/Gasoline to make sure that when the CNG pressure drops, one can still make it on Gasoline, or drive down to the next CNG station for a fill-up. 
      It's very hard for folks in this country to imagine the cost of fossil fuels in Europe and other parts of the world, which is also contributing to the Earth Warming due to ever increasing Green-House emissions, and the cost of health care for those affected by these toxic gases causing them pulmonary and cardiac diseases. In the long run mankind is better off by reducing the emmissions as prescribed under the Kyoto Protocol Treaty, which will help us all to makes this a better world.
       
      Bashir A. Syed   
      ----- Original Message -----
      Sent: Saturday, September 03, 2005 7:15 AM
      Subject: RE: [hreg] Assistance RESPONSE

      All,

       

      There are many ways of calculating the “payback” of a pv system………some which make it look more appealing, some which make it worse, some using very basic calculations, some using complex financial analyses and calculated energy projections.

       

      The method however, that has been presented in this thread, is most peculiar.

       

      First of all, while acceptable to use the NREL average for back-of-the envelope calculations, it probably isn’t acceptable to simply de-rate the STC rating of the array by the inefficiency of it as there are many other inefficiencies that come into play by the time the power from the system in question gets put to work.

       

      This pitfall is illuminated in the example that a 3 kW array will provide the 450 kWh/month (average) or 5400 kWh/year.  To be clear: it would not, at least not in Houston . 

       

      Secondly, and regarding the basis for the calculations we have seen: 

      It will be very hard to install to functionality a quality 3 kW system installed for $18K.  Furthermore, it would seem that the example case is assuming a $.56/kWh rate (5400 kWh/Year for $3K).  Perhaps this includes environmental costs or other “intangibles”, which is most appropriate in a big-picture way, but maybe not so much for a bare-bones payback analysis. 

       

      I am a pv advocate and I believe that a true accounting should incorporate all social and environmental costs, in addition to the financial ones.  However, or perhaps because of that advocacy, I think that a clear representation needs to made as to the limitations, as well as the capabilities, of this technology with respect to people’s energy “needs”.

       

      See below for a more “real world” projection for what the 3 kW system in question might actually do in Houston :

       

      Station Identification

      City:

      Houston

      State:

      TX  

      Latitude:

      29.98° N

      Longitude:    

      95.37° W

      Elevation:

      33 m

      PV System Specifications

      DC Rating:

      3.0 kW

      DC to AC Derate Factor:

      0.770

      AC Rating:

      2.3 kW

      Array Type:

      Fixed Tilt  

      Array Tilt:

      30.0°

      Array Azimuth:

      180.0°

      Energy Specifications

      Cost of Electricity:    

      9.2 ¢/kWh

       

       

       

      Results


      Month

      Solar Radiation
      (kWh/m2/day)

      AC Energy
      (kWh)

      Energy Value (estimated)
      ($)

      3.68     

      252   

      23.18   

      4.12     

      251   

      23.09   

      4.82     

      321   

      29.53   

      4.98     

      315   

      28.98   

      5.24     

      335   

      30.82   

      5.53     

      337   

      31.00   

      5.43     

      338   

      31.10   

      5.44     

      342   

      31.46   

      5.40     

      332   

      30.54   

      10 

      5.19     

      334   

      30.73   

      11 

      4.33     

      277   

      25.48   

      12 

      3.34     

      226   

      20.79   

       

       

       

       

       

       

       

       

      Year 

      4.79     

      3660   

      336.72   

       

       

       

      And here for an output projection for the system one might need (with correct array orientation) to hit their 5400 kWh/year consumption mark:

       

       

      Station Identification

      City:

      Houston

      State:

      TX  

      Latitude:

      29.98° N

      Longitude:    

      95.37° W

      Elevation:

      33 m

      PV System Specifications

      DC Rating:

      4.5 kW

      DC to AC Derate Factor:

      0.770

      AC Rating:

      3.5 kW

      Array Type:

      Fixed Tilt  

      Array Tilt:

      30.0°

      Array Azimuth:

      180.0°

      Energy Specifications

      Cost of Electricity:    

      9.2 ¢/kWh

       

       

       

      Results


      Month

      Solar Radiation
      (kWh/m2/day)

      AC Energy
      (kWh)

      Energy Value (estimated)
      ($)

      3.68     

      377   

      34.68   

      4.12     

      376   

      34.59   

      4.82     

      481   

      44.25   

      4.98     

      472   

      43.42   



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