[RE-wrenches] Load size for off-grid lodge

Fri May 7 06:59:24 PDT 2010

As a bit of a swerve off the path of this string....I am designing a grid-tie system for a building that is being "greenovated". Trying to lock down a LEED req'd percentage shaving of annual demand. I know there is a place to find assumptions from DOE, but I'm not that confident in those because they can't possibly plug in all factors. Any sources out there that might drill down the numbers a bit better? Or do I keep trying to hit the swinging dart board blindfolded? EPRI seems to be designed for utilities, grid EE's and such - haven't found any pertinent load assumption info on the website..... 
Holt E. Kelly
Holtek Fireplace & Solar Products
500 Jewell Dr.
Waco TX. 76712
254-751-9111
www.holteksolar.com

  ----- Original Message ----- 
  From: Allan Sindelar 
  To: RE-wrenches 
  Sent: Thursday, May 06, 2010 11:50 PM
  Subject: Re: [RE-wrenches] Load size for off-grid lodge

  Jason,
  We attempted this about 2-3 years ago for a project on one of Ted Turner's ranches. This was to be a top-of-the-line eco-lodge at 10,000' below a ridge in the northern Rockies in New Mexico, with two 7kW Provens and a 3-phase Sunny Boy/Sunny Island system. Due to the lack of real load analysis, and the need to have large but essentially unknown capacity at the lodge, the initial estimate was about $900K, as I recall. 

  We never did the project, as they decided to go with dual generators. We did get compensated for extensive design work.

  You may need to focus on large efficiencies and then put a usage fraction, like 60%, on the electrical engineer's traditional load calcs. That's what we did. And write in a section stating that you make no warranties as to the sufficiency of the system to meet actual loads, as the loads can't be accurately determined.  

  Here's what I wrote in the initial pre-proposal:

    <!--[if !supportLists]-->I.                   <!--[endif]-->Load Profile Methodology and Limitations

    Typical off-grid PV systems are designed and sized based on a rigorous load analysis as an essential first step. The load analysis is a detailed listing of every electricity-consuming device, with power consumption and expected daily usage figures, used to develop an accurate profile of total expected daily kilowatt-hour consumption. From this data a power system of specific design and capacity is developed.

    This approach is not possible for the XX Lodge, so an alternative approach must be used to establish target design criteria. EPRI (Electric Power Research Institute, the research arm of the U.S. electric utility industry) has developed Technology Assessment Guides to predict power use for various residential and commercial sectors. The comparative sector of lodging at 12,000 square feet in the western U.S., establishes a figure of 223 kilowatt-hours per day. This is a base figure, for conventional design without energy-conserving measures, with adders for electric heat, hot water, cooking and air conditioning, none of which will be used at XX Lodge. 

    From this we have estimated that XX Lodge may be expected to have a total average daily load not exceeding 190 kilowatt-hours per day, or 85% of the EPRI figure. This is the figure used in this preliminary budget analysis. This may be considered to be quite conservative; that is, careful attention to energy-conserving approaches during design and construction are likely to considerably reduce this figure.

  Remember too that if they now have generators, they're not likely to conserve, as generator power is pretty much all-or-nothing, with efficiency unimportant within the gennie capacity. So there's a fair amount of load management and education to fit in.

  Hope this little bit helps.

  <![endif]--> 
  Allan Sindelar
  Allan at positiveenergysolar.com
  NABCEP Certified Photovoltaic Installer
  EE98J Journeyman Electrician
  Positive Energy, Inc.
  3201 Calle Marie
  Santa Fe, New Mexico 87507
  505 424-1112
  www.positiveenergysolar.com

  jason pozner wrote: 
    Hey all,

    I am trying to size a PV/generator system for a 10,000 ft2 off-grid hunting/snowmobile lodge with outbuildings.  The goal is to significantly reduce current generator run time.  I was wondering if any of you have experience or suggestions for calculating time of use of lights, etc in a lodging situation.  My interviews with the rancher have proven fruitless to pin down any time of use of most loads, though I do have an estimated run time for the genny in summer and winter.  I did get a pretty good snapshot of his connected load by turning on all I could on and clamping the feeds.  

    The lodge is 18 rooms, 4 for the help, and a few outbuildings.  Has anyone sized any off-grid lodges?   Any other ways to approach the moving target of such a fluctuating load at a guest lodge?  

    Thanks
    Jay Pozner
    Nunatak Alternative Energy Solutions

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