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
al...@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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