Re: [a-w-h] Energy per Day / 1 day battery

· Mike (and anyone) :-
  I want to send Mike's excellent summary of two major choices facing
people considering getting into wind power (myself, for instance), to a
couple of lists where I've posted wind-power information in the past.

· These two main points are:

(1) how to calculate (a) what size turbine you'll buy, and (b) how big a
battery bank to buy;
         And the other:

(2) The great advantage in using the grid as your storage, over storing in
your own batteries (though you might choose to run them as a UPS).

· I've edited it for those purposes, away from the expressed purpose of
Mike's post.

· -Mike: would you let me post the below, as is? 

· -Anyone else: any comment you believe should be included?   David Mac.

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>... Michael Elliott of Synergy said:
>
>> SPC recommends a diesel genset to try and keep the battery 
>> bank down to a cost effective one day supply (due
>> to the high cost of batteries a one day supply is the only 
>> way you can keep the economics of the system from getting 
>> out of hand. 

At 08:02 8/3/2001 -0600, Michael Klemen wrote:
> ... Even if you went with 4 L-16 batteries, which might cost around $800,
and would be a one-to-two-day-battery, that's not really expensive.
>
>*   2)  I summed up the total energy produced, and
>*       calculated that it produced 2.14 kWh per day
>*       in an 8.54 mph (3.8 m/s) average wind speed for 
>*       those 2 months ...
>So, then, theoretically, this turbine could be rated at 2.14 kWh per day
energy production in an 8.5 mph wind, if I understand the rating correctly.
>
>*   3)  I started with a full battery bank (of varying sizes), and removed
2.14 kWh of energy per day [assuming that constant load is why I bought a
2.14 kWh per day turbine], and added the actual energy produced by the
turbine.
>*     b)   If the energy level at the end of the day was
>*          more than 100% battery capacity, I subtracted
>*          the excess energy that we had to waste and had
>*          no room for in the battery.
>*
> ... we lose energy because we have too much at one time, ...
> $192 ... is extrapolating the energy generation requirement out for 5
years for the life of a cheap battery bank, and at $0.50/kWh for [genset]
generation of the needed energy (which may be excessive).
>So, we get $192 in additional generating cost.
>  If [instead] we triple the capacity of the battery, we would get an
incremental cost of about $400 using cheap 220 AH golf cart batteries, or
about $1600 for [the above] expensive ones.
>
>I am not sure that I would call the incremental costs for adding the extra
battery capacity in this case excessive or even prohibitive as it sounded
like Michael Elliott was suggesting, unless you use expensive batteries. ... 
>Whether you want to hear the genset run that often and if you would want
to haul the extra fuel would be other issues.   
>It is clear to me that we're just not able to store all the energy that's
coming in when we get it...no matter how we size the battery bank.  Even
the 6 day battery with 80% dod [depth-of-discharge] didn't capture all of
the energy from the wind turbine.
>
>So, as Michael Elliott suggested, a one day battery coupled with a diesel
genset is likely to be the most cost effective solution for providing
constant energy.
>
> ... the turbine actually generated 2.14 kWh/day _on_average_ ...  The
USEFUL energy it produced turns out to be between about 1.26-1.48 kWh/day
with up to a 3 day battery bank.  When the winds blow, they blow, and there
isn't enough capacity to store the energy in such a battery bank, so we
_waste_ energy _regularly_.
>
>There is a huge difference between the average energy this turbine is
capable of producing on a daily basis and what it generates each day
_that_we_can_use.
>
>I calculated the average energy wasted [when] we had too much energy, and
it's ... 2.82 kWh - 3.9 kWh REGARDLESS of the battery bank size, and how
much we recharge with the generator!  However, the average energy put into
the battery bank by the generator fluctuated wildly depending on the
battery size and charging scheme (1.81-5.81 kWh).
>
>... I may ask, "Why would I have to put 54.3 kWh of energy into my battery
bank [from the genset] over the course of 2 months when the TURBINE
PERFORMS TO ITS SPECIFICATION?"  It actually did generate 2.14 kWh/day on
average! ... 
>I could say that it performed 41% below its specified rating, because I
had to add 41% of the energy required by my load...even though it produced
the amount of energy it is "supposed" to.  
> ... Energy per month or day works great if you're on the grid and have
something to do with the excess, but when you're off-grid, there's trouble
with that rating, due to the variability of the resource.
>  This was with data that actually measured 8.54 mph (3.8 m/s) average
wind speed.  Those aren't high wind speeds at all. ... remember, power
(energy) is proportional to velocity CUBED! ...

>One final comment on one thing Michael Elliott said ...
>
>> 2) Most sites do not have good site specific month to month 
>> wind speed data.  Clients usually come to us with only a 
>> rough estimate of their wind regime.
>
>I would contend that the rough estimate should be all that is necessary.
The wind speed I measure for a given month changes from year to year.
>
>Sincerely,
>Mike Klemen
>An FAQ on small wind systems is located at
http://www.ndsu.nodak.edu/ndsu/klemen . 
>
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· Comment requested by David.
(David MacClement) davd@ihug.co.nz 
http://www.geocities.com/davdd.geo/index.html#top
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