RE: Re: Wind Turbines and Heating Water

[Graham Kiff <graham.kiff@xxxxxxxx>]

Hi Patrick

The original reason for splitting the battery banks was to be able to
suppl=
y both 24v & 48v (I didn't realise 48v inverters were so readily
available)=
.  The reason for the batteries is purely voltage regulation rather than
st=
orage of power.  I therefore think I can revert to just one bank of
batteri=
es.

The plan was to use all the power produced to heat my thermal store to
~70c=
, then once reached, dump the excess load via the inverted to the grid.  I
=
assume therefore I should use an inverter rated to the maximum output of
th=
e turbine (1.4Kw in this case) - correct?

So my setup will basically be:
Turbine -> 4x12v batteries (in series) -> SEA24 440Amp relay ->
Either	48v DC Immersion Heater
Or		48v Grid-Tie Inverter


Cost-wise I should be able buy everything for ~=A3900
How does this sound?

Cheers
Graham

-----Original Message-----
From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf Of p=
atrick_o_matic
Sent: 19 January 2010 13:53
To: ukha_d@xxxxxxx
Subject: [ukha_d] Re: Wind Turbines and Heating Water

Hi Graham
I have been looking at/designing a similar installation recently.
Here are some fairly random thoughts:

- What is the power storage for? 500W isn't much.
- The normal rule of thumb is to size the battery store based on the
number=
of days 'no generation' that you might have endure. e.g. three-four days s=
uccessive calm days (or cloudy days for solar).=20
- Battery life is contingent on depth of discharge. Ideally you want to
siz=
e your batteries so that they're not discharging more than 20% on average,
=
50% worst case
- The battery discharge characteristics in off-grid situations such as
your=
s are quite demanding chemically. Not sure which Yuasa batteries you are
pl=
anning on using, but normal leisure-style batteries are not up to the job.
=
Wet batteries are perfered. Traction-type batteries are particularly well
s=
uited (e.g. forklift truck type cells). In case you didn't know, it's
gener=
ally not a good idea to extend an existing battery bank over time, or
repla=
ce individual cells within the bank.
- You ask about voltage. Broadly speaking, the higher voltage systems are
m=
ore efficient (lower resistive losses in transmission). 48V inverters are
r=
eadily available (I think Sunny Boy are available in 48V variants). You
may=
also want to consider splitting the inverter, so that intermittent loads (=
e.g. lights) are driven from a load-sensing inverter and continuous loads
a=
re driven from an independent inverter. Inverter load curves vary, but
they=
are generally more efficient when operating at the upper end of their load=
range.=20
- You will need a dump load as well. It may make sense to use this for
spac=
e heating?
- I don't really understand the motivation behind splitting the battery
ban=
ks and then controlling charging? What is the underlying driver for this
be=
haviour - is it being sure there is capacity in one of the banks for
essent=
ial services or something else?

Feel free to mail off-list if this is getting too OT for UKHA

Cheers
Patrick



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