Kw-Hr meters in off-grid systems [RE-wrenches]
Dan Duffield
dand at directpower.com
Mon Jun 2 17:54:04 PDT 2003
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One of the most useful ways to provide feedback to the user, and protect
your initial pv design is to include the re-conditioned analog type
kilo-watt hour meters: with numeric barrel displays that are offered by at
least one company. I always sell two of these units- if i have a client who
wants to do the system right and not just skimp on price.
I use one on the output of the inverter and one on the output of the
genset. By keeping the metering simple and inexpensive, almost any customer
can get a pretty good idea of the demand side of the system. A new
unfamiliar system can prevent a lot of vague ambiguities (possibly present
in the mind of your new customer) as to whether your design was proper.
Good data can and will prevent arguments and legal issues and will make
self evident to the customer the need for additional PV modules and how
many. For example, if the new system owner has a water bed heater or some
other loads they happened to forget; that they needed to include (but
omitted) in the original load profile.
More than all this - they look great and somehow fit into the mental image
of how a system should look by the user who has never seen a full blown
well designed system.
*Caveat
I will NOT use the "enigma cipher" type that have a series of clock dials
- they are very difficult to decode by the new system owner.
Also if you use one on a bi-directional line commutating inverter, do not
purchase the "detent" type as they will not spin backwards.
If the new customer said that there load profile was 10.0Kw-Hrs a day, take
a average and ah ya, if there using 12.0, - They KNOW that they have to buy
more pv panels from you. Feedback means friendly, if simple.
- - - -
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