[RE-wrenches] Xslent?

Peter Parrish peter.parrish at calsolareng.com
Fri Jan 7 15:39:01 PST 2011


I know only a little about Power Factor "charges", but we can figure out
some other "engineering" issues.
 
Power Factor is a measure of the amount of reactive (out-of-phase) power
compared to real (in-phase) power. It is somewhat complicated but the PF is
unity for 100% in phase and 0 for 100% out-of-phase power. 
 
The important thing to remember is that (while holding the real power
constant) for PFs less than unity there is in addition to the real power,
and "in-flow" of power and an "outflow" of power four times a cycle. One
might say, "Why do I care about reactive power? It flows in and out with no
net contribution over the long run!). True, but the in-flow and out-flow
represents higher currents on the lines and more  losses. Or it means that
there have to be oversized service conductors to avoid the extra losses.
Even if the losses are avoided, the higher currents can trip overcurrent
protection devices, and of course the utility company needs to supply (and
take back) the extra currents in real time.
 
What ever is done to reduce the reative power, it has to be done in real
time (with a fraction of 0.016 seconds, the 60 Hz cycle). You can't wait
until later in the evening to solve a problem that is occuring during the
day.
 
Real time compensation can be often done with capacitors alone or in
conjuction with some smart electronics. Remember that for short periods of
time capacitors can store considerable amounts of energy and can smooth out
these reactive currents.
 
I can well imagine how an inverter can be designed to generate both real and
reactive power, and therfore an inverter can reduce the amount of reactive
power that needs to be supplied by the utility company - but not when the
sun isn't shining. I suspect that these types of inverters will have
oversized output circuit wiring to handle the reactive currents without
adversely impacting their efficiency rating. 
 
If I have time this weekend, I will take a look at Apparent's website.
 - Peter
Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com  
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885

 
  _____  

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jamie
Johnson
Sent: Friday, January 07, 2011 2:03 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Xslent?
 
It's an interesting product for a niche market if it actually works as they
say (Disclaimer:I am not claiming that it does), after speaking with an
individual who I believe is the VP of Production for Apparent (use to work
for EnPhase according to their website), he claims that the product is
currently installed at the Google campus on a solar canopy for some of their
EV chargers (can anyone verify this?)
 
They have several other beta installs as well, however the individual I
spoke to said they were only installing small systems at beta test sites
(where the Util co charges for VAR's using separate meters like for EV
charging) for now.  No pricing has been set for the inverters, and they are
not available for sale to installers yet.
 
Apparently they claim the inverter can create/produce VAR's by taking 1 watt
of power from the grid at night or from the solar output during the day and
turning it into approximately 9 VAR's to offset the customers charges for
VAR usage from the Grid.  This is where the KVAh production on the graph
before sunrise and after sunset comes from.
 
I still would need to see a third party head to head comparison test before
I believed it.  Again niche market inverter for when the utility co charges
for VAR's.
 
Jamie
 
 
 
 
-------- Original Message --------
Subject: Re: [RE-wrenches] Xslent?
From: August Goers <august at luminalt.com>
Date: Fri, January 07, 2011 10:24 am
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>

Hi All -

Thanks for the helpful info! We did a little more research on our end and
I guess Apparent is the new brand name for the Xslent product. What
baffles me is the chart where they show that they're producing power
before and after sunrise and sunset:

http://www.apparent.com/products/mgi.html

The system must include batteries? Someone on their marketing team is
really going to town...

Best, August

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of jay peltz
Sent: Thursday, January 06, 2011 4:43 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Xslent?

HI Peter,

I agree with you that for now on residential it makes no sense.
However for commercial that might have to pay extra for PF issues, to have
the inverter adjust for this makes sense.
Its the reason they( inverter companies ) are doing it.
I"ve heard a better more complete reason of course from Bill Brooks, who
maybe can chime in.

sorry got away from me,


jay
peltz power
On Jan 6, 2011, at 2:34 PM, Peter Parrish wrote:

> I can't understand how any inverter WOULDN'T deliver its power with the
> voltage and current 100% IN PHASE.
>
> When the voltage and current are not 100% in-phase that represents
reactive
> power. Reactive power flows positive for a quarter of the AC cycle, then
> negative for a quarter of a cycle, then positive and then negative. The
net
> result over one AC cycle is ZERO power delivered to the load.
>
> So reactive power is worthless.
>
> Worse, it results in higher currents (and voltages) for the same amount
of
> in-phase power, putting additional stress on circuits.
>
> - Peter
>
>
> Peter T. Parrish, Ph.D., President
> California Solar Engineering, Inc.
> 820 Cynthia Ave., Los Angeles, CA 90065
> CA Lic. 854779, NABCEP Cert. 031806-26
> peter.parrish at calsolareng.com
> Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
>

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