Posted by Paul Ciszek on August 9, 2007, 7:57 pm
As I understand, some passive solar heating systems have a few non-passive
elements, such as shades that are raised or lowered according to time or
temperature, vents that open and close, etc. Is there a term of art for
these? If you've got a large area gathering solar heat passively, a few
photocells running shades or vents don't make it an "active" design, IMHO.
Or does "passive" mean "no electricity"? My girlfried suggested "passive-
agressive solar" ;-) But is there an accepted term?
Also, are devices like bimetal strips considered "passive"?
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Posted by gary on August 10, 2007, 2:53 pm
On Aug 9, 1:57 pm, nos...@nospam.com (Paul Ciszek) wrote:
I don't think there is a name for these mixed systems.
I think people get overly hung up on this.
Almost all systems have some level of active control, even if its just
a person raising and lower the shades to prevent night heat loss
through direct gain windows.
Systems that integrate collection and storage into the building
structure tend to be cheaper and lower maintenance, but more
challenging to control. It seems to me that this might be a better
way to classify systems?
Posted by lauxy on August 11, 2007, 11:43 am
El Fri, 10 Aug 2007 07:53:03 -0700, gary escribió:
A passive system is a system than doesn't use any kind or portion of
energy for its performing.
An active system use other energy, of portion of energy produced by
itself for its performing.
Examples of passive and active systems.
In your home-electrical system:
Passive security system: Insulation of wires.
It Avoids electric shocks.
Active security system: Automatic differencial switch
When an insulation failures occurs turns off power-supply
In formula- indi car races:
Passive security system: Earth Ground metalic-sheet.
When a car stops to refill alcohol-tanks, this sheet touches
bottom metalic structure of car. So statical electricity is discharged
to earth. So risk of fire ignition is avoid.
Active security system: ABS and Electronic Traction Control.
In solar-thermal energy:
Passive system: A window oriented to South, whith a little roof
at top of window. In summer, when sun is in more vertical position
the roof projects shadow over window and light and hot doesn't reaches
inside home. In Winter, sun is in less vertical position, the shadow
projected by roof doesn't reach window and light and warm reaches
Active system: A heating- water system with natural circulation of fluid
from pannels to acumulation.
It looks a passive system because it isn't use another
energy to move warmed fluid and hot from panels to
acumulation, there isn't pumps.
0 Well, part of energy of heat is transformed in mechanical
energy to move the fluid. The effect used is convection.