Thanks for the Wikipedia reference. Here is the link:
https://en.wikipedia.org/wiki/Heat_pump
Folks are often puzzled by the "up to 4x efficiency" of heat pumps. "How
is that even possible?" is the most common question. (And the common
sense question as well...)
Well, heat pumps do indeed deliver, typically 3x to 4x the heat as a
resistive heater given the identical wattage input, occasionally even a
bit more. They indeed work, whether you believe in the theory or not.
I replaced a resistive space heater (about $120) in my two car
garage/shop with a heat pump ($1300, Ebay) and it uses *one fifth* the
energy. (SEER 21, 18000 BTU, heating and A/C) Paid for itself in a less
than two years of operation. (Higher SEER rated heat pumps cost
considerably more that lower SEER rated units. They cut fewer corners so
you must pay for that.)
SEER Wikipedia link:
https://en.wikipedia.org/wiki/Seasonal_energy_efficiency_ratio
Ebay link for 18000 BTU 21 to 23 SEER unit for $999, free shipping:
https://www.ebay.com/itm/112410406169
Bill D.
On 11/28/2017 8:00 PM, Rod Hower via EV wrote:
I had to look this up on Wikipedia since a 100% efficient resistive heater is hard
to beat, but I guess I didn't understand that the heat pump is getting added energy
from the environment. "
Heat energy naturally transfers from warmer places to colder spaces. However, a heat
pump can reverse this process, by absorbing heat from a cold space and releasing it
to a warmer one. Heat is not conserved in this process and requires some amount of
external energy, such as electricity. In heating, ventilation and air conditioning
(HVAC) systems, the term heat pump usually refers to vapor-compression refrigeration
devices optimized for high efficiency in both directions of thermal energy transfer.
These heat pumps can be reversible, and work in either direction to provide heating
or cooling to the internal space.Heat pumps are used to transfer heat because less
high-grade energy is required than is released as heat. Most of the energy for
heating comes from the external environment, only a fraction of which comes from
electricity (or some other high-grade energy source required to run a compressor).
In electrically-powered heat pumps, the heat transferred can be three or four times
larger than the electrical power consumed, giving the system a coefficient of
performance (COP) of 3 or 4, as opposed to a COP of 1 for a conventional electrical
resistance heater, in which all heat is produced from input electrical energy.Heat
pumps use a refrigerant as an intermediate fluid to absorb heat where it vaporizes,
in the evaporator, and then to release heat where the refrigerant condenses, in the
condenser. The refrigerant flows through insulated pipes between the evaporator and
the condenser, allowing for efficient thermal energy transfer at relatively long
distances.[5] "
On Tuesday, November 28, 2017 8:42 PM, Bill Dube via EV
<[email protected]> wrote:
If you what to get quite fancy, modern OEMs use a heat pump run with a
small variable frequency drive. About 4x the efficiency of a resistive
heater. No joke, and that is a serious increase in range in the winter.
No doubt, you can get a Leaf compressor cheap in the bone yard.
By adding the proper valving, you have the bonus of air conditioning,
but that is even more of a project. The good thing is, you can reuse the
cars existing air conditioning condensor and evaporator and some of the
A/C plumbing.
It can get quite complicated, however, and a resistive ceramic type
heater core is, no doubt, the simplest option. I'd opt for a "high/low"
switch (series-parallel?) on two ceramic heaters, or some sort of
thermostat on the outgoing air from the heater(s).
Bill D.
On 11/28/2017 4:33 PM, Bob Bath via EV wrote:
Respectfully, when I did Civicwithacord, the goal was defrosting the windshield
effectively, not keeping me warm. Yanking out the dash to install the ceramic
heater in the old fluid core housing was easily the biggest b---h of the
conversion, but the time and look and safety was well worth it!!
Bob Bath, from his iPod, so any misspellings are from autocorrect or fat
fingers on a small device, not cluelessness...
On Nov 28, 2017, at 3:13 PM, Bill Dennis via EV <[email protected]> wrote:
I used a 1500W heater core in my Geo Metro conversion, and I'd say that it
kept the car kinda "warmish" on really cold days. But I think if I'd taken
the time to put extra insulation in the car, that would have helped.
Bill
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