Electric A/c conversion

[lovemysan]

Originally Posted by metromizer

I think you will be disappointed with driving the compressor with an electric motor, that is driven off the alternator. Reason? every time you convert one form of energy to another, you loose efficiency. I have wondered about efficiency ratings for compressors for years, but it seems to me that unless your car is an EV, the most direct drive approach will be the most efficient.

Running that a/c compressor and coupled electric motor off a bank of 'on board batteries' however, that you charge up from a solar photovoltaic system, might have running your car's a/c system for nothing.




I owened couple of 'hardbody' Nissans in the 90's and really liked that a/c feature. I would turn off the a/c buttom while getting on a freeway or climbing a grade. Too bad the 2.4 liter wasn't a little more frugal with the fuel



It just doesn't seem right, almost ridiculous, doesn't it? Yet most automobile a/c systems are set up that way.

I think your right. There would be a serious eff loss using the electric motor drive method. Unfortunately for me I have limited resources and limited amount of time. This project will probly never get off the ground.

[Piwoslaw]

These may be of interest:
How much current does the A/C compressor draw? - GreenHybrid
Prius Air Conditioning System [PDF]
Electric Inverter A/C System for TOYOTA PRIUS Hybrid Vehicle [PDF]

The third link shows that the Prius' electric A/C compressor uses 19% less fuel compared to the engine driven compressor of an older Prius version.
Since the Prius' A/C system uses higher voltage, the compressor itself is 40% smaller and 53% lighter than a conventional electrically driven compressor.

The Prius' system is electric to allow the use of A/C while in stealth (engine off) mode, so I wonder if this will be adopted in more cars as gas-saving engine start-stop systems become more popular? I guess that the major obstacle is the power needed. Running the A/C @ max at a 90-second red light may drain your battery enough to leave you stranded. High voltage systems, where are you?

[fatman57]

I was recently thinking of doing this to my car. It doesn't have air conditioning and is a mid-engine car so I was thinking of a front install.

I agree that any change of energy souce will add losses to a system - will not a DC motor do?

Or more radical how about getting A/C from the alternator BEFORE the diodes while still allowing current to flow to them to feed the rest of the car?

[photovoltaik]

An inverter is an electrical device that converts direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits

[sid]

Add a thermostat to turn your A/C clutch on and off. I designed and built my own out of parts I had laying around the house (I'm an electronics engineer). But, prior to this, I was using a household wall thermostat to control the A/C clutch. The reason I ended up building my own is that the wall thermostat I used (which was also laying around the house, hence, free) had too much hysteresis (wasn't cycling enough, would get too cold and then too hot, needed to switch more frequently), but it was better than nothing.

Maybe there are off the shelf thermostats that have adjustable hysteresis. I didn't research it as I was too cheap to buy a new thermostat and could quickly build my own for free.

[BamZipPow]

Originally Posted by sid

Add a thermostat to turn your A/C clutch on and off. I designed and built my own out of parts I had laying around the house (I'm an electronics engineer). But, prior to this, I was using a household wall thermostat to control the A/C clutch. The reason I ended up building my own is that the wall thermostat I used (which was also laying around the house, hence, free) had too much hysteresis (wasn't cycling enough, would get too cold and then too hot, needed to switch more frequently), but it was better than nothing.

Maybe there are off the shelf thermostats that have adjustable hysteresis. I didn't research it as I was too cheap to buy a new thermostat and could quickly build my own for free.

In this thread I started at 4x4wire I came across the Dwyer Instruments TCS thermocouple controllers which may work fer yer setup. They are industrial controllers so they are very robust and durable. The price might scare you away...but sometimes if you want consistency...you need to pay the price if you can't design/build one on yer own.

Just so you know...I never did hook up my TCS module...but I still plan on using it on my truck fer something.