AC to DC Refrigeration: Power System Conversion

[blessed]

Hello guys,
I am trying to redesign the Power supply system of a 4hp, 230VAC, (actually 3hp compressor +1hp circulating pump) single phase Refrigeration system to use off grid solar power supply, without the need for expensive true sine wave inverters.
Expected gains are to avoid the expensive start up currents of the present system by using DC a compressor and DC pump to be driven directly off solar panels and (trojan batteries at night) and hopefully use a lesser power requirement than the AC arrangement would have required. The chiller is currently run on a 10KVA deisel generator.

I would need your thoughts, expertise and opinions on how to make this design as simple as possible.

Kind regards

 

[gar]

160607-0740

A DC motor will have brushes. This is a maintenance problem, but you have good starting torque.

A DC brushless motor is really an AC synchronous motor with electronics to make it look like some sort of DC motor.

For your present AC induction motors do you really need a good sine wave or is an approximation ok?

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[blessed]

Thanks @gar.
Power supply at the site where the chiller is located has become seriously epileptic in recent times, this being the reason why I am trying to make use of the abundant sunlight at the location.

I caught the DC compressor idea when I saw DC solar freezers from steca ( http://www.steca.com/index.php?Steca-PF-166-240-en ) being run directly off solar panels and charge controllers without the need for an inverter.

More so, the stated performance of steca's 100W dc freezer is very similar to another 140W, 220VAC freezer that I have used in the past, requiring 1.25KW Generator to get it started and running whereas the dc freezer runs on a single 140W solar PV panel. Now Steca doesn't have any offering that suits my current cooling need as stated in the opening post.
It is on this background that I am trying to redesign the power supply system of my current facility to be powered directly of solar panels and charge controllers without having to go through an inverter.

 

[blessed]

I therefore thinking of what components to remove from the AC powered chiller and what to add to make run as simple as possible off PV solar panels and charge controller only.
I appreciate your thoughts and ideas.

 

[topgone]

I therefore thinking of what components to remove from the AC powered chiller and what to add to make run as simple as possible off PV solar panels and charge controller only.
I appreciate your thoughts and ideas.

Definitely, you need to remove the AC compressor and replace it with a DC compressor! You also have to check if your chiller fans are of universal type (meaning, can run on either AC or DC power). If your unit has indicating lamps, you have to check those if those can be run on the available DC voltage that you will be using.

 

[gar]

160612-0943 EDT

blessed:

What is a charge controller? Some sort of electronic switch and other components.

What is an inverter? Same answer, but there could be other types.

Why do you need a pure sine wave inverter? I don't know, but it is probably most a result of added motor heating. Then is that a problem? Possibly not.

Solar panels. On average you probably need an array with a power rating 3 to 4 times your average load power. Suppose your average load power is 5 * 1 kW / 2 = 2.5 kW. Assume an array of 10 kW is required. To this you need to add batteries of at least about 2.5 *24 kWh. That provides some slack, but can't handle dark days.

You could use refrigeration energy storage and reduce battery size. This means using excessive cooling during sunlight and using some of the thermal time constant to ride thru non-sunlight.

Contact Besoeker on the question of motor heating with a simple pulse waveform inverter. These inverters use a single rectangular pulse at the sine wave peak with a peak voltage value set at the sine wave peak voltage, and a pulse width adjusted to produce an RMS voltage equal to that of the sine wave.

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[Saturn_Europa]

Just out of curiosity, is this a missionary guest house?