Home Pasteurisation Evolution

I've been playing with some equipment for work recently which has given me a few new ideas about the home pastuerisation rig.

Specifically;
- I cannot get anywhere near the efficiency I want out of the cooling unit using peltier plates. Instead I will do the following;

1. Use a tuckerbox freezer adjusted to run very very cold.

2. Supply power from the battery bank (still to be built). Use an inverter (probably out of a UPS, I have a 3kW unit in the shed now), for the 240VAC conversion.

3. Put a stainless beer keg in the freezer and fill it with methylated spirits (~90% ethanol, ~10% Methanol, so a melting point of -100 degrees or thereabouts). Plumb the keg to fill from the top, drain from the bottom (one fitting?).

4. Find a pump capable of dealing with the nasty nature of ethanol/rubber reactions, and the extreme cold.

- Control system.

1. Proface GP377 screens are very easily configured, can operate as a modbus master (a common industrial communications standard). So would be perfect for making this unit a standalone system. Should be able to get them fro under $200 each. Here's one on ebay.

2a. Control via a micro PLC. Either a Klockner Moeller PS141 or a Siemens S7-200, both of which I have on the shelf.

OR

2b. Control using some of these. This works really well because they can be addressed individually and the Proface can handle the transfer between them. There's a bit more work involved in this application, as I'd have to build a seperate TTL control supply (5VDC system) and interface it out using either solid state 5V relays or standard coil/contact relays.

The real benefit of this method is the analog control flexibility I gain from it. Analog points on PLC's a really (REALLY) expensive. By using a unit with heaps of analog channels and D/A channels as well as PWM Channels, I get heaps more opportunity to do decent control of the fluid.

- Hot water supply.
Either use a large solar collector, or a series of 24VDC heating elements on the battery bank. Both are fine, as electric-> heat conversion is spectacularly efficient.


Should start construction sometime.....