Anyone have a rule of thumb when the 'break even' point of a chiller system is financially 'positive'? My water bill is approaching $300/month(60K gallons)as I am using town water for all my cooling. But I'm worried that I might just be swapping a high water bill for a high electric bill. Lots of ideas being kicked around and I'm even thinking of using a temporary/portable swimming pool for a heat sink. Anyone done something similar?
How big is your still? We have twin 600 gal cooling reservoirs that keep us going without chilling the water in 90 F weather. If it's just for cooling your still, then a small, relatively cheap chiller can run all night and get your reservoir down for the day.
There's the rub- you have to spend money for a reservoir (even for just the still condenser) or the relative higher load at the outset of the condensing may overwhelm the chiller with hot return if you size your chiller marginally or decide to increase your capacity on the hot input side.
In almost all cases, if you are running city water, the payback for switching over to a chiller is normally 2 -3 years, depending on what you locale does not only in the cost of water but also sewers since most cities sewer treatment are woefully undersized, there is going to be a heavy hit coming to pay for all the older plants.
If you are located up North, I also have offered an option drycooler for winter use that will only use the circulator pump and fan motor (like a radiator) to charge up you water reservoir, which up in the far North, you may be able to use for up to 6 months of the year, paying for almost 1/2 of the electric used by the chiller and paying for itself in the first year.
Calculating the payback unless you have a year of production utility breakdowns would be speculative, but if you have them, it's not too bad a thing to figure once you size the chiller and compare.
For a rough example, a 5 ton chiller with pump, input will run somewhere around 8 KW, times hours in use, times cost cents/kwh.
You have to have a 50 amp service for 230/1/60, so there's that cost as well as minimal piping.
Does this help?
Thanks for all the answers guys. I think the first item I need to do is move from a manually controlled system to a couple of PID temp controllers with proportional valving as well as some flow monitors. Once I get some good data sets I'll let you know what I find.
Go old school, 5 gallon bucket, timer, and a thermometer. Take a reading mid-run, probably another towards your end.
You should be able to get a good handle on your input temps (measure the temp at the faucet after a few minutes of running, the delta t and a flow rate during the run.
You'll probably get a more accurate reading this way than using an inexpensive flowmeter, anything accurate costs a small fortune.
If you can calibrate your temp gauges from a known temp and know how to adjust, you should be ok without costing you too much.
Gauges can be anywhere from 2 to 5 degrees off, which is a lot when you are attempting to measure your BTU/hr load of your still, even after you measure your flow (in a bucket- a good tip for anyone!).
Good luck to you!