[DavidNJ]

This picture from Multiaqua's documentation show a storage tank on their chiller system:

The say if the volume in the system is less 50 gallons, a tank is needed. I've seen other chiller tanks that can be a few hundred gallons. And the IceBank storage tank that is also several hundred gallons.

The IceBank runs the chiller at night to create a large capacitance of cold/frozen water. Then it recovers it during the next day. Where electricity is metered by load condition, it allows a the chiller to run during lower cost periods. It also lets the chiller have a effective greater peak capacity and spend more of its time operating at full load. Cooling the subfreezing temperatures does deduce the chiller efficiency which is only partially made up for by cooler evening temperatures: http://www.calmac.com/products/icebank.asp .

While the IceBank may be excessive for an application with out system load metered electricity, what is the optimal way to store chiller capacity. Since most don't have inverter-powered variable speed compressors, where do you buffer the extra capacity? Without taking advantage of the phase change to ice, don't even small solutions result in huge tanks?

Which chiller storage tanks work best and how are they best sized?

Thanks,

David

P.S.
This diagram shows two banked Multiaqua chillers sharing a single storage tank. Multiaqua sells the tanks in 20 and 42 gallon sizes.

 

[Shophound]

Have you run a Manual J on your house, yet?

Blower door test?

Infrared scan of envelope?

Constant speed chiller compressors (single stage) vary capacity with hot gas bypass valves.

But we're talking about a chiller that at best needs to crank out 42 -45 degree water for human creature comfort purposes. All a chiller on a loop cares about is loop temperature setpoint and circulation. It will bang on/bang off to maintain loop temp if it doesn't have more sophisticated staging/capacity control. For creature comfort you could probably put a five degree deadband between bang off/bang on and not feel any loss of comfort inside the house.

At minimum a chilled water loop should have an expansion tank.

 

[flange]

ice storage is a solution used several ways. first, in situations where there are peak/offpeak rates where building ice off peak can be advantageous in saving energy dollars. you can build ice during offpeak hours at a reduced charge, then use the ice to produce chilled water during peak hours, thereby lowering consumption during the day. some times this is done to shave the load during the day, in other cases it is sized to completely carry the laod during the day. need lots of tank capacity to do that. for commercial buildings, this can be a big energy saver.
as far as the buffer tank, they again are used in different ways. in your case, the buffer tank would be designed to give your system enough water capacity to prevent the chiller from short cycling, especially during low load conditions. in some cases though, they are used to give you short burst of extra capacity via reserve. as a example, we built a plant that makes a product that requires 200 gpm for a forty five minute burst about every hour and a half. instead of installing a chiller that could handle that entire load of almost 100 tons, we used a five thousand gallon buffer tank that runs at 42 degrees all day, and only needed a thirty ton machine. big difference in first cost and energy use. toward the end of the burst, tank temp comes up a few degrees, but then the chiller runs during the satisfied period to bring the entire 5500 gallons back to temp for the next cycle. instead of having say a 100 tonner cycking on/off.