Compressed R134A refrigerant as a store of energy?

[seanspotatobusiness]

How much energy is used to compress e.g. 0.8 Kg (typical mass in a typical fridge freezer; edit: I've just seen that 0.8 kg is not normal at all; it's more like 150 g - this means my idea should be quite cheap and compete well with rechareable batteries) R134A refrigerant and could it be economical to have extra R134A in a fridge/freezer loop to store potential energy during solar hours or wind energy gluts when energy is cheapest? Could a manufacturer include a larger reservior in the design so it could charge up at the most economical time? Could it compete with LiFe4P batteries (obviously it wouldn't replace batteries but it could let a user use a smaller and therefore cheaper battery)?

It looks like R134A costs about £20 per Kg but is probably cheaper for a manufacturer using it by the ton and I suppose that it doesn't wear out like batteries either.

If you think this question is better answered with a different refrigerant, then that's also interesting to me; I just picked 134A because a quick Google said it was the current preferred type.

 

[russ_watters]

Store energy how? As a compressed gas? And recovered as a compressed gas? How would this differ from regular compressed air storage, (which isn't great)? Or are you meaning to store heat? Details are missing and what have you researched tried to calculate on your own?

 

[seanspotatobusiness]

Store energy how? As a compressed gas? And recovered as a compressed gas? How would this differ from regular compressed air storage, (which isn't great)? Details are missing and what have you researched tried to calculate on your own?

Thanks for responding. You'd be deferring energy usage to when it was cheapest or when your solar panels were generating power. Obviously you couldn't efficiently use this to run your PC. You'd use the compressed R134A to cool the inside of a refrigerator/freezer. It would be better than compressed air because R134A undergoes a phase change at convenient temperature and pressure and that phase change involves moving a large amount of heat.

To try to answer the question myself, I looked up "enthalpy of fusion R134A" but instead of getting a single value, there are tables of values for different temperatures and pressures and I don't know what is appropriate to use. Even when I find out how much energy is released on compressing a given mass of refrigerant, I still don't know whether it makes functional sense in the context of how a fridge/freezer works.

 

[russ_watters]

Thanks for responding. You'd be deferring energy usage to when it was cheapest or when your solar panels were generating power. Obviously you couldn't efficiently use this to run your PC. You'd use the compressed R134A to cool the inside of a refrigerator/freezer. It would be better than compressed air because R134A undergoes a phase change at convenient temperature and pressure and that phase change involves moving a large amount of heat.

So, there is such a thing as thermal storage, is that what you mean? You aren't trying to get electricity back?

A couple of things to note about thermal storage:

1. The phase change isn't free.
2. The refrigerant is not the storage medium, it's just what you use to run the cooling cycle. The storage medium is usually water/ice.

 

[seanspotatobusiness]

Yes, thermal storage; not trying to get electricity back.

I realise that phase change isn't free. That's fine.

So fridge/freezers don't have a reservoir of liquid refrigerant? I hoped that the compressor turned on every so often to fill the reservoir which would then slowly be released into the evaporating coils and then this reservoir could be swapped for a larger one. :( Never mind. Thanks again for responding.

 

[russ_watters]

So fridge/freezers don't have a reservoir of liquid refrigerant?

No, there's really no reason why they would. It would just be a waste of refrigerant.

More importantly, you should realize the amount of storage you are talking about is enormous. The US unit of refrigeration is a ton. It means a literal ton of ice per day. My air conditioner for my house has a capacity to provide three of them (though probably only uses about half a ton).

So, ice is used because it is cheap.

:( Never mind. Thanks again for responding.

No prob, you were close at least!