Using a heat pump with a high temperature storage tank?
I’ve read about how a new type of heat pumps systems that is attached to high temperature storage tank. These are being used in Europe and Iceland /Greenland with great success but don’t know if anyone in Connecticut or the Northeast has done anything like this.
How I understand these systems works is the heat pump draws the available heat from either air or ground/geothermal pretty much year round at any opportunity and pumps the heat through a heat exchange and concentrator (?) into a high temperature storage tank.
Later that stored high temperature heat is drawn through the heat exchanger as needed to warm a tank of ‘low’ temperature hot water to warm the house and the domestic hot water. The method of distributing the heat inside the house can be any of the conventions methods such as baseboard, in floor heat, forced hot air, etc.
The high temperature storage tanks are supposed to be “off-the-shelf” equipment used for solar house and various industrial uses. These tanks are super insulated and are filled with different types of heat storage material like ‘molten salts’ or different mixes of sand and oils, etc. and hold the heat at many hundreds (thousands?) of degrees so that a very large amount of BTUs can be stored in a small footprint.
When the house needs cooling the heat pump draws the heat out of the house through the normal means and instead of ‘dumping’ the heat outdoors instead sends it back into the high temperature storage tank for later use in the cold winter months. Should the high temperature storage tank ever reach its maximum storage capacity, i.e. it becomes ‘full’ any excess heat that is pulled from the house during the cooling season is ‘dumped’ outdoors in the conventional means.
It sounds like the heat pump can be a smaller unit since it only needing to ‘fill’ the storage tank to its max capacity at a slow ‘trickle charge’ rate over a whole summer season and therefore only needs to be sized just to take care of the ‘instant’ cooling needs of the house on a hot summer day rather than sized to try and heat the house on a cold 40F winter day.
With the stored heat it also sounds like it does not appear that the outdoor winter temperature matters much since the house is getting it's heat from the storage tank and not the outdoor air so no ‘back up’ system would be needed except if there was a very long cold period where more heat was used than was stored. This also assumes the storage tank(s) were sized large enough and were ‘filled up’ before the cold period arrived. I’m not sure how this system works if it is first installed during the winter heating season where the system would not have had time to harvest and store any summer heat yet.
There sounds like a lot of calculations have go into designing this kind of system to figure out how much heat can be collected and what size tanks (‘low’ temp and ‘high’ temp), the different heat exchangers, pumps, controllers, etc.
I’m not sure I’ve got all the details right, but I'm wondering if any one builds and install these types of systems.