A common design for a geothermal heat pump system is shown above. Multiple heat pumps are run in either heating or cooling mode and these are feed into a main header. Using 4 motorized valves, this example gives the system 4 different heating and cooling options as shown above, with a maximum efficiency of just over 400%.

Although this system is heating and cooling at the same time, this is not true simultaneous heating. Each heat pump can only run in either heating or cooling mode but not both at the same time. In heating mode, heat is drawn from the boreholes and in cooling mode, heat is dumped to the boreholes.
 

       Heating - energy taken from boreholes               Cooling - energy dumped to boreholes
 

However if you look closer at the operating temperatures you see that when the heat pump is in heating mode, the evaporator side is actually cooling the water from the source. Rather than dumping this colder water to the boreholes, it is better to use it in the building’s cooling system. In this way, the heat pump heats and cools simultaneously, only using the input power for one unit.
 

Similarly, when you are cooling, the excess heat can be used to heat the building’s hot water or heating system, rather than dumping the excess heat to the boreholes.
 

When in heating only or cooling only mode, performance ratios of 4.5:1 can be achieved, reducing costs by up to 70% over traditional systems. However if both sides of the machine can be used simultaneously as shown above i.e. simultaneous heating and cooling, performance ratios of 9:1 are possible (4.5 cooling and 4.5 heating : 1 electrical input).

Many commercial buildings will have heating and cooling profiles similar to the graph below, from which simultaneous heating and cooling loads can be identified.
 

Example of a heating/cooling profile for a commercial building
 

At times when the heating load is greater than the cooling load, the excess energy can be taken from boreholes and conversely, when the cooling load is greater than the heating load, the excess energy can be dumped to the boreholes.
 

            Heating Load > Cooling Load                             Heating Load < Cooling Load
 

Also due to the fact that the system is coupled to a heat sink, direct passive cooling using the heat source water is possible. As this type of cooling only requires 2 circulating pumps, ratios of up to 25:1 are possible.
 

Passive Cooling