GCHP systems and thermal energy storage

We've all seen water towers in many communities. They're filled with a small pump during off-peak times and the height of the water maintains pressure in the water system during peak times. They are designed to hold enough water to supply the community during the peaks. One of the main benefits is that the pump used to supply water to the community can be much smaller than it would be if it had to supply enough water under pressure during peak use.

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In designing a GCHP system to supply hot water for a project, storage can be used to reduce the size of the heat pump needed to ensure adequate hot water for times of peak use. And because an integral part of a GCHP system is the GHX, the size (and cost) of the GHX can be reduced along with the size of the heat pump equipment. 

In systems with large peak cooling loads, energy storage can also be very beneficial. Chilled water or ice storage tanks have been commonly used with conventional chiller systems for 30 or 40 years. Integrating them with a GCHP system has the additional benefit of reducing the size and cost of the GHX connected with it. Since 2004, several systems have been built that take advantage of ice storage tanks to reduce the peak heat rejection load to the GHX, including: 

• St. Pierre Bible Fellowship Church, St. Pierre, MB
• The Heart Doctors, Rapid City, SD
• IKEA Store, Centennial, CO

An article published in the ASHRAE Journal (April, 2013) describes the use of energy storage integrated with a GCHP system in much greater detail.