Design and monitoring of an innovative geothermal system including an underground heat-storage tank

• Published in: International journal of green energy Vol. 13; no. 8; pp. 822 - 830
• Main Authors: Bonamente, Emanuele, Moretti, Elisa, Buratti, Cinzia, Cotana, Franco
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 20-06-2016
• Subjects: Boreholes; Design engineering; Geothermal; Geothermal heat pumps; Grounds; heat storage; Heating; heating and cooling; Monitoring; Reduction; renewable energy sources (RES); system monitoring; Tanks; MED, Italy
• ISSN: 1543-5075; 1543-5083
• DOI: 10.1080/15435075.2016.1161630

The design, implementation, and setup of an innovative layout for geothermal heating and cooling systems are presented. An underground heat-storage tank, used as a thermal flywheel, decouples the utility side of the system (i.e., the heat pump) from the geothermal side (i.e., the boreholes). The innovative layout allows for a more efficient exploitation of the ground energy reservoir and a sensible reduction of investment costs.
A pilot system has been realized for a commercial building near the city of Perugia, Italy. The design of the heat-storage tank, the heat exchangers, the monitoring system, and the operation modes were carefully studied. The heating performance monitoring shows that the innovative approach allows for a significant reduction of the ground heat exchangers, hence requiring for fewer and/or shorter boreholes (up to 75%) while still supplying the total energy need. The peak-power demand is covered taking advantage of the high thermal capacity of the water inside the tank, while the reduced-size geothermal boreholes are used with a higher duty cycle to independently provide the total energy need.