Geothermal heat pump

The geothermal heat pump senior design team is tasked with designing an optimized geothermal system and cost-benefit analysis for St. Gertrude's Monastery in Cottonwood, Idaho.



Design Task
The task is to develop a program to model generalized geothermal heat pump systems using Engineering Equation Solver (EES). In addition, the completed design should include a cost-benefit analysis for geothermal (horizontal ground coupled and water storage coupled), electric steam, biomass fuel, and coal fire boiler systems. The results will be used to determine the best alternative to the existing coal fire boiler located at St. Gertrude's Monastery.

Background
This project was brought to the University of Idaho Engineering Department in the fall of 2013 by the sisters of The Monastery of St. Gertrude. The sisters proposed the task of designing a system, preferably a geothermal heat pump, that would replace their existing coal fire boiler. This switch in systems was desired for a couple reasons; the existing system was not very reliable, cost effective, or environmentally friendly. The sisters collectively decided that they would like a system that would meet all of these reasons, and a geothermal heat pump was chosen.

Team Experience
 The Entropy Police 







Design Goals

 * Develop an EES program for generalized geothermal heat pump systems
 * Validate model using existing geothermal system in the adjacent Spirit Center building
 * Design a system for optimized cost and efficiency
 * Determine best alternative to existing coal fire boiler using a cost-benefit analysis

Design Specifications

 * Develop geothermal heat pump system while retaining current heat delivery of hot water and steam radiators
 * Heat pump system does not need to be used for cooling
 * Fluid delivered to radiator must be at or in excess of 100 degrees Fahrenheit
 * Building is 49485 square feet
 * Yearly total heating load is about 921.7 MBtu, with maximum monthly heating heating loads of 261 MBtu
 * The frost line in Cottonwood, Idaho is about 18 inches
 * Ground temperatures are fairly constant at about 64 degrees Fahrenheit, while on site cisterns have a water temperatures of 52 degrees Fahrenheit

Background Research
Geothermal heat pumps are great alternatives for heating systems in many cases. Although they have high initial costs, they are able to operate with efficiencies in excess of one hundred percent. This generally allows for a 5-10 year payback period. Heat pumps can also work in reverse, which means that during the summer months, they can be used for cooling. They work by taking advantage of the grounds' relatively constant temperature, which is the winter, is warmer than the outside air, and in the summer is colder than the outside air. This is a fairly sustainable resource, and requires only a fraction of the energy costs of traditional systems.

Interview with Sue Tacke

 * Price range:
 * Less than a million. There will be nonmonetary benefits. Environmental preferable.
 * Heating costs:
 * $75000/year
 * Current system: Radiator’s preferred over air-blown heaters.
 * Client expectations:
 * Develop options for an infrastructure for the radiator’s.
 * First estimate was 1.2 million dollars
 * Preferable that the current distribution system is the same
 * What are the alternatives to coal including electricity, geothermal, etc.?
 * Solar would be an option for running the geothermal system.
 * Initial information
 * Square footage of the main building: 55000 sq ft for annex and main building
 * Boiler: 75-80% efficiency
 * Typically use one boiler at a time unless it is really cold. Currently satisfactory.
 * In 2011, a ME and HVAC vendor looked at the building and seeing if geothermal was an option. The system specs came in at $700,000.
 * Steam radiators are only in the chapel.