Teaching Geothermal Energy in an Undergraduate Renewable Energy Engineering Program

Toni Boyd, Senior Engineer, Geo-Heat Centre, Oregon Institute of Technology

Andrew Chiasson, Program Manager, Geo-Heat Centre, Oregon Institute of Technology

Jamie Zipay, Professor, REE Program Director, EERE Department, Oregon Institute of Technology

ABSTRACT

The Renewable Energy Engineering (REE) program launched at Oregon Institute of Technology (OIT) in 2005 is the first ABET accredited program in renewable energy engineering in the US. The main objectives of the program were to provide graduates for careers as professionals in energy engineering and focus on renewable energy disciplines. One of these disciplines is geothermal energy. Geothermal energy usage has been a focus of the OIT campus in Klamath Falls through the Geo-Heat Centre for research, campus heating with a direct use system and most recently a low temperature geothermal power plant. With the presence of various campus resources in geothermal it is only natural to add this focus to the REE program with a course sequence in Geothermal Energy Engineering and Applications.

This paper presents the design, development and evaluation of an undergraduate course sequence with a focus on the energy source and applications such as direct use heating, geothermal heat pumps and geothermal electrical power production. Originally the REE program had a single course that was more of a survey on geothermal energy but the program students were requesting a stronger focus in this area of renewable energy. This led to the development of a three term senior sequence that is presented in this paper.

One of the main objectives is to provide an engineering and science foundation with regards to geothermal energy. This includes areas such as geothermal heat sources, reservoir geology, and thermodynamics of the energy conversion processes. Another objective area is the site exploration, drilling, and evaluation of energy extraction capability. This area also provides background for analyzing environmental and economic impacts of such energy solutions. The focus is kept on the engineering design and analysis of geothermal energy resources. These objectives are met in the first course in the sequence.

Another main objective is applying the science by way of actual applications converting geothermal energy. These objectives are met mostly in the two remaining courses in the sequence on Geothermal Heat Pumps and Geothermal Electrical Power Generation. The Direct Use Heating System (HVAC) application is presented in the first course. The focus is on design, development, impacts and efficiency of the conversion processes in the sequence. Students in the program have expressed a great deal of interest in this approach. This is evidenced by an increase in student involvement in geothermal resources on campus through special project classes, design competitions and senior capstone projects. Some of the program graduates have also been considering continuing educational opportunities in geothermal energy.

INTRODUCTION

Geothermal EnergyThe energy situation facing the world today has brought about an increased interest in better utilization of renewable energy sources for solving problems in heating and cooling, electrical power generation and transportation. Much of the current focus has been on renewable generation sources such as solar, wind, hydroelectric, solar thermal, bio-fuels and bio-gas, and others. Many of these sources require an energy storage system due to the intermittent nature of the source such as solar or wind. One source that does not have this requirement is geothermal energy, it is not intermittent and as long as the geothermal fluid flows energy is available for conversion and usage. Currently geothermal energy provides a small percentage of renewable energy utilization worldwide [3] due to the geographic limits of geothermal as illustrated in Table 1. Geothermal Energy represents 2.8% of the total production of electricity in the US and 4% of the gross production of electricity. When compared to other renewable sources for electrical power generation the percentage for geothermal increases to 8.3% for capacity and 10.7% of total production. In the US geothermal energy distribution is concentrated on the west coast [3] as illustrated in Figure 1 a US Geothermal Resource map and the overall percentage usage has increased in the western US over the last decade. This demonstrates the significance of geothermal energy on the west coast for production of electricity. In the geothermal course sequence a course in geothermal power plants was determined to be essential.

Ref. www.eia.doe.gov [3]

Figure 1 Geothermal Resource Distribution Map [3]

Geothermal energy has the capability of being utilized for heating and cooling as well as generating electricity from geothermal power plants with the main constraint being the temperature of the geo-fluid. As illustrated in the resource map in Figure 1 the blue shaded areas are best suited for heating and cooling and other applications called direct use [2] while the red areas are better suited for power plants. Direct use was added as the application focus in the first course of the sequence.

Geothermal heat pumps can also be used for heating and cooling without the requirement of a geothermal resource present (the white areas of map) such as for direct use or power plants. The main constraints on developing geothermal heat pumps are economic and environmental. The costs can elevate in colder climates due to increased depth of the piping and development of the heat pump footprint. This information was integral in the decision to have the second course focus on geothermal heat pumps. As the energy costs continue to rise there is an increase in demand for heating and cooling systems based on geothermal heat pumps and a need for engineers with backgrounds in these areas to develop these systems.

Part of the interest in a geothermal course sequence was the increased presence of geothermal energy usage on the OIT campus. The OIT campus has had a geothermal direct use heating system in place since the late 1960’s. Currently all campus heating is geothermal and the cooling is from electrical chillers. This energy resource is provide by three production wells with a

temperature of 192 ºF and flow rate of 980 gpm in the southeast corner of the campus. These resources led to the establishment of the Geo-Heat Centre at OIT a centre of excellence that provides engineering support for geothermal on campus, geothermal research and geothermal resource development in the western US region. Most recently the campus has added a small scale low enthalpy power plant on campus (binary cycle) that generates 280 kW (installed capacity) of electrical power using the production wells, it is the first combined heat and power production plant in Oregon. The most recent project was the drilling of a 5300 foot deep well to provide a geothermal fluid for a larger power plant (1.75 MW installed capacity) that is in the development phase. With this strong presence of geothermal energy production and “working” labs it makes sense to add a strong course sequence in geothermal energy for the REE program. Renewable Energy Engineering in EducationMany of today’s students entering college are well aware of the energy issues that face both the US and the world. These students want to help solve these problems by choosing careers involved in energy especially renewable or alternative energy and are looking for college degrees and programs that focus in these areas. Although the area of renewable energy has a strong presence in graduate engineering programs it has been somewhat absent in undergraduate engineering. There are some two year technical programs that focus on installation and site support and some graduate programs that focus on research and development areas in renewable energy. But at the undergraduate level renewable energy engineering has been limited to some EE or ME programs offering a course or a track of two to four courses in renewable energy or electrical power systems but few focused BS degrees in renewable energy engineering.

The Renewable Energy Program began in 2005 as a Renewable Energy Systems program with a focus on science and technology of renewable energy systems (RES). In 2007 the program was redesigned as a Renewable Energy Engineering (REE) program after consulting with the RES industrial advisory board (IAB). The IAB suggestion was to provide a BS in Renewable Energy Engineering that would allow graduates to take a FE exam for PE licensure and still maintain the original program focus of applied engineering and systems engineering. The program team also saw an increased need for undergraduate RE engineers in areas such as applications, test, site analysis and selection as well as research and development support. The program is a blend of electrical, mechanical and civil engineering with a core focus of courses such as AC/DC Circuit Analysis, Electronic Devices, Solid State Devices, Control Systems, Statics, Thermodynamics, Heat Transfer, Fluid Mechanics and Programming. The main program goal is to provide graduates for careers in energy engineering with an emphasis on renewable energy integration and systems. This goal is accomplished through the RE core classes with required classes such as PV Systems, Fuel Cells and more, electives such as Solar Thermal, Bio-Fuels and Bio-Mass, Geothermal and more and a Senior Capstone Project.

A Senior Sequence (three courses) was recently added to the program to provide a specialized course in system design in target areas of renewable energy such as Power Systems, Energy Storage, Green Building Design and Geothermal Systems. This sequence is intended to insure that the four areas of renewable energy are covered with an emphasis on system design:

1. Generation: Generation of energy from the renewable source.2. Storage/Conversion: Storing or converting the renewable energy to a usable form.3. Integration/Design: The integration of the energy to the existing grid or building envelop for use.4. Use/Applications: End usage of energy for heating/cooling, transportation or electrical power.

The focus of this paper is on the Geothermal System sequence that was implemented in the 2011-12 academic year and is also offered again in this academic year. Not all sequences are offered every year due to resources and student interest.

GEOTHERMAL COURSE SEQUENCE

Initially the REE program had a single course in Geothermal Energy and Applications that intended to cover the basics of geothermal energy production and site analysis and development with an emphasis on the engineering. This course also presented an overview of various geothermal energy uses and applications such as direct use, geothermal heat pumps and geothermal power plants. This course had a prerequisite of thermodynamics, heat transfer and fluid dynamics to establish a good engineering foundation and background for topics in the course. To try to cover all the material in a single ten week course (quarter system) required that the applications be presented with breadth but not much depth. Feedback from students suggested that this was not adequate and more engineering and design depth was needed.

This led to the development of the current three term senior sequence course that is the topic of this paper. The sequence continues the focus on systems engineering and not a strong focus on the geology or sustainability of geothermal systems. The first course is a course in general geothermal energy and is very similar to the original single course. The second course covers geothermal heat pumps and the third course covers geothermal power plants. This sequence expands the coverage of geothermal uses and applications with a focus on the engineering design of such systems. The prerequisites still remain the same to provide the basic engineering foundation in thermodynamics, heat transfer and fluids. Details on the three courses are provided in the following sections.

First Course: Geothermal Energy and Direct UseThe first course covers the three main areas of geothermal energy and heat resources, basic applications (focus on direct use) and economic and environmental impacts of using geothermal energy as detailed in the following table below. The first portion of the course introduces the

geothermal heat resource and geologic features associated with it to provide an understanding of the benefits and constraints of the resource. Site exploration is covered for an understanding of how a site is selected for energy conversion with an emphasis on the engineering and data acquisition such as using geo-thermometers, seismic, resistivity and gravity surveys. Another area covered is the site preparation for drilling and heat extraction with a focus on drilling technology, platforms and environmental and economic impacts.

WEEK TOPICS1 Course Introduction, Thermodynamics Review, Geothermal Heat Generation2 Basic Applications (power generation, direct use, heat pumps), Geology, Tectonics3 Site Exploration(geological, geochemical, geophysical, surface)4 Test and Site Drilling, Platforms, Operation5 Energy Economics and Environmental Impacts6 Geothermal Resource Reservoir (basic models, requirement)7 Direct Use (heating/cooling, aquaculture, agriculture, industrial)8 Basic Systems (thermodynamic models, losses, piping, heat transfer)9 HVAC System Designs and Equipment, Geothermal Fluid Temperature Requirements10 Equipment (pumps, piping, heat exchangers, selection)11 Final Exam, Research Paper and/or Final Direct Use Project

The final portion presents an in depth look at direct use applications (shown in Table 2 on Direct Use in the US [3]) with a focus on heating and cooling (HVAC designs). System models and temperature requirements [2] are used to design basic systems using principles of heat transfer and losses. Basic HVAC equipment is covered such as pumps, piping, heat exchangers, chillers through system design and case studies. The other geothermal applications such as power plants and heat pumps are covered but not at much depth. This provides a good look at geothermal energy for the students just taking a single elective course in geothermal (not the whole sequence) with a focus on direct use space/district heating applications. The main heat exchanger for the OIT heating system is shown in Figure 2 below.

Table 2 Direct Use Applications in the US [3]

Use Installed Capacity

(MWt)

Annual Energy Use

(TJ/yr = 1012 J/yr)

Capacity Factor

Individual Space Heating

139.89 1,360.6 0.31

District Heating 75.10 773.2 0.33

Air Conditioning (Cooling)*

2.31 47.6 0.50

Greenhouse Heating 96.91 799.8 0.26

Fish Farming 141.95 3,074.0 0.69

Agricultural Drying ** 22.41 292.0 0.41

Industrial Process Heat ***

17.43 227.1 0.41

Snow Melting 2.53 20.0 0.25

Bathing and Swimming ****

112.93 2,557.5 0.72

Subtotal 611.46 9,151.8 0.48

Geothermal Heat Pumps

12,000.00 47,400 0.13

Total 12,611.46 56,551.8 0.12* Other than heat pumps; ** Includes drying or dehydration of grains, fruits

Figure 3. Plate Heat Exchanger in the OIT College Union [3]

Second Course: Geothermal Heat PumpsThe second course in the sequence presents a strong engineering design focus on geothermal heat pump applications. This course covers a topic of geothermal heating that is not as restricted to certain geographic areas and is increasing in usage in the US [4]. In this course heat pump fundamentals and operation is covered initially to develop a background in basic heat pumps with an emphasis on the thermodynamic cycles as shown in Figure 4. System operation, design and equipment selection is covered for different applications and uses (both residential and commercial). The prerequisite for this course is still thermodynamics, heat transfer and fluids and not the first sequence course (it would be helpful though). This allows this course to be used as a single elective for REE program students in heat pumps. The basic principles of geothermal energy from the first course are not required here so the course focus is on geothermal (ground source) heat pumps. After the basics of heat pump operation and design are covered the course presents coverage of the design and operation of traditional heat exchangers, down-hole heat exchangers (vertical and horizontal). Another area covered is HVAC building design using geothermal heat pumps with a focus on equipment, piping, pumps and heat exchangers. The main portion of the course covers the different types of heat pump systems with regards to design, operation, efficiency and impacts.

Figure 4 Heat Pump Operating in Heating Cycle [4]

The detail of course topics are given in the following table.WEEK TOPICS1 Course Overview, Heat Pump Fundamentals2 Heat Pump Fundamentals/Operation, Heat Pump Air Ventilator3 Select Heat Pumps, Requirements, Ground Coupling4 Closed Loop Vertical, Single Borehole Heat Exchanger (HEX)5 Design Multi-Borehole HEX6 Closed Loop Horizontal HEX, Earth Tubes7 Surface Water Heat Pump Systems8 Building Designs: Piping, Pumps, Hydronics9 Open Loop Groundwater Heat Pump Systems10 Project Design/Presentations11 Final Project

As in the first course the pedagogy is on system design and application with a final design project using heat pumps for heating a building.

Third Course: Geothermal Power PlantsThe final course in the senior sequence is about using geothermal energy to generate electrical power. The course begins with a background in geothermal power plants covering development, US/World distribution, basic types of plants and comparison to other traditional power plants [1]. The next section covers reservoir physics and simulation models for the geothermal resource. The coverage here is expanded from the first course to add mathematical models to the physical model presented in the earlier course as well as flashing, drawdown pressure, fluid flow and mass flow measurements and model adjustments.

The next area of the course covers the main types of power plants with a focus on energy conversion, thermodynamics, PH (Pressure/Enthalpy) and SH (Entropy/Enthalpy) models and diagrams in the engineering design and operation. Each plant type has a section on operation, equipment, layout, efficiency/losses and economic and environmental impacts. The main traditional high enthalpy plants such as dry steam, single flash and double flash are covered first [1] before moving on to low enthalpy power plants using a closed loop binary cycle (Figure 5, 6, 7). Binary cycle power plants are being utilized more and the course devotes more time to this type [5]. For this type coverage is added for the basic binary cycles (Organic Rankine and Kalina) and basic refrigerant selection. The course topic details are given in the following table:

WEEK TOPIC1 Course Overview, Geothermal Energy Review2 Geothermal Reservoir, Physical Models3 Reservoir Pressure Models, Drawdown Pressure, Flashing4 Dry Steam Power Plants (operation, conversion and design)5 Single Flash/Double Flash Power Plants (operation, conversion and design)6 Single Flash/Double Flash Power Plants (equipment, design, impacts)7 Binary Cycle Power Plants (Rankine/Kalina Cycles, operation and conversion)8 Binary Cycle Power Plants (equipment, design, closed loop, impacts)9 Binary Cycle Power Plants (case studies, project)10 Enhanced Geothermal Systems. Hybrid Systems11 Final Exam, Project, Research Paper As in the first course the pedagogy is on system design and application with a final design project using case studies of regions for different types of power plants and a research paper. Students are also given the project opportunity using a study of the small scale binary power plant on campus.

FIGURE 5. Binary Cycle Power Plant at the OIT Campus [3]

Figure 6 Binary Cycle Power Plant Building and Cooling Tower [3]

Figure 7 Binary Cycle Power Plant Block Diagram [5]

Other ActivitiesStudents have been involved in other courses, project and internships in areas related to geothermal energy. Many students have found part-time employment through the OIT campus Geo-Heat Centre working on the research data bases in the centre. Recently an elective course was offered for a group of students that competed in the National Renewable Energy Lab (NREL) geothermal site analysis competition for the Rio-Grande Rift zone in southern New Mexico. Another class was offered to students to develop a Geothermal HVAC System retrofit for a school district in Northern California. Some recent student projects include a senior project on design and test of a new type down-hole heat exchanger and a class project on the feasibility of solar thermal enhanced geo-fluids in power generation. The combination of the geothermal senior sequence, various geothermal class projects and special topic classes provide a strong program focus on geothermal energy for this new and unique program. RESULTS and CONCLUSIONS

Course OutcomesThe addition of this course sequence to the REE program has added an increase in design focus (program outcome C – System Design) and engineering problem solving (program outcome E) in the area of thermodynamics, heat transfer and fluid flow in a renewable energy system such as geothermal. This was accomplished with the increase in depth provided by the sequence over just breadth that was provided by the single course in geothermal systems. This sequence also provided a better system look at environmental and economic impacts of engineering solutions (program outcome H). This area is a strong focus in the course comparing geothermal environmental pollution and costs to traditional power generation systems and HVAC systems. The strong project focus of the course sequence allows the students to use HVAC analysis tools and data acquisition systems (program outcome K) in an engineering environment. The course

sequence is currently being used in the program assessment plan for outcomes H and K with more planned for the future.StudentsThe biggest impact of this course sequence has been observed in program students in course enrollments, student projects and internship opportunities. The course sequence was offered in academic year 2011-12 and currently in 2012-13. It currently has the highest enrollment with most planning on taking the full sequence (some students take one or two courses as electives. Student interest in geothermal projects has also increased with some special project courses such as a Geothermal HVAC project class that had three student teams working on developing proposals for a Geothermal HVAC retrofit of an older gas fired boiler system. The course had twenty students enroll for this project (we expected 10). A student project team participated in a NREL regional geothermal site assessment and placed well in the competition and received an invitation to a poster session at the annual GRC meeting. The course sequence is taught by REE program faculty and Geo-Heat Centre senior engineers that has introduced the students to the Geo-Heat Centre and has provided opportunities for internships in areas of geothermal energy and research. Students have been working internships in areas such as research databases, well testing, power plant support and geothermal heat pump surveys through the Geo-Heat Centre and other regional summer internships. FutureThe REE program is currently launching an MSREE program and the plan is to offer a track on Geothermal Energy that can be cross-listed with the undergraduate course sequence. Students will be able to use this sequence to build a foundation for on campus graduate level research and projects in geothermal energy systems. There is currently an undergraduate research project pending through an NSF grant to fund undergraduate research in geothermal power plant modeling and simulation and enhancing power production using a concentrated PV hybrid type of system. This project will fund a team of 8-10 students for a long term research project over a three year time frame. There is also interest from an engineering consulting firm to partner with OIT on the research part of the plant enhancement. Students in the course sequence will be given top priority for consideration and many have already expressed interest in the pending project. The relationship between the REE program and the Geo-Heat Centre will continue to grow and provide more unique opportunities in geothermal energy education for the REE stsudents.

REFERENCES:[1] DiPippo, Ronald; “Geothermal Power Plants”, Butterworth-Heinemann, 2nd Edition 2008

[2] Glassley, William; “Geothermal Energy: Renewable Energy and the Environment” , CRC Press, 2010

[3] Lund, John; Boyd, Tonya; Gawell, Karl; and Jennejohn, Dan; “The United States of America Country Update 2010” Geo-Heat Quarterly Bulletin 29/1 Oregon Institute of Technology, Klamath Falls, OR 2010.

[4] Lund, John; Sanner, B; Rybach, L; Curtis, R; and Helstrom, G.; “Geothermal (Ground Source) Heat Pumps – A World Overview” Geo-Heat Quarterly Bulletin 25/3 Oregon Institute of Technology, Klamath Falls, OR.

[5] DiPippo, Ronald; “Small Geothermal Power Plants: Design, Performance and Economics” Geo-Heat Quarterly Bulletin 20/2 Oregon Institute of Technology, Klamath Falls, OR.