Embracing the Future: The Ball State University Geothermal Project

Abstract

Ball State University will convert its campus from a coal-fired and natural gas-fired district heating system to a closed loop heat pump chiller district heating and cooling system serviced by more than 4,100 geothermal boreholes. It will be largest district ground source geothermal system in the United States. On May 29, 2009, an article in the The New York Times called Ball State “a pioneering university” for undertaking the initiative. The installation will include an integral programme of research designed to inform the industry – especially the owners of 65,000 other district-heated buildings in the U.S. – how to significantly reduce the “first costs” and risks associated with intensive borehole drilling, piping, and looping. These issues are cited in a 2008 Department of Energy (DOE)-sponsored study as a major impediment to the more widespread adoption of geothermal systems. The planned research will incorporate 2D resistivity programming, geological surveys of the impact of high-density boreholes on ground temperature, assessment of the role of soil and water pH, evaluation of the influence of variable system water flow, analysis of hydrological data, and verification of the claims made by new geoexchange pipe manufacturers for dramatically increased thermal transfer (40–50%) and the concomitant reduction in the number of required expensive boreholes (20–35%) to service a load.

Appendices

Proof of Concept: Heat Pump Chillers with Geothermal Storage

Produced for Ball State University

Prepared by and Kirk T. Mescher, PE of

MEP Project No. B20.08. 01

January 28, 2009

Table of Contents

Introduction

The Concept

The Application

Conclusion

Appendix A: Heating and Cooling Loads

Appendix B: Flow Diagram

Appendix C: Borehole Design Report

Introduction

In today’s economic climate of high and rising fuel costs, many managers of large 24-hour facilities do well to examine new and creative ways to trim energy bills. One smart option is to examine the potential of a source that is already available, repurposing heat that is ordinarily discarded by the HVAC system’s condenser.

By utilizing heat pump chillers with geothermal storage instead of ordinary chillers, the temperature of this formerly waste heat can be increased until it is suitable for a wide variety of heating applications, and utilized when it is needed.

This report provides a proof of concept for heat pump chillers with geothermal storage. It will allow Ball State University to have an introductory understanding of this type of system, as well as some preliminary operational costs developed by Kirk Mescher of CM Engineering, in order for university personnel to evaluate the compatibility of this technology with their campus.

The Concept

Heat Pump Chillers

A compound centrifugal chiller is a special kind of centrifugal chiller that utilizes a combination of two (i.e. compound) compressors, instead of just one, and a component called an intercooler. The additional compressor and the intercooler allow the compound centrifugal chiller to produce condenser water at a much higher temperature than was previously possible with a standard centrifugal chiller. No longer fit only for rejection out of the cooling tower, this hot water, which can reach up to 150°F, is useful and can be utilized in a variety of heating applications that, until a few years ago, were the domain of boilers and heat pumps. Hence, this chiller is commonly called a heat pump chiller.

Although the advantages of this type of chiller are enormous, not every facility is a good fit, since not all facilities require simultaneous heating and cooling. Large facilities with 24-hour operation, such as hospitals, hotels, and universities, which have year-round demand for both heating and cooling, have tremendous potential to save energy. However, a careful examination of the loads throughout the year is prudent, in order to ensure that the heating and cooling produced by these chillers will be sufficiently utilized.

In addition, the second compressor can be turned off when the heating load is low. Although this will reduce the temperature of the condenser water leaving the chiller, it can be hot enough to meet the requirements of summer heating applications, such as reheat and domestic water, which typically do not require the high temperatures associated with winter heating. This will also allow the chillers to operate more efficiently, in the same way as a standard single compressor centrifugal chiller.

Geothermal Storage

Many facilities require simultaneous heating and cooling, but utilize only a fraction of its peak heating during the summer. In this case, a heat pump chiller can still offer tremendous benefits with the addition of a renewable technology called geothermal storage. This allows a facility to store the heat it produces in the summer and use it in the winter. This is achieved by heating the earth several hundred feet below the ground inwhat is called a loop field. This loop field is an area of land with several bores that are several hundred feet deep. Each bore houses u-shaped pipes that routes hot water and cold water down deep into the rock in the earth where it rejects or obtains load. This bedrock is an excellent thermal storage device. It can be charged with heating energy during the summer, hold this heat with minimal losses, and discharge it for utilization in the winter.

The Application

System Sizing

By examining the heating and cooling loads provided by university personnel (see Appendix A), a heat pump chiller plant with geothermal storage, including all distribution piping, was sized to meet the needs of the university’s campus. Calculated by CM Engineering, the estimated annual electrical consumption for this system will be 50 million kWh and the annual operating cost will be $2.1 million.

System Layout

Three locations are proposed for the new heat pump chillers: a new energy centre on the east side of the campus, and a new second energy center on the north side of the campus, and the third existing energy center on the south side of the campus. The new heat pump chillers can be connected directly to the existing chilled water piping system. A new hot water piping loop will need to be added to carry the hot water to the buildings. The source of the hot water, the three heat pump chiller plants, will be connected to this new hot water piping loop with branch pipes. Additional branch pipes will connect this loop to the destination of the hot water, the hot water side of the heat exchangers that currently use steam to provide hot water inside the buildings. For the buildings that do not have these heat exchangers, new air handling unit coils and terminal equipment will need to be installed, in order to accommodate the hot water. The current district heating and cooling system will remain in place and operational during the conversion.

A flow diagram of this system is shown in Appendix B. The system will provide 44°F chilled water throughout the year, and 150°F hot water in winter design conditions (with both compressors running). The hot water temperature will decrease proportionately with the outside air temperature, to a minimum of 110°F in summer design conditions (with one compressor running). This hot water will be used for domestic hot water and summer heating applications, which do not require the hotter 150°F water.

The hot water is circulated using variable frequency drive (VFD) pumps to the existing buildings until their immediate needs are met. If any heat is remaining, it is routed to a heat exchanger that deposits heat into the geothermal storage. This typically occurs during the summer. Conversely, during the winter, when an additional heat source is needed, heat is removed from the geothermal storage.

The specifics on the loop field are contained in Borehole Design Report in Appendix C. It is estimated that 3,750 bores will be needed. They will be 400 feet deep and 15 feet apart from each other. They will house two 1-inch u-bend pipes per bore. The grout thermal conductivity, which is a measure of how effectively the bedrock can hold heat, is estimated to be 0.84 Btu/hr·ft·°F.

Conclusion

It is clear that heat pump chillers with geothermal storage offer tremendous potential for energy savings for Ball State University. It is our hope that this report will offer some helpful information, as we continue to perform further analysis on this type of system to meet the heating and cooling needs of the campus.

Appendix A: Heating and Cooling Loads

Building Name	Address	Year Built	Area (ft2)	Heating Load (MBtuh)	Hot Water (gpm)	Cooling Load (tons)	Chilled Water (gpm)
Carmichael Hall	1701 W. McKinley	1967	22,963	574	38	58	138
Johnson Hall (JA Botsford-Swinford; JB Schmidt-Wilson)	1601 N. McKinley	1967	262,432	6,561	437	141	338
LaFollette Halls (Village Expansion)	1515 N. McKinley	1964	531,792	13,295	886	211	507
Lewellen Pool	1400 N. McKinley	1967	56,415	1,410	94		0
Health/Phys Activities Building	1740 W. Neely	1989	110,710	2,768	185	186	445
Irving Gymnasium	1700 W. Neely	1962	135,039	3,376	225	186	445
Worthen Arena		1990	193,267	4,832	322	448	1,075
Architecture	1212 N. McKinley	1970	146,750	3,669	245	333	799
Subtotals				36,484	2,432	1,562	3,748
Robert P. Bell Building	1211 N. McKinley	1982	106,500	2,663	178	141	338
David Letterman Building	1201 N. McKinley Ave	2005	86,351	2,159	144	128	307
Edmund F. Ball Building	1109 N. McKinley	1986	84,594	2,115	141	256	614
Arts and Journalism Building	1101 McKinley	2000	207,141	5,179	345	218	522
Bracken Library	1100 N. McKinley	1972	321,800	8,045	536	640	1,536
University Theatre	920 N. McKinley	1960	83,667	2,092	139	179	430
Teachers College Building	901 N. McKinley	1966	125,650	3,141	209	288	691
Noyer Hall	1601 W. Neely	1962	238,320	5,958	397	448	1,075
Woodworth Halls	1600 W. Riverside	1956	164,626	4,116	274	202	484
Pruis Hall	1000 N. McKinley	1971	18,170	454	30	128	307
Bracken House	2200 W. Berwyn Rd.	1937	13,227	331	22	19	46
Whitinger Business Building	1200 N. McKinley	1978	93,763	2,344	156	160	384
Studebaker Halls East	1301 W. Neely	1965	97,406	2,435	162	51	123
Studebaker Halls West	1401 W. Neely	1964	242,080	6,052	403	294	707
Park Hall	1550 Riverside	2006	194,600	4,865	324	282	676
Music Building	1810 W. Riverside	1956	45,036	1,126	75	83	200
Music Instruction Building	1809 W. Riverside	2003	86,179	2,154	144	179	430
Emens Auditorium	1800 W. Riverside	1963	82,101	2,053	137	243	584
Arts and Communication Bldg.	1701 W. Riverside	1957	47,010	1,175	78	83	200
Health Center	1500 W. Neely	1962	19,527	488	33	32	77
DeHority Halls	1500 W. Riverside	1960	138,140	3,454	230	205	492
North Residence Hall	1400 W. Neely	2008	190,480	4,762	317	230	553
Subtotals				67,159	4,477	4,490	10,775
North Quad	1901 W. Riverside	1926	126,543	3,164	211	294	707
Applied Technology	2000 W. Riverside	1948	93,274	2,332	155	205	492
Fine Arts Building	2021 W. Riverside	1935	74,085	1,852	123	198	476
Cooper Physical Sciences	2111 W. Riverside	1965	130,090	3,252	217	461	1,106
Cooper Nursing	2111 W. Riverside	1965	47,580	1,190	79	122	292
Cooper Life Sciences	2111 W. Riverside	1968	113,843	2,846	190	442	1,060
Ball Gymnasium	Campus Drive	1939	83,197	2,080	139	115	276
West Quad	2301 W. Riverside	1936	57,593	1,440	96	109	261
Lucina Hall	2120 W. University	1927	60,014	1,500	100	128	307
Burris School	2201 W. University	1928	130,745	3,269	218	250	599
Elliott Dining	2100 W. Gilbert	1990	13,228	331	22	45	108
Wagoner Halls	301 N. Talley	1957	75,680	1,892	126	13	31
Elliott Hall	401 N. Talley	1937	51,627	1,291	86	32	77
Administration Building	2000 W. University	1912	54,136	1,353	90	96	230
Student Center	2001 W. University	1951	171,165	4,279	285	410	983
Burkhardt Building	601 N. McKinley	1924	61,439	1,536	102	70	169
Subtotals				33,606	2,240	2,989	7,173
Central Chiller	West Campus Drive	1965	7,909	198	13
Field Sports Building	1720 W. Neely	1983	47,736	1,193	80		240
Greenhouses	Christy Woods	1965	4,381	110	7
Heating Plant	2331 W. Riverside	1924	18,685	467	31
South Service Bldg.	Campus Drive	1967	4,800	120	8		30
Expansion			300,000	7,500	500	640	1,500
Totals			5,873,486	144,749	9,650	9,680	23,196

Appendix B: Flow Diagram

(June 30, 2009 update: One-pipe distribution system has been changed to a two-pipe distribution system)

Appendix C: Borehole Design Report