LBNL-50023
An Engineering-Economic Analysis of Combined Heat and Power
Technologies in a µGrid Application
Prepared for the
United States Environmental Protection Agency
Principal Authors
Owen Bailey, Boubékeur Ouaglal, Emily Bartholomew, Chris Marnay, and Norman Bourassa
Ernest Orlando Lawrence Berkeley National Laboratory
1 Cyclotron Road, MS 90-4000
Berkeley CA 94720-8061
29 March 2002
This work was supported by the Energy Supply and Industry Branch of the U.S. Environmental
Protection Agency, and prepared for the U. S. Department of Energy under Contract No. DE-AC03-
76SF00098. This work was also supported by the Edna Bailey Sussman Foundation.
An Engineering-Economic Analysis of Combined Heat and Power Technologies in a µGrid Application
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An Engineering-Economic Analysis of Combined Heat and Power Technologies in a µGrid Application
Table of Contents
Table of Contents .................................................................................................................................iii
List of Figures and Tables..................................................................................................................... v
Acronyms ............................................................................................................................................. vi
Acknowledgements .............................................................................................................................vii
Executive Summary ...........................................................................................................................viii
1. Purpose of Research ........................................................................................................................ 1
1.1 Objective .................................................................................................................................. 1
1.2 Method ..................................................................................................................................... 1
2. Background on µGrids and CHP Technology ................................................................................ 3
2.1 Introduction to µGrid Concept................................................................................................. 3
2.2 Introduction to CHP................................................................................................................. 4
2.3 End-Use Applications of CHP .................................................................................................7
2.4 Technologies for CHP.............................................................................................................. 8
2.4.1 Reciprocating Engines ................................................................................................... 9
2.4.2 Microturbines............................................................................................................... 10
2.4.3 Fuel Cells ..................................................................................................................... 11
2.4.4 Heat Exchangers .......................................................................................................... 14
2.5 Cooling Technologies ............................................................................................................ 14
2.5.1 Absorption Chillers...................................................................................................... 14
2.5.2 Desiccant Dehumidification......................................................................................... 15
3. Model of Combined Heat and Power............................................................................................ 17
3.1 DER-CAM review ................................................................................................................. 17
3.2 Methodology: Modeling CHP................................................................................................ 17
3.3 Mathematical Formulation..................................................................................................... 19
3.3.1 Parameters and Variables Defined for the CHP Model ............................................... 19
3.3.2 Objective Function....................................................................................................... 22
3.3.3 Constraints ................................................................................................................... 22
3.4 Data on CHP technologies ..................................................................................................... 24
3.4.1 Data for Generation and CHP Technologies ............................................................... 24
3.4.2 Absorption Cooling Technologies data ....................................................................... 25
3.5 Data on Thermal and Electrical Loads................................................................................... 27
3.5.1 Introduction.................................................................................................................. 27
3.5.2 Background .................................................................................................................. 28
3.5.3 Data Description and Preparation ................................................................................ 28
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An Engineering-Economic Analysis of Combined Heat and Power Technologies in a µGrid Application
3.5.4 Selection of Microgrid Oaks........................................................................................ 29
3.6 Assumptions of Model........................................................................................................... 36
3.7 Results of the Model .............................................................................................................. 38
3.8 Discussion of Results............................................................................................................. 42
3.9 Limitations of Analysis.......................................................................................................... 43
4. Conclusion..................................................................................................................................... 45
4.1 Summary of Research ............................................................................................................ 45
4.2 Future Work ........................................................................................................................... 46
References ........................................................................................................................................... 49
Appendix A: Mathematical Model...................................................................................................... 53
Introduction ..................................................................................................................................... 53
Model Description........................................................................................................................... 53
Additions to the Model.................................................................................................................... 54
Justification for Using GAMS......................................................................................................... 55
Mathematical Formulation .............................................................................................................. 56
Variables and Parameters Definition .......................................................................................... 56
Problem Formulation .................................................................................................................. 58
Appendix B: Energy Analysis of Microgrid Oaks .............................................................................. 61
Performance specifications for installed technology ...................................................................... 61
Input parameters.............................................................................................................................. 61
Assumptions.................................................................................................................................... 61
Constants ......................................................................................................................................... 61
Calculations..................................................................................................................................... 61
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An Engineering-Economic Analysis of Combined Heat and Power Technologies in a µGrid Application
List of Figures and Tables
Table 1: Results of DER-CAM CHP Model of µGrid............................................................................ ix
Figure 1: CHP versus Separate Heat and Power Energy Flows.............................................................. 6
Figure 2: Capstone Microturbine with an Attached CHP Unit ............................................................... 8
Table 2: Comparison of Fuel Cell Types ................................................................................................ 12
Figure 3: Single Effect Absorption Chiller ............................................................................................. 15
Figure 4: Energy flow of CHP System.................................................................................................... 18
Table 3: CHP Generation Technologies.................................................................................................. 25
Figure 5: Thermal Cooling Capacity ($/kW) versus Cooling Capacity for Absorption Chillers ........... 26
Figure 6: Thermal Cooling Capacity ($/kW) versus Cooling Capacity for Small Absorption Chillers . 26
Table 4: Description of Microgrid Oaks ................................................................................................. 30
Table 5: End Uses Recorded for Buildings in Microgrid Oaks .............................................................. 31
Figure 7: Microgrid Oaks January Weekend Electrical Load................................................................. 32
Figure 8: Microgrid Oaks July Weekday Electrical Load....................................................................... 32
Figure 9: Microgrid Oaks January Weekend Natural Gas Load (simulated data) .................................. 33
Figure 10: Microgrid Oaks July Weekday Natural Gas Load (simulated data)...................................... 33
Figure 11: Monthly Average Electrical Load for Microgrid Oaks ......................................................... 35
Figure 12: Monthly Average Gas Load for Microgrid Oaks .................................................................. 35
Table 6: Results of DER-CAM CHP Model of µGrid............................................................................ 38
Table 7: Electricity Generation for Microgrid Oaks, Results of “DER plus CHP” Scenario ................ 39
Figure 13: Electricity Loads for July Weekday ...................................................................................... 40
Figure 14: Electricity Load Supplied by Installed Capacity and Cooling Effect................................... 40
Figure 15: Heat Loads in January ........................................................................................................... 41
Figure 16: Heat Loads Supplied by NG purchases and CHP in January ................................................ 41
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