Post on 27-Oct-2018
Efficiency and Environmental Comparisons Combined Heat & Power (CHP) Separate Heat & Power (SHP)
Combined Heating & Cooling (CHC)
The enclosed information is provided to explain and illustrate some of the differences between Cogeneration and Trigeneration; Combined Heat & Power (CHP) and Separate Heat & Power (SHP); and to introduce Combined Heat & Cooling (CHC) as a (re)emerging technology for providing heat, power, and cooling in district energy systems. For these illustrations it is necessary to select a common fuel type for calculation and comparison of overall system efficiencies. Whereas natural gas is the fossil fuel of choice for many new base load grid power plants as well as distributed cogeneration plants it is the fuel selected for the comparisons herein. Although the figures for Stanford University energy loads and system comparisons are real, the comparisons of efficiency in the initial Examples are for simplicity based on balanced heat, power, and cooling loads. The Examples also represent overall average system performance and in reality heat, power, and cooling loads are rarely balanced and change regularly through the day and year. While these Examples can be used for indicative high level comparisons of efficiency and environmental performance of these technologies, specific calculations on much more discrete intervals (e.g. hourly loads) using actual equipment performance data will provide more accurate comparisons of any energy systems being compared. Nevertheless as the Examples indicate, for a wide range of heat & power loads in cogeneration settings; or heat, power, and cooling loads in trigeneration settings; the calculations suggest that the use of SHP with modest amounts of heat recovery and/or renewable power will quickly eclipse the overall efficiency and environmental performance of even the best 100% gas fired cogeneration systems. The comparative economics of the Example systems herein are dependent on site specific energy, capital, and O&M costs. At Stanford local economics favored SHP with Heat Recovery and Renewable Power, even with state mandates for 33% renewable power, due to the substantial amount of heat recovery possible. Substantial amounts of heat recovery and/or the use of ground source heat exchange may also be possible in many other district energy systems and yield surprising results when considering long term life cycle costs. For complimentary assistance in evaluating the potential for heat recovery in your system please contact: Joseph Stagner, P.E. Executive Director Department of Sustainability and Energy Management Stanford University 327 Bonair Siding Stanford, CA 94305-7255 650-721-1888 (work) jstagner@stanford.edu More information on SESI may be found at: http://sustainable.stanford.edu/sesi A copy of this document may be found at: http://sustainable.stanford.edu/sesi-technical
Introduction
Cogeneration: Heat & Power Combined Heat & Power
(CHP) Separate Heat & Power
(SHP)
POWER
HEAT
Steam Boiler or
Hot Water Generator
On-site or Off-site Power
Generation
Cogeneration Unit
POWER
HEAT
Trigeneration: Heat, Power, & Cooling
Steam Boiler or
Hot Water Generator
On-site or Off-site Power
Generation
Combined Heat & Power (CHP)
Separate Heat & Power (SHP)
COOLING
Steam or Electric
Powered Chillers
Cogeneration Unit
Steam or Electric
Powered Chillers
POWER
HEAT
Trigeneration: Heat, Power, & Cooling
On-site or Off-site Power
Generation
Combined Heat & Power (CHP)
Combined Heat & Cooling (CHC)
COOLING
Steam or Electric
Powered Chillers
Cogeneration Unit
Heat Recovery
Chiller
Efficiency (Natural Gas fuel basis)
Gas In
Gas In
Gas In POWER
HEAT
Steam Boiler or
Hot Water Generator
On-site or Off-site Power
Generation
Cogeneration Unit
POWER
HEAT
Steam Boiler or
Hot Water Generator
On-site or Off-site Power
Generation
COOLING
Steam or Electric
Powered Chillers
Cogeneration Unit
Steam or Electric
Powered Chillers
Gas In
Gas In
Gas In
Cogeneration Efficiency = Heat + Power Total Gas In
Trigeneration Efficiency =
Heat + Power + Cooling
Total Gas In
Combined Heat & Power (CHP)
Separate Heat & Power (SHP)
Note that for SHP the Total Gas In may be reduced by the use of Renewable power generation
Note that for SHP the Total Gas In may be reduced by the use of Renewable power generation
Example Energy Diagrams
Combined Heat & Power (CHP aka Cogeneration) Separate Heat & Power (SHP) Combined Heat & Cooling (CHC aka SHP + heat recovery)
Natural gas selected as comparative base fuel All figures based on gas High Heating Value (HHV) Example figures based on balanced electricity, heating, and cooling loads
…but conclusions hold for other typical district energy system load balances too
Respective line losses for delivery of gas and electricity from production sources to final point of use are excluded but may be included for your site if you know the centroid of the respective production sources serving you
Example Calculations- Perfectly Balanced Cogeneration Plant
Cogen unit Power out: 35,849 btu
(=10.50 kwh)
CHP Efficiency
Prime Mover (Cogen) Efficiency = [Useful H + P Work] / Gas In Trigeneration Efficiency = [Net useful H + P + C ] / Gas In
Example: Cogeneration work (usable CHP unit output) = 31,000 + 35,849 = 66,849 btu Trigeneration work (usable overall system output) = 31,000 + 31,000 + 31,000 = 93,000 btu If total gas in to CHP = 95,650 btu: • Prime Mover efficiency =
66,849/95,650 = 70%
• Trigeneration Efficiency = 93,000/95,650 = 97%
.55 kw/ton *2.58 ton hr = 1.42 kwh to chiller &
CT
31,000 btu waste heat
to chiller
35,846 btu to atmosphere (incl.
machine heat)
1.42 kwh
9.08 kwh
31,000 btu to hot water
POWER to Buildings 31,000 btu (=9.08 kwh)
HEAT to Buildings 31,000 btu
COOLING to Buildings 31,000 btu
(= 2.58 ton-hr) (70% prime mover
cogeneration unit; maximum efficiency using high
efficiency electric chillers and no steam chillers)
Example Calculations- Separate Heat & Power + Heat Recovery (without renewable power)
9,300 btu (30%)
waste heat to HRC
1.32 kw/ton * .77 ton-hr = 1.02 kwh to
heat recovery chiller
9.08 kwh
.99 kwh
SHP + HR Efficiency
Prime Mover (Grid Power Plant) Efficiency = Power Out / Gas In Trigeneration Efficiency = [Net useful H + P + C ] / Gas In
Example: Prime Mover work = 11.09 kwh * 3,413 btu/kwh = 37,850 btu Trigeneration work (usable overall system output) = 31,000 + 31,000 + 31,000 = 93,000 btu If gas to grid plant = 74,216 btu • Prime Mover efficiency =
37,850/74,216 = 51%
If total gas to system = 74,216 + 21,434 = 95,650 btu • Trigeneration Efficiency =
93,000/95,650 = 97%
.55 kw/ton *1.81 ton hr = .99 kwh to chiller & ct
25,079 btu to atmosphere
(incl. machine heat)
21,700 btu (70%)
waste heat to chiller
11.09 kwh = 37,850 btu @ 51% efficiency =
74,216 btu gas in to grid power plant
18,219 btu @85% efficiency = 21,434 btu gas in
to hot water generator
1.02 kwh
POWER to Buildings 31,000 btu (=9.08 kwh)
HEAT to Buildings 31,000 btu
COOLING to Buildings 31,000 btu
(= 2.58 ton-hr)
12,781 btu hot water (incl.
machine heat)
18,219 btu hot water
(Combined Heat & Cooling Plant with 30% Heat Recovery and 51%
Grid Gas Power Plant)
Example Calculations- Relative Trigeneration Efficiency (without renewable power)
Cogen unit Power out: 35,849 btu
(=10.50 kwh)
CHP Efficiency
Prime Mover (Cogen) Efficiency = [Useful H + P Work] / Gas In Trigeneration Efficiency = [Net useful H + P + C ] / Gas In
Example: Cogeneration work (usable CHP unit output) = 31,000 + 35,849 = 66,849 btu Trigeneration work (usable overall system output) = 31,000 + 31,000 + 31,000 = 93,000 btu If total gas in to CHP = 95,650 btu: • Prime Mover efficiency =
66,849/95,650 = 70%
• Trigeneration Efficiency = 93,000/95,650 = 97%
.55 kw/ton *2.58 ton hr = 1.42 kwh to chiller &
CT
31,000 btu waste heat
to chiller
35,846 btu to atmosphere (incl.
machine heat)
1.42 kwh
9.08 kwh
31,000 btu to hot water
POWER to Buildings 31,000 btu (=9.08 kwh)
HEAT to Buildings 31,000 btu
COOLING to Buildings 31,000 btu
(= 2.58 ton-hr)
12,781 btu hot water (incl.
machine heat)
18,219 btu hot water
9,300 btu (30%)
waste heat to HRC
1.32 kw/ton * .77 ton-hr = 1.02 kwh to
heat recovery chiller
9.08 kwh
SHP + HR Efficiency
Prime Mover (Grid Power Plant) Efficiency = Power Out / Gas In Trigeneration Efficiency = [Net useful H + P + C ] / Gas In
Example: Prime Mover work = 11.09 kwh * 3,413 btu/kwh = 37,850 btu Trigeneration work (usable overall system output) = 31,000 + 31,000 + 31,000 = 93,000 btu If gas to grid plant = 74,216 btu • Prime Mover efficiency =
37,850/74,216 = 51%
If total gas to system = 74,216 + 21,434 = 95,650 btu • Trigeneration Efficiency =
93,000/95,650 = 97% 11.09 kwh = 37,850 btu @ 51% efficiency =
74,216 btu gas in to grid power plant
18,219 btu @85% efficiency = 21,434 btu gas in
to hot water generator
.55 kw/ton *1.81 ton hr = .99 kwh to chiller & ct
25,079 btu to atmosphere
(incl. machine heat)
21,700 btu (70%)
waste heat to chiller
.99 kwh
1.02 kwh
9,300 btu (30%)
waste heat to HRC
1.32 kw/ton * .77 ton-hr = 1.02 kwh to
heat recovery chiller
9.08 kwh
.99 kwh
SHP + HR Efficiency
Prime Mover (Grid Power Plant) Efficiency = Power Out / Gas In Trigeneration Efficiency = [Net useful H + P + C ] / Gas In
Example: Prime Mover work = 11.09 kwh * 3,413 btu/kwh = 37,850 btu Trigeneration work (usable overall system output) = 31,000 + 31,000 + 31,000 = 93,000 btu If gas to grid plant = 74,216 btu • Prime Mover efficiency =
37,850/74,216 = 51%
If total gas to system = 74,216 + 21,434 = 95,650 btu • Trigeneration Efficiency =
93,000/95,650 = 97%
.55 kw/ton *1.81 ton hr = .99 kwh to chiller & ct
25,079 btu to atmosphere
(incl. machine heat)
21,700 btu (70%)
waste heat to chiller
11.09 kwh = 37,850 btu @ 51% efficiency =
74,216 btu gas in to grid power plant
18,219 btu @ 5% efficiency = 21,434 btu gas in
to hot water generator
1.02 kwh
POWER to Buildings 31,000 btu (=9.08 kwh)
HEAT to Buildings 31,000 btu
COOLING to Buildings 31,000 btu
(= 2.58 ton-hr)
12,781 btu hot water (incl.
machine heat)
18,219 btu hot water
If 33% power comes from renewables and 67% from a new 51% HHV efficient gas fueled grid power plant then total gas used to operate the system =
(74,216*.67) = 49,725 btu (power)
+ 21,434 btu (hot water generators)
= 71,159 btu gas in
Trigeneration Efficiency (gas basis) =
93,000/71,159 = 131%
(vs 97% for very high efficiency perfectly balanced and optimized cogen plant or SHP + HR alone ...34% less gas used, 34% less GHG, and lower water use)
See Comparative Trigeneration Efficiency chart for example comparisons of relative gas trigeneration efficiency for perfectly balanced CHP; SHP; and SHP plants with heat recovery and/or renewable power (example for balanced loads; all gas fuel source; and new equipment in all cases- calculations for each specific energy system are required based on local loads and equipment mixes)
Example Calculations- Relative Trigeneration Efficiency (with renewable power)
60%
80%
100%
120%
140%
160%
180%
200%
220%
60%
80%
100%
120%
140%
160%
180%
200%
220%
45% 50% 55% 60% 65% 70% 75%
Rela
tive
Nat
ural
Gas
Trig
ener
atio
n Ef
ficie
ncy
(HHV
)
Prime Mover Natural Gas Efficiency (HHV)(Cogen CHP unit or Grid Power Plant)
Relative Natural Gas Trigeneration Efficiency in District Energy Systems with both Heating & CoolingCombined Heat & Power (CHP) vs. Separate Heat & Power (SHP) vs. Combined Heat & Cooling (CHC) Systems
(Balanced Electricity, Heating, & Cooling Loads)
CHC 70%; 33% RE
CHC 30%; 30% RE
CHC 30%; 0% RE
SHP; 30% RE
SHP; 0% RE
CHP; 0% RE
Perfectly Balanced Cogeneration Plant
CHC = Combined Heat & Cooling (SHP with Heat Recovery)SHP = Separate Heat & Power (on-site boilers + grid power)CHP = Combined Heat & Power
Current Nominal New Grid Baseload Gas Power Plant Efficiency2
SHP
CHC with 30% Heat Recovery
Practical Maximum Efficiency of NewGrid Baseload Gas Power Plant?1
Current Average Existing CA Grid Gas Plant Efficiency1
70% minimum CHC + 33% minimum renewable power
1. ref: THERMAL EFFICIENCY OF GAS-FIRED GENERATION IN CALIFORNIA, Michael Nyberg, California Energy Commission, August 2011.2. ref: Oakley Generating Station, Ca, et. al.
Comparative Trigeneration Efficiency
Energy Diagrams- Stanford System
Energy System Options Considered
A. 100% Gas Fueled Options Business As Usual: Maintain Existing Cogeneration System Hygeneration: Maximum Efficiency Gas Fired Cogeneration using Internal
Combustion Engines with Partial Heat Recovery and Steam to Hot Water Conversion
B. Grid Electricity Options (shown with and without Renewable Power included) Separate Heat & Power and Steam to Hot Water Conversion Combined Heat & Cooling (CHC): SHP + Heat Recovery and Steam to Hot Water
Conversion CHC + Ground Source Heat Exchange (GSHE)
BAU- Cardinal Cogeneration
4,400,000 mmbtu
Electricity
Total = 2,643,775 mmbtu
248,983,788 kwh
Gas in
Cogeneration Efficiency (electricity + heating )
1,900,782 mmbtu 3,860,868 mmbtu
= 49.2%
849,782 mmbtu
Cogeneration Efficiency (electricity + heating)
2,643,775 mmbtu 4,400,000 mmbtu = 60.0%
Electric Chilling @ .66
kw/ton 31,285,190 kwh
Cogen Heating
Boiler Heating
Steam Chilling @
12.18 lb/ton
1,062,255 mmbtu
-105,943,244 kwh -361,584 mmbtu
254,000 mmbtu
-708,988 mmbtu
Gas saved
Gas in 169,856 mmbtu
New Grid Gas Power Plant Efficiency
361,584 mmbtu 708,988 mmbtu
= 51.0%
1,316,255 mmbtu
Waste heat to atmosphere
47,691,222 ton-hr
20,777,778 ton-hr
1,062,255 mmbtu
135,885 mmbtu
388,960,000 kwh
1,327,520 mmbtu
Waste heat to atmosphere
248,983,788 kwh -347,404 mmbtu
Waste heat to atmosphere
1,756,225 mmbtu 1,225,753 mmbtu
249,333 mmbtu
572,295 mmbtu 106,773 mmbtu
2,747,778 kwh 9,378 mmbtu
Waste heat to environment
(distribution line loss)
147,140 mmbtu
Total usable heat & power (cogeneration work) out =
1,900,782 mmbtu
Total usable heat, power, & chilling (trigeneration work) out
= 2,722,410 mmbtu
Trigeneration Efficiency (electricity + heating + cooling)
2,722,410 mmbtu 3,860,868 mmbtu
= 70.5%
Total usable heat out = 1,051,000 mmbtu
Total usable electricity out = 849,782 mmbtu
Total usable chilling out = 821,628 mmbtu
Total natural gas consumed @ 100% fossil power = 3,860,868 mmbtu
All figures based on gas
HHV
Hygeneration (IC) with Hot Water
2,564,378 mmbtu
HRC Chilling @ 1.51 kw/ton
HRC Heating
Electricity
Total = 1,830,966 mmbtu
18,659,174 kwh
248,983,788 kwh
Gas in
Trigeneration Efficiency (HW) (electricity + heating + cooling)
2,722,410 mmbtu 2,615,621 mmbtu
= 104.1%
849,782 mmbtu
Cogeneration Efficiency (electricity + heating)
1,830,966 mmbtu 2,564,378 mmbtu
= 71.4%
Electric Chilling @
.491 kw/ton 27,054,774 kwh
Cogen Heating
Boiler Heating
13,327,982 ton-hr
823,324 mmbtu
-446,499 kwh
-1,524 mmbtu
-2,988 mmbtu
Gas saved Gas in
54,231 mmbtu
Gas Power Plant Efficiency
1,524 mmbtu 2,988 mmbtu
= 51.0%
823,324 mmbtu
Waste heat to atmosphere
55,141,018 ton-hr
223,620 mmbtu
823,324mmbtu
46,096 mmbtu
295,236,427 kwh
1,007,642 mmbtu
5,207 mmbtu
248,983,788 kwh
Waste heat to atmosphere
0 mmbtu
Waste heat to atmosphere
-1,464 mmbtu
Waste heat to atmosphere
733,412 mmbtu 762,479 mmbtu
661,692 mmbtu 92,338 mmbtu
92,192 kwh
315 mmbtu
Heat Recovery
Chiller (COP = 5.66)
(1.51 kw/ton)
Waste heat to environment
(distribution line loss)
42,040 mmbtu
Cogeneration Efficiency (HW) (electricity + heating)
1,900,782 mmbtu 2,615,621 mmbtu
= 72.7%
Total usable heat & power (cogeneration work) out =
1,900,782 mmbtu
Total usable heat, power, & chilling (trigeneration work) out
= 2,722,410 mmbtu
Total usable heat out = 1,051,000 mmbtu
Total usable electricity out = 849,782 mmbtu
Total usable chilling out = 821,628 mmbtu
159,936 mmbtu
Total natural gas consumed = 2,615,621 mmbtu
All figures based on gas
HHV
Separate Heat & Power with Hot Water
1,900,623 mmtu
36.7 lb
969,318 mmbtu
Trigeneration Efficiency (HW) (electricity + heating + cooling)
= 85.4%
Electricity
Gas in
284,007,654 kwh
New Grid Gas Power Plant Efficiency
969,318 mmbtu 1,900,623 mmbtu
= 51.0%
68,469,000 ton-hr
1,093,040 mmbtu Boiler
Heating
32,837,786 kwh
1,285,929 mmtu
Gas in
Electric Chilling @
.4796 kw/ton
849,782 mmbtu
248,983,788 kwh 248,983,788 kwh
2,722,410 mmbtu 3,186,552 mmbtu
Waste heat to atmosphere
931,305 mmbtu
Waste heat to atmosphere
1,134,053 mmbtu
821,628 mmbtu 112,075 mmbtu
7,461 mmbtu 2,186,080 kwh
Waste heat to environment
(distribution line loss)
42,040 mmbtu
= 106.6% 2,722,410 mmbtu 2,553,011 mmbtu
‘Relative’ Gas Trigeneration Efficiency (HW) with 33% Renewable Electricity
(electricity + heating + cooling)
Total usable heat out = 1,051,000 mmbtu
Total usable electricity out = 849,782 mmbtu
Total usable chilling out = 821,628 mmbtu
Total usable heat & power (cogeneration work) out =
1,900,782 mmbtu
Total usable heat, power, & chilling (trigeneration work) out
= 2,722,410 mmbtu
Cogeneration Efficiency (HW) (electricity + heating)
= 59.7% 1,900,782 mmbtu 3,186,552 mmbtu
= 74.5% 1,900,782 mmbtu 2,553,011 mmbtu
‘Relative’ Gas Cogeneration Efficiency (HW) with 33% Renewable Electricity
(electricity + heating )
Total natural gas consumed @ 100% fossil power = 3,186,552 mmbtu;
2,553,011 mmbtu w 33% RPS
All figures based on gas
HHV
Combined Heat & Cooling (CHC) with Hot Water
2,151,012 mmtu
36.7 lb
1,097,016 mmbtu
Heat Recovery Chiller
(COP = 6.30) (1.327 kw/ton)
61,238,537 kwh
46,148,106 ton-hr
762,781 mmbtu
Cogeneration Efficiency (electricity + heating)
= 74.8%
Heating
Electricity
Gas in
321,422,769 kwh
Gas Power Plant Efficiency
1,097,016 mmbtu 2,151,012 mmbtu
= 51.0%
22,320,894 ton-hr
330,259 mmbtu Boiler
Heating
10,539,926 kwh
388,540 mmtu Gas in
HRC Chilling @ 1.327 kw/ton
Electric Chilling @
.4722 kw/ton
849,782 mmbtu
248,983,788 kwh 248,983,788 kwh
1,900,782 mmbtu 2,539,552 mmbtu
267,851 mmbtu 35,973 mmbtu
Waste heat to atmosphere
364,362mmbtu
Waste heat to atmosphere
1,053,996 mmbtu
660,518 kwh 2,254 mmbtu
Waste heat to environment
(distribution line loss)
42,040 mmbtu
= 104.3% 1,900,782 mmbtu 1,822,548 mmbtu
‘Relative’ Gas Cogeneration Efficiency with 33% Renewable Electricity
(electricity + heating)
Total usable heat out = 1,051,000 mmbtu
Total usable electricity out = 849,782 mmbtu
Total usable heat & power (cogeneration work) out =
1,900,782 mmbtu
553,777 mmbtu
Total usable chilling out = 821,628 mmbtu
Total usable heat, power, & chilling (trigeneration work) out
= 2,722,410 mmbtu
Trigeneration Efficiency (electricity + heating + cooling)
= 107.2% 2,722,410 mmbtu 2,539,552 mmbtu
= 149.4% 2,722,410 mmbtu 1,822,548 mmbtu
‘Relative’ Gas Trigeneration Efficiency with 33% Renewable Electricity (electricity + heating + cooling)
Total natural gas consumed @ 100% fossil power = 2,539,552 mmbtu;
1,822,548 mmbtu @ 33% RPS
All figures based on gas
HHV
Combined Heat & Cooling with GSHE and Hot Water
2,261,298 mmtu
36.7 lb
1,153,262 mmbtu
Heat Recovery Chiller
(COP = 6.30) (1.327 kw/ton)
87,215,445 kwh
65,045,550 ton-hr
1,075,138 mmbtu
Cogeneration Efficiency (HW) (electricity + heating)
= 83.3%
Heating
Electricity
Gas in
337,902,706 kwh
Gas Power Plant Efficiency
1,108,036 mmbtu 2,261,298 mmbtu
= 51.0%
3,423,450 ton-hr
17,902 mmbtu Boiler
Heating
1,673,040 kwh
21,061 mmtu
Gas in
HRC Chilling @ 1.327 kw/ton
Electric Chilling @
.4887 kw/ton
849,782 mmbtu
248,983,788 kwh 248,983,788 kwh
1,900,782 mmbtu 2,282,359 mmbtu
41,081 mmbtu 5,710 mmbtu
Waste heat to environment
53,129 mmbtu
Waste heat to atmosphere
1,105,084 mmbtu
30,433 kwh 104 mmbtu
Waste Heat to Open Loop Ground Source Heat
Exchange System instead of Cooling Towers
Heat Extracted from Open Loop Ground
Source Heat Exchange System
226,770 mmbtu
Waste heat to environment
(distribution line loss)
42,040 mmbtu
= 124.3% 1,900,782 mmbtu 1,528,593 mmbtu
‘Relative’ Gas Cogeneration Efficiency (HW) with 33% Renewable Electricity
(electricity + heating)
GSHE Pumps = 900,000 kwh
(3,072 mmbtu)
Trigeneration Efficiency (HW) (electricity + heating + cooling)
= 119.3% 2,722,410 mmbtu 2,282,359 mmbtu
= 178.1% 2,722,410 mmbtu 1,528,593 mmbtu
‘Relative’ Gas Trigeneration Efficiency (HW) with 33% Renewable Electricity
(electricity + heating + cooling)
Total usable heat & power (cogeneration work) out =
1,900,782 mmbtu
Total usable heat, power, & chilling (trigeneration work) out
= 2,722,410 mmbtu
Total usable heat out = 1,051,000 mmbtu
Total usable electricity out = 849,782 mmbtu
Total usable chilling out = 821,628 mmbtu
780,547 mmbtu
Total natural gas consumed @ 100% fossil power = 2,282,359 mmbtu;
1,528,593 @ 33% RPS
All figures based on gas
HHV
-
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
3,500,000
4,000,000
4,500,000
Cardinal Cogen Gas HW Generators &
Electric Chillers
Gas IC Engine Cogen + Heat
Recovery
Heat Recovery Heat Recovery + GSHE
Gas HW Generators &
Electric Chillers w 33% RPS
Heat Recovery w 33% RPS
Heat Recovery + GSHE w 33% RPS
mm
btu
Stanford Energy Supply OptionsNatural Gas Use (2020)