Development of the First Combined Heat and Power plant · PDF fileDevelopment of the First...

Development of the First Combined Heat and Power plant in the

Caribbean (CHP–District Energy)

April 7 - 9, 2015 Houston, Texas

Presented in the DistribuGen Conference & Trade

Show for Cogeneration/CHP 2015

Colombs

Energy

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This paper will be presented by: Alfredo Colombano from Colombs Energy, Bruce K. Colburn and Martin T. Anderson from EPS Capital Corp.

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CONSORCIO ENERGETICO PUNTA CANA MACAO (CEPM),

• Is a privately owned utility company engaged in generating, transmitting, and distributing electricity through two isolated integrated power systems serving the fast growing tourism-based Punta Cana-Bávaro and Bayahibe regions in the Dominican Republic.

• Serves 60 hotels with approximately 35,000 rooms in these tourist

destinations as well as approximately 17,000 commercial and residential customers.

• Company’s installed capacity is 90 MWe with Wartsila and Hyundai diesel engines operated using HFO.

• CEPM also supplies thermal energies (5,000 TR chilled water, hot water and steam), with sales of: • 700 GWhe/year of electric energy, • 44 GWhcw/year of chilled water, • 22 GWhdhw/year of domestic hot water.

CEPM Overview CEPM’s Facts

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District energy systems produce steam, hot water or chilled water at a central plant. The steam, hot water or chilled water is then piped underground to individual buildings for space heating, domestic hot water heating and air conditioning. As a result, individual buildings served by a district energy system don't need their own boilers or furnaces, chillers or air conditioners. The district energy system does that work for them, providing valuable benefits including:

What is a District Energy ?

Improved energy efficiency Enhanced environmental protection Fuel flexibility Ease of operation and maintenance Reliability Comfort and convenience for

customers Decreased life-cycle costs Decreased building capital costs Improved architectural design flexibility

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From: International District Energy Association (IDEA)

Energy - Efficiency Comparisons

From: International District Energy Association (IDEA)

5

10 MWe (40%) 8 MWe

2 MWe

5 MWcw

(1,421 RT)

Fuel Oil Energy HFO

25 MW (100%)

Chiller with

electric

compressor

Chilled Water production with Electric Chiller

(Without Cogeneration)

COP 2.5

6

8 MWe (40%)

5 MWcw 1,421 RT)

Fuel Oil Energy HFO 20 MW (100%)

20% of reduction

Absorption Chiiler

COP 0.71

Chilled Water Production with Absorption Chiller

(With Cogeneration)

7 MWth (35%)

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• As part of the expansion of CEPM’s services to an Energy Services Company (ESCO), our team developed the First CHP-District Energy system in the Caribbean.

• This system provides 5,000 TR of chilled water (using Absorption Chillers) and Domestic Hot Water (DHW) to Hotels located near to CEPM’s power plant.

• Waste heat comes from the exhaust gases and cooling water (Jacket water, Oil Cooler, Intercooler) of Wartsila Diesel Engines 18V32 Vasa (6 MWe each) that consume Heavy Fuel Oil (HFO).

• The distance from the power plant and the different Hotels is about 2.5 miles (4 kilometers), making the new hot water loop a viable installation process.

CEPM’s CHP-District Energy Project Overview

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• Cooling is provided by locally based absorption chillers and the heat exchanger used to produce DHW (Domestic Hot Water) for both cooling and domestic hot water were installed inside the hotels.

• The HTHW (High Temperature Hot Water) is produced in the power plant with a temperature of roughly 248ºF (120ºC).

• At the hotel this HTHW supplies the thermal energy to drive single stage absorption chiller units.

• The HTHW output after being used to provide chilled water via the absorption chillers is then connected to an additional set of heat exchangers to produce DHW, and the “spent” HTHW loop temp water is then sent back to the power plant with a temperature of +/- 158ºF (70ºC).

CEPM’s CHP-District Energy Project Overview (cont.)

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• In this way a large delta T 90ºF (50ºC) can be effected by using the single loop to serve two purposes, first high quality heat to run the absorbers, and second the lower temperature resulting water out of the chillers used for all or part of domestic hot water generation.

• The key goal and advantage of this project is to recover waste heat from the operation of the existing diesel engines with an electric efficiency of 39.5%, and produce thermal energy which used to be wasted away and instead reuse part of it from the exhaust gases to create new economic value.

• Only about 16% of the heat is recoverable due to limitations imposed by the dew point of the exhaust gases when HFO with 2.5 % Sulfur is used, about 25.2 % on the cooling water which is only recoverable to the level of about 9.1% , and the remainder is low temperature water used via cooling water to dump heat, with roughly an additional 3% by radiation to the surrounding area.


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• The sole reason the power company would consider this type of additional new investment is that their system MWe load has been growing about 5% per year, so redeploying some electrical load into thermal does not really hurt their business economically, and the lower resulting lower utility costs to the resort hotels provides an economic incentive to those resorts to continue dealing with the utility, which otherwise the resorts would not have to.

• All is economically done that benefits both the utility and the large resorts, to say nothing of helping control costs to the other local customers (more and more local businesses and homes are connecting to this grid, some having had their own small generator systems, or connected to an adjacent power source).


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• The overall approach utilized as a business case was to “take over” the operation and maintenance responsibility at the resorts for the chiller plants, including compressors, chilled water pumps, condenser water pumps, and cooling towers, as needed, and install new absorption chiller systems, and thermal heat recovery systems, so that in the end “chilled water, and domestic hot water heat” are being sold.

• The heating system was similar in that the existing boilers and pumps were taken over by the utility, so that burden was removed from the resorts. The actual system results are sold as “thermal KWH” to the owners.

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• The existing electric chillers are still used in summer peaking via electronic remote dispatch since there is insufficient heat through the loop for such peaks, but again, it is not relevant to the owner anymore since they buy delivered results. The paper will present the overall issues, and provide an overview of the results from this implementation process.

• It involved a few years of planning and budgeting, and securing written long term agreements from enough resorts to get the project rolling, with the rest presumed to come aboard as new loads once they could see the facility in long term operation, as has occurred in other district heating projects in Europe and the USA.

• The project was completed in 30 months and has been in operation now for 2 years.


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CHP-District Energy Building Blocks

Diesel Engine or Heat Source

• Heat balance

• Waste Heat Quality (Combustion Gases & Cooling Water Temperatures)

• Type of Fuel

Waste Heat Recovery Systems

• WHRU Gas & Water side Corrosion Issues

• Combustion Gases Dew point

• Load and Temperature Control

• Water/Water Heat Exchanger

Waste Heat Transmission &

Distribution Circuit

• High Temperature Hot Water Vs Steam

• Maximum pressures & Temperatures

• Circuit Pressurization

• Differential Temperature (Supply and Return)

• Variable Vs Constant Flow

• Electric Energy for Water Pumping

• Water Hammer & Pressure Surge

• Water Chemical Treatment

Chilled Water Plant

• Single –Stage Vs Double –Stage Absorption Chiller

• Electric Motor Driven Compressor Chiller

• Adsorption Chiller (future)

End Users

(Hotels)

• Thermal Load Hourly Profile

• Electric Load Hourly Profile

• Thermal Base load Vs Peak Load

• Thermal Energy Storage?

• Thermal energy Billing meter

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E - 1

Wartsila HT Cooling

System

LT Cooling System

LT Cooling System HT Cooling System

Condenser Water Cooling

Systems (Cooling Tower

TowerTech)

Electric Driven Chiller Water

Cooled

Chilled Water Systems

Absorption Chiller (Broad)

Schematic of CEPM CHP-District Energy (Cooling/DHW )

EX3

EX2

EX4

248 ºF (120 ºC)

Main Feeder Pumps

158 ºF (70 ºC)

Domestic Hot Water DHW

Chilled Water (CW)

Expansion Tank

176 ºF (80 ºC)

140 ºF (60 ºC)

44.6 ºF (7 ºC)

Electric Driven Chiller Air

Cooled

195.8ºF (91ºC)

122 ºF (50ºC)

COP = 0.70

Diesel Engine or

Heat Source

Waste Heat Recovery System

Chilled Water Plant



End Users

(Hotels)

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Data Collection and Analysis

Load Characterization

and Modeling

Chiller Plants Design

High Temp. Hot Water

System Design

Waste Heat Recovery System Design

Impact over the CEPM

Electric Load

Economic Power

Generation Dispatch

Available Waste Heat from CEPM

Power Generators

Project Main Activities

CAPEX and Cost of

Service for Thermal Energies

DHW Plants Design

Tariff Negotiation with Hotels

Optimization

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Radiation 455.7 kW (3.0%)

Low Temperature Cooling Water 2,450 kW (16.1%) (*) (50C/122F)

High Temperature Cooling Water 1,382 kW (9.1%) (*) (91 C/ 195F)

Exhaust Gases Waste Heat Recoverable 2,430 kW (16%) (**) 350 C/ 662 F)

Exhaust Gases Waste Heat Non Recoverable 2,430 kW (16%) 350 C/ 662 F)

Electric Energy 6,000 kWe (39.5%)

Exhaust Gases

4,860 kW (32%)

Cooling Water

3,832 kW (25.2%)

3,812 kW (25.2%)

Fuel Input HFO

15,190 kW

(100%)

Diesel Engine Energy Balance (HFO)

6,000 kWe (39.5%)

9,812 kW (64.7%)

Notes: (*) Depend on the configuration of charge air coolers (One-stage or two-stage charge air cooler (**) Depend on the outlet temperature of exhaust gases from waste heat recovery boiler, limited by the Dew Point of the combustion gases (Sulfur %)


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Radiation 455.7 kW (3.0%)

Low Temperature Cooling Water 2,450 kW (16.1%) (*) (50C/122F)

High Temperature Cooling Water 1,382 kW (9.1%) (*) (91 C/ 195F)

Exhaust Gases Waste Heat Recoverable 3,330 kW (21.9%) (**) 350 C/ 662 F)

Exhaust Gases Waste Heat Non Recoverable 1,530 kW (10%) 350 C/ 662 F)

Electric Energy 000 kWe (39.5%)

Exhaust Gases

4,860 kW (32%)

Cooling Water

3,832 kW (25.2%)

4,712 kW (31.0%)

Fuel Input

NG 15,190

kW (100%)

Diesel Engine Energy Balance (NG)

6,000 kWe (39.5%)

10,712 kW (70.5%)

Notes: (*) Depend on the configuration of charge air coolers (One-stage or two-stage charge air cooler)


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Waste Heat Recovery System Waste Heat

Recovery System

2,430 kWth (16%)

1,382 kWth (9%)

248ºF (120ºC)

170.6ºF (77ºC)

Diesel engine Wartsila 18V32 Vasa HFO

662ºF (350ºC)

329ºF (165ºC)

Fuel Oil Energy HFO 15,190 kW (100%)

Exhaust Gases HEX3

WHRU

HEX 2

All figures are indicative

6,000 kWe (39.4%)

195.8ºF (91ºC)

3,812 kWth (25%)

662.0

331.0

296.5

250.0

248.0

194.5 194.5

170.6

195.8 187.6

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

WHRU Hot end WHRU Cold end HEX2 Hot end HEX2 Cold end

Tem

pe

ratu

re º

F

Exhaust Gases Temperature WHRU Water Temperature

High Temp. Hot water Temperature HT Circuit Temperature to HEX2

HFO # 6 100 %

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Waste Heat Recovery Systems Temperature Profile Waste Heat

Recovery System

HT Cooling Water

This temperature is limited by the minimum metal temperature in the tube

This temperature is limited by the Flue Gases Dew Point temperature

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To avoid corrosion of the tubes, we must limit the outlet temperature of the exhaust gases recovery unit so that the temperature in the metal tube is not below the dew point exhaust gases, for example a sulfur content of 2.5% the curve indicates 93.3 C (200 F), while more will lower the temperature of the exhaust gases more heat is recovered but is limited by the dew point.

Minimum Design Tube Metal Temperature Waste Heat

Recovery System

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Minimum Design Tube Metal Temperature

Other literature indicates conservative values of the design temperature of tube metal. In this case to a sulfur content of 2.5% the curve indicates about 121.1 C (250 F), this fuel which take the value to adjust the water inlet temperature to the recovery unit, the temperature of the surface of the tube exposed to the exhaust gases tends to this value.

From: Steam 41th Edition The Babcock & Wilcox Company

Waste Heat Recovery System

HFO

Business Model Option 1 • Produce High Temperature Hot Water (HTHW) 248 ºF (120ºC) • Produce Chilled Water (CW) in power plant at CEPM 44.6 ºF

(7ºC) 5,000 TR • Distribute Chilled Water (CW) to the hotels This option seems more expensive, because the temperature differential is only 9ºF (5ºC), which implies a large flow circulating (13,333 GPM) in the distribution net work and therefore larger pipe diameters (Diameters 24 to 30 inches)

Chilled Water 44.6 -53.6ºF

(7 - 12ºC) 5,000 TR

17,585 kWr 13,333 GPM

Delta T = 9ºF (5ºC)

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High Temperature Hot Water (HTHW)

248 - 176ºF (120 - 80ºC) 25,121 kWte 2,381 GPM

Delta T = 72ºF (40ºC)

COP = 0.70



Business Model Option 2

• Produce High Temperature Hot Water (HTHW) 248ºF (120ºC) • Distribute High Temperature Hot Water 248ºF (120ºC) • Produce Chilled Water (CW) 44.6ºF (7ºC) in each hotel 5,000 TR • Produce Domestic Hot Water (DHW) 140 ºF (60ºC) in each

hotel This option seems less expensive, because the temperature differential is 72ºF (40ºC), which implies a small flow circulating (2,198 GPM) in the distribution net work and smaller pipe diameters (Diameters 14 to 16 inches)

This option also allows to supply Domestic Hot Water to the hotels

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High Temperature Hot Water (HTHW)

248 - 158ºF (120 - 70ºC)

31,402 kWte (include 6,280 kWte for DHW)

2,381 GPM Delta T = 90ºF (50ºC)

Chilled Water 44.6 -53.6ºF

(7 - 12ºC)

COP = 0.70

COP = 0.70

COP = 0.70



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Advantages of HTHW over steam heat distribution systems: • The amount of blow down required by a boiler depends on the amount

and nature of the makeup water supplied. HTHW systems have closed circuits, require little makeup, therefore, practically never require blow down whereas steam systems commonly lose about 1% to 3 percent of the total boiler output because frequent blow downs are required. Operation within closed circuits permits reducing the size of water treating systems to a minimum

• Due to the heat storage capacity of HTHW systems (large mass of water), short peak loads may be absorbed from the accumulated heat in the system.

• The closed recirculation system reduces transmission and thermal losses to a minimum while practically eliminating corrosion and scaling of generators, heat transfer equipment, and piping.

• Both supply and return high temperature water piping can be run up or down and at various levels to suit the physical conditions of structures and contours of the ground between buildings without the problems of trapping and pumping condensate

High Temperature Hot Water (HTHW) System Vs Steam System:

Chilled Water 1,000 kW (284 TR) (44.6ºF/7ºC)

COP = 3

Chilled Water Plant

Where

QC is the heat removed from the cold reservoir. W is the work or heat consumed by the heat pump.

Coefficient Of Performance (COP)

QC W Electric Motor Driven Centrifugal

Compressor Chiller

Electric Motor Driven Centrifugal

Compressor Chiller Energy Balance

Electric Energy 333 kWe

Cooling Water 1,333 kW

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High Temperature Hot Water 1,428 kW (248ºF/120ºC) (Minimum 208ºF/98ºC)



Single-Stage Hot Water

Absorption Chiller Energy Balance


COP = 0.7

Chilled Water Plant

Where



QC W Single-Stage Hot Water Absorption

Chiller

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Double-Stage Hot Water

Absorption Chiller Energy Balance

COP = 1.4

Chilled Water Plant

Where



QC W Double-Stage Hot Water Absorption

Chiller High Temperature Source 714 kW

(356ºF/180ºC)


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End Users

(Hotels) Cooling Monthly Profile

0

100

200

300

400

500

600

700

800

900

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CD

D (

ºF)

Punta Cana Cooling Degree Day CDD

The cooling load is highly correlated with the Cooling Degree Day CDD and in a hotel is also influenced by the room occupancy

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End Users

(Hotels) Cooling Load Vs. DHW Load Hourly Profile

As shown there are two peaks in demand for DHW (red line) one at 8:00 and one at 18:00, these peaks do not coincide with the peak cooling demand therefore HTHW demand that drives the absorption chiller; in order to exploit the maximum of the thermal energy from HTHW circuit that leaves the absorption chillers to heat the DHW, tanks are used to store thermal energy during off peak hours.

-

200

400

600

800

1,000

1,200

1,400

1,600

0:00

1:00

2:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:0

0

11:0

0

12:0

0

13:0

0

14:0

0

15:0

0

16:0

0

17:0

0

18:0

0

19:0

0

20:0

0

21:0

0

22:0

0

23:0

0

Load

kW

Day's Hours

Typical Hotel CW and DHW Load Profile

CW Load (kW) DHW Load (kW) HTHW for Abs Chiller

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Reduction of 25% of the electrical energy (kWh) consumed by the resorts versus the option of not cogeneration, this is because about these resort group consumed 34% of the electrical bill to produce chilled water before the district project energy was implemented. This implies that the utility consume 25% less fuel to supply electric power to these resort group and can delay the expansion of electrical transmission and distribution networks.

The base demand for chilled water of the resorts was covered by the new absorption chillers plus reuse of limited amount of existing peak cooling with the current older electric chillers.

All demand for domestic hot water was supplied to the resorts group by the district energy, therefore the fuel consumption in the domestic hot water boilers was reduced to zero. This is meaningful given that all were operated from Diesel or GLP, which is very expensive.

The results of this project to date can summarize as follows:

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The overall COP of the systems with pumps, fans, compressors before was about 2.7, and the overall system after around COP=15 in winter, and about 7 or so for 365 days (due to the reuse of the older electric chillers for peaking purposes). The business case required that the resort owners sign long term contracts to insure the new cogen system loop and appurtenance s could be appropriately amortized..

This project demonstrated that you can use waste energy to produce thermal energies (chilled water and domestic hot water) required in the resorts for the comfort of its customers, in such a way that both the resorts benefit through total cost reduction as compared to the previous all electric load case, and the utility wins through actually increasing net revenues in a cost effective way which helps to cement a long term relationship with large key customers. This then becomes truly a win-win situation for all, which is one of the avowed goals of any third party cogeneration project.

The results of this project to date can summarize as follows:

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Fuel Oil and Greenhouse Gas Emissions Reduction

With this cogeneration approach, about 25% of thermal energy is recovered to drive absorption chillers and DWH heat exchangers and reduce the Fuel consumption by 35,740 Bbl/year of HFO and 32,881 Bbl/year of LPG. The Greenhouse gas emission is reduced by over 28,872 metric tons CO2/year.

Greenhouse Gas emission reduction effects

Chilled Water ProductionAbsorption Chillers TR 5,000

Electric Chillers Displaced TR 5,000

Electric Chillers Displaced kWcw 17,585

Coefficient Of Performance (weighted) COP 6.0

Electric Power for Chillers Displaced kWe 2,931

Load Factor 0.95

Electric Energy for Chillers Displaced MWhe/year 24,390

GHG emission factor for HFO Power Generation tCO2/Mwhe 0.8084

Avoided CO2 emissions tCO2/year 19,716

Avoided Fuel Oil (HFO) Bbl/year 35,740

Domestic Hot Water ProductionDomestic Hot Water Production displaced from boiler kWdhw 6,280

Load Factor 0.50

Domestic Hot Water Production displaced from boiler MWhdhw/year 27,506

GHG emission factor for LPG tCO2/MWhdhw 0.3329

Avoided CO2 emissions tCO2/year 9,158

Avoided Fuel (LPG) Bbl/year 32,881

Total Avoided CO2 emissions tCO2/year 28,874

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Questions?

Alfredo Colombano BSIE, MBA, CEM, DGCP, REP Engineering Director Colombs Energy +1 281 686 2083 [email protected] [email protected] Bruce K. Colburn PhD., P.E., CEM, DGCP Project Energy Efficiency Engineer EPS Capital Corp. +1-610-525-4438 [email protected] Martin T. Anderson Energy Efficiency Engineering Manager EPS Capital Corp. +1-610-368-3703 [email protected]

mailto:[email protected]




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