District Energy / Second Quarter 2011 7© 2011 International District Energy Association. ALL RIGHTS RESERVED.

University Medical Center at

Princeton in New Jersey is a

leading teaching hospital and

acute care facility with a national repu-

tation for excellence. Established in

1919, it is a unit of Princeton HealthCare

System (PHCS) and is affiliated with the

University of Medicine and Dentistry

of New Jersey – Robert Wood Medical

School, The Cancer Institute of New

Healthy Success:Hospital energy system showcases best practicesGuy Molinari, PE, LEED AP, Senior Vice President, Concord Engineering Group; Thomas Batten, PE, Project Manager and Lead Mechanical Engineer, Concord Engineering Group

Feature Story

Jersey and The Children’s Hospital of

Philadelphia. Early in 2012, the hospital

is due to be replaced by a $447 mil-

lion new state-of-the-art facility, the

University Medical Center of Princeton

at Plainsboro (UMCPP), located just

2.5 miles from the center of Princeton.

Designed by a team of international-

ly renowned architects and consultants,

the new 636,000-sq-ft hospital will incor-

porate the latest green building technol-

ogies. Among its green features is an

efficient on-site central energy plant that

has the capacity to supply the facility

with 100 percent of its heating, cooling

and power. The project was developed

by NRG Thermal LLC, a wholly owned

subsidiary of Princeton-based NRG

Energy Inc., which will also own, operate

and maintain the plant. The planning

The University Medical Center of Princeton at Plainsboro is set within a 171-acre health campus that currently also includes medical offices and a skilled nursing and rehabilitation center; proposed other uses for the campus include pediatric outpatient treatment, adult and child daycare, senior independent living, assisted living, health and fitness, and a 32-acre public park.

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8 District Energy / Second Quarter 2011

and construction of this plant created an

innovative model for securing financial

support and operating campus energy

systems that can be replicated on similar

projects throughout the country.

Making Every Dollar Count In 2005, PHCS presented its plan

for the new UMCPP. It was an opportu-

nity to build a hospital from the ground

up with the most advanced medical ser-

vices, easy patient access and room for

future expansion. PHCS aimed to use

green building practices while incorpo-

rating a variety of environmentally

friendly and sustainable initiatives. To

accomplish this, the company decided

to outsource the financing, design, con-

struction, ownership, operation and

maintenance of its energy operations.

NRG Thermal was selected for the job.

After careful review and assess-

ment, NRG determined the new hospital

would benefit from its CHP+NRG® pack-

age, a combined cooling, heating and

power (CCHP) plant that supplies elec-

tricity while producing steam for heat-

ing and sterilization, and chilled water

for air conditioning. A long-term energy

services agreement established that

NRG would provide electric and thermal

energy to the hospital through a collat-

eralized investment. This forward-think-

ing outsourcing decision freed up capi-

tal that would otherwise be required to

finance the energy plant. The additional

capital would allow PHCS to invest in

what it knows best: delivering excep-

tional health care services.

Outsourcing the energy plant

freed up capital and allowed

PHCS to invest in what it knows

best: delivering exceptional

health care.

In executing a third-party design-

build-own-operate-and-maintain con-

cept, NRG sought the expertise of

Concord Engineering Group (CEG) of

Voorhees, N.J., for its engineering and

construction management services with

a specialization in power plant and dis-

trict energy plant projects.

As the plant’s engineer and con-

struction manager, CEG provided NRG

with a competitive construction man-

agement fee structure that, in combina-

tion with the hospital’s initiatives and

NRG’s expertise in financing, developing

and operating similar projects, served

as a catalyst to move the project for-

ward. The ability to integrate engineer-

ing and construction management from

a single firm as a single point of respon-

sibility was a significant factor in meet-

ing scheduling and cost constraints for

the $34 million design-build project.

This unique approach toward con-

struction of the CCHP plant, known as

NRG Princeton Energy Center LLC, has

been the key to its successful construc-

tion to date. All major equipment was

prepurchased and prepackaged for

delivery to the site, thereby minimizing

installation and maintenance costs as

well as accelerating the project sched-

ule. By integrating engineering, con-

struction and startup, NRG and CEG

were able to meet the project’s sched-

ule and budget. This arrangement

required that CEG share in the respon-

sibility of all project aspects. The NRG-

CEG partnership has resulted in lower

overall installation costs for NRG as the

owner-operator. The integrated

approach unified responsibility, elimi-

nated ‘finger pointing’ and minimized

change orders.

Alternative funding was another

component of the project’s economics

that made it feasible. A significant grant

from the local utility, Public Service

Electric & Gas, provided funding directly

to PHCS for energy efficiency upgrades

for the central plant and hospital HVAC

systems. The project also received com-

mitments for a $1.9 million Clean

Energy Solutions American Recovery

and Reinvestment Act Combined Heat

and Power Program grant administered

by the New Jersey Board of Public

Utilities and the New Jersey Economic

Development Authority (NJEDA), a

$3 million Clean Energy Solutions

Capital Investment (CESCI) Fund no-

interest direct loan and a $2 million

CESCI grant from the NJEDA.

According to Barry S. Rabner, PHCS

chief executive officer and president,

the CCHP plant will have an estimated

payback of less than five years with

annual savings of hundreds of thou-

sands of dollars.

Third-party outsourcing to NRG,

CEG’s construction management

approach and financial support through

grant programs have established a prov-

en best-practice model for executing

major capital construction projects.

Utilizing the Latest Technology NRG Princeton Energy Center will

use a 4.6 MW Solar® Mercury 50 gas tur-

bine matched to a supplemental-fired

heat recovery steam generator. For a

turbine of its size, the recuperated

Mercury 50 has the lowest emissions of

any prime mover and the lowest heat

rate compared to other turbines, with

an electrical efficiency exceeding 38 per-

cent. The high-temperature exhaust

available for energy recovery made it an

attractive choice to meet the needs of

the 150-psig steam distribution system

already designed by the hospital.

The natural gas turbine requires a

compressor system to boost the utility

gas pressure, which varies significantly

from winter to summer conditions. The

seasonal fluctuations presented an

opportunity for significant energy sav-

ings, since suction pressure has an

exponential effect on compressor brake

horsepower requirements. CEG worked

with the compressor vendor to develop

a controls strategy to minimize energy

consumption of the parasitic load,

which will contribute directly to the

plant’s generating capacity during peri-

ods when electrical demand is highest.

The result is a system that has

increased maintenance benefits and an

expected payback within two years.

A 1 million-gal thermal energy stor-

age (TES) system is another unique

aspect of the plant design that provides

substantial operating energy cost sav-

ings, capacity for future load growth

and useful operational flexibility.

Economies of scale associated with

large-capacity TES plants typically pro-

duce the most favorable economics.

© 2011 International District Energy Association. ALL RIGHTS RESERVED.

District Energy / Second Quarter 2011 9© 2011 International District Energy Association. ALL RIGHTS RESERVED.

This is especially relevant when installed

during new construction when capital

cost can be offset by capital savings

associated with downsizing convention-

al chiller plant capacity. However, in

order to meet the hospital’s require-

ments, the chiller plant capacity was not

reduced. The main benefit of TES in this

case is the ability to offset approximate-

ly one-third of the hospital’s total

demand in a congested area of the PJM

grid. During peak electric price periods,

cogenerated electricity sold to the grid

enhances TES system economics.

Another benefit is the tank’s ability to

flatten thermal and electrical demand

profiles, improving the overall perfor-

mance of CCHP when used with a

hybrid chiller plant.

By itself, the cost of constructing

the TES system yielded a simple pay-

back of 10 years, which fell within the

local utility’s 15-year maximum required

payback period and therefore was eligi-

ble for partial funding. If the capital

credit for the equivalent additional chiller

plant capacity provided by the TES sys-

tem is incorporated in the analysis, the

simple payback period drops to just

under three years.

Another plant design feature is the

use of a deaerator feedwater preheater.

Typically used in large utility power

plants, this unit could result in adverse

conditions such as coil steaming or

gas-side condensation when used in a

small system where there is a wide

range of steam production. Proper

selection of the unit was therefore

important to avoid these operational

issues and had to consider the actual

range of exhaust temperature and load

combinations. The preheater is

expected to provide an increase in

overall cycle efficiency of 2.5 percent

and will help achieve an annual cycle

efficiency greater than 65 percent

higher heating value (HHV), which

accounts for heat rate degradation over

time. The peak overall cycle efficiency

is expected to be above 77 percent

HHV (86 percent lower heating value)

with the heat recovery steam generator

fully fired.

One consideration in selecting the

power generation, boiler and chiller

plant equipment was the need to

accommodate future load growth. The

hospital had constructed the main

patient tower with the ability to expand

by two floors, which would increase the

total heating, cooling and electrical

loads by approximately 25 percent. The

plant was designed with the ability to

meet the future demand even with fail-

ure of major equipment such as a chill-

er or boiler. The resulting high initial

capital cost of meeting the redundancy

target placed further emphasis on ener-

gy efficiency to provide an economically

attractive project.

CEG and NRG evaluated several

other technologies, including direct-con-

tact heat recovery systems for the tur-

bine exhaust on the back end of the

heat recovery steam generator and

packaged backpressure steam turbines.

However, these technologies were not

The $34 million NRG Princeton Energy Center will be fully operational in 2012 when hospital construction is completed.

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10 District Energy / Second Quarter 2011 © 2011 International District Energy Association. ALL RIGHTS RESERVED.

found to yield an attractive payback for

this project. One important consider-

ation regarding the application of energy

conservation measures was coordina-

tion with the design and construction

schedule of the hospital and its utility

services. For example, evaluation of a

backpressure steam turbine would have

required increasing the distribution pip-

ing size throughout the hospital during

an advanced stage of construction and

would have had major schedule as well

as financial impacts on the project.

While specification of efficient

equipment across its load range is

important, control and operation of

each of the components in the context

of system performance is critical to

minimizing long-term energy costs. The

plant will use several coordinated layers

of energy optimization software for

control of the turbine generator and

chilled-water systems. First, a proprie-

tary dispatch software system will fore-

cast market volatility and electricity

prices at the local hub of grid operator

PJM ahead of the utility’s published

locational marginal pricing based on

weather, fuel costs, market behavior

and historical data. The system will also

model all thermal and power loads on

both a 24-hour and seven-day day hori-

zon. In real time, the system uses an

adaptive model mapping load and mar-

ket system outputs to make recommen-

dations for operation of major equip-

ment to maximize the economic benefit,

including the charging and discharging

rates of the system TES tank, operation

of the hybrid electric and steam-fired

chillers, and turbine operation while

avoiding ‘short cycling’ of equipment.

The ‘demand shift’ ability of the TES

allows flexibility in targeting the highest

electrical export prices, resulting in

atypical operation when compared to

conventional cost-avoidance strategies.

In this way, the TES tank enhances the

site’s ability to export electricity,

increasing the project’s economic merit.

The second layer of programming

will include chiller plant optimization

software based on the overall energy

partitioning of the dispatch software.

The ‘wire-to-water’ control algorithms

automatically modulate the chilled-

water pumps, condenser water pumps

and cooling tower fans to maintain a

minimum kilowatt-per-ton ratio based

on site load, temperature differential

and outdoor air enthalpy. Variable-

speed chillers were selected because of

their ability to perform efficiently at

lower condenser water temperatures, a

condition that will occur frequently

when the TES tank is charged at night.

CEG selected chilled-water control

valves for each of the hospital’s air-

handling units to achieve a site chilled-

water temperature differential of 18

degrees F, which minimizes pumping

horsepower. This high temperature dif-

ferential is particularly critical and

most difficult to achieve in off-peak

conditions where the equipment will

operate for more than 95 percent of

the year.

The CHP+NRG system provides

multiple layers of redundancy in

power provision.

The CCHP design enhances power

reliability by supplying electricity from

four independent sources. Most hospi-

tals are powered only through a main

utility grid and backup generators that

service crucial areas. The CHP+NRG

system provides multiple layers of

redundancy in power provision – first

System Snapshot: NRG Energy Center Princeton

System Owner and Operator: NRG Thermal LLC

Location: University Medical Center of Princeton at Plainsboro, N.J.

Steam/Combined Heat and Power System Chilled-Water System

Startup Year Full operation begins in 2012 (steam service for construction heating Full operation begins in 2012 (chilled-water service

began in 2010, full service to hospital begins 2012) was available in late 2010, full service to hospital

begins 2012)

Total Square Footage Served 636,000 sq ft 636,000 sq ft

Plant Type Combined cooling, heating and power (CHP+NRG®); Variable-speed chillers and distribution with Solar Mercury 50 gas turbine with heat recovery steam generator and 1 million-gal chilled-water thermal energy conventional boiler plant storage and advanced ‘wire-to-water’ control

Plant Capacity 50,000 lb/hr steam, 4.6 MW electricity, 3,000 tons chilled water, 10,000 ton-hr TES

6 MW emergency diesel generators

Number of Boilers/Chillers 3 3

Fuel Types Natural gas, fuel oil Electric, steam

Distribution Network Length Approx. 3,000 ft Approx. 3,000 ft

Piping Type Insulated carbon steel Insulated carbon steel, ductile iron direct-buried to TES

Piping Diameter Range Up to 10 inches Up to 18 inches

System Pressure 150 psig N/A

System Temperatures 366 F steam, 200 F condensate 40 F supply/58 F return

Source: Concord Engineering Group

District Energy / Second Quarter 2011 11© 2011 International District Energy Association. ALL RIGHTS RESERVED.

from the on-site gas turbine, backed by two independent,

full-capacity power feeders from the grid, with an additional

source of power available from three 2 MW diesel generators.

The turbine, which has black start capability, can provide

redundancy even without the continued use of the diesel

generators. “The hospital will literally be a powerhouse,” says

CEO Rabner of PHCS.

The environmental benefits of the plant are substantial,

eliminating 18.1 million lb of annual carbon emissions.

According to Bob Henry, NRG senior vice president of business

operations, “Efficiency is the key. We’ll get about 70 to 73 percent

versus 30 to 35 percent from a traditional power plant. Every

source of energy is used to the extent possible, which benefits

both the hospital and the environment.”

New Jersey officials, including the state Board of Public

Utilities, have welcomed the new CCHP plant and its clean

technology benefits, in line with the state’s commitment to

reduce emissions and increase energy efficiency by 2020.

Plainsboro Mayor Peter Cantu says the plant will set a new

higher energy efficiency standard for local developers. The

New Jersey Hospital Association also applauds the plant as a

model for hospitals seeking to improve operational efficiency.

NRG Energy Center Princeton is expected to be fully func-

tioning in 2012 when the construction of the six-story hospital

is complete. The plant is already delivering steam and chilled

water for construction heating and cooling.

If you feel you have what it takes to be part of a great team, please visit us on-line for full details and to apply:

The City of Surrey, British Columbia, Canada is a place of innovative transformation and accelerated growth—where the future is limitless and possibilities are endless. If you are excited about helping to build the city of tomorrow—and you share our values of integrity, service, teamwork, innovation and community—join us today.

Energy Manager In this newly created position, you will champion energy strategies and projects to support our efforts to achieve our

clean energy vision and goals. You will lead the City’s District Energy initiatives, including the implemen-tation of the City’s first district energy system, which is focused on meeting the needs of civic facilities under construction in our City Centre.

Outsourcing its energy center allows PHCS to focus on its

core mission of providing health care while delivering a cost-

effective operation that benefits the surrounding community

and the environment. As CEG President Michael Fischette

concludes, “Creative third-party financing partnerships and

innovative engineer/procure/construct solutions eliminate bar-

riers for large-scale facilities interested in reducing costs while

fostering environmental stewardship.”

Guy Molinari, PE, LEED AP is senior vice president of Concord Engineering Group and director of operations for the engineering, commissioning, construction management and design-build sectors. Molinari has more than 30 years’ project management experience with industrial, commercial

and power generation projects. Currently he is senior engineering and construction manager for the central utility plant and cogeneration project at the University Medical Center of Princeton at Plainsboro, N.J. Molinari can be contacted at gmolinari@ceg-inc.net.

Tom Batten, PE, is project manager and lead mechanical engineer, Concord Engineering Group. Batten has directed interdisciplinary teams through all phases of master planning, design, construction and operational startup of cogeneration and central utility plant projects. He possesses

extensive plan and specification and design-build experience in the fields of institutional and commercial heating, cooling and power generation. His email address is tbatten@ceg-inc.net.

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