ASHRAE Journal - December 2019 - 40

SOLVING PROBLEMS

Efforts are underway to convert the natural gas infrastructure over time to renewable natural gas (RNG)† to
support significant long-term carbon. CHP has long
used digester and biogas as fuel sources, and CHP systems deployed today can readily operate on increasing
percentages of RNG over time. A variety of engine and
gas turbine manufacturers are testing and operating
CHP systems on high percentage hydrogen fuels in
preparation for increasing use of RNG and hydrogen
fuels in the future.
"Off-peak generation of hydrogen from renewable
energy sources provides a strategic benefit to the electric grid and a future zero carbon source of fuel for CHP
plants," Sweetser said.

Resilient Power and Stabilizing the Grid

As a distributed energy resource, CHP systems can
keep the lights-and heating and cooling-on during
extended grid outages. A CHP system that runs every day
and saves money on a continuous basis is more reliable
in an emergency than a backup generator system that
only runs during emergencies, according to Hedman.
He said there are numerous examples of hospitals, university dorms and other critical facilities that remained
fully operational during Superstorm Sandy because of
their CHP systems, while the utility grid was down for
days and, in some areas, weeks.1 On-site CHP systems
provided continuous power and heat to facilities such as
South Oaks Hospital in Amityville, N.Y., and Princeton
University in New Jersey (see sidebar, Working with the
Local Utility to Achieve Resiliency), allowing them to maintain critical services and, in many cases, provide refuge
and support to the surrounding community. In contrast,
back-up generators failed at NYU Langone Medical
Center and Bellevue Hospital, forcing both hospitals to
evacuate patients to other medical centers. During the
Northeast blackout in 2003, half of New York City's 58
hospitals suffered backup generator failures. The New
York State Energy Research and Development Authority
(NYSERDA) surveyed 24 CHP sites located in areas
affected by Sandy, and found every facility in which the
CHP system was designed to operate during a grid outage maintained power and services during the storm.

†Renewable

Working with the Local Utility
To Achieve Resiliency

Princeton University: Princeton, N.J.-Princeton's microgrid is a
gas turbine CHP system capable of producing 15 MW.
The CHP system is a chiller and thermal energy storage plant and was installed and commissioned in
1996. The CHP plant normally operates connected
with the local utility. The university built the CHP
plant to reduce life-cycle costs, operate at a lower carbon footprint and increase reliability.
Event: Superstorm Sandy: Oct. 29, 2012
Hurricane Sandy knocked out power in Princeton's
immediate area late at night. The University was dark
for about 20 minutes, and the local utility restored
power long enough for Princeton to restart its gas
turbine. The CHP plant operated in island mode until
shortly before midnight on Oct. 31 when the university reconnected to the main grid. Princeton and the
local utility coordinated how much the university
would receive from the grid as the grid stabilized and
returned to operation.
Throughout the event, Princeton's critical research
projects and computing services continued uninterrupted by the storm.
Each distributed energy resource technology offers different capabilities and performance characteristics in
relation to resilience.
The combination of a controllable source of generation, such as CHP and energy storage, along with
the integration of other variable distributed energy
resources is most likely to deliver an optimal source of
resilient power for an individual facility with the lowest
carbon footprint" said Sweetser.
"Having a CHP plant with sufficient capacity working
in conjunction with renewable energy integrated with
the grid will provide an additional layer of resilience,
which can have minimal cost impact as long as this is
designed into the system at the start. There are many
considerations to providing resilience with any on-site
power system whether it is CHP or renewable energy,"
said Foley.

natural gas (RNG) is a term used to describe biogas, or gas resulting from the decomposition of organic matter under
anaerobic conditions that has been upgraded for use in place of fossil natural gas. The principal constituents are methane and carbon
dioxide. The biogas used to produce RNG comes from a variety of sources, including municipal solid waste landfills, digesters at water
resource recovery facilities (wastewater treatment plants), livestock farms, food production facilities, organic waste management operations, or gasification.

ASHRAE JOURNAL

ashrae.org

D E C E M B E R 2 0 19

https://www.ashrae.org/

ASHRAE Journal - December 2019

Table of Contents for the Digital Edition of ASHRAE Journal - December 2019