ASHRAE Journal - December 2019 - 43

SOLVING PROBLEMS

understand and deal with the variations of thermal load
to be able to get it right. It's the type of thermal load
(steam, hot water, etc.), the physical characteristics, the
temperature, as well as the seasonal variations, that all
need to be brought together."
If the plant will also provide cooling, designers
must know the cooling load too, said Sweetser. Once a
designer understands the loads, they can begin to look at
integrating renewables and how to optimize the system
and the CHP plant, he said.
Facility owners need to determine what is needed
to meet their resilience requirements, he said. Some
facilities must base decisions off life-safety issues and
economics.
Sweetser advised designers to consult with ASHRAE's
Combined Heat and Power Design Guide, and talk with
experts when designing CHP systems. Sweetser and
Foley developed the design guide for ASHRAE. Hedman
contributed to the guide.

Integrating Controls

Foley said opportunities exist to enhance CHP performance by, "leveraging modern controls to provide better
functionality at a relatively low cost. Systems are modeled and monitored to ensure that system performance
is able to be maintained through all possible operating
scenarios and seasons."
Today, a third-party controls company will probably
layer controls on top of existing controls systems when
CHP systems are coupled with PV, boilers, chillers, a diesel generator or other equipment, said Foley.
"Controls need to be expanded to account for the
interconnection of exportable renewable energy, metering of various outputs and integration of the technologies including avoidance of rapid voltage excursions,
etc.," said Foley. "There is going to be a lot to this, and it
really becomes a microgrid type approach rather than
simply adding two separate system controllers."
Foley said he believes this is one of the more signiﬁcant
areas for development.
"We probably need development of cost-effective
hybrid controllers to be more mainstream and embedded in the technology controllers as opposed to separate
items," he said.
He said controllers help CHP operations and can
reduce maintenance outages and extend operating
hours.

"CHP systems have more sensing equipment, which
can pull data every ﬁve seconds. Operators can then look
at that day to catch any red ﬂags, which can eliminate
the need for scheduled maintenance," Foley said. "It's
just using better technology, better sensors, better data
integration to manage maintenance much better, so that
I have longer run times at lower costs."

Looking Ahead

As the industry continues to integrate intermittent
renewable energy sources with CHP plants, the more it
will learn.
Further development of renewable natural gas and,
eventually, renewably generated hydrogen coupled with
CHP system's inherent efﬁciency and resilience beneﬁts,
bode well for this technology in the decarbonized energy
world of the future, said Sweetser.
"Leveraging information technology allows us to better
understand not only existing conditions, but also better
project future conditions so that we can provide the best
mix of resources with a wide variety of tools. This will
allow us to dial in maximum energy efﬁciency, maximum reliability or minimum emissions depending on
needs at that time," said Foley.
Sweetser recommends engineers and project developers look into the new U.S. DOE Packaged Combined
Heat and Power eCatalog (https://chp.ecatalog.lbl.
gov/). The eCatalog is a public, web-based platform
for users who want to learn about packaged CHP
systems. This online tool is designed to help remove
installation barriers, lower project costs and installation times and reduce some of the perceived risks of
installing CHP.
Anyone can use the tool to review standardized electrical
and thermal performance data for packaged CHP systems. DOE has conducted a comprehensive review of the
engineering and performance test data submitted by CHP
packagers. The review process assures users that recognized packagers have the engineering, design, assembly,
installation and service capabilities necessary to provide
packaged CHP systems that can be easily installed and
commissioned and that deliver stated performance.

References

1. Oak Ridge National Laboratory. 2013. "Combined Heat and
Power: Enabling Resilient Energy Infrastructure for Critical
Facilities." https://www.energy.gov/sites/prod/ﬁles/2013/11/f4/
chp_critical_facilities.pdf.
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ASHRAE JOURNAL

https://chp.ecatalog.lbl.gov/ https://chp.ecatalog.lbl.gov/ https://www.energy.gov/sites/prod/files/2013/11/f4/chp_critical_facilities.pdf https://www.energy.gov/sites/prod/files/2013/11/f4/chp_critical_facilities.pdf http://www.ashrae.org

ASHRAE Journal - December 2019

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