POWER February 2017 - 30

COMBINED HEAT AND POWER
6. Green steam. An extensive upgrade to the Kendall Cogeneration Station in Cambridge,
Mass., which began operations in 1949, has doubled its output to the regional district heating
system. Moreover, converting its once-through cooling system to an air-cooled condenser reduced
the plant's impact on metropolitan Boston's Charles River ecosystem. Source: POWER/
Gail Reitenbach
tions, hospitals, hotels, museums, and government
buildings throughout Boston and
Cambridge. But for many years, it was underutilized:
The plant was capable of supplying
substantially more steam than the
DH system used. There was also another
problem, an issue that wasn't recognized
when the plant was built but that began
drawing attention in the 1990s. The plant's
use of cooling water from the Charles River
was having an impact on the aquatic ecosystem,
as the warmer temperatures caused
by the cooling effluent were contributing to
toxic algae blooms. As a result, environmental
groups and the EPA began pressuring
the plant's owners to phase out its original
once-through cooling (OTC) system.
Veolia acquired the DH system in 2005
and began looking at an upgrade and expansion
project that would fully
leverage
that is sold to the local utility and heat process
water that is used on-site at the farm and
processing plant.
The options for this kind of " plug-andplay "
CHP are growing rapidly. Other companies
such as Dresser-Rand and Czech firm
Tedom are also offering turnkey, containerized
CHP systems in the hundreds-of-kilowatts
range. Most of these are engine-based
systems, but Hampson said microturbines
are seeing increasing use because of their
efficiency. For locations with access to solid
fuel, such as wood waste rather than biogas,
there are also solutions available. Entrade
and Spanner Re2 manufacture systems in
tens-of-kilowatt capacities that gasify and
combust wood pellets or chips to produce
heat and power.
Another growth area is wastewater treatment
plants, which Hampson said accounted
for the largest share of new CHP installations
by type of facility that ICF saw in 2015. " It's
been a major source of new capacity, " she
said. These projects are growing not just in
number but in size as well: The Marselisborg
Wastewater Treatment Plant in Aarhus, Denmark,
recently installed a biogas-powered
CHP system that not only makes the plant
fully self-powering but also allows it to supply
excess power and heat to the local grid
and DH network (see the item in this month's
Global Monitor).
Yet another trend is the use of landfill
30
gas (LFG). LFG has long been captured
and exploited for power on site, but recently,
developers of institutional CHP
projects have looked at building pipelines
to carry LFG to their facilities, rather than
relying on their utility's natural gas hookup.
(One example is the Duke University
project, which hopes to eventually transition
to biogas.)
District Heat: Everything Old Is
New
DH and CHP have long gone hand-in-hand,
with DH systems often set up to take steam
from a thermal plant supplying power to the
same area. Systems like these have often
been operating for many decades-there are
DH networks in the eastern and northeastern
U.S. that are more than 100 years old. Natural
gas-fired DH has drawn renewed interest
in recent years because of efficiency and environmental
advantages offered over fuel oil
(not to mention the cost advantages as gas
prices have fallen), but making the best use
of these aging systems can require some substantial
upgrades.
One such project was recently completed
by Veolia at the Kendall Cogeneration Station
in Cambridge, Mass. (Figure 6). The
256-MW, 7FA-based plant has supplied
power to the surrounding area since 1949,
and it currently supplies DH services to
more than 250 medical research instituwww.powermag.com
Kendall's
capacity while making the overall
system more efficient and environmentally
friendly. The first step was running a second
steam pipeline from Kendall (which was then
owned by GenOn) to Veolia's DH system.
That 7,000-foot extension, which came online
in 2013, doubled the amount of steam
it was able to take from Kendall. With the
upgrade, Veolia's 26-mile-long DH network
now gets 75% of its steam from the plant, reducing
reliance on smaller on-site boilers and
increasing overall efficiency.
When Veolia and its partner, I Squared
Capital, acquired Kendall in 2014, the second
phase began. That $112 million project, completed
in October 2016, replaced the old OTC
system with a new air-cooled condenser. Together,
the upgrades have reduced both air
pollution in the surrounding area and thermal
pollution in the river.
Boston is not the only eastern city to look
at upgrades to its DH system. Pittsburgh is
also in the midst of a multi-faceted project to
improve the efficiency and carbon footprint
of its downtown DH system, which is actually
two different networks in and around the
city center. NRG operates one of them, and
it has been tasked by the city with building
a third. The planned Uptown EcoInnovation
District will employ a modern steam
plant powered by Cleaver-Brooks boilers
and serve several major customers, including
the Consol Energy Center and the UPMC
Mercy medical center. The $61 million project
received approval from the city council in
September 2016 and is only one of four new
energy districts the city is looking at developing.
NRG is also looking at adding a new
combined cycle CHP plant to the DH network
it operates and helping develop a series
of CHP microgrids. ■
-Aaron Larson and Thomas W. Overton,
JD are POWER associate editors.
POWER | February 2017

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POWER February 2017

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