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The cogeneration plant is really the
heart of our district energy system

and I think that an important thing
understand is that if we have

a hundred and fifty buildings that we're
serving,

there's maybe twelve thousand people on our
campus as the daytime population.

Normally, without the cogeneration
plant we'd need a

hundred and fifty boilers

and a hundred and fifty air-conditioning
systems.

With the central energy plant and
district energy I'm able to have

three boilers

and eight chillers

instead of one in each building.

There's three major pieces to the energy
complex. The furthest

is the cogen plant. That's where we make all our
steam and electricity.

The middle section is the chilled
water plant that's where we make

chilled water for the immediate

cooling needs of the campus.

And then the glass and stone building

was built as our

thermal storage plant.

The thermal storage plant is really
about

buying electricity when it's
inexpensive

and cooling the water that we use for
cooling the campus

and then delivering that water when the
value of electricity is quite high.

This is the thermal storage plant

that we have a variety of electric

and steam driven equipment

and large equipment and small equipment

and we value that tremendously, because
then we can pick the most optimal

piece of equipment on any given day

for the environmental conditions and the
campus demand.

The hot exhaust from the gas service
leaves this way. It's about 950 degrees Fahrenheit

It goes out through a catalytic converter
to absorb the carbon monoxide,

and then it turns this corner
and will go through this boiler

to capture the heat.

We take all the hot exhaust gas
and use that to turn water into steam

to heat the campus.

A typical central power plant might be

twenty-five to forty-five percent
efficient, but

by doing a cogeneration process we're
able to double that or even more.

If I put one unit of energy into the
gas turbine,

I get about one-third that unit of
energy out as useful electricity.

And about two-thirds comes out as hot
exhaust. So, by capturing that waste heat

or that exhaust heat,

now our overall process is

seventy and

can be as high as eighty-percent efficient.
The whole facilities engineering

department at Princeton

is working very hard on

reducing our environmental footprint.
Our new neuroscience laboratory is being

built to very very high energy
efficiency standards. Similarly, our new

chemistry laboratory, the Frick new
chemistry laboratory

is built with

very very high efficiency fume hoods and
they are used

only as much as they are needed

so in lots of ways we not only

improved the efficiency of our
production, but also reduce our

total use.

Over the twenty-five or thirty or even
hundred-year life

of some of our utility investments,

we save much much more than it costs us to
build the equipment

and our environmental footprint is much
much lower

by using district energy compared
to

distributed individual boilers and chillers.

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