| Benefits
Many
benefits to building owners for deploying CHP systems for buildings
include the following:
Reduced
energy costs
Building
owners can reduce their energy costs by deploying CHP systems
because compared to conventional systems these systems provide
the following advantages:
-
Increased energy efficiency
-
Reduced demand charge
-
Reduced peak electric energy costs
As
discussed in the section on Basics,
CHP systems can offer much higher energy efficiency than conventional
stand-alone equipment items for similar degree of power reliability,
comfort cooling, heating and indoor air quality. Because of the
higher energy efficiency of the CHP system, it consumes nearly
40% less fuel than conventional systems. The reduced fuel consumption
can significantly reduce energy costs.
The
cost of electricity to buildings is generally based on power demand
(measured in kW) and electric energy usage (measured in kWh).
The power demand charge is generally a monthly charge ($/kW) based
on the peak/maximum power used during a month for a specified
period, generally 15 minutes to 30 minutes. Power demand charge
rates can vary with time-of-year. CHP systems reduce power demand
in two ways: 1) by generating some of the power at site, and 2)
by using thermal energy from power generation equipment, instead
of electricity, for operating cooling, heating and/or humidity
control equipment.
The
charge for electric energy usage generally varies with the time-of-year
and the time-of-day. This charge is the highest during peak periods,
generally from 9AM until 3PM, and the least during off-peak period,
generally from midnight until 7AM. Therefore, primary reduction
in electric energy cost savings for using CHP systems comes from
avoiding purchase of electric energy during peak periods.
Reduced
life-cycle costs
Even
though the initial cost of CHP systems for buildings is higher
than purchasing all electric power needs and using conventional
chillers and boilers for cooling, humidity control and heating
needs, the life-cycle cost of the CHP systems is often lower because
of the energy cost savings over its useful life of more than 20
years.
Attractive
return on investment
As
discussed above, on an overall basis, CHP systems can reduce energy
costs for buildings. If the incremental installed cost of CHP
systems over conventional systems is treated as an investment,
and the annual savings in its energy costs are treated as the
return on that investment, the return can be very attractive.
Improved
power reliability
Economic
losses due to power outages in the U.S. have cost American businesses
billions of dollars. The following table shows the economic impact
of power outages on some industries.
| Industry |
Average
Cost of Power Outage,
$/hr |
Brokerage
Operations |
6,480,000 |
Credit
Card Operations |
2,580,000 |
Airline
Reservations |
90,000 |
Telephone
Ticket Sales |
72,000 |
Cellular
Communications |
41,000 |
Since
CHP systems generate power on-site or near-site, these systems
improve power reliability by either reducing or eliminating a
building's dependence on the electric power grid, and by providing
an additional power option to the building. Also, because CHP
systems are located at or near buildings, power outages experienced
because of losing a distribution line are improbable.
The
higher the number of buildings that use CHP systems, the lower
the demand on the electric grid will be. In areas where the grid
is at or near capacity, the reduced demand provided by CHP will
result in increased grid reliability.
Improved
economics for enhancing indoor air quality
Controlling
humidity of indoor air is an important aspect of enhancing indoor
air quality in building. It is important to keep humidity in the
indoor air to below 60% to prevent growth of mold, mildew and
bacteria.
Traditionally,
humidity reduction is accomplished using chillers that lower the
temperature of incoming air to below the dew point temperature
and condensing out the moisture and then sometimes reheating the
air to bring it back to a comfortable temperature. This approach
requires a lot more energy than using a desiccant system that
reduces humidity without reducing air temperature.
Desiccant
systems use a medium that directly removes the moisture from the
air and then uses low-energy heat to regenerate the medium so
that it can be reused. The heat available from the exhaust gases
of power generation equipment in the CHP system can be used to
regenerate the desiccant. Therefore, deployment of CHP systems
that incorporate desiccant systems, improve the economics of enhancing
indoor air quality.
Improved
environmental quality
Integrated systems for CHP for buildings improve efficiency of
energy utilization to as much as 85% compared to that of about
35% for conventional systems. Increased efficiency of energy utilization
decreases the amount of fossil fuel consumed per unit of energy
used and leads to 45% reduction in air emissions compared to conventional
centralized power plants.
Also
of increasing interest, is the relationship of indoor air quality
to our health. In order to prevent the growth of mold, mildew
and bacteria, it is important to keep humidity in the indoor air
to below 60%. CHP for buildings can help improve indoor air quality
by supporting the use of a desiccant dehumidification system to
dry the air. Desiccant systems use a material that directly removes
the moisture from the air then use heat, such as that provided
by the exhaust gases of the power generation equipment in the
CHP system, to regenerate the desiccant. This provides a very
energy efficient and cost effective method of dehumidifying indoor
air, rather that using an air conditioner to "over cool" the air
to remove humidity.
Reduced
energy consumption
As
discussed above, integrated systems for CHP for buildings increase
efficiency of energy utilization from 51% for conventional
power generation systems to as much as 85%. Therefore, the
use of these systems reduces the consumption of fossil fuels,
for a unit of energy required for a building, by about 40%
of that used by conventional systems. In other words, conventional
systems require 65% more energy than the integrated systems,
as shown in the diagram in the section on
basics. This is
important for prolonging the period of availability of our scarce
fossil fuel resources (natural gas, oil and coal) and reducing
our dependence on imported fuel and on nuclear energy.
Homeland
Security
Besides
the lost revenues, hazardous conditions, and inconveniences,
a major blackout, similar to that which occurred in August
2003 in the northeastern part of the U.S., represents a threat
to homeland security. High-voltage transmission centers and
large central power plants have already been identified as
vulnerable targets for terrorist attacks. Therefore, all systems
that reduce the potential for future major blackouts or reduce
the impact of such blackouts improve homeland security.
Since
overloading of grids is one of the primary reasons for major
blackouts, CHP systems improve homeland security because the
facilities that use CHP systems generate some power on-site
and thus, reduce the load on the electric power grid. Since
CHP systems also reduce our dependence on large-capacity central
generation plants, these systems improve homeland security
by reducing the impact if a large central power plant is shutdown.
In
the event of a major gird failure or the loss of a large capacity
central generating station, for any reason, including a terrorist
attack, CHP systems reduce the impact of such failures because
the facilities that use CHP systems can continue to operate
to the extent of their on-site generation capacity. For example,
during the August 2003 blackout, over 30 hospitals in the region
that use CHP systems were able to continue some level of routine
operations.
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