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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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