Transcript The Smart Grid Enabling Energy Efficiency and Demand

The Smart Grid
Enabling Energy Efficiency and
Demand Response
Clark W. Gellings
Chapter 2: Electric Energy Efficiency in
Power Production & Delivery
Brevard Community College
ETP1400 Distributed Electrical Power
Generation and Storage
Bruce Hesher
433-5779
Acronyms
Note to students:
Chapter 2 is loaded with acronyms.
They are fair game for test questions!
Introduction
There is a lot of effort going into end user energy
efficiency, but what about the electric use efficiency of the
power plant itself and of the distribution network? A
measure of the efficiency of a power plant is the Btu input
needed for a given KWH output.
Power plant improvements
include methods to improve
overall efficiency.
Power delivery system
improvements include better
efficiency transformers, better
voltage control, and reactive
power control (power factor
correction on the source side)
Power Plant and Delivery System
Improvements
Condition monitoring and assessment uses sensors and
communications to monitor plant and grid performance.
Readings are compared to historic readings, theoretic
models, and comparable plant performance. Some power
plant operators subscribe to commercial databases that
enable them to track and compare results.
The objectives are to optimize performance and manage
maintenance.
Q: should the grid monitor the condition of power
plants in addition to the delivery system and react
accordingly?
Power Plant Electricity Use
Power plants use electricity to drive pumps, fans, and
conveyors. Motors are the largest use. 5-7% of the energy
generated by steam power plants (coal, biomass, gas, and
nuclear) is used on-site.
Hydro-power, Wind, and
photovoltaic power plant use less.
Pumps and fans must be adjusted
for loading and climate conditions.
Adjustable speed drive (ASD) motor
controllers are used to improve
efficiency. Controlling motors drives
requires monitoring and
communications.
Power Plant Lighting
Lighting efficacy is a measure of a lights output in lumens
divided by its energy input in watts (Lm/W). 683Lm/W is
the theoretic maximum or 100% efficiency level.
Most types of electric power plants are large facilities and
use a lot of lighting. Power plants benefit in multiple ways
by reducing their own power requirements:
• They can sell the power instead of using it.
• They can use less fuel to meet the demand.
• They produce less CO2 and other taxable pollutants.
Power Plant Space Conditioning and
Domestic Water Heating
There is a lot of energy in temperature. Making atoms
vibrate faster requires lots of energy.
Dense matter like water takes a proportionally larger
amount of energy. Water is 800 times denser than air.
While it requires less energy to heat air, space heating
still uses a lot of energy due to the larger surface areas
available to loose the heat/cool. Most space conditioning in
power plants is used to cool.
Building Infiltration
(outdoor air exchange)
A major cause of energy loss in space conditioning is due
to air entering or leaving a conditioned space. Infiltration
results from temperature and pressure differences.
While a sealed building with no
outside air exchange would be good
for heating and cooling costs, there
are standards for indoor air quality
that require some air exchange
between indoor and outdoor air.
Energy Audit
A professional energy auditor can examine and test your
homes heating and cooling systems, insulation, windows,
and etc. They test the AC ducts for leakage and the home
for places where heat penetrates in summer or is lost in
winter.
A blower door test uses
special fans to depressurize
the home and pressurize the
AC ducts to measure their
performance and locate
leaks.
see: www.energyconservatory.com
See Where Heat is Penetrating
Thermographic pictures or video are sometimes used by
energy auditors while a blower door test running. The
blower door helps exaggerate air leaking through defects in
the building shell.
Thermal cameras
are expensive.
They are a tool of
the trade for energy
auditors.
Attic and Exterior Wall Insulation
Most homes in Florida do not have enough
insulation. Inspect your attic. Fiberglass batting
that is the depth of a 2x4 truss has about R-15.
For R-30, run a second layer using care not to
block soffit vent air flow.
The DOE recommends that homes in zone
2 (Florida) have R-30 to R-60. Insulation
improves both heating and cooling costs!
Puncture the vapor barrier with a small
pointed object like a nail, placing holes 2-3
inches apart to prevent moisture build up
between layers.
Motors
Processes driven by electric motors typically consume
80% of the electricity used in electricity production.
Implementing electric adjustable speed drives (ASD) on
motors in power plants will improve their efficiency.
Adjustable speed drives or variable-speed drive (VSD)
are equipment used to control the speed of machinery.
Steam generator water feed pumps, fuel supply pumps,
cooling water pumps, and fan motors are all used in power
plants.
See http://en.wikipedia.org/wiki/Adjustable-speed_drive
EPRI Demonstrations
EPRI conducted research programs using ASD on the
auxiliary motors of electric generating stations. By using
modern electronic motor control to vary flow rates instead
of valves, better efficiencies are achieved. EPRI
conducted tests at the facilities of four utilities. They used
ASDs that employed various electronic devices including
Gate turn-off thyristors (GTOs) and Pulse Width
Modification (PWM) controller integrated circuits.
Two conclusions resulted:
• The potential for energy savings by controlling
process flow with motor speed is real.
• Reliability of large ASDs is not an issue.
See: TRIAC dimmer switch.
Efficiency in Power delivery p43
Transmission and distribution accounts for losses of about
7%. Transmitting electricity at high voltage reduces the
fraction of energy lost to resistance. For a given amount of
power, a higher voltage reduces the current and thus the
resistive losses in the conductor. Raising the voltage by a
factor of 10 reduces the current by a factor of 10 and
therefore the I2R (resistive) losses by a factor of 100.
At extreme high voltage (>2MV) coronal discharge losses
are large. Hollow conductors with large diameters and
stranded cables help reduce these losses.
As of 1980, the longest cost-effective distance for DC
electricity was 7,000 km (4,300 mi) (4,000 km (2,500 mi) for
AC), although all present transmission lines are
considerably shorter.
Power Factor Correction
In AC, reactances can cause losses due to the phase
mismatch between the power signal and the load. Many
large loads are inductive (motors). Electrical loads that are
not purely resistive, have a load impedance that is at a
phase angle. They do NOT consume more energy
because of it. They do however cause more current to be
cycled back and forth between the power source and the
load thereby causing greater losses in the system.
When the load is inductive
(motors), the current in the
circuit will lag the voltage.
Apparent Power
Work is done by the Real Power (Watts) but, the power
source and load cycle some power back and forth. This is
the Reactive Power (VAR). The power supply and wiring
must be large enough for the resulting Apparent Power (VA).
This large amount of energy transfer between the source
and load causes larger energy consumption.
The Power Factor
(PF) is the ratio of
W/VA or the cosine
of the phase angle.
note: This is why UPSs are rated in VA not Watts.
Reducing Power Factor Losses
If a capacitor with a reactance equal to the reactance of
the inductive load (motor) is place in series with the load,
the net reactance is 0! Calculating the size of the capacitor
is left to other courses or the manufacturer of the motorized
equipment. This topic is covered in EETC1025.
If the losses due to the energy cycled back
and forth are reduced, smaller gauge wire
can be used, less heat is created, equipment
can last longer, and energy is saved.
Power Factor Correction is typically only
done when there are a lot of inductive loads.
Conservation Voltage Reduction p43
Keeping tight voltage control also reduces power losses.
therefore, some utilities have implemented conservation
voltage reduction (CVR) techniques. If the voltage is
dropped the current also drops and the product of voltage
and current (power) drops a lot. Keeping the voltage on
the low end of the acceptable range saves power. CVR
factor is defined as the percentage in power reduction that
results form a 1% reduction in voltage.
Utilities often reduce the voltage during critical peak
periods (CPP). Sensitive loads such as computers may not
operate reliably with lower line voltages.
Distribution Transformer Efficiency
Developments in transformer technology can also save
power. There are 3 classes of transformers used in power
distribution:
• Low voltage, dry transformers up to 600V.
• Medium voltage dry transformers 601-34,500V.
• Liquid-immersed for voltages up to 2.5MVA.
Liquid filled transformers are the most efficient with
losses of only about 0.25%. Medium voltages have losses
of about 5% and Low voltage losses are about 2%.
Individual transformer losses are small, but with over 25
million installed transformers in the distribution grid they
constitute the largest total losses.
Transformer Losses
There are 2 types of significant losses in transformers:
Core losses result from magnetizing and de-magnetizing
the transformer core during normal operation. Amorphous
core transformers can reduce these losses by up to 80%
but are more expensive. But there higher cost is coming
down and wider adoption is expected.
Winding losses are due to the
resistance of the winding
material (copper or aluminum).
Newer more efficient
transformers use copper
windings.
Solid State Intelligent Universal
Transformers (IUT) p49
Act like power supplies for entire buildings providing the various
voltages and frequencies needed.
Energy Efficiency: The existing transmission systems supply more power
through the same wires.
Flexibility: Able to reliably deliver diverse power such as 400 Hz service,
DC service (for hybrid electrical systems) and three phase power from a
single phase line.
Power Quality: Sag correction and harmonic filtering can be built in to the
IUT.
Configurable: Because one device can be used in many configurations,
inventory, spare parts, and maintenance costs can be reduced.
Environmental Concerns: Contain no hazardous liquid dielectrics, such
as conventional transformers. The hazards and costs of spills and
cleanups will be avoided.
See: http://www.siliconpower.com/_Documents/IUT-Applications.pdf
Advanced Distributed Automation (ADA)
p50
The IUT is one component in a broader strategy called
ADA. Traditional Distributed Automation (DA) automates
control of basic distribution switching functions. ADA is
concerned with complete automation of all of the controllable
equipment and functions in the distribution system to improve
its strategic operation. Inoperability. communication, and
control to improve various aspects of the systems is the
intent.
Advanced Distribution Automation is a term coined by the
InteliGridsm project in North America to describe the
extension of intelligent control over electrical power grid
functions to the distribution level and beyond.
Conclusion p51
The smart grid as a concept must extend from power
production through delivery to end-use. Concepts of
functionality employing sensors, communications, and
computational ability can be effectively used to reduce
energy consumption, reduce emissions from power
production, and to improve reliability in the frontend of the
electricity value chain.