Transcript Ensuring Reliable Electricity Supplies Using Distributed Generation

Ensuring Reliable Electricity Supplies
Using Distributed Generation
Gregory Tress
Carnegie Mellon University
Overview
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Introduction
The Power Grid
Power Disruptions
Infrastructure Issues
Distributed Generation
Solutions
Introduction
• What is distributed generation?
– EPA definition:
“Small, modular, decentralized, grid-connected or offgrid energy systems located in or near the place
where energy is used.”
• Goals for electricity generation and delivery
– Reliable
– Affordable
– Efficient
– Environmentally friendly
Introduction
• What is the problem?
– We are addicted to electricity
– We can consume any amount of power at any time
– In most cases, this is not a problem
– Under the right circumstances,
it can be a big problem
Introduction
• What is the problem?
– Northeast Blackout, 14 Aug 2003
– 50 million people affected
Before
During
The Power Grid
Generation
Transmission
Distribution
substation
substation
substation
The Power Grid
The classic model
High power flow
in transmission lines
substation
Electricity
substation
substation
The Power Grid
What can distributed generation do?
substation
Electricity
substation
substation
“Distributed”
Generators
Power Disruptions
• Classification
– Power shortages
• Blackout: complete loss of power
• Rolling blackout: intentional, temporary shutoff
• Brownout: voltage reduction, may be intentional
– Power quality issues
• Voltage and frequency fluctuations
Power Disruptions
• Commercial and Industrial Impact
– U.S. economy is losing over $100 billion / year
$35
Billions of Dollars
$30
$25
Power Quality
Issues
$20
$15
Power Outages
$10
$5
$0
Digital
Economy
Continuous
Fabrication
Process
and Essential
Manufacturing
Services
Power Disruptions
• Commercial and Industrial Impact
– Critical economic sectors are at risk
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Data storage, retrieval, processing
Research and development operations
Telecommunications
Financial operations
Precision and general manufacturing
Transportation
Utilities (e.g. water, natural gas)
Power Disruptions
• Residential consumer impact
– Power-sensitive high-tech devices
• Possible equipment damage
• Expensive to replace or repair
• Possible irreversible data loss
– Essential devices
• Refrigeration
• Heating and cooling
• Medical
Infrastructure Issues
• Why isn’t the system reliable now?
– High peak demand
– Delivery bottlenecks
– Grid fragility
– Power Loss
Infrastructure Issues
• The demand pattern
– Higher during the day, lower at night
– Higher in the summer, lower in the winter
– Result: highest during the day in the summer
• Why does this matter?
– We don’t know how much higher it will be
Infrastructure Issues
• The demand pattern
– Sample residential area: winter vs. summer day
Maximum transmission capacity
0
12
24
0
12
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Infrastructure Issues
• The bottleneck
– “Inadequate investment in transmission infrastructure...
costs consumers tens of billions of dollars a year in higher
energy costs and lost productivity”
-- National Commission on Energy Policy
Infrastructure Issues
• The bottleneck
– Transmission loading relief events (TLRs) recorded when lines reach
full capacity
– Quantitative indicator of transmission congestion
3500
3000
2500
2000
1500
1000
500
0
TLRs
Infrastructure Issues
• The fragile grid
– Equipment limitations
• Safety systems (e.g. circuit breakers) are designed to
prevent dangerously high power flow
• Customers don’t know how high total demand is
– Cascading failure
• A single equipment failure can cause a chain reaction
• Lack of redundancy increases risk and severity
Infrastructure Issues
• Power loss
– Transmission loss 6-8% during peak demand
– Heat released into atmosphere
Net electricity use by sector, 2007
OTHER
4%
INDUSTRIAL
23%
RESIDENTIAL
33%
TRANSMISSION AND
DISTRIBUTION LOSSES
9%
COMMERCIAL
31%
Distributed Generation
• Classification
– Dispatchable
• Turned on and off when necessary
• Fossil fuel, biofuel powered
– Intermittent
• Not precisely controllable or predictable
• Solar, wind
Distributed Generation
Clean power
… but at what cost?
Distributed Generation
• The impact of intermittent generation
– Reliability decrease
• Maximum generation doesn’t necessarily match up
with maximum demand
– Transmission increase
• Wind and solar have specific geographic requirements.
Delivering this power to other areas will add to existing
transmission congestion.
Distributed Generation
• Dispatchable generators: the solution?
– Can satisfy peak demand
– Not susceptible to transmission bottlenecks
– Increase grid stability and redundancy
– Reduce atmospheric power losses
Distributed Generation
• Dispatchable generators: the solution?
– High efficiency
• Up to 90% for combined heat and power generation
– Works well with intermittent generation
• Operates when wind and solar can’t
– Flexible local fuel sources
• Can use existing natural gas lines or locally-produced
biomass/biofuels.
– National energy security
Distributed Generation
• Dispatchable generators: the downside
– Environmental impact
– Public opposition
– Additional points of failure
– Capital cost
• $500-$1000 per kW to install typical generator unit
• Average residence uses 1-2kW; more during peak
• $500-$4000 or more per household over lifetime of the
generator, plus land, upkeep, etc
Solutions
• Combination of factors is at fault
– Each problem can be fixed independently
– Distributed generation can solve most at once
• Reliability is limited
– Impossible to reach 100%
Solutions
• Standards already exist
– FERC Order 888 & 889 (1996)
• Opens transmission lines to competition
– FERC Order 2006
• Small generator interconnection agreements and
procedures
– IEEE Standard 1547
• Standard for interconnecting distributed resources with
electric power systems
Solutions
• Government has spoken
– Energy Policy Act 2005
• $800 million for distributed projects and research
• Includes focus on reliability, efficiency, emergency
supply, effect on rates, advanced metering, residential
grid connectivity, grid design and planning
– Environmental Regulations
• EPA Clean Air rules in effect
• National preference for clean, “green” power
Solutions
• A question of value
– High cost for non-obvious increase in reliability
– Desire for cheap power vs. desire for reliability
– Some customers are already installing their own
systems (or backup supplies)
– Should we force all customers to pay for
distributed generation?
Solutions
• Do we need distributed generation?
• Other options:
– Add transmission capacity
– Reduce consumption
– Implement variable-rate billing
– Deploy electricity storage units
– Sell smart appliances
– Do nothing
Conclusion
• There’s no clear winner
– Distributed generation (both intermittent and
dispatchable) is already being adopted without
much government intervention
– Many consumers may not want distributed
resources or care about reliability (this must be
assessed before making policy decisions)
– Environmental impact can still be significant, even
with high efficiency and limited operating time
Conclusion
• Incentives can still be helpful
– Potential market in individuals, groups, or
businesses for whom distributed resources would
be cost-effective
– Directed incentives or financial assistance would
enable adoption for specific economic sectors
– It may not be for everyone.
Thank you