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Ensuring Reliable Electricity Supplies Using Distributed Generation. Gregory Tress Carnegie Mellon University. Overview. Introduction The Power Grid Power Disruptions Infrastructure Issues Distributed Generation Solutions. Introduction. What is distributed generation? EPA definition:

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ensuring reliable electricity supplies using distributed generation

Ensuring Reliable Electricity Supplies Using Distributed Generation

Gregory Tress

Carnegie Mellon University

overview
Overview
  • Introduction
  • The Power Grid
  • Power Disruptions
  • Infrastructure Issues
  • Distributed Generation
  • Solutions
introduction
Introduction
  • What is distributed generation?
    • EPA definition:

“Small, modular, decentralized, grid-connected or off-grid energy systems located in or near the place where energy is used.”

  • Goals for electricity generation and delivery
    • Reliable
    • Affordable
    • Efficient
    • Environmentally friendly
introduction1
What is the problem?

We are addicted to electricity

Introduction
  • 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
introduction2
Introduction
  • What is the problem?
    • Northeast Blackout, 14 Aug 2003
    • 50 million people affected

Before

During

the power grid

Generation

Transmission

Distribution

The Power Grid

substation

substation

substation

the power grid1
The Power Grid

The classic model

substation

High power flow

in transmission lines

Electricity

substation

substation

the power grid2
The Power Grid

What can distributed generation do?

“Distributed”

Generators

substation

Electricity

substation

substation

power disruptions
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 disruptions1
Power Disruptions
  • Commercial and Industrial Impact
    • U.S. economy is losing over $100 billion / year
power disruptions2
Power Disruptions
  • Commercial and Industrial Impact
    • Critical economic sectors are at risk
      • Data storage, retrieval, processing
      • Research and development operations
      • Telecommunications
      • Financial operations
      • Precision and general manufacturing
      • Transportation
      • Utilities (e.g. water, natural gas)
power disruptions3
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
Infrastructure Issues
  • Why isn’t the system reliable now?
    • High peak demand
    • Delivery bottlenecks
    • Grid fragility
    • Power Loss
infrastructure issues1
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 issues2

0

0

12

12

24

24

Infrastructure Issues
  • The demand pattern
    • Sample residential area: winter vs. summer day

Maximum transmission capacity

infrastructure issues3
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 issues4
Infrastructure Issues
  • The bottleneck
    • Transmission loading relief events (TLRs) recorded when lines reach full capacity
    • Quantitative indicator of transmission congestion
infrastructure issues5
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 issues6
Infrastructure Issues
  • Power loss
    • Transmission loss 6-8% during peak demand
    • Heat released into atmosphere
distributed generation
Distributed Generation
  • Classification
    • Dispatchable
      • Turned on and off when necessary
      • Fossil fuel, biofuel powered
    • Intermittent
      • Not precisely controllable or predictable
      • Solar, wind
distributed generation1
Distributed Generation

Clean power

… but at what cost?

distributed generation2
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 generation3
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 generation4
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 generation5
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
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%
solutions1
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
solutions2
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
solutions3
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?
solutions4
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
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
conclusion1
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.
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