|
INTRODUCTION
Electric curtailment options have been offered by the electric utilities to residential, commercial, and industrial customers as a means to manage their load in cases of low spinning reserves. The utility provides economic incentives in the form of interruptible rates, and the customer is called upon to shed loads, or the utility remotely interrupts main electric feeds to a customer or air-conditioner equipment for residential customers. The service curtailments or interruptions generally negatively impact the customer's production process or compromises thermal comfort of occupants if service interruptions persist over several hours. Very little research and product development has been done to investigate strategies to perform load-management with acceptable and controlled impacts to the customers.
This Program Element had five research projects that explored strategies and communication protocols to reduce peak electrical loads in buildings, individually and in groups. Projects 3.1 and 3.2 address load reduction in individual buildings using demand controlled ventilation and night ventilation to pre-cool the building mass. Project 3.3 investigated methods to allow appliances to turn themselves off in response to sensed conditions on the electrical grid (without a command from a utility controller) as well as methods to detect high stress in the grid. Project 3.4 promoted the continued development of communications protocols to integrate lighting controls into the HVAC BACnet control standard and to allow two-way communication through the utility meter between the building control system and the electric utility grid managers. Project 3.5 explored practical ways to coordinate load reduction among buildings on a common utility meter while minimizing comfort impacts on occupants.
Back to top
3-1. DEMAND-CONTROLLED VENTILATION ASSESSMENT
A joint project between Purdue and NIST,
investigated energy
and cost savings associated
with demand-controlled
ventilation (DCV).
In addition to energy
and economic simulation
and analysis supported
by field experiments,
the project provided
a general study of indoor
air quality implications
of demand controlled
ventilation.
- In most cases, the payback period associated
with demand controlled ventilation with economizer
override was less than two years.
- The greatest cost savings and lowest payback
periods occur for buildings that have variable
and unpredictable occupancy levels, such
as auditoriums, gyms and retail stores.
- The greatest savings and lowest payback periods
occur in the more extreme inland climates.
Mild coastal climates have smaller savings
and longer payback periods.
Research Team: This project was a joint effort between Purdue University (Jim Braun,
Kevin Mercer, and Tom Lawrence) and NIST (Andy Persily and Steven Emmerich).
Amy Musser with the University of Nebraska collaborated with the NIST research
team. Todd Rossi and Doug Dietrich provided data collection services and
field support, and Lanny Ross with Newport Design Consultants provided
field support as well. Honeywell Corporation was a match fund partner,
providing DCV controllers and other hardware for the Project.
Back to top
3-2. NIGHT VENTILATION WITH BUILDING THERMAL MASS
As an alternative to leaving HVAC equipment
off during unoccupied
hours, this project
examined ventilating
with cool air during
night and early morning
hours to lower the
temperature of the
building mass. Taking
advantage of the
thermal storage capabilities
of the building structure,
this technique
can shift a significant
portion of a building's
on-peak cooling requirements
to off-peak
periods, reducing
both energy and demand
costs. The goal of
the project was to develop
a simple, low-cost
algorithm that could be
integrated within
a controller for packaged
air conditioners
with economizers, such as
rooftop units.
- The algorithm was tested in simulations and
a retail building located in southern California.
The simulated building types included small
office buildings, sit-down restaurants, retail
stores, and schools (spaces including classroom
wing, auditorium, gymnasium, and library).
- The greatest savings were predicted for buildings
in coastal climates. Significant savings
were also predicted for hot inland climates.
- The electrical energy savings varied between
zero and about 8%. The electrical demand
cost savings associated with night ventilation
varied between zero and about 28%, whereas
the total electrical cost savings ranged
from zero to about 17%.
Research Team: Jim Braun, Kevin Mercer, and Tom Lawrence of Purdue University conducted this research project. Todd Rossi and Doug Dietrich of Field Diagnostic Services, Inc., provided data collection services and field support. David Jump with Nexant, Inc. and Lanny Ross with Newport Design Consultants provided field support as well.
Back to top
3-3. SMART LOAD CONTROL AND GRID-FRIENDLY APPLIANCES
Smart Load Control and Grid-Friendly Appliances had the objective of developing
smart load controls for residential and commercial appliances such as air-conditioners,
refrigerators, electric hot water heaters, and other electric appliances,
which would enhance the dynamic stability of the power system to prevent
far-reaching blackouts, and support the restoration of the power system
after power outages. A key to the smart controller was to develop methods
to detect the onset of a high stress event on the electric grid and then
turn off the appliance or cycle it into a low power consumption mode.
- Two load controller prototypes were developed, built, and tested.
- The first load controller prototype responded to under-frequency events
and rapid decay in the grid frequency. This controller is reactive in its
response to major electric grid events. It responds within a fraction of
a second to an imbalance of generation and load and turn off electric appliance.
The advantage of this controller is its simplicity and that it operates
autonomously with requiring communications from the utility or grid operator.
- The second load controller prototype was developed for the real-time statistical
and spectral analyses of the grid-frequency. The objective of this controller
was to detect high grid stress conditions as a pre-cursor for impending
problems in the California power grid.
- Significant insights into the complexity of detecting grid stress conditions
were gained through dynamic simulations of the western US interconnected
power system (WECC) and analysis of real data from two major outages in
California.
Research Team: Michael Kintner-Meyer, R. Guttromson, D. Oedingen, and S. Lang with Battelle
conducted this research project.
Back to top
3-4. EXTENDING BACnet FOR LIGHTING CONTROL AND INTERFACING BUILDING SYSTEMS
WITH UTILITIES
This project focused on developing software
objects for the BACnet
HVAC standard to include
lighting controls
and utility meters. The
concept was to use
the BACnet communications
protocol to promote
an open (as contrasted
with proprietary)
control scheme that would
include lighting
and energy meters as well
as HVAC. NIST worked
closely with the ASHRAE
standards committee
responsible for the BACnet
standard and a number
of international organizations
to create consensus
for the scope and functionality
of the proposed objects.
Progress was made
in both areas.
- Two lighting control features, one to allow
grouping of lighting control commands and
one to interface to the DALI lighting protocol,
should be part of the BACnet standard before
the end of 2003.
- Two utility interface features related to
remote meter reading were recently published
for public comment.
- Integration of lighting controls and utility
meters into the BACnet standard will promote
energy conservation by giving building operators
the opportunity to work on a single controls
platform.
Research Team: Steven Bushby, David Holmberg, and Stephen Treado with NIST conducted
this research project.
Back to top
3-5. AGGREGATED LOAD SHEDDING
MIT researchers worked closely with the Los
Angeles County Government
to devise methods
to reduce electrical
demand in groups of
buildings under a
common utility meter. The
County's original
interest was to find manual
control sequences
that could be used to meet
the local utility's
call for load reduction
under an interruptible
power rate. The goals
were to understand
what actions to take and
what load reduction
to expect, to measure
the load to assure
that the reduction actually
occurred, and to
estimate what the comfort
or productivity impact
might be. MIT undertook
simulation studies
as well as short-term
experiments to answer
these questions.
- Non-Intrusive Load Monitors (described more
fully under Project 2.1) as well as environmental
sensors were installed to provide feedback
to the County staff as well as the researchers.
- The control method explored was to simultaneously
raise the zone thermostat setpoints or shut
off the chillers for a period of time. Based
on the specific building models, load patterns,
weather conditions and rate structure used
in this research, a peak load reduction of
2 - 14% and a cost-based peak load reduction
of 2 - 12% for aggregation cases of two or
three buildings with thermostats as control
variable was achieved.
- Using night cooling (both fan-based and chiller-based),
a 27% peak load reduction and around a 20%
cost reduction in a two-building case was
observed.
Research Team: Les Norford, Peter Armstrong, and Helen Xing with MIT conducted this research project. Lanny Ross with Newport Design Consultants provided field support.
Back to top
|
