1.
SYSTEMAND METHOD FOR USINGA
NETWORK OF THERMOSTATS AS TOOL TO
VERIFY PEAK DEMAND REDUCTION
CROSS-REFERENCE TO RELATED
APPLICATIONS
This application is a continuation of U.S. patent applica
tion Ser. No. 137037,162, filed Feb. 28, 2011, now U.S. Pat.
No. 8,131.506 which is a continuation of U.S. patent appli
cation Ser. No. 12/183,949, filed Jul. 31, 2008, now U.S. Pat.
No. 7,908,116, issued on Mar. 15, 2011, which claims the
benefit of priority under 35 U.S.C. S 119(e) to both U.S.
Provisional Application 60/963,183, filed Aug. 3, 2007; and
U.S. Provisional Application No. 60/994,011, filed Sep. 17,
2007, the entireties of which are incorporated herein by ref
erence and are to be considered part of this specification.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the use of thermostatic HVAC
controls that are connected to a computer network as a part of
a system for offering peak demand reduction to electric utili
ties. More specifically, the present invention pertains to use of
communicating thermostat combined with a computer net
work to verify that demand reduction has occurred.
2. Background
Climate control systems such as heating and cooling sys
tems for buildings (heating, ventilation and cooling, or HVAC
systems) have been controlled for decades by thermostats. At
the most basic level, athermostat includes a means to allow a
user to set a desired temperature, a means to sense actual
temperature, and a means to signal the heating and/or cooling
devices to turn on or offin order to try to change the actual
temperature to equal the desired temperature. The most basic
versions of thermostats use components such as a coiled
bi-metallic spring to measure actual temperature and a mer
cury Switch that opens or completes a circuit when the spring
coils or uncoils with temperature changes. More recently,
electronic digital thermostats have become prevalent. These
thermostats use solid-state devices such as thermistors or
thermal diodes to measure temperature, and microprocessor
based circuitry to control the switch and to store and operate
based upon user-determined protocols for temperature Vs.
time.
These programmable thermostats generally offer a very
restrictive user interface, limited by the cost of the devices,
the limited real estate of the small wall-mounted boxes, and
the inability to take into account more than two variables: the
desired temperature set by the user, and the ambient tempera
ture sensed by the thermostat. Users can generally only set
one series of commands per day, and to change one parameter
(e.g., to change the late-night temperature) the user often has
to cycle through several other parameters by repeatedly press
ing one or two buttons.
As both the cost of energy and the demand for electricity
have increased, utilities Supplying electricity increasingly
face unpleasant choices. The demand for electricity is not
Smooth over time. In so-called "Summer peaking locations,
on the hottest days of the year, peak loads may be twice as
high as average loads. During Such peak load periods (gen
erally in the late afternoon), air conditioning can be the largest
single element of demand.
Utilities and their customers generally see reductions of
Supply (brownouts and blackouts) as an unacceptable out
come. But their other options can be almost as distasteful. In

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the long term, they can build additional generating capacity,
but that approach is very expensive given the fact that Such
capacity may be needed for only a few hours a year. And this
option is of course unavailable in the short term. When con
fronted with an immediate potential shortfall, a utility may
have reserve capacity it can choose to bring online. But
because utilities are assumed to try to operate as efficiently as
possible, the reserve capacity is likely to be the least efficient
and most expensive and/or more polluting plants to operate.
Alternatively, the utility may seek to purchase additional
power on the open market. But the spot market for electricity,
which cannot efficiently be stored, is extremely volatile,
which means that spot prices during peak events may be as
much as 10x the average price.
More recently, many utilities have begun to enter into
agreements with certain customers to reduce demand, as
opposed to increasing Supply. In essence, these customers
agree to reduce usage during a few critical periods in
exchange for incentives from the utility. Those incentives
may take the form of a fixed contract payment in exchange for
the right to cut the amount of power Supplied at specified
times, or a reduced overall price per kilowatt-hour, or a rebate
each time power is reduced, or Some other method.
The bulk of these peak demand reduction (PDR) contracts
have been entered into with large commercial and industrial
customers. This bias is in large part due to the fact that
transaction costs are much lower today for a single contract
with a factory that can offer demand reduction of 50 mega
watts than they would be for the equivalent from residential
customers it could take 25,000 or more homes to equal that
reduction if these homes went without air conditioning.
But residential air conditioning is the largest single com
ponent of peak demand in California, and is a large percent
age in many other places. There are numerous reasons why it
would be economically advantageous to deploy PDR in the
residential market. Whereas cutting energy consumption at a
large factory could require shutting down or curtailing pro
duction, which has direct economic costs, cutting consump
tion for a couple of hours in residences is likely to have no
economic cost, and may only result in minor discomfort—or
none at all if no one is at home at the time.
Residential PDR has been attempted. But there have been
numerous command and control issues with these implemen
tations. The standard approach to residential PDR has been to
attach a radio-controlled switch to the control circuitry
located outside the dwelling. These switches are designed to
receive a signal from a transmitter that signals the compressor
to shut off during a PDR call.
There are a number of technical complications with this
approach. There is some evidence that “hard cycling the
compressor in this manner can damage the air conditioning
system. There are also serious issues resulting from the fact
that the communication system is unidirectional. When utili
ties contract for PDR, they expect verification of compliance.
One-way pagers allow the utility to send a signal that will shut
of the A/C, but the pager cannot confirm to the utility that the
NC unit has in fact been shut off. If a consumer tampers with
the system so that the A/C can be used anyway, the utility will
not be able to detect it, absent additional verification systems.
One way in which some utilities are seeking to address this
issue is to combine the pager-controlled thermostat with so
called advanced metering infrastructure (AMI). This
approach relies on the deployment of 'Smart meters' elec
tric meters that are more sophisticated than the traditional
meter with its mechanical odometer mechanism for logging
only cumulative energy use. Smart meters generally include a
means for communicating instantaneous readings. That com