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International Performance
Measurement & Verification Protocol (IPMVP), who literally wrote the book on
measuring and verifying energy savings, makes a few comments about
data gathering ... we agree, and offer a better solution!
Trend Logs are Not a Viable Data Collection Tool
The facility energy management system (EMS) can
provide much of the monitoring necessary for data collection.
However, the system and software must be fully specified to
provide this extra service as well as its primary real-time
control function. For example, significant use of trending
functions may impair the basic functions of the EMS. Some
parameters to be monitors may not be required for control. These
extra points must be specified in the design documents.
—IPMVP, Concepts and Options for Determining
Energy and Water Savings, Volume I
EnergyWitness™ solves the data collection problem. It's true,
running enough trend logs to gather all the points needed for M&V
will crush the building automation system (BAS), keeping it from its
primary function—control. EnergyWitness
gathers all the data, from every BAS point (control and monitoring),
and adds meter, utility, and weather data. It is organized
and stored in our data warehouse
where it's kept permanently, creating a historical record of
operations. The data is collected at 15 minute intervals
directly from the devices through OPC, resulting in no performance
degradations in the BAS.
All the data, all the time, no penalties. Perfect for M&V.
A Control System is for Control ... A Data Warehouse is for
Information
... where a contractor is responsible for some
operations controlled by the system, EMS security arrangement should
ensure that persons can only access functions for which they are
competent and authorized.
—IPMVP, Concepts and Options for Determining
Energy and Water Savings, Volume I
There is simply no good reason to allow any risk of operational
integrity to exist for the purpose of data collection. Even though
the BAS may restrict access to certain functions, a far better
approach is to pull data for M&V from a separate data warehouse that
cannot affect ongoing operations and control. Using EnergyWitness,
the data is available in
EWDataWarehouse, never more than 15 minutes old, secured with
read-only access, and completely separate from the BAS control
functions.
Interval Data is the Answer
... most EMSs record "change of value" (COV) event recordings
that are not directly used for calculating energy savings without
tracking time intervals between individual COV events (Claridge et
al. 1993, Heinemeier and Akbari 1993). It is possible to tighten COV
limits in order to force the trending towards more regular
intervals, but this can overload system which are not designed for
such data densities.
—IPMVP, Concepts and Options for Determining
Energy and Water Savings, Volume I
Instead of trying to force COV data into usable time intervals,
use interval data to begin with. EnergyWitness
collects data in regular 15 minute intervals.
We synchronize the data intervals so that you can look at them
across multiple BASs, meters, utilities, and weather, and know what
each part of the facility is doing at any point in time. There's no
need for post-processing routines to convert COV data—no need to
deal with trend logs at all to collect data for M&V. EnergyWitness is designed to handle
these data densities; designed to present normalized data in regular
intervals.
We don't call ourselves
Interval Data Systems for nothing.
With the interval data collected in the warehouse, you have
access to any points, any trends with just a mouse click or two
through EWViewer. You can just as easily
export data into Excel or a comma-quote format file. Or, if you have
Excel-based analysis routines or measurement calculations, our
plug-in architecture will allow you to integrate them directly into
EnergyWitness.
You Can't Measure What You Can't See
Come see for yourself how EnergyWitness measures up to the task
of data collection and verify that it's the right tool for your
performance M&V efforts. We're happy to schedule a live
demonstration. Just contact us by phone at 617-744-1091 or by e-mail
at info@intdatsys.com.
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