ENERGY WAREHOUSING AND VIRTUAL
METERING
EIS data collection only goes so far
toward the entire reporting needs of an energy management
office. There may be a limit to how much sub-metering
an organization can afford to install. Therefore,
some areas may not have data available specific
to their boundaries and so their energy use remains
unreported. Also, as an organization evolves over
time its infrastructure may not continue to correspond
to the physical layout of utility supply lines and
metering capabilities. Relocating those supply lines
and meters may not be practical. Using virtual metering
to ractionalize or combine real meter data for reporting
purposes fulfills those extended needs of an energy
management office.
In a typical EIS the meter data is the lowest level
of reporting capability. So, if each building has
only one meter, then buildings are the lowest reportable
area. Large buildings today may contain multiple
operational areas that require individual reporting
capability. A virtual meter might define these areas
as a percentage of the floor space of the real metered
area. The EIS divides the consumption recorded among
the areas in the same proportions as the floor area.
However, the EIS administrator may base the formula
for proportioning the consumption on any criteria.
For instance, if multiple departments share the
fiscal responsibility for the building, the percentages
would be established accordingly and utility cost
reimbursement made much easier.
The meter definition table is the backbone of the
whole EIS system. Most large complexes have hundreds
of meters; a table to track them along with their
characteristics is definitely required. Figure 12-8
shows an abbreviated meter definition table for
some electric meters in a small school district.
The table includes the fields required to use virtual
metering. We will be creating virtual meters to
obtain consistent electric consumption data at the
building level. The EIS joins the meter definition
table with the readings table to produce reports.
Only meters with values in the EXPRESSION field
are reportable. The EIS reports data from other
meters as part of a virtual meter expression. Let’s
take a look at each of the schools in the table.
Note: For the sake of simplicity, the examples below
involve schools with buildings that all have similar
energy- consumption such as classrooms and offices.
So, defining the virtual meters in terms of square
footage is reasonable in these cases. Once EIS administrators
understand the concept of virtual metering they
will see opportunities to apply these principles
to situations that are more realistic. In order
to account for areas of high energy consumption
such as a cafeteria, they can use temporary informational
metering or estimates to create valid expressions
for virtual meters.
Energy management offices need to be able to track
energy consumption at equivalent levels, such as
at the building level. Typically engineers do this
using informational meters. Fractionalizing and
combining real meter readings into virtual meters
is an alternative as well as complementary approach
to providing that capability. The ability to easily
integrate virtual metering into the EIS framework
makes it a viable alternative to informational metering
on a large scale. As long as the EIS design keeps
virtual meter definitions and data closely related
to their real counterparts, the EIS can easily report
on virtual meters just as it reports on real meters.
Virtual metering provides a means to report energy
consumption along lines other than the physical
boundaries represented by the metered area itself.
However, any one virtual meter has no more ability
to qualify data than a real meter. Each virtual
meter represents only one utility type (electric,
gas, water, etc.) and is defined by only one expression.
That expression relates to the one unique physical,
organizational or functional boundary that a real
meter possesses. Also, remember that virtual meters
may only represent estimated consumption values.
Still, virtual metering opens the doors to some
powerful analysis features.
For more information contacts at:
info@intelen.gr
