ZEMCH 2019 International Conference Proceedings April.2020 | Page 152
1. Introduction
Energy performance indicators have been extensively discussed in numerous studies worldwide.
For example, Pérez‐Lombard et al.[9], Borgstein et al.[1] have presented well‐organized reviews of
these studies. In summary, the Total Energy Use Intensity (TEUI; e.g. kWh/㎡·a), which the sum of all
annual energy sources’ consumption divided by gross floor area, is still commonly used as a
performance indicator due to its feasibility. The sole dependence of the government on the TEUI may
be attributable to the fact that other prospective performance indicators require too much information
that is difficult to collect within limited time and resources. The TEUI is an aggregated quantity of all
end uses, however, its meaning is non‐indicative and not useful for identifying opportunities and
prioritizing potential actions in a more detailed diagnosis (Mathew et al., 2008). In an assessment, not
only TEUI but also an end‐use related indicator should be considered to ensure confidence of the
assessment.
The development of IoT technology has made the price of their related instruments cheaper; the
cost of power meter, gas meter have been lowered so far (roughly 100–300 dollars in USD) However,
in order to know (measure) how much energy is consumed at end‐uses, it still costs a certain level. The
problem is the installation (labor) cost that consists of approximately 50% or higher of the total cost.
This is one of the major impeding factors for the promotion of end‐uses metering in small‐ and medium‐
sized buildings (<3,000 m2) (Wang et al., 2012; Katipamula et al., 2012). The total cost is relatively high,
and only a few buildings (>10,000 m2) are worthwhile for trials. In other words, most small‐ and
medium‐sized buildings (<3,000 m2) may not have worthwhile, and end uses in such buildings have
remained a national blind spot to those promoting policies related to energy efficiency, or those
promoting a business.
Another problem is that even if each end‐use is sub‐metered, there is no national benchmark of
similar buildings due to the lack of samples, so it is difficult to determine whether the amount of end
uses is appropriate. Only by addressing the shortage of samples can a national benchmark be set. This
means that the cost barrier must be solved first.
This study proposes a cost‐effective method for generating such practical indicators, by dividing
the monthly total energy consumption into cooling‐related energy (summer‐sensitive energy, Ec),
heating‐related energy (winter‐sensitive energy, Eh), and baseload energy (weather‐insensitive energy,
Eb). Our method utilizes inflection points (or shoulder months) that occurred in spring and autumn,
when the main energy use shifted from heating to cooling, and from cooling back to heating, to
represent the whole year.
The cost for collecting monthly utility bills nationwide is now nearly zero from the benefit of the
national energy database (Kwak et al., 2017). Due to the merits of cost‐effectiveness, it is expected that
three end uses (Ec, Eh, Eb) be easily accumulate and cumulative frequency distributions also be made.
It is a favorable starting point to for uncovering energy inefficiencies in small‐ and medium‐sized
building stock by Ec, Eh, Eb benchmarking.
The idea of disaggregating the baseload, heating, and cooling loads using monthly total
consumption data has been studied, for example in regression‐based (Kissock et al., 2002), simulation‐
based (NBI, 2017), and rule‐based (Iyer et al., 2015) approaches. The rule‐based approach simply splits
the total energy use into weather‐insensitive energy use (i.e., baseload energy use) and weather‐
sensitive energy use (i.e., cooling and heating energy uses) using a set of rules considering the monthly
variation. The merit of such a rule‐based approach emerges in real‐life situations in which the end‐uses
information is required, but difficult to obtain.
The set of rules for disaggregation is often criticized due to its simplicity; therefore, verification
(pros and cons) was conducted in this study. As a preliminary validation study, eight end‐uses (cooling,
heating, domestic hot water, lighting, ventilation (fan), appliances, indoor transportation, and water
supply) of two office buildings were measured and the data were pre‐ and post‐processed for validation.
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ZEMCH 2019 International Conference l Seoul, Korea