Option Selection Considerations Flashcards
RETROFIT ISOLATION OPTIONS A AND B ARE BEST APPLIED WHEN:
The physical properties of the EEM allow the impacted energy flows to be separately measured.
Any interactive effects of the EEM on the energy consumption and demand of other facility equipment can be reasonably estimated or assumed to be insignificant.
Only the performance of the systems affected by the EEM is of concern, or savings from each EEM need to be reported.
Expected savings from the EEM(s) are too small to be detected using Option C or to justify the expense of using Option D.
Sub-meters already exist to isolate energy consumption and demand of affected systems, or adding sub-meters would be feasible.
The energy influencing factors (i.e., independent variables and static factors) which affect energy consumption and demand are not excessively difficult or expensive to monitor.
There is no need to directly reconcile savings reports with changes and payments to energy suppliers.
WHOLE FACILITY OPTIONS C AND D ARE BEST APPLIED WHEN:
There is a high level of interactive effects from the EEM or energy interactions between EEMs.
The energy flows impacted by the EEM(s) cannot be separately measured.
The level of savings expected is high enough to use Option C and reporting a facility’s overall
performance, rather than EEM performance, is preferred.
There are many unique EEMs whose energy flows would be difficult to measure individually.
Baseline period energy data are not available (Option D).
Granularity of Savings
Retrofit isolation allows the narrowing of the measurement boundary to reduce the effort required to monitor independent variables and static factors when EEMs affect only a portion of the facility. This allows reporting savings a the EEM level. However, boundaries smaller than the total facility usually require additional meters at the measurement boundary and introduce the possibility of significant unmeasured interactive effects.
Since in this case measurement is less than the total facility, the results of retrofit isolation approaches may not be fully apparent in utility bills if the savings are small compared to total facility energy use. Facility changes beyond the measurement boundary and unrelated to the EEM will not be reported by retrofit isolation approaches but will be included in the utility’s metered consumption and/or demand. Otherwise, savings determined through whole facility approaches can be related to utility bills.
Interactive effects
For an EEM, which reduces the power requirements of electric lights, the measurement boundary includes only the power to the lights. However, lowering lighting energy may also lower any mechanical cooling requirements and/or raise any heating requirements. Such heating and cooling energy flows attributable to the lights cannot usually be easily measured. They represent interactive effects that may have to be estimated rather than included within the measurement boundary.
Energy measurements required
The energy quantities required in the IPMVP’s savings equations can be measured by one or more of the
following techniques:
Utility or fuel supplier meter data and invoices or data directly from the utility meter including any adjustments to the readings that the utility makes.
Special meters isolating the energy flows to an EEM or portion of a facility from the rest of the facility. These measurements may be periodic or continuous throughout the baseline and reporting periods and may use temporary or permanent meters.
Separate measurements of the key parameters used in computing energy consumption and/or demand.
o The sample rate of the measurements should be adequate given the rate of variation in the value of the parameters to be measured, and measurement intervals coordinated across measured parameters, including independent variables.
Measurements of proxy variables after validating their relationship with energy consumption or demand. In some cases, a measured proxy variable may be substituted in place of direct measurement of energy consumption or demand where the relationship between the two has been proven in situ.
o For example, if a consistent relationship has been proven via measurements between the output signal from a variable-frequency drive controller and the power draw of the controlled fan, then the output signal may be used as a valid proxy measurement for fan motor power.
Energy simulation that is calibrated to actual energy consumption and demand data for the system or facility being modeled during either the baseline or reporting period.
Where a key parameter needed to estimate savings is already known with adequate accuracy or when it is more costly to measure than justified by the increase in certainty of savings, then direct measurement may not be necessary or appropriate. In these cases, estimates may be made of some of the EEM’s key parameters, but others must be measured (Option A).
M&V Cost Limitations
The cost of the M&V effort must be aligned with the value of the project, the level of energy variation within measurement boundary, and the expected savings. The related costs and accuracies of the Options are discussed in Section 10 – M&V Cost & Uncertainty in Savings. Generally, average M&V costs should be less than 10% of the cost savings being assessed.
Low Energy Variation, Low-Savings EEM.
EEMs with low savings cannot typically afford much M&V, based on the 10%-of-savings guideline, especially if there is little variation in the measured energy data.
The use of Option A is favored. A short reporting period may be considered, for example, in the case of a constant-speed exhaust-fan motor that operates under a constant load according to a well-defined schedule.
High Energy Variation, Low-Savings EEM.
Low-saving EEMs cannot generally afford much M&V, as noted above. However, with a high amount of variation in the energy data, the all-parameter measurement techniques of Option B may be needed to achieve the required accuracy in savings reporting.
Option B is preferred if feasible. Keeping M&V costs low and appropriate relative to the level of savings expected can be a challenge, and sampling techniques may sometimes reduce Option B costs. Option C may not be suitable based on the general guidance that savings should generally exceed 5% to 10% of a facility’s metered use to be quantifiable.
Low Energy Variation, High-Savings EEM.
With low variation in energy consumption and demand, the level of uncertainty is often low. However, since a high level of savings is expected, small improvements in accuracy may have monetary rewards large enough to merit more precise metering and data analysis.
Options B and C are generally most suitable. A high-savings EEM may be measurable with Option C but requires a means to monitor static factors to detect the need for non-routine adjustments. Using Option B, in some cases, may reduce the number of static factors to track without reducing accuracy. Additional costs may be justified to enable accurate reporting. For example, if the savings from an EEM are
$1,000,000 annually, an annual M&V cost of
$20,000 (2% of savings) may be reasonable.
High Energy Variation, High-Savings EEM.
High-saving EEMs allow for high level of rigor which may include extensive data collection and analysis. The baseline and reporting periods may have to span multiple normal cycles of facility operation to capture variations in savings.
Consider using Options B, C, or D. However, savings are likely to show in the utility records, so Option C techniques may be used with careful monitoring of static factors to detect the need for non-routine adjustments
Key Parameters - Example
Key parameters are critical variable(s) identified to have a significant impact on the energy savings associated with the installation of an EEM. In retrofit isolation methods, key parameters may be combined to define energy demand and consumption of the load, which is subject to the EEM.
For an EEM involving upgrading lighting equipment, electrical demand (kW) can be determined from amps, volts, and power factor, and consumption (kWh) determined from the corresponding hours operated.
For an EEM such as replacing a gas-fired boiler, thermal energy performance may be determined by measuring gas flow rates, system operating temperatures, and hot water flow rates over time.
Option A allows the use of both measured and estimated values to calculate baseline and reporting period energy, whereas Option B requires the direct measurement of demand and energy consumption OR the concurrent measurement of all the parameters necessary to determine demand and energy consumption. Generally, the accuracy in verified savings reported by Option B is higher than those using Option A.
What do you evaluate when planning a retrofit isolation procedure?
The amount of variation in the baseline period’s energy use and related key parameters (e.g., loads and hours of operation),
How the EEM will impact those key parameters,
Level of rigor required in reported savings, and
Any risk management agreements between stakeholders.
Conditions of variable load or variable operating hours require more rigorous measurement and computations than constant loads, constant hours, or scheduled hours of operation. Generally, where a key parameter varies during the baseline period or when that parameter will be impacted by the EEM, that parameter should be measured.
Constant Values
A parameter may be considered “constant” where measured values do not change within a defined range (e.g., +/- 10%) during a period of interest.
Minor variations may be observed in the parameter while still describing it as constant. The magnitude of variations that are deemed to be “minor” must be reported in the M&V Plan.
Once proven constant, the frequency of measurement may be reduced to a minimum of once during any reporting period. Otherwise, it should be treated as an estimated value.
