o ak r idge n ational l aboratory u. s. d epartment of e nergy measurement and verification of...
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Measurement and Verification of Geothermal Heat Pump ECMs
John A. Shonder
Oak Ridge National Laboratory
FEMP M&V SummitNew Orleans, LA
May 5, 2003
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Motivation for this work
Streamline M&V process for geothermal heat pump projects
Build on existing FEMP M&V guidelines Develop a template that specifies in detail what
the M&V should encompass Annual measurements Calculations Reporting
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
GHP Tech Specific Super ESPCs
GHP ECMs in Regional Super ESPCs
Other Regional and Tech Specific Super ESPC
GHP makes up a significant fraction of the $363M investment to date under DOE’s Super ESPC
15%
4%
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
The Family Of GHP Systems
Equipment manufactured in a variety of sizes and configurations
Residential -- Each GHP has its own ground loop
200 Ft.
20 Ft.
25 Ft.
4 Ft.
One heat pump on its own loop
Commercial: Multiple GHPs on common loop, central pumping
subsystem
HeatPump
HeatPump
HeatPump
HeatPump
DPSignal Wire to Drive
Transducer
Variable Speed DrivePump
PurgeValves
Aux.Pump
Interior PipeHeaders
A
A
HeatPump
Multiple heat pumps on a common loop
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
How an M&V plan for a GHP project is developed in practice
ESCO proposes a plan based on customer’s requirements, company’s experience and interpretation of FEMP M&V guidelines
Site personnel, HQ support agency, and PF review the plan and suggest changes
Iterate as necessary until everyone is satisfied -- which takes time
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Development of baseline and guaranteed savings estimate ESCO must develop guaranteed savings estimates
for the installed ECMs to establish payment stream In all but the simplest projects, savings estimates
require modeling with BEA software Pre-retrofit (baseline) Post-retrofit
Modeling with BEA software is virtually always done in GHP because loads are required for borefield sizing
Since it’s being done anyway, calibrated BEA model can be an integral part of M&V
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Developing these estimates can be a challenge
In commercial applications, GHPs often replace systems supplied by a central plant (CHW, HTHW, steam) Building level energy use data is extremely rare Central plant fuel use data may or may not exist Pumping power? Heat loss between plant and buildings? Steam/water losses?
Use as-built plans to develop building models, calibrate to short-term metering data to develop baseline
Update model to incorporate GHPs
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Similar problems arise in residential projects
Lack of energy use data Meters on individual residences are rare May be only one meter for the entire base/facility Some meter housing areas separately
Calibrated? Read correctly? All read on same date?
Others use allocation formulas Usually assigns a constant percentage Is it meaningful to calibrate to?
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
We see the calibrated simulation model as an integral part of M&V (like Option D) Use calibrated simulation to develop baseline
annual energy use Replace pre-retrofit equipment with GHPs in
calibrated simulation and re-calculate annual energy use
Guaranteed annual savings = some fraction of post-retrofit prediction minus baseline
Annually, spot check a random sample of the GHPs (and pumping subsystem) to ensure they are performing as modeled in the software
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
What would be done annually Select a random subsample of installed units (3 to 5%
of total, or 3-5% in each building) Annually or semi-annually (e.g., during last week of
August, on work days between the hours of 2:00 and 4:00 PM): At each of the selected heat pumps, measure steady-state
EER and capacity to ensure they are within +/-X% of modeled values (catalog performance)
Measure EWT to ensure it is below design value For systems with central pumping, on each central loop
measure pumping power, motor speed and pressure drop, ensure power is +/- X% of modeled power at these conditions
Prove that the system is performing the way it was modeled in the BEA software
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
GHP components
Compressor
Water-to-refrigerant coil
Air-to-refrigerant coil
Expansion valve
FanAir filter
Entering air
Conditioned air (Supply)
Heat recovery coil
Reversing valve
Water loop
p/t plug
Power
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Performance (capacity and EER) depends on a number of factors
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Measurements to be taken from each selected heat pump
Water pressure drop across water-to-refrigerant heat exchanger
Temperature of entering and leaving water (steady state)
Electrical power (steady state) Entering air temperature (and RH if
cooling)
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
M&V measurementson heat pump unit
Compressor
Fan
Electrical power
Entering air dry bulb temperature, relative humidity (in cooling)
LWT
EWT
P
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Required calculations Water pressure drop determines flow rate Flow rate and temperature difference determine
heat of rejection (absorption) Power and heat of rejection determine capacity Power and capacity determine EER Entering air dry bulb and RH determine wet bulb
temperature (accuracy is a concern) Water flow rate, EWT, EA DB/WB specify
performance
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Finding catalog performance for the given operating conditions
May require interpolation
Other mfrs publish data for 80/67 only, plus “correction factors” for other conditions
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Annual deliverable for M&V
Spreadsheet containing all data and calculations Written report presenting
Average steady state efficiency and capacity of each measured heat pump
Percent by which this efficiency is above or below catalog performance
Average pumping power, compared to modeled pumping power
Peak EWT measured at each heat pump Any problems the tests highlighted, and corrective
actions taken Bottom line -- statement that savings is being
achieved
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
The annual M&V can be considered as small-scale retro-cx
Check hose connections, filter, drain pan, reversing valve, etc.
Low capacity may indicate charge problems
High EWT may indicate flow problems, or underdesigned borefield
Check of pumping subsystem may indicate control problems
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Plan must allow flexibility
Some buildings have large water-to-water heat pumps for OA pre-treatment Measure performance of OA pre-treatment heat pumps
plus random subset of zone heat pumps in each building
Some heat pumps have desuperheater loops to produce hot water Must ensure that these do not run during the
measurements Ensure that they function
And other special conditions which must be examined on a case-by-case basis
Standing column well: Two large projects going in under Super ESPC
submersible pump
perforated intake
discharge
sleeve
formation
soil
A A
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Lake
HDPE Coils withUV Protection inLoose Bundles
A
A
Common Loop Conditioned by Surface Water
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
The same plan can serve for residential systems as well
Preventive maintenance requires periodic visits to residences
M&V measurements can be performed as part of a normal service call
In some projects ESCO has on-site service organization that could perform the measurements
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Implications of this proposal
It’s imperative that we have confidence in the baseline Army ESPC audit specifically mentioned baseline
development as a problem area We must also have confidence in the BEA
software FEMP guideline specifies accuracy of calibrated
simulation model More rigorous temporary metering may be
required during project development Installed equipment must include provisions for
annual measurements
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Benefits of the M&V template
Streamline project development process by reducing time required for negotiation
Provide confidence that ECM is delivering guaranteed savings
Annual retro Cx of the subsample and the pumping system ensures correct performance
Will highlight any operating problems sooner rather than later
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Other issues being addressed
Not all hourly simulation programs represent vertical/horizontal bore GHPs accurately We have compared six commonly available programs We will recommend acceptable software
For other system types (standing column well) there are no proven system representations in common BEA software GHP core team will intervene Motivating research to develop practical tools for other
GHP system types as needed PFs must take great care in assessing ESCO savings
estimates
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
We are working with a major heat pump manufacturer to determine
Is the measurement plan viable? Can the required measurements be performed
accurately in the field? Is the manufacturer confident that heat pumps
will perform “as advertised”? Particular concern is determining wet bulb
temperature Measurements are being taken in the
manufacturer’s laboratory to verify proposed techniques
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Current activities In the short term, GHP Core Team assisting ESCOs and
PFs in development of M&V plans Maintaining a central database of GHP M&V plans and
annual M&V reports Developing “Guide to Measurement and Verification for
GHP Systems” Specify required measurements and instrumentation Model M&V plan for three different systems Include case studies from real projects
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Where we stand now
We have the beginning of a plan Work is at an early stage of development We are seeking the assistance of others to
develop consensus ESCOs Federal agencies FEMP M&V experts GHP manufacturers ASHRAE IGSHPA