Proposed Testing Methodology and

Laboratory Facilities for Evaluating

Residential Fuel Cell Systems

Mark W. Davis

Building Environment Division

Building and Fire Research Laboratory

NISTIR 6848
NISTIR 6848

Proposed Testing Methodology and

Laboratory Facilities for Evaluating

Residential Fuel Cell Systems

Mark W. Davis

Building Environment Division

Building and Fire Research Laboratory

January 2002

U.S. Department of Commerce

Donald L. Evans, Secretary

Technology Administration

Phillip J. Bond, Under Secretary for Technology

National Institute of Standards and Technology

Arden L. Bement, Jr., Director
Introduction

Fuel cells are emerging as one of the most promising technologies for meeting the nation’s 

energy needs. Fuel cell efficiencies, approaching 60 %, are nearly twice as efficient as 

conventional power plants.1 Fuel cells are environmentally clean and emit almost none of the 

sulfur and nitrogen released by conventional generating methods. In addition to electricity 

generation, waste heat from residential fuel cells can be captured to provide space or water 

heating, further increasing the overall efficiency. Manufacturers of fuel cell technologies predict 

that residential fuel cell units will be on the market within the next two years. One manufacturer, 

Plug Power*, is currently beta testing approximately 40 residential fuel cell units. 

Currently, ASME, ANSI, NFPA, and other standards organizations are developing standards for 

fuel cells. The ANSI and NFPA standards address the safe operation, construction, installation, 

and acceptable performance of all fuel cell units. The ASME standard seeks to rate the 

performance of a wide range of fuel cell types and sizes. The ASME standard calls for testing at 

a single, steady-state point of operation. 

The ASME single point comparison does not accurately reflect the performance of a fuel cell 

unit in a residential setting. The electrical load of a residence is transient in nature. 

Additionally, if the fuel cell unit is providing a portion of the space or water-heating load, the 

flow rate and temperature of the water being supplied to the fuel cell will vary. A method of test 

and accompanying rating methodology to accurately capture the overall performance of 

residential fuel cell units will provide prospective owners with the information needed to make 

informed selections. 

The National Institute of Standards and Technology (NIST) proposes a test method and rating 

methodology that will capture the overall performance of a residential fuel cell system in the 

same manner that NIST derived methods of tests exist for heat pumps, gas furnaces, water 

heaters, and other household appliances. The test method will take into account any 

inefficiencies associated with the fuel cell stack and reformer; the conversion efficiency of the 

inverter; and any useful water or space heating contributions. The test method will identify and 

specify environmental and electrical load parameters that may affect performance, as well as the 

effect of transient loads on the system performance. Finally, rating methodologies will be 

developed that allow the annual performance of a residential fuel cell unit to be determined 

under representative load and climatic conditions for a specified geographical location. The 

rating methodologies would be a valuable tool allowing the fuel cell industry, as well as 

consumers, to evaluate the electrical and thermal energy output of residential fuel cells and 

maximize their efficiency. These efforts would continue NIST’s history of collaborating with 

the Department of Energy and industry to develop metrology and standards that define the 

energy efficiency of heat pumps, gas furnaces, water heaters, and other household appliances. 

 

1

 Source – Department of Energy, Fossil Energy – Fuel Cell Power Systems Overview web site, “http://www.fe.doe.gov/coal-power/fc-sun” * Certain trade names and company products are mentioned in the text or identified in an illustration in order to adequately specify the 

experimental procedure and equipment used. In no case does such an identification imply recommendation or endorsement by the National 

Institute of Standards and Technology, nor does it imply that the products are necessarily the best available for the purpose. 
This report describes the test procedures and laboratory facilities required for the development of 

these rating methodologies. A brief introduction to fuel cells, their operation, and the key 

parameters that affect the performance of residential fuel cells is included. The tests required to 

determine the relative performance of the units, along with the necessary instrumentation, are 

described. Finally, a detailed explanation of the proposed test facility is provided. 

Background

Fuel cells convert stored chemical energy directly to electrical energy in a very clean and 

efficient manner. Proton exchange membrane fuel cells (PEMFC) are the predominant type of 

fuel cell being considered for residential use, but solid oxide fuel cells (SOFC) are also being 

developed for this purpose. PEM fuel cells are low temperature (80 °C to 120 °C) units, which 

allows for fast startup times. SOFCs are high temperature fuel cells (700 °C to 1000 °C), which 

provides an excellent source of waste heat for combined heat and power (CHP) applications. 

Both types of fuel cell use hydrogen and air to create direct current electricity. 

Generally, residential fuel cell units are the combination of three major components. The 

reformer takes a hydrogen rich fuel and strips off the hydrogen. Most often, the source of 

hydrogen is a hydrocarbon fuel, such as natural gas, propane, or methanol. Due to the high 

operating temperature of SOFCs, the hydrocarbon fuel can be reformed internally, which 

eliminates this costly component. The fuel cell takes the hydrogen along with oxygen from the 

air and creates electricity through an electrochemical process. Finally, the inverter takes the 

direct current electricity from the fuel cell and transforms it into alternating current, compatible 

with the electricity grid. To increase the efficiency of the system, the heat produced by the unit 

can be used for space or water heating, although heating water will be the most likely 

application. 

Fuel cells have many modes of operation. Ideally, the fuel cell would provide all of the power to 

the home, which is termed independent operation. The fuel cell could also work with the 

existing power grid to supply power. This grid-connected operation can be done several ways. 

For example, the fuel cell could be sized to provide a baseline level of electricity with the grid 

supplying the extra power needed to supply the electrical load. This mode, which is usually 

called baseline operation, would allow the unit to run at its maximum efficiency at all times. 

Alternatively, the fuel cell unit could be used in a peak-shaving mode. The majority of power 

would be supplied from the grid, but any power required greater than a pre-set limit would be 

supplied by the fuel cell. Peak-shaving is generally used in commercial or industrial settings to 

reduce demand charges during peak electricity usage times. However, if the unit is not running 

constantly and cools down while not in use, the start-up time can be significant, which severely 

impacts the efficiency. Each of these operating modes forces the residential fuel cell unit to act in 

a different manner, which complicates the formulation of test methods and rating procedures. In 

any mode of operation, there are many parameters that affect the performance of residential fuel 

cell systems. These parameters, shown in Figure 1, must be accounted for to ensure an equitable 

rating procedure. This compliation of parameters resulted from conversations with several fuel 

cell manufacturers. Some of the parameters relate to the operation and application of the fuel 

cell, while other parameters describe the input conditions. 
Parameters

Fuel Application

Electric 

Load

Mode of 

Operation

Thermal Load

Environment

Age @ Rating

Base Load

Unit Location Thermal Source

Peak Shaving

Heating Value

Type Composition

Shut-Down

Start-Up Load Profile

Load Profile

After Prescribed Operation 

Time Out-of-the-Box

Humidity Solar Load

Pressure

Ambient Temp.

Air Quality

Independent Premium Power

Stand-By Grid Connected

Parameters

Fuel Application

Electric 

Load

Mode of 

Operation

Thermal Load

Environment

Age @ Rating

Base Load

Unit Location Thermal Source

Peak Shaving

Heating Value

Type Composition

Shut-Down

Start-Up Load Profile

Load Profile

After Prescribed Operation 

Time Out-of-the-Box

Humidity Solar Load

Pressure

Ambient Temp.

Air Quality

Independent Premium Power

Stand-By Grid Connected

Figure 1. Parameters affecting the performance of residential fuel cells 

The fuel, electrical load, thermal load, and environmental conditions all affect the output of the 

fuel cell unit. With respect to the fuel, different types of fuel have different heating values. In 

addition to changes of heating value between fuel types, the heating value of a fuel may change 

over time, depending on the source of the fuel. The electrical and thermal loads have a 

significant effect on the performance of the unit. The performance of all three major 

components, the reformer, fuel cell, and inverter, depends on the electrical output of the unit. 

Also, each component reacts differently to transient changes in the supplied power. In combined 

heat and power units, the thermal load also impacts the performance of residential fuel cells. In 

applications where the primary function of the residential fuel cell unit is to provide useful heat, 

the units actually adjust their electrical output to control the outlet temperature of the heat 

exchange fluid. Therefore, whether used primarily to supply electricity or heat, the load profile 

affects the performance of the unit. 

Environmental conditions have a significant effect on the performance of the unit. The air 

temperature and pressure both affect the oxygen concentration, which affects performance. The 

quality of the air also affects the oxygen concentration. Since the inlet gas streams to the fuel 

cell must be humidified, the relative humidity of the air also plays a key role in the unit’s 

performance. 

Developing an equitable test method and rating methodology requires that each of these 

parameters be measured. Additionally, some of these parameters must be controlled in such a 

way that helps determine the effect on the fuel cell unit’s performance. The effect of each of the 

parameters on the fuel cell performance must be determined before a test procedure can be 

developed. The series of tests presented in the following section will help determine those 

effects. 
Description of Test Procedures

To determine the seasonal efficiency of a residential fuel cell unit, its performance with respect 

to some of the key parameters must be measured under steady state and transient loads as well as 

during start-up of the unit. Four separate tests are envisioned to determine the overall 

performance of residential fuel cell systems: steady state, steady state with thermal load, 

transient, and the initial start-up. 

Steady State Test

A steady state test would measure the electrical performance of the unit at a prescribed set of 

inlet conditions (ambient temperature, relative humidity, and electrical power factor). The 

efficiency would be measured as the ratio of useful energy output by the unit to the energy 

supplied to the unit. Under steady state conditions without a thermal load, the efficiency can be 

calculated as shown below. 

fuel auxiliary

electrical

q q

q

+

η = (1) 

 where: 

 qelectrical = electrical output of the fuel cell unit (kW·h), 

 qfuel = energy content of the fuel supplied to the unit (kW·h), 

qauxiliary = energy supplied to the fuel cell unit in addition to the primary fuel source 

(kW·h) 

During the steady state test, the load and environmental conditions would remain constant. The 

variables needed to compute the efficiency in Eq. 1 would be measured at prescribed time 

intervals. The test would conclude when the electrical efficiency did not vary greater than two 

percent. It is envisioned that this test would be repeated for a number of rating conditions in 

order to provide a performance map of the unit’s electrical efficiency. 

Thermal Load Test

For residential fuel cell units that produce useful heat as well as electrical energy, the thermal 

load test would measure the overall efficiency of the unit at prescribed inlet conditions. The 

useful heat is transferred to a fluid, usually water, which is maintained at a specified inlet 

temperature and flow rate. Similar to the steady state test, the efficiency can be calculated as the 

ratio of useful energy output by the unit to the energy supplied to the unit, but in this case, the 

useful energy output includes both thermal and electrical energy as shown below. 

fuel auxiliary

electrical thermal

q q

q q

+

+

η = (2) 

 where: 

 qelectrical = electrical output of the fuel cell unit (kW·h), 

 qthermal = thermal output of the fuel cell unit (kW·h), 

 qfuel = energy content of the fuel supplied to the unit (kW·h), 

qauxiliary = energy supplied to the fuel cell unit in addition to the primary fuel source 

(kW·h) 
The thermal output of the unit would be computed as the sum of the heat output measured 

periodically as shown below. 

( ) ∑ 

















 ⋅ ⋅ ⋅ − ⋅∆ =

•

3600

V C T T t

q P Outlet Inlet

thermal

ρ (3) 

 where: 

ρ = the density of the heat transfer fluid (kg/m3), 

•

V = volumetric flow rate of fluid (m3/s), 

 CP = specific heat of the fluid (kJ/kg K), 

 TOutlet = temperature of the fluid at the outlet of the CHP unit (°C), 

 TInlet = temperature of the fluid at the inlet of the CHP unit (°C), and 

∆t = time between measurements (s). 

Similar to the steady state test, the load, heat transfer fluid, and environmental conditions would 

remain constant throughout the testing period. Measurements would be made at a prescribed 

time intervals, and the test would conclude when the overall efficiency did not vary greater than 

two percent. Again, the test would most likely be repeated for a number of rating conditions in 

order to provide a performance map of the unit’s overall efficiency. 

Transient Test

The transient electrical performance of residential fuel cells may have a significant effect on the 

efficiency of the unit, especially in grid-independent applications where the electrical load 

changes rapidly. The magnitude of this effect would be measured by repeatedly changing the 

load level according to a prescribed load profile with the rating conditions held at fixed values. 

If transient electrical loads have no effect on the efficiency of the unit, the efficiency would be 

equal to the time-weighted sum of each load level. For the sample load profile shown in Figure 

2, the time-weighted efficiency would be the average of the efficiencies at the two load levels. 

0

1

Time

% Rated Load

Figure 2. Sample load profile for transient electrical performance test. 
The electrical efficiency would be measured in the same manner as the steady state test over the 

period of the test. The transient test would be performed at several rating conditions to establish 

the overall effect of transient electrical loads on the performance of residential fuel cell systems. 

Start-Up Test

When residential fuel cells are allowed to cool below operating temperature, the unit must reheat 

to the appropriate temperature before producing power. The start-up test will determine the 

amount of time required to reach an operational temperature from ambient conditions and the 

relative electrical performance of the unit as it reaches steady state. To prepare for the test, no 

power would be drawn from the unit allowing it to cool to the ambient temperature of the 

environmental chamber. Then, power would be drawn from the unit initializing its start-up 

procedure, which would bring the unit to an operational temperature over some period of time. 

Data would be recorded as the unit heats up. The environmental conditions would remain 

constant throughout the test. The test would continue until the electrical efficiency of the unit, 

which would be measured as in the transient load test, becomes steady within 2 %. 

For each of the four tests, a large environmental chamber will control the ambient temperature 

and relative humidity. The ambient temperature, relative humidity, and barometric pressure of 

the chamber will be measured with a type T thermocouple, relative humidity transducer, and a 

barometric pressure transducer, respectively. Determination of the electrical and overall 

efficiency in each of the tests will utilize a programmable AC load to adjust the power level and 

the electrical power factor. A Watt-hour meter will measure the power produced by the unit. An 

additional meter will be used to measure any auxiliary electrical power used by the unit. To 

determine the energy content of the fuel, the flow rate and heating value must be measured. A 

dry-type gas meter will measure the flow rate, and the heating value will be measured in situ 

with a calorimeter or by using fuels with certified heating values. Finally, the thermal load test 

requires the measurement of the useful heat transferred to a fluid as shown in Eq. 3. The inlet 

and outlet temperature will be measured with type T thermocouples. The flow rate of the heat 

transfer fluid will be determined with a flow meter, and the density and specific heat of the fluid 

(usually water) are well established tabulated values. These measurements will provide the 

necessary information for the development of a test procedure and rating methodology for 

residential fuel cell units. 

Description of Test Facility

A test method or rating methodology that permits the comparison of various residential fuel cells 

requires the accurate and precise measurement and control of the parameters identified in the test 

procedures. These measurement and control parameters are summarized in Table 1, and 

described in detail in the following subsections. A schematic of the test facility is shown in 

Figure 2. Table 2 provides an estimate of the time required to complete the construction, 

calibration, and evaluation of the test facility relative to the receipt of funding. Finally, a 

complete list of parts and instrumentation described is found in Appendix 1. 
Ambient Environment

A large environmental chamber will control the ambient environment of the residential fuel cell 

test facility. The chamber can maintain the ambient temperature from –12 °C to 40 °C with an 

uncertainty of ±0.1 °C. It can also hold the wet bulb temperature within ±0.1 °C over a range of 

relative humidity of 10 % from 95 %. 

The air temperature, pressure, and relative humidity measurements will be made by 

thermocouples, a barometric pressure sensor, and a relative humidity transducer, respectively. A 

grid of type T thermocouples will be positioned at the air intake of the residential fuel cell unit. 

This will provide an average air inlet temperature for the unit. 

A Setra model 270 barometric pressure transducer will measure the absolute pressure of the 

environmental chamber. The pressure transducer has a range of 600 mbar to 1100 mbar and an 

accuracy of ±0.5 mbar. The inlet air relative humidity will be measured with a Vaisala* model 

HMP 240. This instrument measures the dewpoint temperature, which can be translated to 

relative humidity. The sensor is able to measure the dewpoint temperature at any relative 

humidity (0 % to 100 %). It has an accuracy of 0.6 °C over the applicable temperature and 

humidity range of the environmental chamber. All three of these instruments will output a signal 

voltage to be recorded by the data acquisition system. 

 Table 1. Measurement variables for test facility 

Subsystem Measurement Control 

Temperature Temperature 

Ambient Environment Pressure 

Relative humidity Relative humidity 

Flow rate 

Temperature 

Pressure Fuel Supply 

Heating value 

Inlet temperature Inlet temperature 

Heat Transfer Fluid Outlet temperature 

Flow rate 

Voltage Voltage 

Current Current 

Output power Output power 

Power Factor Power Factor 

Electrical 

Input power 

Table 2. Schedule of residential fuel cell test facility relative to receipt of funding 

Task Month of Completion 

Acquire Instrumentation 2nd

Construction and Integration of Test Facility 3rd

Development of LabVIEW frontend 4th

Calibration and Evaluation 5th
Figure 2. Schematic of residential fuel cell test facility

RFCU

Fuel In

Air InWater In Water Out

-+

Chilled WaterReturnChilled WaterSupply

Environmental Chamber

Calorimeter

BP RH TC

Pump

TC TC

Flow

Meter

Watt Meter

Current

Volt

PT TC Flow

Meter 

g

AC LoadData Acq.Ice Pt Ref

Temp

Control

Legend

WH

#1

WH

#2

WH

#3

HX

RFCU

Fuel In

Air InWater In Water Out

-+

Chilled WaterReturnChilled WaterSupply

Environmental Chamber

Calorimeter

BP RH TC

Pump

TC TC

Flow

Meter

Watt Meter

Current

Volt

PT TC Flow

Meter 

g

AC LoadData Acq.Ice Pt Ref

Temp

Control

Legend

RFCU

Fuel In

Air InWater In Water Out

-+

Chilled WaterReturnChilled WaterSupply

Environmental Chamber

Calorimeter

BP RH TC

Pump

TC TC

Flow

Meter

Watt Meter

Current

Volt

PT TC Flow

Meter 

g

AC LoadData Acq.Ice Pt Ref

Temp

Control

RFCU

Fuel In

Air InWater In Water Out

-+

Chilled WaterReturnChilled WaterSupply

Environmental Chamber

Calorimeter

BP RH TC

Pump

TC TC

Flow

Meter

Watt Meter

Current

Volt

PT TC Flow

Meter 

g

AC LoadData Acq.Ice Pt Ref

Temp

Control

Legend

WH

#1

WH

#2

WH

#3

HX

BP Barometric Pressure Transducer Reg Fuel Filter – Regulator

RH Relative Humidity Transducer HX Heat Exchanger

PT Pressure Transducer WH Water Heater Tank

TC Thermocouple RFCU Residential Fuel Cell Unit

BP Barometric Pressure Transducer Reg Fuel Filter – Regulator

RH Relative Humidity Transducer HX Heat Exchanger

PT Pressure Transducer WH Water Heater Tank

TC Thermocouple RFCU Residential Fuel Cell Unit
Fuel Supply

Currently natural gas appears to be the predominant fuel for residential systems, but some 

manufacturers are considering propane, methanol, or hydrogen as fuel choices. The 

environmental chamber is capable of supplying natural gas. Additional equipment would be 

needed in order to provide these other fuel options. The fuel temperature, pressure, and flow rate 

will not be controlled during testing. The test facility will have the capability to measure the fuel 

flow rate, temperature, and pressure. The fuel will first be regulated to an appropriate operating 

pressure using an American Meter Company* CR4000 residential natural gas regulator. The fuel 

flow rate will be measured with a diaphragm gas flow meter, which can measure the volumetric 

flow rate of any dry gas. The American Meter Company* AL-425 is capable of measuring flows 

of 0.2 m3/min (425 scfh) at 0.18 m (7 in) of water column, which exceeds the design flow rate 

for natural gas, 0.15 m3/min (320 scfh), as shown below. The design flow rate of propane is half 

that of natural gas (NFuel = 8). 















 ⋅ ⋅ ⋅ ⋅

⋅ = •

P

R T

n F V

Power SR

N

N

V

Fuel cell

H

CH 2

4 (4) 

 where, 

H2 N = number of hydrogen atoms in a molecule of hydrogen gas (2), 

N = number of hydrogen atoms in a molecule of fuel (natural gas = 4) Fuel

Power = power produced by the fuel cell (10000 W), 

 SR = stoichiometric ratio of hydrogen (2), 

 n = number of electrons involved in the electrochemical reaction (2), 

 F = Faraday’s constant (96484 C/mol), 

 Vcell = design voltage of a single cell in the fuel cell stack (0.5 V), 

R = gas constant (8.314 J/mol K), 

T = temperature of natural gas (298 K), and 

P = pressure of natural gas (101.3 kPa). 

The gas meter is fitted with a remote pulse totalizer that can be used to measure the gas 

consumption over a period of time. The output of the meter can be scaled to accommodate fuel 

gases other than natural gas. The temperature of the fuel will be measured directly before 

entering the residential fuel cell unit by inserting a type T thermocouple in the fuel piping. The 

pressure of the fuel will also be measured directly before entering the unit. An Omega*

 PX303 

series pressure transducer will send a 0-5V signal to the data acquisition system to record the fuel 

pressure. It has an accuracy of ±0.25 % of full scale. 

The heating value of the fuel will be measured using a Cutler Hammer*

 gas calorimeter. The 

calorimeter provides a continuous measurement of the higher heating value (HHV) of any 

gaseous combustible fuel. To measure the HHV, a stream of fuel is drawn into the calorimeter 

(prior to measurement of the flow rate entering the fuel cell unit) along with a fixed ratio of air. 

The mixture is combusted, and the resulting energy is used to heat a stream of air. The 

combustion products are returned to the conditions of the reactants, which provides the higher 

heating value. The calorimeter, which graphically outputs the heating value to a stripchart, is 

fitted with a retransmitting slidewire millivolt generator that produces a signal voltage 

corresponding to the heating value of the fuel. This millivolt signal will be read by the data 
acquisition system. For non-gaseous fuels, such as methanol, the heating value will be sampled 

throughout the test period and measured afterward by separate laboratory. 

Thermal Load

Those residential fuel cell units that are supplied with a combined heat and power system require 

a fluid to be heated with the waste heat from the fuel cell. Most likely, the CHP system will 

supply heat to domestic hot water, but it may also be used for space heating as well. In the case 

of a domestic hot water heating system, water will be supplied at a specified inlet temperature 

and flow rate. The range of water inlet temperatures could vary from the temperature of the 

NIST chilled water supply, 6 °C (42 °F), to the typical maximum domestic hot water 

temperature, 70 °C (160 °F). The inlet water temperature would be controlled with a series of 

three 0.2 m2

 (50 gal) domestic water heating tanks heating recirculated water to the specified 

temperature. The first tank, which is located at the exit of the heat exchanger, will be controlled 

to the specified inlet temperature by an Omega*

 CNi8 temperature controller. The last two tanks 

will only hold the water to provide sufficient thermal mass. The heated water exiting the CHP 

system on the residential fuel cell unit will be cooled below the inlet temperature using a 

stainless steel brazed plate heat exchanger and the 6 °C (42 °F) chilled water supply. The heat 

exchanger has an active area of 0.6 m2

 (6.5 ft2). This system and the required instrumentation 

can be seen in Figure 2. 

The domestic hot water subsystem will have the capability to measure the flow rate of the water 

running through the CHP as well as the temperature difference between the inlet and outlet of the 

water. The temperature at the inlet and outlet will be measured with type T thermocouples. The 

flow rate will be measured with an Omega*

 FTB-102 turbine flow meter. The meter has a range 

of 4.7·10-5 m3

/s (0.75 GPM) to 4.7·10-4 m3/s (7.5 GPM), and the accuracy of the unit is 0.5 % of 

the 0 V to 5 V reading. The water will be circulated with a centrifugal pump at approximately 

1.9·10-4 m3

/s (3 GPM). 

Electrical Load

The electrical output of the fuel cell unit will be managed by four NH Research*

 4600 series AC 

loads in parallel. Each is capable of drawing 3000 Watts of AC power at various power factors 

or crest factors. The load can operate in any one of four modes: constant current, constant 

voltage, constant resistance, or constant power. It is also capable of drawing power at 

frequencies from 45 Hz to 440 Hz, and the power factor can be adjusted from 0 to 1 either 

leading or lagging. 

While the AC load has the capability to measure the votlage, current, and power, more accurate 

measurements will also be made using two Hewlett Packard*

 3458A digital multimeter and a 

Yokogawa* WT 1000 digital Watt meters. One Hewlett Packard* 3458A will measure the 

output voltage and the other will measure the output current. With the measurement of the 

output power with the Yokogawa*

 Watt meter, the phase between the voltage and current 

waveforms can be determined as well, as shown below. A current transformer is required to 

scale the current to a measureable level for the Watt meter. 




 



 ⋅ = −

W

V A

cos 1 φ (5) 

 where V = RMS voltage, 

 A = RMS current, and 

 W = active power. 

Data Acquisition System

All of the measured data will be collected and saved electronically. A Hewlett Packard 34970A 

will measure all of the thermocouple, voltage, and current signals. The thermocouple signals 

will pass through a Kaye*

 K170 ice point reference to provide a high level of accuracy for the 

temperature measurements. The ice point reference keeps the junctions of 24 thermocouple 

channels at the ice point within 0.05 °C. The data acquisition system will be controlled using a 

LabVIEW program that will read all of the measurement signals, control any necessary 

parameters, collect and save data, and provide a graphical interface to the test operator. 

Conclusion

The residential fuel cell test facility specified above has the capability to measure and control the 

key variables affecting the performance of proton exchange membrane and solid oxide 

residential fuel cell units. The facility can control the ambient temperature and relative 

humidity; the inlet temperature of the heat transfer fluid for CHP applications; and the voltage, 

current, and power factor of the electrical output. The control of these variables allows the 

measurement of changes in performance with respect to one parameter. Quantifying the changes 

in performance according to isolated variables will lead to a greater understanding of residential 

fuel cell units, and this understanding will aid the creation of test procedures and rating 

methodologies that will help customers compare different units to make informed buying 

decisions. These test procedures will be developed in concert with fuel cell manufacturers 

through professional organizations such as ASHRAE, ASME, etc. This collaboration will 

specify the number of tests, rating conditions, and other details important to the test procedures 

and rating methodologies. 

Acknowledgements

We would like to thank Jerry Caesar and the Advanced Technology Program at NIST for 

funding this research. We appreciated the help of George Earle III, Richard Maddaloni, and 

Richard Romer at Plug Power, and James Cross III and John Batal at Nuvera Fuel Cells in 

developing a list of key parameters influencing fuel cell performance. 
escription Model Manufacturer 

r CR4000 American Meter Company 

AL-425 with Remote Pulse Totalizer American Meter Company 

ansducer PX303 Omega 

ple (type T) GTMQSS-062G-6 Omega 

 Cutler-Hammer 

le GTMQSS-062E-6 Omega 

ressure Transducer 270 Setra 

mperature Sensor HMP240 Vaisala 

hermocouple GTMQSS-062G-6 Omega 

ow Meter FTB-102 Omega 

eat Exchanger 35115K27 McMaster-Carr 

emperature Controller CNi8 Omega 

Water Heater 3570K32 McMaster-Carr 

t meter 1000 Yokogawa 

meter HP3458A Multimeter Hewlett-Packard 

meter HP3458A Multimeter Hewlett-Packard 

Load 4600-3 NH Research 

iplexer HP34970A Hewlett-Packard 

Point Reference K170 Kaye