Site Overview

Image source:
Delaware County Electrical Cooperative

The site chosen for the demonstration is a typical residence in upstate New York, located at the edge of the distribution grid. The home has an existing connection to the grid but it is expected that the propane fuel cell and energy storage system will provide 100% of the energy needs of the home during the demonstration period.

The average daily load at the site is 47.6 kWh, with a peak daily load of 67 kWh. The average power draw is 1.98 kW with an expected maximum draw of 15.2 kW.

Energy Storage System

Image source: Gaia Power Technologies

The energy storage and control system chosen for the demonstration is the PowerTower (Gaia Power Technologies). Two 5.5 kW battery storage units were installed for a total capacity of 11.0 kW. The individual batteries are 600 amp-hour, deep discharge lead-acid units.

The integrated energy control system includes battery charge control, inverters, control of fuel cell output, and in-home load control. System monitoring data is through an HTTP interface. The system can be configured for peak-shaving when attached to the distribution grid, or it can provide 100% of the power for an off-grid configuration.

Propane Fuel Cell

Image source: Plug Power

The fuel cell chosen for the demonstration is the GenSys model 5C, manufactured by Plug Power. Its 5 kW output is powered by a 1000 gallon propane tank. This fuel cell is designed for onsite power generation and includes an integrated power inverter and energy storage module. It is also fitted with a thermal recovery system that provides hot water and space heating. Data monitoring and control of the fuel cell is provided through a controller board with a 'Modbus' interface.

The Plug Power fuel cell utilizes Proton Exchange Membrane (PEM) technology. Benefits include quick startup, variable output, and operation at relatively low temperatures.

System Connection and Operation

Image source: Gaia Power Technologies

This diagram illustrates the system layout and configuration. 120V AC power from the existing distribution grid is fed to the fuel cell to provide power during startup. Power from the grid is also connected to AC Input 2 of the PowerTower storage and control module.

120V AC power from the fuel cell is then routed to AC Input 2 of the PowerTower through a transformer, which also provides a 240V feed. The AC output from the PowerTower goes to the site's electrical service panel. Relays controlled by the PowerTower are used to switch the main electrical service panel between the grid and the output of the PowerTower. Under ordinary operation of the system, all power is provided by the PowerTower.

Control of large loads, such as a hot tub, is accomplished through the use of relays controlled by the PowerTower. This facilitates load shaving during peak demand times.

Data Acquisition and Monitoring

(Click image for larger view.)    Image source: EnerNex Corporation

Data acquisition and monitoring is performed using 'Signature System' monitoring equipment manufactured by Dranetz-BMI, Inc. The primary instrument is a Model 5590 DualNode, which integrates the functionality of the Model 5530 EPQ DataNode and the 5500 Series InfoNode in a single package.

The 5530 EPQ DataNode is an advanced power quality monitoring device that collects 384 samples per cycle and is capable of capturing transient events in the 1 microsecond range. Events can be triggered by current or by voltage transients. Two 5530 EPQ DataNodes are being utilized in this demonstration, including the one integrated into the DualNode, which monitors the output power supplied by the PowerTower to the residence. An additional 5530 DataNode monitors the AC inputs to the PowerTower from the grid and from the fuel cell.

The 5500 Series InfoNode is a web-based information concentrator that can gather power quality data from a wide variety of instruments, and then store and forward the data in IEEE PQDIF format. It also provides a rich, web-based user interface for data display and analysis. In addition to the two 5530 DataNodes, the InfoNode also collects data from an Adam module, which monitors various temperature and fuel level settings for the fuel cell.

Additional data acquisition and monitoring is facilitated through the use of a data concentrator manufactured by Axis Technologies. This device reads and stores the status information from the fuel cell via the 'Modbus' interface and it records status information from the PowerTower via its HTTP interface. All status variables are recorded permanently on a 30-second interval.

Remote monitoring capability is provided by a broadband satellite internet connection. An encrypted virtual private network (VPN) provides a secure connection between the remote site and the monitoring service at EnerNex Corporation. Data analysis is provided via a web application at this site.

Preliminary Findings

Image source: EnerNex Corporation

In continual normal operation, the fuel cell and energy storage system has proven capable of supplying 100% of the site load, except when the load on either leg rises above 5.5 kW or 45 amps. When the load reaches either level, the load shedding relay operates. If necessary, the full load is transferred back to the grid temporarily. This occurred several times during August and September of 2005, resulting in momentary interruptions of the supply that lasted approximately 2 cycles.

Noticable flicker has been observed in the system, and is believed to be due to large loads (such as the hot tub).