Distributed Energy Resources Test Facility Virtual Tour (Text Only)
Distributed Generation and Storage
Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be converted into electricity using a generator or inverter.
Microturbines are a new type of combustion turbine used for stationary energy generation applications. They are small combustion turbines-approximately the size of a refrigerator-with outputs of 25 kW to 500 kW and can be located on sites with space limitations for power production.
Microturbines are composed of a compressor, a combustor, a turbine, an alternator, a recuperator, and a generator. Waste heat recovery can be used in combined heat and power systems to achieve energy efficiency levels greater than 80%.
A photovoltaic array converts sunlight directly into electricity and is made of cells of semiconductors such as crystalline silicon or various thin-film materials. Photovoltaics produce DC electricity and need inverters to connect to the utility grid.
A battery is a device that converts the chemical energy contained in its active materials directly into electrical energy by means of an electrochemical oxidation-reduction (redox) reaction. Batteries produce DC electricity and need inverters to connect to the utility grid.
Fuel cells can be used to produce clean energy from hydrogen. A fuel cell consists of two electrodes-a negative electrode, or anode, and a positive electrode, or cathode-sandwiched around an electrolyte. Hydrogen is fed to the anode, and oxygen is fed to the cathode. Activated by a catalyst, hydrogen atoms separate into protons and electrons, which take different paths to the cathode. The electrons go through an external circuit, creating a flow of electricity. The protons migrate through the electrolyte to the cathode, where they reunite with oxygen and the electrons to produce water and heat.
Fuel cells produce DC electricity and need inverters to connect to the utility grid.
An electrolyzer works by splitting water into hydrogen and oxygen atoms. This is done by passing an electric current through the water. Hydrogen collects at the negatively charged cathode and oxygen collects at the positively charge anode. Hydrogen produced from electrolyzers can then be stored and used as needed with fuel cells.
Reciprocating Engine-Generator Set
Reciprocating, or piston-driven, engines are a widespread and well-known technology. Also called internal combustion engines, reciprocating engines require fuel, air, compression, and a combustion source to function. To make electricity, the engines are typically connected to synchronous generators that produce grid-compatible AC power.
Depending on the ignition source, reciprocating engines generally fall into two categories: (1) spark-ignited engines, typically fueled by gasoline or natural gas, and (2) compression-ignited engines, typically fueled by diesel oil fuel.
Interconnection and Testing Technologies
Data Acquisition and System Control
Because many of the parameters tested involve sub-cycle transient times, a relatively high-speed data acquisition system is necessary to perform testing. To accomplish this, a power analyzer capable of sampling rates up to 5 million samples per second is used. Voltage and current measurements are accurate to ±0.2% of the reading values, with the time scale accurate to ±0.05%. The data acquisition and system control allows for the monitoring of up to 25 various devices (generation, storage, and loads).
The switch panel allows for easy interchangeability of equipment pieces once they are interconnected to the electrical buses. The AC bus can connect up to 15 AC devices (DG, loads, utility, etc.), and the DC bus can connect up to 10 DC devices (batteries, PV, fuel cell, etc.).
The AC and DC electrical buses are the wire connections that allow the various devices to be interconnected. The current system is capable of handling up to 200 kW of generation.
Inverters convert DC electricity to AC electricity that is compatible with the utility grid. Inverters not only do the power conversion for DC devices but also include protection and synchronization functions.
These switches allow the interconnection of synchronous generators to the utility grid. These switches monitor the DG and utility and provide protective functions and synchronization between the two sources. Paralleling switches allow the DG to remain in parallel with the utility, and transfer switches only operate when the utility goes down.
This unit produces various electrical surges that can be used to test the reaction of electrical devices to electrical problems such as lightning strikes. Specific tests can be programmed based on IEEE and IEC standards.
Electric Power Systems
Electrical Distribution System
The electrical distribution system is the portion of an electric system that is dedicated to delivering electric energy to an end user. The distribution system is made up of wire conductors that deliver electricity, transformers that convert electricity voltage levels, and protective devices (such as sectionalizers, reclosers, fuses, and circuit breakers).
Utility Grid Simulator
The utility grid simulator is a specially designed AC power supply. Four units are paralleled to provide a combined capacity of 250 kVA (200 kW) at 480 V with the use of a transformer. This design allows fully programmable control of individual phase voltage, current, and frequency. Output regulation and total harmonic distortion are less than 1% for normal 60-Hz operations. The grid simulator is capable of fast response times, responding to a 100% step load change in less than 300 ms. The grid simulator can reproduce disturbances such as sags, swells, and harmonic problems with the utility.
The load banks used at the test facility are customized versions of commercial load banks. The units can provide 165 kW of resistive loads and 404 kVAR of inductive and capacitive loads. Step sizes as small as 125 W and 312.5 VAR can be achieved. A LabView graphical user interface controls the unit through serial ports back to the system control.