The hype is over in distributed generation (DG) — and good riddance! Sure the technology is promising. And, yes, DG has the potential to add value for both customers and utilities. But before DG can really move forward, we have to overcome the fear, the greed and the hype fomented by early DG proponents who dared to proclaim: “The grid is dead.”
No, the grid is not dead. I don't know of a single line taken out of service because of DG. But I do know of a certain microturbine vendor that mysteriously pulled the plug on what was to become “the next great consumer product.”
To check on the status of DG, IEEE Kansas City (Missouri) Chapter President Jim Berard sponsored a DG conference earlier this year in conjunction with Transmission & Distribution World. Berard works at one of Kansas City's innovative contractors, Mark One Electric Co., where crews hook things up and make them work. We invited only speakers who could discuss something that was already operating. Here is what we found:
With the exception of Capstone Turbine, the microturbine market is several years from general deployment.
Commercial fuel cells are even further out but making gains.
The real action in DG is in natural gas fueled reciprocating engines.
Larger customers continue to look for applications for combined heat and power gas turbine applications.
Commercial packages are available to connect DG to the grid.
Utilities are looking to DG installations to address capacity needs.
With my appetite whetted for DG, I decided to take a road trip. My first stop was the American Electric Power (AEP, Columbus, Ohio, U.S.) Dolan Technology Center. Lab Manager Dave Nichols showed me around the 500-kW outdoor test site where engineers evaluate microturbines, reciprocating engines and fuel cells. With access to capacitive, resistive and reactive load banks, engineers check out characteristics such as voltage support and load following.
I then went across the highway to AEP's new Walnut Test Facility. With four outdoor testing bays, this site will accommodate aggregate generation up to 10 MW. Currently, two cells are operational with 1.5 MW capacity each. Both sites have the capacity to inject power into the local 13.2-kV distribution grid. AEP is making these sites available to utilities and vendors, which should speed up the commercialization process for DG. I also witnessed AEP's NAS® battery demonstration up and operating. This high-density sodium-sulfur battery was developed by NGK of Japan and first installed by Tokyo Electric (see T&D World, February 2002).
AEP now feeds the lighting and receptacle circuits of its Gahanna regional distribution operations headquarters from the NAS battery, which is a 500-kW uninterruptible power system (UPS) for voltage dips and can pump 100 kW back into the system for peak shaving. The battery was quiet and unobtrusive. ABB's modular power conversion system was fairly compact with each battery set sporting its own bidirectional inverter. One caution, sodium and sulfur are solid at ambient temperatures, so it is critical that cells remain at about 320°C (608°F) to ensure longer life.
After my stop at AEP, I continued on my road trip to Detroit Edison and parent-company DTE Energy (Detroit, Michigan, U.S.). You might recall that DTE Energy made a significant commitment to DG with an investment in Plug Power, makers of a proton exchange member (PEM) fuel cell; GE Capital is now an investor as well. I toured the Hancock Generating and Switching Station where Plug Power fuel cells provide charging current to station backup batteries feeding both the substation and five peaking turbines. I found that on a typical Plug Power installation, the stacks make up a small portion of the overall package. The reformer, which extracts hydrogen from natural gas, along with the power inverter consumes the majority of the space.
Detroit Edison is also connecting DG to the grid to alleviate overloading the system, thus enabling the utility to delay new construction. In some instances, the utility is keeping the lights on while addressing special interest groups who are actively fighting system upgrades.
Hawk Asgeirsson, supervising engineer of resource planning, took me to see the DG installation of a 1 MW Deutz natural gas fueled reciprocating engine at the 4.8-kV Adair Substation. The system, which provides voltage support and meets heavy summer loads, was installed by subsidiary DTE Energy Technologies (d/tech), which provides DG services nationwide. I subsequently met with the president of d/tech, Paul Horst, who informed me that he finds few commercial and industrial customers who want to engineer, build, operate and maintain DG; they prefer to contract for packaged services. Accordingly, Horst's group has an active strategic operation center from which they can monitor and control DG remotely, while providing customers with data on both energy usage and system conditions.
For electric utilities weaned on the generation and delivery of electricity, adding interconnected small-scale generation with appropriate instrumentation and control is not that a big a deal. The threat posed by DG was over-hyped. The reality of DG is setting in. We now have tested, operating DG connected to the power-delivery system. Now it is up to us to apply common sense as we work through the many details required when connecting dispersed generation to the grid.