Diesel standby generator sets are basic equipment in water and wastewater treatment plants. They’re designed to start immediately, ramp up quickly to full load, and power essential plant equipment until main utility power is restored.

Now, Kohler Power Systems has introduced KD Series diesel gensets, designed from the ground up to deliver standby power in compact and highly efficient packages from 800 kW to 4 MW. The units are powered by Kohler G-Drive diesel engines with fuel injection and engine management systems engineered to optimize performance.

The engines run smoothly and quietly with low vibration even under extreme operating conditions, extending service life. The common rail direct fuel injection system generates high injection pressures to maximize efficiency. This enables high power density and kilowatt displacement in packages that deliver high fuel economy.

Jim Rummel, senior product manager for large diesel, and Steve Zielke, marketing manager – vertical segments, talked about the KD Series in an interview with Treatment Plant Operator.

TPO: What makes this generator set series a good choice for standby power?

Rummel: Kohler has been in the generator business since 1920. We are one of four companies in the world that build their own engines and gensets at 2 MW and above, and we’re the only one who builds our own engines specifically for generators. The development of this series has gone on for seven years, and we’ve been able to focus on the latest technologies and design techniques to build a world-class product.

TPO: What specific advantage does this series offer to water and wastewater facilities?

Rummel: Because of the large startup loads these facilities get from pumps and other equipment, we created a product line with very strong motor starting capabilities and very quick startup times. All KD Series generators comply with the international ISO 8528-5 Class G3 requirements for transient load performance. Because of how quickly they adapt to load, users can do startup and restore operations very quickly.

TPO: How rapidly can these units accept load in an emergency?

Rummel: The KD Series surpasses the NFPA requirement for 10-second startup time to full load. The KD1000, with a 1,000 kW capacity that is a sweet spot for many wastewater applications, reaches 90 percent of rated voltage and frequency in 6.2 seconds from cold start. If it’s already running and idling, it completes the zero to 100 percent load step significantly faster than that.  

TPO: What are some of the key design innovations in this product line?

Rummel: Our common rail system reaches injection pressures of over 2,200 bar. Much of the efficiency starts there. Because of this process, we see low fuel consumption, high power density, and high kW displacement coming together to create an efficient package. Our system is also unique in that we don’t use the fuel to cool the engine. That means when designing day tanks and fuel delivery systems, you don’t need to incorporate chillers or oversize the day tank to account for warm fuel that’s being returned.

TPO: What else about this product have customers responded to favorably?

Rummel: Engineers have been excited about our fuel lift. The KD1000, for example, reaches a fuel lift of 14 feet. That means more flexibility in where they can put the day tank without needing a booster station. So for example, if the genset sits above a day tank that is narrow and deep, there is no worry about the engine being able to suck out fuel when that tank gets low.

TPO: What is the benefit of high kW displacement in these engines?

Rummel: The KD1000 displacement is 27 liters; most other products in the market at that capacity are 30 to 33 liters or above. The result is a smaller footprint, less weight, less steel, fewer isolation pads and easier service. Because of this and other efficiencies built-in, we are very competitively priced even with all the innovation this series contains.

TPO: How are these generator sets controlled?

Rummel: The engines incorporate the Kohler Diagnostic (KODIA) System, which monitors all functions. It communicates seamlessly with the genset controller, which is also the user interface. Users can download data on anything happening with the engine and genset itself using a full-color display screen. We also supply switchgear and automatic transfer switches, or ATS. For standby, users can have a break-before-make system, where the utility power goes out and then the generator starts, or a make-before-break system, where the ATS senses that the utility is about to lose power and starts the genset ahead of it.

TPO: Do you envision these gensets being used for some form of load management or demand response in conjunction with utilities?

Rummel: Absolutely. For more complex systems that involve paralleling multiple units and integrating with the utility, we offer total system integration.
Zielke: We have extensive experience in the wastewater industry with our Engineering Solutions department and our ability to integrate entire systems. That is coupled with our distribution network. In the U.S. alone, we’ve installed hundreds of large gensets in wastewater facilities.

TPO: What has been the response from customers and prospects since this series was introduced?

Rummel: Over several months, we held local events where our distributors had a generator set available for demonstrations. We invited many consulting engineers and people from the wastewater industry. The customer feedback has been really positive. We had a sales plan for the first 12 months after release, and we reached that plan within six months. This series has been accepted at a rate twice as fast as we projected. The customers see the advantages.