Demonstrating Portable Energy
Portable gas and diesel generators help power many aspects of the global economy. Construction companies and the remote communities depend on gensets to provide heat and power in areas where connecting to the grid is not possible. They are also used to power outdoor events, concerts, military operations or provide a critical source of power in disaster areas. In the developing world, generators also help to overcome issues associated with unreliable, outdated and non-existent electricity grids.
The vast majority of commercially-available generators are designed to run on fossil fuels. However, a new equipment package could change that by allowing these gensets to be fueled with biomass-based syngas. Funding for the project was provided the the U.S. DOE National Energy Technology Laboratory.
An ongoing project led by the University of Minnesota Morris and California-based All Power Labs LLC has resulted in a fully integrated solution that combines All Power Lab’s unique gasification system with a genset, a system housed in a single 20-foot shipping container. The result is the PowerTainer, a portable system that allows a diesel generator to run on more than 90 percent biomass syngas.
Additional organizations participating in the project include Cummins Power Generation and the University of Minnesota Center for Diesel Research, and HGA Architects and Engineers. According to Jim Barbour, a staff scientist at UMM, Cummings provided the genset to the PowerTainer project, offered engineering consultation services, and participated with the integration of the genset with the gasification system. The Center for Diesel Research helped optimize the operation of the diesel engine on syngas.
Syngas Genset Technology
The heart of the PowerTainer is a multi-staged biomass gasification system developed by All Power Labs. According to Jim Mason, company founder and director, the innovative system is a modified version of a fixed-bed, down-draft reactor. “We have separated the drying from the pyrolysis, and drive those off of waste heat from the engine,” he says.
The multistate heat exchange system, Mason continues, functions to return all the waste heat flows from the gasifier and the engine to the appropriate process points within the reactor. “This is how we create temperature conditions that take care of the tar in the reactor,” he says.
The tar treatment method is one element that makes the gasification system unique. Rather than dealing with tar removal downstream, an aspect of operation that can complicate the system and also requires bulky equipment, the technology deals with tar in the gasification system itself.
“We do that by the separation of different process stages within the reactor,” Mason says. The gasification system is overlaid with a highly effective automation system that works with maps of the reactor that specify where tar is and is not generated. The automation system can operate the reactor with a high degree of sophistication to control, within certain parameters, where gasification occurs. The automation system, combined with the heat-exchanger that pushes a large quantity of heat back into the system, allows for tar production to be minimized.
The gaseous fuel that results is produced through an on-demand basis for the genset. The gasifier responds to the load variations of the engine, Mason says. The syngas produced by the gasifier is not very energy dense, which makes storing it inefficient.
The syngas can fuel both spark-ignited engines and diesel engines. When the syngas is fed into a spark-ignited engine, it can replace 100 percent of the fossil fuel that would normally enter that system. When the syngas is fed into a diesel generator, such as the one contained within the PowerTainer, the producer gas must be mixed with a small injection of diesel fuel. Current evaluations show that it should be possible to replace more than 90 percent of the diesel with biobased syngas.
Other than changing the speed control of the engine, Mason says that no other changes were made to the Cummins genset that is a part of the PowerTainer.
In addition to the gasification system and Cummins genset, the standard 20-foot shipping container also houses a small filter train, a hopper and an electronic automation system. Mason notes that the inclusion of a hopper in a demonstration-scale operation is unique. However, he says the team did not want that component of the project to be an afterthought. Rather, the goal was to fabricate an entire, compact, fully-integrated system that could encompass all aspects of operation, from fuel-feeding to power-generation.
Regarding feedstock, the PowerTainer has been optimized to gasify corn cobs. All Power Labs has also designed similar gasifiers that are optimized for wood chips. Mason says the gasification system does have some limits regarding how small the biomass can be. Specifically, it cannot take in shredded or granular fuels.
The PowerTrainer Goes Public
UMM hosted a demonstration of the PowerTainer in June. “The engine ran just beautifully,” Barbour says. “It performed well.” Approximately 50 people attended the event, representing a wide variety of interests, from university researchers to industry professionals, farmers and entrepreneurs.
The two-year project is now in its last six months, and is scheduled to conclude in December. During the final stage of the project work will focus on emissions evaluations. The work will be completed using university lab equipment, including gas analyzers. “We also have an instrument that actually measures soot, which is an important emissions issue with diesel engines,” Barbour says.
UMM Economics Professor Arne Kildegaard will also develop an economic model that will address equipment and operational costs, Barbour says. The analysis will include comparisons to more conventional means of small-scale power generation, such as the steam turbine found on campus.
The ultimate goal of the project is commercialization. While specific plans for commercialization or licensing haven’t been released, Mason is able to provide cost estimates for a future commercial version of the PowerTainer. Based on gasification systems fabricated and sold by his company, the estimated cost would be within the $1 to $2 per watt range, most likely between $1.30 and $1.70 per watt. Theoretically, using these figures, a 100 kW system could represent between $130,000 and $170,000 in capital expenses.
All Power Labs has been supplying gasifier experimentation kits on a commercial basis for approximately four years. For the past year and a half, the company has also sold larger-scale integrated gasifier-genset skids, called PowerPallets. Overall, Mason estimates his company exports 60 percent of the systems it builds.
Regarding the PowerTainer project, both Mason and Barbour stress that the distributed power generating potential of the system is one of the most important aspects of the system’s development. Distributed power generation helps overcome some of the logistical problems associated with biomass procurement, shipping and storage. In the form of a portable system, like the PowerTainer, distributed power systems that are capable of operating on biomass fuel also offer contractors, farmers, and others more control over the source of power they use. In addition, the use of locally-sourced biomass can help insulate those who own the systems from price shocks in the commodity market.
Author: Erin Voegele
News Editor, Biomass Magazine