The Department of Defense (DoD) has been mandated to increasingly derive energy from renewable resources. A review of DoD installations revealed that 170 of them have large land areas containing significant biomass resources. Typically biomass is left onsite to decompose or is land-filled at great expense, but not used as fuel. Converting this biomass resource to heat and/or electricity lowers an installation’s dependency on fossil fuels and directly contributes to DoD’s energy goals.
The objective of this demonstration was to generate data under realistic conditions on a DoD facility to allow analyses of the technical and economic viability of the BioMax® technology for widespread deployment at other DoD facilities in the future. The selected demonstration test site was Fort Carson, Colorado. This site was relatively near to the Community Power Corporation’s (CPC) headquarters, key for providing technical support for this first prototype system. Woodchips salvaged commercially from beetle-killed pine were selected as the feedstock. It was rationalized that the data generated at one DoD site could be extrapolated to a large number of other DoD sites, taking into account differences in feedstock costs, local energy costs, and local labor costs.
The BioMax® technology uses a downdraft gasification process to convert the energy trapped in biomass into a synthesis gas that is cooled, filtered, and utilized to power gensets, which create electrical and thermal energy. The BioMax® 100 system is highly automated, moving feedstock from a walking floor trailer, through the dryer, and into the gasifier based upon the electrical load needs of the site. The system can alert the operator of alarm conditions via computer, tablet, or smart phone.
During the field test, the BioMax® 100 had a steadily increasing monthly availability for the system that was approaching the program goal of 80%. The highest monthly availability attained was 74%, occurring in the last month of the field test. On a weekly basis, there were 4 weeks where the availability exceeded 80%, but only two of them were consecutive.
A life-cycle cost analysis was performed for the BioMax® 100 system operating as a base-load provider, which showed the small system had a relatively high capital cost, but a relatively low fuel cost assumed to be $40/dry ton (about $3.50/million British thermal units [Btu] [MMBtu], if the wood were burned in a boiler operating at 80% efficiency). Feedstock cost varies from a negative, avoided disposal cost to over $100/dry ton based upon the site, transportation logistics, etc. The assumed $40/dry ton is a reasonable average based on CPC’s experience with BioMax® systems at various locations in the contiguous United States. A BioMax® system cannot compete economically with grid power in most DoD locations, except in Hawaii and other remotely located facilities having very high fossil fuel costs.
For the case of generating electricity at sea level (assuming no recovery of waste heat) with the BioMax® 100 system, the electricity produced must be valued at over $0.335/kilowatts (kW) of electrical energy (kWe) per hour (kWeh) to result in a simple payback period of 7 years or less. With recovered waste heat, 7-year simple payback periods can be achieved with lower electrical values, which depend on the value of the displaced fuel used for heating. For example, with a heating fuel cost of about $4.65/MMBtu (contiguous U.S. industrial average 2013 for natural gas), the electrical value needs to be over $0.29/kWeh. With the displaced heating fuel cost of $4.10/gal of fuel oil, the electrical value can be near zero with waste heat recovery for a simple payback period of 7 years. Operating the BioMax® 100 system at higher elevations results in engine de-rating and consequently lower levels of electrical generation and recovered waste heat levels, both of which impact negatively on the economic projections.
The BioMax® 100 system has difficulty competing with electrical grid power and natural gas in the contiguous United States. However, for remote locations that are not served by the grid or by natural gas, the BioMax® 100 is very competitive with long-term generation of electrical power and recovered waste heat, compared to generating the same amount of power with two 60 kW Tactical Quiet Generators (TQGs). Operating the BioMax® 100 over an assumed 15-year life with biomass at $40/dry ton is projected to have a life cycle present value of +$323,904, compared to producing the same amount of electrical power using two 60-kW TQGs, fueled with diesel at an assumed average contiguous U.S. price of $4.10/gallon having a negative present value of -$3,308,559. Over the long run, the lower cost of biomass, compared to JP-8, more than compensates for the initial high capital cost of the BioMax® system.
Prior to shipping to Fort Carson, exhaust emission testing showed that the system had extremely low levels of emitted pollutants in the exhaust gas. The projected maximum yearly air emissions were so small that it appeared a permit to operate the BioMax® 100 system was not required by the State of Colorado. Nonetheless, Fort Carson required a Colorado permit to operate the system on its premises, which resulted in a significant program delay.
After a short period of operation, the custom-designed engine developed mechanical problems, which resulted in its replacement with two General Motors spark-ignited engines that CPC had modified slightly to accommodate fueling with gasoline, producer gas, or a combination of the two during startup of the gasifier. Fueling with gasoline only occurs during startup of the system. This required new gaseous emission testing and a new operating permit, which delayed the field testing several months.
The commissioning period at Fort Carson lasted much longer than planned before unattended operation was attained. This prototype system required numerous control code changes and some minor equipment changes. Nearly all of the program goals were met or exceeded. For example, the maximum sustainable, net electrical power at Fort Carson’s elevation was 83 kW (104 kW net at sea level), compared to the goal of 75 kW at an unspecified altitude. The maximum sustainable recovery of waste engine heat was 180 kW thermal, which extrapolates to 226 kW thermal at sea level, compared to the goal of 150 kW thermal recovered.