Under the skin of a made-for-military microgrid
Powering remote military structures and installations in hostile areas far away from reliable diesel fuel convoys is a critical capability and one that is drawing significant funding and innovation. Claire Apthorp speaks to lithium battery manufacturer Enerdel, which is part of a team developing innovative power conversion technologies to create a hybrid solar battery and storage system for the US Air Force.
The reliance on diesel to power generators at remote military forward operating bases (FOBs) proved an immense challenge for US forces operating in Afghanistan throughout the last decade. The vehicle convoys needed to deliver the diesel to the FOBs quickly became a favoured target for improvised explosive device (IED) attacks, putting the lives of men and women travelling through these hazardous environments at risk.
In 2013, the US Marine Corps released a brief to industry regarding the use of diesel powered generators at its FOBs in Afghanistan. It revealed that in a three-month period 299 fuel and supply missions were carried out. During these missions there were 17 IED events and six casualties.
The need to overcome this issue and keep personnel out of harm’s way has prompted the US military to invest in finding new ways to keep FOBs powered with research into alternative fuel sources – not just as an effort to save lives, but also to yield cost savings by reducing fuel costs.
The forward operating base of the future
In March 2016, researchers from the US Air Force Research Laboratory teamed up with the University of Dayton Research Institute (UDRI) and launched a year-long programme to demonstrate new energy technologies designed to significantly reduce the amount of diesel fuel needed to power remote military installations.
This programme, now underway at the Joint Base San Antonio’s Basic Expeditionary Airmen Skills Training facility, will use energy-efficient insulation and lighting, improved heating, ventilation and air conditioning systems and smart controllers, advanced batteries for energy storage and delivery, solar cells and other technologies to generate and manage cleaner energy while reducing energy demand and environmental impact.
EnerDel became involved in the project when the mobile hybrid power system (MHPS) it was developing attracted the interest of the team.
The company has been involved in grid energy storage and hybrid power systems since 2010. In a 2013 US Marine Corps Experimental FOB (ExFOB) event it demonstrated a 10kW split phase MHPS with 40kWh of energy storage, a 10kW diesel generator, and a 10kW inverter all mounted on a military style trailer.
“This unit was primarily used to demonstrate fuel savings by running the generator at its optimum fuel consumed to power produced level anytime the generator was on,” says Tod Becherer, sales manager for grid and energy storage at EnerDel. “The energy consumed from the load was subtracted from the energy produced with the excess energy directed into the energy storage system (ESS); once the ESS was topped off, the generator would be turned off and the loads supported with power being drawn from the ESS.”
The success of this demonstration led to a contract from the US Army Corps of Engineers at the Engineer Research and Development Center – Construction Engineering Research Laboratory (ERDC-CERL). ERDC-CERL requested that EnerDel develop a system that would use the army’s tactical quiet generator (TQG) integrated into a system that uses an onboard 15kW TQG, available solar inputs, an 80kWh ESS, and 45kW 208VAC 3 Phase 60Hz inverter with controls and I/O capable of also controlling an external TQG up to 60kW, with separate outputs for critical and non-critical loads and automatic load shedding. Additionally, EnerDel designed the system to be able to combine the output of the inverter using stored energy and the generator in parallel in order to support loads of up to 60kW.
This MHPS was installed at an experimental FOB laboratory where it replaced a 30kW generator that was running 24 hours a day, 7 days a week. The 30kW generator was supporting peak loads of up to 27kW, but its average load was only close to 5kW and was consuming about 54 gallons of fuel per day. Once installed in place of the 30kW generator, the MHPS reduced fuel consumption to about 11.5 gallons per day.
Solar energy as a power source
Based in part on the success of this demonstration, the UDRI team requested that EnerDel supply eleven smaller systems that would only use solar energy as the means of charging the ESS. These systems were to be connected with solar arrays that are mounted as integral parts of tent shades.
“Ten of the eleven systems were installed at the base on solar shades that are installed above the personnel tents for recruits undergoing training for conditions at FOBs,” says Becherer. “These systems switch the power feed to each tent’s lighting and environmental control units from the grid to solar and stored energy as it is available.
“Once the sun is down and the ESS has depleted its energy to its targeted state of charge, the system returns the loads back to the grid power. Studies between various sites are being evaluated in an effort to determine the viability of solar as a power source in actual FOBs.”
The one year demonstration project is now drawing to a close. The USAF and URDI are in the process of reviewing and compiling the data and will be issuing their report in the near future. Meanwhile, EnerDel is continuing development efforts to further ruggedise its MHPS and produce solid state controllers.
These targets are being pursued in order to reduce weight, costs, parasitic system energy losses and to make the system more flexible in the fit, form and function of the application - all vital requirements that will help change the way military and industry views power production alternatives.
“Hybrid power production as a micro-grid solution eliminates the need for long transmission lines, centralised grids and controls that carry power across thousands of miles, and a distributed or micro-grid could be used to provide cost effective power in a wide variety of applications,” says Becherer.
This potentially includes civilian and paramilitary applications, with the same or less militarised versions used by state or local disaster relief agencies for small to medium sized mobile power stations for hurricane, flooding or other disaster relief situations. Similarly, in remote areas these systems could be scaled to become fuel efficient micro-grids.
“The demand for distributed energy storage systems over the next five to ten years is expected to grow rapidly as utilities and industrial players install renewable generation and energy storage across the globe,” says Becherer. “Today, the cost remains high, but we are already seeing dramatic reductions in other industries as demand increases, and the cost of solar equipment has plummeted over the past two decades.
“The main hurdles are producing a robust product with remote monitoring from a central point to anticipate maintenance issues or dispatch more fuel, changing the paradigm of the power consumer and industry, and gaining product awareness with the opportunity to prove performance and reliability as a viable alternative to the present emergency and conventional power systems.”