Going hybrid



Nicknamed the Prius of the seas, the USS Makin Island is a hybrid diesel-electric ship that relies on electric motors for power at low speeds. On its maiden voyage in 2009 it saved almost $2 million in fuel costs sailing around South America from Mississippi to its home port in San Diego, California.



Next year the navy plans to test-drive its Great Green Fleet, a strike group including an aircraft carrier and escort ships powered either by nuclear fuel or 50-50 blends of biofuels and conventional fuel. The carrier's aircraft will also run on a mix of biofuel and aviation fuel. The fleet is scheduled to be deployed for regular use in 2016.



(Image: US Navy)

Cutting through the waves



The navy is making a number of smaller changes to its existing fleet that together add up to significant increases in fuel efficiency. New antifouling coatings like those applied to the guided missile cruiser USS Port Royal (left) help keep the hull free of barnacles and other marine organisms. This reduces drag and can increase fuel efficiency by as much as 12 per cent.



Other drag-reducing innovations include stern flaps – horizontal fins extending from the back of the hull which reduce drag on the hull by reducing turbulence in the water as it flows past the stern. The navy has already installed such flaps on a number of its ships, resulting in at least a 4 per cent reduction in fuel use.



(Image: Marshall Fukuki/US Navy) Advertisement

Biofuelled fighter



The "Green Hornet", an F18 Super Hornet fighter jet, flew at 1.7 times the speed of sound on a 50/50 blend of biofuel and conventional fuel in April last year. The biofuel was made from the seeds of Camelina sativa, a flowering plant that can be grown in marginal agricultural land and so does not compete with food crops – the navy has a policy not to use biofuels such as corn-based ethanol, which come from land that could be used for food production.



US Secretary of the Navy Raymond Mabus says existing technology will allow the US navy and marines to meet their 2020 goal of getting half their fuel from renewable sources, but next-generation biofuels such as those derived from algae would give higher yields and likely be more cost-effective.



(Image: Liz Goettee/US Navy)

Green marines on the front line



Instead of hauling fuel to the front lines, US soldiers are beginning to get their power from the sun. Instead of diesel fuel, photovoltaic panels paired with batteries provide continuous power to marines in the field. The system, known as the Ground Renewable Expeditionary Energy System (GREENS), is currently being used at US forward operating bases in Sangin district, Afghanistan.



Transporting fuel to the front lines in guarded convoys is expensive, both financially and in soldiers' lives: a US marine is killed or wounded guarding one in every 50 convoys. A number of solar power devices are now being tested for remote bases.



(Image: John F. Williams/US Navy)

Roll up solar



US marines in Sangin district, Afghanistan, also carry roll-up solar blankets in their packs rather than heavy batteries. The flexible panels, known as the Solar Portable Alternative Communication Energy System (SPACES), take less than a minute to plug in and are used for recharging radios and GPS devices. The system allows the soldiers to lighten their load by carrying fewer batteries and remain away from established camps longer without being resupplied: their patrols typically need to come in for fresh batteries every three to four days. SPACES recently allowed a US patrol to go three weeks without a battery resupply.



(Image: US Navy)