Two years ago, as fallout from the recession forced the Richmond Ambulance Authority to reassess its fleet strategy, the service hit upon a novel idea to cut costs and improve efficiency: It added solar panels to its ambulances.
The RAA’s first experience with solar power had come in 2008, when it decided to trial a solar panel on a support vehicle housed in a location without auxiliary power. That vehicle had an 80-watt panel installed and wired through a charge controller directly to its battery. Results were good: “The solar charge,” found RAA’s Fleet Manager Dan Fellows, “decreased the rate at which the battery discharged from the load of the accessory mobile communications and computers.” It also contributed to a general reduction in wear and tear. “It’s been three years,” Fellows says now, “and the vehicle has only had one battery replacement. And that was due to the headlights being left on.”
Based on the success of the support vehicle and facing a need to re-equip RAA’s fleet with a new model of chassis, Fellows began to plan a larger solution that would incorporate the panels not only to maintain battery life, but to provide powered “life support” to the vehicles’ many electrical systems. This would reduce the need for engines to run at high revolutions (high idle). The change would be eco-friendly by reducing noise, saving fuel and cutting emissions.
The reengineering was done by Excellance in Huntsville, AL, which remounted existing modules onto new gas-engine chassis and added the solar panels. It returned the first unit to Richmond in December 2010. The Ford 6.8L V10 chassis incorporates two 130-watt solar panels on the module roof linked directly to the main batteries through a dedicated charge controller and aftermarket engine idle system.
RAA chose the engineering configuration after considerable research of similar projects. Using solar panel technology is not new; even in EMS a few agencies have experimented with it. Richmond’s team identified that some agencies use solar systems to charge accessory batteries or reduce fuel consumption by shutting down at hospitals. That wouldn’t work for RAA, which operates in a high-performance, system-status planned environment, rarely having the opportunity to shut vehicle offs.
RAA’s employee-led redesign group determined the best use of the solar technology was to charge the vehicle batteries directly, thus offsetting the additional loads from laptop chargers, mobile gateways, radios and other systems.
By a year after the first two vehicles were put into service, RAA had added six additional gasoline/solar chassis ambulances to its fleet, and the remount-and-refurbish schedule will deliver another every 10 weeks for the foreseeable future. RAA has not replaced a single battery or starter on the new vehicles.
Adds Fellows: “We see in the reports from our onboard systems that batteries on vehicles with solar are not cycled as often or as deeply as those on non-solar vehicles, thus preventing premature battery and charging system failure. All systems retain full electrical charge from the permanently topped batteries, and the vehicle’s engine management system has not had to engage the high idle. The result is lower fuel consumption.”
An added and unexpected bonus came from installing the six-foot panels directly over the patient compartment: They created a “tropical roof” effect by placing an extra layer between the sun’s radiation and the internal compartment, making the A/C system more effective.
Data assessment of fuel consumption adds to the success story. Removing the need for high idle means the engine doesn’t work as hard or use as much fuel. RAA’s analysis of gasoline versus diesel ambulances revealed the true efficiency: The new ambulances deliver an average of 7.1 miles per gallon (calculated on constantly idling vehicles and miles driven) at a current operating cost of 47 cents per mile run. Diesel costs 66 cents a mile to operate (see Table 1).