City Trees

locations to power them. Office buildings were an easy fix by adding an outdoor outlet where needed. Substation locations had a building with power, but not in a good location to supply the robot mowers. This needed a little more thought, but after incorpo- rating the Construction and Design group, a simple and cheap fix was concocted. With the low power usage, a 10kVA transformer that is typically used for street lighting and is readily available was installed with a standard meter loop. This allowed an outlet to be installed outside the substation fence but still on the property. For approximately the same cost as the transformer and installation, a solar-powered generator can be used, which virtually eliminates the carbon footprint of the robot mower. The small, portable generators can be hidden in plain sight within the substation fence to deter theft while effec- tively powering the robot mower. One of Liberty's rural substations has approximately six acres (2.4 ha) of grass inside the fence, and the Union Labor Agreements requires a substation electrician to be present while it is being mowed. The solar generator, combined with the robot mowers, was a perfect solution to reduce the cost and allow Liberty's sub- station electricians to work on more important tasks. Using the solar generator for a source of clean, renewable energy to power the robot mowers further adds to Liberty Utilities' sustainability image. The robot mowers themselves are touted as being more sustainable in the unique way they maintain the grass. More frequent mowing maintains the lawn at a specific height for a golf course look, but it also has the advantage of recycling the cuttings faster due to the smaller size of the blade of grass. This eliminates the clumps of thatch that are left between mowing and the patches of dead grass that follow on subsequent mowing. Maintaining the grass at near-constant height also reduces the stress caused by cutting too much at once. Healthier grass requires less inputs/fertilizers to keep it looking good and thus reduces the costs as well. Another benefit is reduced noise pollution. The robot mowers operate at a noise level of 57 decibels (dBs) and can be run at night virtually unnoticed. Having a conversation next to the mower while it is oper- ating is easy in comparison to a conventional mower that operates at around 100 dBs and requires ear protection. This feature is useful in urban settings where the mower can operate under the stealth of night and not disturb the neighbors. Adding on to the quiet operation is the ability to remove a person from the equation completely. Drive time between mowing locations is eliminated, as well as >> urban-forestry.com 29 New robot mowers require a new way to think about landscape design and maintenance.

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