Charging ahead with renewables

29 September 2013

REO has recently completed the development of an electric vehicle charging station under the brand name ‘REO-Move’.

The objective was to develop and build a functional charging station for electric vehicles – more particularly for use by the company’s own internal logistics fleet. The charging unit is housed in a carport to allow users to work safely and comfortably, and is entirely supplied from renewable resources.

At the moment, many of the power generation technologies the renewable energy sector relies upon function reliably and efficiently only in certain geographical areas where climate or topography permits. But there are opportunities to combine these generation technologies to make the most of what is available at a single location.

Take REO’s approach as an example. The company's REO-Move project began in 2011 as the basis for a vehicle charging port. It integrates several methods of harvesting energy by utilising a free-standing tracking solar panel unit and a wind turbine which work in partnership according to prevailing weather conditions to charge electric vehicles.

The maximum power output of the scheme is currently 5.5kW but REO believes this can be easily scaled up using larger elements. Such is REO-Move’s current charging capacity that a Renault Twizy can be charged with this system in about 3.5 hours, giving the car a range of 100km.

The efficient use of solar energy in the free-standing tracking solar unit is guaranteed at over 45 percent and, thanks to its modular design, it took just five weeks to build. Furthermore, individual components can be easily substituted, which allows alternative products and new technologies to be tested and validated as and when they become available.

At present, the surface area of this installation is ten square metres, providing a power output of 1.5kW, but the option exists to extend this up to 25 square metres, with a corresponding increase in power output.

A nine metre high wind turbine was also erected near the site in 2012. It can produce up to 3.5kW at full load and even produce electricity at wind speeds as low as 2.4 metres per second. The associated cabinet can charge eight 12V, 195Ah lead-acid batteries, which have a total capacity of about 14kW, using an inverter which provides a uniform output voltage of 230V.

The total cost of the project, which covers an area of 170 square metres, is expected to run to about €31,000 with a construction time in the region of 15 months. REO UK managing director, Steve Hughes comments on the finer points of the REO-Move system and how the company was able to draw on its own resources to complete the project:

“A typical electric vehicle charging station usually involves converting ac to a controllable dc voltage,” says. “There are ripple currents that need to be reduced to ensure that the battery receives a workable current and voltage. Unlike conventional lead-acid batteries, electric vehicle batteries do not like high ripple voltage and current, as it shortens their lifespan.

“Ripple frequency also needs to be mitigated and REO products help in those instances where new battery technology is more susceptible to impairment and likes to have a more defined charging envelope. We are moving towards manufacturing very low ripple battery charging systems.

“Historically people have used a belt-and-braces approach such as dc thyristor rectifier configurations. We offer a whole range of products, including things like electromagnetic compatibility (EMC) input filters to solve ripple issues within the dc section.”

As a result of the project, when REO customers ask the company to develop components and products for their own renewable applications, REO can more easily demonstrate competence in this market. This includes high quality inductive components, EMC engineering, bespoke product formats and designing to target within agreed timeframes and objectives.

The project is now up and running successfully at one of REO’s locations, and plans are already in the pipeline for another station at another site to help reduce its logistics costs.