Energy Efficiency Made Simple Vol IV 2015

No conversation about electrical energy could be complete without including transportation. Electric vehicles have been around since the development of storage devices, but only recently have they been seriously considered.

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Electric mobility solutions – enormous operational energy cost savings A English, FreedomWon

A n advanced EV drivetrain design by the company the author represents, in collaboration with the Zest WEG Group, is using highly efficient Permanent Magnet (PM) motors and a direct current (dc) input version of the WEG CFW 11 three phase inverter. This system has been installed in various conventional vehicles by removing the original engines and fitting in their place a combination of electric motor, motor controller (inverter) and lithium batteries. The energy efficiency of Electric Vehicles (EVs) described in this article has resulted in an operational energy cost saving of up to 90%. This is substantiated by case study data from a game lodge in Botswana, which is operating FreedomWon Electric 4x4 game drive vehicles and electric river boats.

of Chobe Game Lodge has started the process of converting its entire 4x4 and boat fleet to electric power.

Talking efficiency The energy efficiency of EVs is about 83% comparing the energy used to charge the vehicles to the energy ultimately transferred onto the vehicle drivetrain. This compares to 25% for petrol engines and 40% for diesel engines in terms of the efficiency for converting fossil fuel energy placed in the tank to useful mechanical energy. These efficiencies are based on a steadily running engine under a constant load. A petrol or diesel internal combustion engine will exhibit far lower overall efficiencies in the real world, where stopping, starting and idling occurs frequently. The efficiency drop under these conditions with an electric vehicle is by contrast very small. The more efficient transfer of energy to the vehicle drive system means lower cost of operation. The use of solar energy to charge EVs eliminates direct costs and operational CO 2 gas generation altogether and relies purely on an upfront investment in a photovoltaic array and a stationary battery for night time charging. The 83%efficiency is very much the leading edge in EV design and is made possible by the WEG ‘Wmagnet’ PMmotor with an efficiency of 95,3% [1] the WEG CFW11 Inverter of 97% [2], the charger of 93% [3] and the ‘round trip’ (charge – discharge) efficiency of the Lithium Iron Phosphate cells of 97% [4]. The formula therefore is: Overall Efficiency = 0,95 x 0,93 x 0,97 x 0,97 = 0,83, or 83%.

Figure 1: A 2010 Fiat500 which has been converted to pure electric drive.

The substantial reduction in operational costs results not only from the fact that the energy input cost is as little as 10% of a conventional vehicle, but because there is no drivetrain maintenance on these EVs. Chobe Game Lodge in Botswana is operating two Electric Land Rovers and an electric boat. These vehicles are used for game viewing excursions around the Chobe National Park and on the Chobe River. The lodge records the monthly energy consumption on its electric fleet and is able to compare this to the consumption figures achieved by the same vehicles before they were converted. This data has been used as real world unequivocal evidence of the excellent possibilities for reduction in energy consumption and carbon generation by using EVs. As a result of the extremely positive data obtained as well as the obvious benefit of a silent electric game drive vehicle, the management

Slow driving through the game park in sandy conditions accentuates the efficiency comparison because the WEG PM motor maintains its efficiency of 95% through most load and speed scenarios, whereas a diesel or petrol motor becomes significantly less efficient in such an erratic and high-load drive profile. Figure 2: PM motor attached to the Land Rover Defender Transfer Case with a special adaptor housing ready to be installed into an EV Conversion.

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ENERGY EFFICIENCY MADE SIMPLE 2015