I wonder how many people have fantasised about driving their vehicle on nothing but solar energy. The Battery Clinic have come up with a solution that may start a revolution in realising this dream.
Up to now solar power have only been used to power the lights and air conditioning of a vehicle. In this configuration called Solar Assist, the sun's energy is directly contributing to the propulsion of the vehicle.
200 watts of solar panels are mounted on the roof of a 2001 Estima hybrid, which could theoretically collect 2 Kilowatts of power on a good summer's day. In reality this would be not more than 1 Kilowatt on a good sunshine day and much less in winter.
Power gathered from the panels are stored in the 12 volt battery system unless the batteries are fully charged, in which case it will be shunted to the heat sinks. On first look it does not seem that such a small amount of power can make any impact on the fuel economy of the vehicle, but the reality is very different.
Solar Assist
With Solar Assist, solar energy directly powers the electric motors through the Power Jockeys. This extra power also helps to hold up the voltage of the 12 volt battery system maximising the electric drive mode of the hybrid vehicle.
In stop and start situations where the weight of the vehicle have to overcome inertia the fuel economising effect of solar assist is not apparent. Solar energy previously stored in the 12 volt batteries would have some contribution but this would not be much.
When the vehicle is in motion it takes less energy to keep the vehicle in motion and this is where Solar Assist comes into it's own. It was possible to keep the Estima Hybrid at 100 KPH running at 20 Kms/Litre fuel economy. On the slight downhill slope the economy was much better. As a result the first test with the vehicle on combined street and motorway driving was 15.2 Kms/Litre. This is much better than can be achieved by the vehicle without Solar Assist.
Potential and Implications
Free energy from the sun to drive our vehicles is certainly a seductive proposition. It does not seem possible that two hundred watts on a vehicle roof can make any difference to the fuel economy.
Fortunately the reality is that it made it possible to maintain driving speeds of 90 - 100 KPH at 20 Kms/Litre or better in the Estima Hybrid which weighs 1.7 tonnes. Although the fuel economy in city driving is not improved by much it can be made better with higher capacity HV batteries and possibly more Power Jockeys. We can also increase the wattage of solar panels.
I do not see electric vehicles taking over our motor vehicle industry any time soon. I do however believe that hybrids are the way of the future at least for now until we find a better alternative. Increasing the fuel economy of hybrids can make them competitive in fuel economy even against pure electrics. Changing the fuel source to ethanol and bio diesels will make these vehicles totally sustainable in terms of carbon emissions.
Hybrids are durable, economical and fun to drive. The future is with us now. We should embrace it.
