Wednesday, April 17, 2013

Yet Another Solar Vehicle!

Comment by Dr.Anumakonda Jagadeesh

I have seen yet another Solar Three wheeler called AASTHA designed by students of Mother Theressa College of Engineering and Technology, Peddapalli.

These types of designs will never be practicable. Here is the critical analysis.

The charging of batteries by the solar panel depends on the tilt angle facing south. Why solar panels for power as well as for water heating are faced south? For maximum efficiency. Don’t the students know this simple truth?

That is why Commercial solar/ electric vehicles designed by reputed automobile makers have separate solar panels for charging (not mounted on the vehicle).

Moreover when vehicle is moving incidence of sunlight is less rather than when the vehicle is stationary. Also how to find south facing free from obstacles place to charge the panels on the vehicle? Why the Solar PV and Solar Water heaters are mounted on terraces/in places where there are no obstacles? To get maximum solar insolation.

Tilt mounts 

Solar panels are most efficient when oriented directly towards the sun, and their output can drop as the angles diverge. Some solar panel installations therefore include a way of tilting the panel when parked, for maximum power.

Power increases can be in the range of 10% to 20%, but only when you're able to park with the tilt facing South, and only when you're willing to climb up onto the roof of your vehicle to set up the tilt. For this reason, many owners decide against the added complexity and cost of a tilt mount.

They also have problems if they don't get direct sunlight, as it reduces their power output.

It was not stated what type of Solar Panels were used on the Vehicle.Further it was stated,” The vehicle moves at a speed of up to 50 kilometres per hour smoothly and with out any sound pollution”. First of all did they drive for 50 kms? On What Terrain? Why this loose statement?

Another statement of contention,” The students said that the vehicle could be operated during the day time with the help of solar energy and switched over to battery back-up during nights for up to 40 kilometers”. Can they prove this? My experience with solar reading light shows it requires 8 hours charging. On a thumb rule solar charging takes 2.5 times electrical charging. Is the panel of the vehicle such a small one?

Thin film vs. Monocrystalline panels in grid connect systems 

Quite often we're asked about the advantages of monocrystalline panels over their amorphous thin film counterparts; particularly in home solar power grid connect systems.

In all our grid connect packages, we only use monocrystalline panels (except in very specific circumstances) for the following reasons:

Monocrystalline solar panels need far less surface/roof area - and roof space is very valuable real estate when it comes to solar energy related electricity production. You may have just enough roof space to deck it out in thin film panels now; but what about later if you wish to upgrade? We've seen instances where home owners have had to rip up all their thin film panels and sell those at a loss in order to boost the size of their solar power system.

In the future, solar energy may also have a huge role in personal transport. For example, Honda is working on a hydrogen car which will be powered by the sun . In this case a 4-5KW solar power system will create the energy to power a small pump station on the side of the house, creating hydrogen from water during the day which will then be available as fuel for the car.

With the world rapidly moving towards renewable energy sources and with developments such as Honda's, we envision a time in the not-too-distant future where the type of solar array used; specifically the ability to scale up, will also factor into house price values.

Mono-crystalline solar module comparisons (showing similarities of panels)

There are limits to using Photovoltaic (PV) cells for vehicles 

  • Power density: Power from a solar array is limited by the size of the vehicle and area that can be exposed to sunlight. While energy can be accumulated in batteries to lower peak demand on the array and provide operation in sunless conditions, the battery adds weight and cost to the vehicle. The power limit can be mitigated by use of conventional electric cars supplied by solar (or other) power, recharging from the electrical grid.
  • Cost: While sunlight is free, the creation of PV cells to capture that sunlight is expensive. Design considerations: Even though sunlight has no lifespan, PV cells do. The lifetime of a solar module is approximately 30 years. Standard photovoltaics often come with a warranty of 90% (from nominal power) after 10 years and 80% after 25 years. Mobile applications are unlikely to require lifetimes as long as building integrated PV and solar parks. Current PV panels are mostly designed for stationary installations. However, to be successful in mobile applications, PV panels need to be designed to withstand vibrations. Also, solar panels, especially those incorporating glass have significant weight. To be useful, the energy harvested by a panel must exceed the added fuel consumption caused by the added weight.
To get the most from solar panels, you need to point them in the direction that captures the most sun. But there are a number of variables in figuring out the best direction. This advice applies to any type of panel that gets energy from the sun; photovoltaic, solar hot water, etc. We assume that the panel is fixed, or has a tilt that can be adjusted seasonally. (Panels that track the movement of the sun throughout the day can receive 10% (in winter) to 40% (in summer) more energy than fixed panels.

Solar panels should always face true south if you are in the northern hemisphere, or true north if you are in the southern hemisphere. True north is not the same as magnetic north. If you are using a compass to orient your panels, you need to correct for the difference, which varies from place to place. Search the web for “magnetic declination” to find the correction for your location.

The next question is, at what angle from horizontal should the panels be tilted? Books and articles on solar energy often give the advice that the tilt should be equal to your latitude, plus 15 degrees in winter or minus 15 degrees in summer. It turns out that you can do better than this - about 4% better.

It is unfortunate that 136 year old National Newspaper publishing such news items without proper authentication. This is the third in the series in this month itself. First it was solar bicycle by ITI students, Solar Tricycle. Such sensational news without proper verification will lower the reputation of the century old Newspaper of repute.


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