Malaysia is so hot, why can’t we have a solar-powered EV? Here’s why it won’t work

The premise is quite simple – Malaysia has a very hot and humid tropical climate. In the afternoon, the surface temperature on an unsheltered car’s roof is hot enough to fry an egg.

So why can’t car manufacturers, especially our (quasi) national brands Proton and Perodua, come out with a simple, affordable electric vehicle (EV) with roof-mounted solar panels that will charge the car’s traction battery?

Think about this, the bulk of an EV’s cost is its battery, so if an EV can be charged as it drives along under the sun, wouldn’t it also means that it can make do with a smaller, cheaper battery?

Also, if you can charge an EV simply by parking under the sun, why would you need to be bothered by the lack of public charging facilities?

Better still, why can’t we build EV chargers that are powered by the sun? This way, the EV charger will rely less on the power grid, which in Malaysia, more than 80 percent of our electricity come from dirty fossil fuels.

Also read: Are electric vehicles (EV) truly cleaner than combustion-engine cars?

Like many things in life, if you have a brilliant idea and wondered why no one else has commercialized it yet, it’s probably because it’s actually a very stupid idea.

Weird but true, Malaysian sun is not very good for solar power

This might sound counter-intuitive, but actually Malaysia is not a very good place for photovoltaic solar panels to work, because our sun’s rays are too weak. Yes, that's not a typo.

Remember that we are not talking about solar-powered water heaters (those don’t generate electricity, only store heat, works very well here), but electricity-generating photovoltaic panels.

Photovoltaic solar panels work on an entirely different principle. Light intensity, not heat, is all that matters.

Specifically, photovoltaic panels work on the principle of photons – the atoms of light – knocking electrons on a silicon semiconductor’s p-n junction. If a photon strikes an electron hard enough to knock an electron into the next energy band, electricity is generated. Heat has nothing to do with it, although it is often present.

If you’ve experienced Australian sun, even in cold seasons, you will understand how bright the sun can be. Their sun is not hot, but it’s so bright that it’s hard to walk outdoors without a sunglass, that’s the kind of sunlight solar panels need.

Even in supposedly colder Europe, the sun there can on a clear day, be a lot brighter than what most Malaysians are used to.

Solar radiation is measured in units of Watt per square metre, or Watt-hour per square metre, when it’s integrated over a period of time.

In Malaysia, our sunlight intensity averages around 4.75 kWh/m². That’s only slightly better than the four weather-seasons USA’s 4.58 kWh/m².

Australia on the other hand, averages around 5.35 kWh/m2.

These are according to the World Bank’s Global Photovoltaic Power Potential study.

The other reason why solar panels generate less power in Malaysia is because our sky has many clouds and a solar panel’s efficiency drops considerably if it doesn’t get direct sunlight.

This is not to say that solar power has no future in Malaysia. Quite the contrary. Construction of large scale solar farms is seeing a lot of activity in Malaysia, as solar panel cost has come down considerably in the last decade.

The trick is to optimize a solar panel's placement. Solar panels work best in the northern region of Peninsular Malaysia, where sunlight is the most intense.

Size does matter – how long and how wide?

Solar panels are a notoriously inefficient method of generating electricity but we use it anyway because prices of solar panels have come down low enough and the investments will pay for itself over time because sunlight is free.

Solar panels have an energy efficiency of around 15 percent but more expensive ones made from fancier, purer materials may boost it to 20 percent.

To put it into perspective, even the lousiest petrol-burning combustion engine in an entry-level car, with no electrification to improve efficiency, can convert 25 percent of the fuel’s energy into motion. A full-hybrid car can boost this to 40 percent.

But the problem with inefficient solar panels is not something that you can fix simply by throwing more money at it – it’s a question of physics.

The working principle of all solar panels are governed by the Shockley–Queisser limit, which without going too much into quantum physics, says that no matter what you do, a solar panel’s efficiency cannot improve beyond 33.7 percent.

Since an individual solar panel generates very little power, you are going to have to scale it up with a lot of panels.

If you are going to build a car that relies on the sun for charging, you are going to need an incredibly large array, which results in two possibilities, none of it good – the car needs to be very big (which increases weight and cost), or it’s going to look really ugly because you need an almost flat surface that extends as long and as wide as possible.

Since the roof surface alone is not going to provide enough space for the solar panels, you will have to throw away the rear windscreen, and replace it with a video camera-feed view for the driver.

As for solar-powered EV chargers, it’s not very practical because public EV chargers are typically installed in urban locations, at ground level, which means that it will be surrounded by taller buildings / structures, which will cast a shadow over it, thus limiting its optimal operating hours to just no more than a few hours a day.

Chasing after the sun

Many large scale solar farms have fancy computer-controlled motors that individually adjusts the solar panels to follow the sun as it moves across the sky, just like a sunflower.

In the real world, the actual power generated by solar panels fluctuate a lot, and can be influenced not just by cloud, but also dust on the solar panels, and the angle of the sun.

Ideally, you will want the sun’s rays to hit the panels at right angles.

Now imagine trying to get around these limitations and install solar panels on a car…and you will quickly see why this is not going to work.

Production cars with solar panels

Still, that hasn’t stop car manufacturers from including solar panels on some hybrid and electric vehicles.

Solar panels may not be powerful enough to power a car but in today's very strict CO2 emissions regulations world, every little bit helps. Plus, prices of solar panels have been coming down.

The Toyota Prius for example, has been offered with a solar roof package since 2009. The solar panels don’t charge the car’s traction battery. Instead, it powers the Prius’ air-conditioning system’s blower (only) to cool down the cabin on a hot day. Owners can either remotely activate the blower using the car’s key fob, or set it to automatic when leaving the car.

This package was offered on Thailand market Prius models (third generation ZVW30) but not Malaysia, which also once sold the Prius.

Toyota is also testing a Prius Plug-in Hybrid prototype with an 860 W solar panel – four times higher than the production car’s 180 W unit, but that’s also because the surface area is four times as big, covering the rear windscreen and bonnet too.

The first generation Nissan Leaf also had solar panels on the rear spoiler, but it only charges the 12V battery, not the high-voltage traction battery.

The fully-electric Ioniq 5 also offers roof-mounted solar panels as an optional extra but it doesn’t do much, adding no more than 5 km of driving range per day.

Hyundai doesn’t say what’s the power output of the Ioniq 5’s solar panels but the current generation Hyundai Sonata Hybrid uses a 200 W solar panel. That’s not a lot of power but Hyundai says it reduces discharge of the 12V battery, which is especially relevant to Korean drivers because many cars in Korea are fitted with security dash cams as a standard dealer-fitted accessory.

Many of these dash cams are active all the time (but operating in power saving / sleep mode when car is parked) and will continue to draw power from the 12V battery so the trickle charge from the solar panels are appreciated.

Meanwhile, a Dutch start-up called Lightyear believes that it is possible to build an EV that's charged by the sun. And yes, you can still drive it at night (it can still be plugged in for charging, just like any other EV).

The Lightyear One will be launched next year, and will be built by Finnish contract manufacturer Valmet Automotive. 

It has a claimed driving range of 725 km. The company claims that for every hour the Lightyear One is exposed to summer sun, it can generate 12 km of driving range.

Like Toyota’s solar-charged Prius Plug-in Hybrid prototype, the Lightyear One doesn’t have a rear windscreen, relying on video cameras for rear vision.

Prices are estimated at USD 165,000 (about RM 700k, excluding local taxes) in the US - almost twice that of a Tesla Model S.

As emission reduction measures take centre stage, expect to see solar roof to be discussed more often than carbon fibre roof in the near future.