With initiatives around the world such as Solar Impulse (www.solarimpulse.com) and the World Solar Challenge (www.worldsolarchallenge.org) powering forward with projects aimed at harnessing the energy of the sun, it helps to have a grasp of some of the finer details of solar technology. In this post, we’ll outline some highlights of this technology that is poised to play a pivotal role in the future of sustainable transportation.

How do I get energy from the sun?

If there are no clouds on a given day, 1 square meter of the earth can receive at least 1000 watts, or 1 kilowatt (kW) of energy from the sun. That’s enough to power your typical microwave oven, which is generally 600-800 watts. Or a lot of other things!

Solar energy can be captured in several ways:

–          Photovoltaic: this involves the conversion of sunlight into electricity

–          Solar thermal: using the heat generated by the sun (e.g. for heating water)

–          Concentrated solar: using mirrors to reflect sunlight into a concentrated field for heating

These are known as “active solar” techniques, as opposed to “passive solar”, which refers to things such as orienting your home to capture sunlight.

Tell me about solar photovoltaic!

For transport, we’re most interested in photovoltaic (PV). This is where solar panels come in. They allow us to harness that 1000 watts discussed earlier in a very simple way. But…there’s a catch. Humans haven’t figured out a way to capture 100% of this energy. Instead, there are some losses.

A lot, in fact. Current solar PV technology generally converts between 10 and 30 percent of the sun’s energy to electricity. Those panels you see on people’s houses likely have an efficiency between 10-20%, although Panasonic, SolarCity and SunPower have produced panels at around the 22% mark. In general, above 20% can begin to get expensive. Over 25% is mostly the realm of high end applications. Think military, aerospace etc.

The three most common types of solar panels are:

–          Amorphous silicon: cheap but inefficient (i.e. larger and heavier for the same amount of power)

–          Polycrystalline: more efficient than amorphous, cheaper than monocrystalline but less efficient

–          Monocrystalline: most efficient and most expensive

(The mono and poly types can be very output-sensitive to shadows due to how the individual cells are wired.)

New developments

There are some new technologies beginning to surface which promise greater efficiencies:

–          Semprius (www.semprius.com) have successfully tested panels up to 35% efficiency. Another aspect of solar technology is that their performance drops as temperatures rise, and Semprius’ design aims to minimize this impact.

–          Alta Devices (www.altadevices.com) are using a material known as gallium arsenide for panels due to its better electrical conversion properties. They have been achieving results in the 28-31% efficiency range.

–          Solar Junction (www.sj-solar.com) are conducting research which they claim will allow solar efficiencies to break into the 50% range.

But when it comes to industries such as aerospace, purely looking at efficiency won’t cut the mustard. Fortunately, researchers at MIT have recently developed the thinnest, lightest solar cell ever. You can read about it here: http://news.mit.edu/2016/ultrathin-flexible-solar-cells-0226

Photovoltaic technology was first invented in the late 1800’s, with commercial production beginning to take place around the 1950’s. With heightened focus now on climate change and renewable technologies, there’s an exciting future for solar power in the transport arena. We’ll keep an eye on things and keep you updated on the latest innovations!