Comments on: Sharp expanding beyond silicon in solar

Company experiments with new materials and techniques--and even partners with a bank--to push solar energy forward.

[Blito]

Solar on cars

Pretty soon I will just be able to snap my fingers for all my energy consumption needs, and then... it will still cost money. Someone will charge me for snapping my fingers

If they do get solar to except more energY mnaybe solor powered cars will become more viable.

[Seaspray0]

Who knows, but probably not

If you are interested in solar cars, they do hold a race once a year that goes cross country using solar powered cars. They are purely experimental, expensive, and not designed for general purpose use. I beleive the winner went about 40 mph average.

Perhaps one day you will see an electric car that suppliments its charge with solar, but will also plug into a wall outlet for charging. A pure solar car doesn't have the energy capacity to maintain what we expect in automobile performance.

[Below Meigh]

It is needed

I really expected embedded solarcells (or solarpaint) to have been there already. Enough to cool a car interior, trickle charge batteries and any owner devices within.
Instead, we have automakers more concerned with price-gouging the green buyer, and focused on "bling" rims a lowprofile tires...on SUVs and Trucks! No wonder the Japanese should get a pat on the back for their determination at providing a solution.

[shadowself]

Numbers don't seem to add up

Supposedly the lensed solar arrays are 36% efficient.

Supposedly a 12.5 foot by 16 foot (approximately 18.6 square meters) outputs 2.9 kW.

The solar constant (the amount of light hitting the Earth) is over 1.35 kW per square meter. Even assuming 50% of that is lost in the atmosphere (which it's not, but I'm too lazy at the moment to look up the actual percentage) this would be over 675 watts per square meter. Thus a minimum of 12.5 kW falls on that 18.6 square meter array.

With only 2.9 kW out (in the form of electricity) and over 12.5 kW in (in the form of light) This gives an average efficiency of about 23% -- no where near the claimed 36%.

Numbers don't add up

I think alot of the panel space is taken up by the lens and the actual solar panel area coverage is much less.

[Hardrada]

Numbers may add up

Well, the article is not well written so there is this uncertainty about the numbers, but the 2.9 kW could add up.

It is 1 kWp/m^2 on the Earth's surface, so:
1 kWp/m^2 * 18.6 m^2 * 36% = 6.7 kWp can be converted at direct normal sun. Their number of 2.9 kW is 43% of 6.7, so there are two options:

1. They are being conservative and adding losses for inverter, performance ratio, actual cell efficiency due to not be a lab-based cell and temperature differences (possibly the 36% efficiency is only for non mass-produced cells). However, 43% is a large loss.

2. They are not talking about peak wattage but rather average wattage over the course of the solar irradiation cycle (for instance, 24 hours). For a flat-panel non-tracking PV panel, the irradiation gets about an equivalent of 5 hours per day of full peak sun (1 kW/m^2). For a tracking panel, this could maybe be 10 hours I am guessing, which is about 42%. So they are then quoting a maximum power output averaged over the course of a day, with optimum tracking and optimum cell efficiency.

I think #2 is most likely.

[pzev]

microconcentrator cells

What has to be kept in mind about microconcentrators is that they magnify the sunlight hitting so instead of one sun your getting 100x suns thereby increasing the effective efficiency. In concentrators you are trading off high cost PV semiconductor real estate for lower cost concentrator so on a $/W basis you are ahead. For an American microconcentrator design see SunPower's ATP project at http://jazz.nist.gov/atpcf/prjbriefs/prjbrief.cfm?ProjectNumber=99-01-4040

[pzev]

solar PV on cars

Back in the 1990s a number of thin film PV companies (notably ARCO Solar)developed thin film a-Si sunroofs to power a fan to keep car temperatures down during the summer. This application never attracted enough interest from customers. Remember that to power a car you need 60-100 kWatts of power. A 4 sg ft solar panel provides 100-200 watts so even stored in a battery solar PV doesn't provide enough energy to make a significant contribution to battery recharging.