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About LinkBacksThey're probably proportionally far less cost efficient though, at least for some time.
They're probably proportionally far less cost efficient though, at least for some time.
If you could have this efficiency at today's PV prices then breaking even would be a lot easier. Since they are showing miniature devices and targeting the mobile phone market then I suspect that this technology is very cost prohibitive and difficult to scale (see OLED!).
Breaking even with today's PV technology is still possible if you take a bet that electricity prices will sky rocket in future due to today’s government dithering on energy generation (unable to decide on nuclear but not investing enough in alternatives).
I suspect TeePee meant breaking even as a country, not as an individual claiming completely unsustainable 'green' subsidies from the government. You can't have everyone selling power to the grid at three plus times the buy price.
The only people to really benefit from nonsense like that are those who manage to get a share of the subsidies, the manufacturers, and the inevitable scrapping teams when a load of the stuff is torn back down again when someone realises it's not as 'sustainable' as they made out.
Yes, subsidies are for manufacturers but are presented as if the consumer benefits (manufactures just inflate prices accordingly). Like someone would give you money for buying stuff!
I still think that it would be a great feeling if you could be energy independent but if that ever became affordable, the government would start taxing us for daylight.
In the US, the government pays the consumer about 20% of the cost of solar panels.
There are also government payouts for electric cars. It still doesn't make the Chevy volt a viable option.
I don't think it's as bad as it was, but a while back in the UK, the government would nearly pay for solar panels with subsidies, then you'd get something like 30-40p per kWh for exported power. Not only that, but IIRC the way it was/is metered meant you'd get paid that price even for power you used yourself - i.e. you could still be making money while placing a net *load* on the grid.
I think the feed in tariff was 44p per kWh and then a further 3p or so for every kWh sold back to the grid. You had to pay full price for the panels. As soon as the subsidy was cut in half, the price offered by the approved installers dropped significantly as well to match the break even period. I know this because I wanted to install a PV array before the proposed revise of the FIT scheme but the government realised that they were offering too good a deal so they changed everything almost 4 months early.Originally Posted by watercooled
These kinds of subsidies are never for the consumer. They are there to encourage industries to invest in such technologies (here’s an oxymoron for you, a risk-free investment). It is the same with electric cars. If the grants were taken away then the car prices will adjust straightaway
I know some locals who had panels installed on that ~40p tariff and, I could be mistaken, but I thought I remembered them saying they had help paying for the panels too.
Either way, you'd need some seriously cheap and efficient panels to make them genuinely worthwhile in the UK. Investment can only help so much.
Advertisements will be advertisements. It's no more laughable than Lynx adverts.
I am not convinced by either claims of money saving nor eco-friendliness. But if they can get something that works.. well, quite a bit better than they do now, I will pay a decent penny for one.
For multi-days hike where I am off the grid and spending 10 hours or so under the sun each day, I like the idea of something that is self-rechargeable. But it still need to be more efficient than what I've seen.
Yeah I 'get' them for times when you need power when off-grid, but they're simply not worth the money/inconvenience otherwise. As for a 4" solar panel which needs to overcome the minor issues of needing to be nearly completely transparent and being able to work through your pants, I'm sceptical to say the least.
Ironically, ATM, I generally make a concious effort to keep my phone out of direct sunlight; heat isn't great for them and I like to avoid baking an uncovered camera sensor.
As I said, this just screams 'gimmick' at the moment, although of course, the technology may develop into something useful down the line.
Note that these are mostly concentrator cells. Single junction cells, like silicon based ones, can only convert a certain wavelength of light. You can do some maths and work out how much this is, for a 100% quantum efficient cell - that is every single photon gets converted - this is around 25-30% if I remember (check out the Schockley-Quessier limit). As you can see, the effort in Si has pretty much topped out. There are issues with reflectance and other instrumentation losses that stop you hitting the full efficiency and there comes a point where it's just not feasible economically to do better. For most people, around 20% is 'good enough' to power small electronics and home installations. These are also single-sun measurements, i.e. 1000W/m^2.Turns out 44% isn't "too good to be true" just a general improvement from previous panels.
Solar cell Efficiency - Wikipedia
Single junction cells will never beat around 50%. Interestingly you can never go above 86% with an infinite number of junctions. You do this by integrating over the SQ curve, shown below:
If you have multiple junctions within the cell, you can cream off other wavelengths of light. Triple junctions are popular on satellites, for instance. They're also super expensive because of that indium. Ultimately we'd like to have an n-junction panel which can cover virtually the entire solar spectrum. The top performers are traditionally 3-junction concentrators, but you can see that single junction GaAs is catching up. Nitride based panels are shaping up and can theoretically reach 70%.
The lab has a big light bulb that can put out roughly the power of the Sun or a concentrated version. The SQ calculations depend on intensity, so you can bump the theoretical efficiency up. These are marked by the (XXXx) under some panels. This is also why you'd want concentrator systems for power plant, shove a few high efficiency panels on a tower and direct all the light at it and you don't need loads of little crap panels everywhere.
Their actual webpage says:
"Conversion efficiency confirmed by the Fraunhofer Institute for Solar Energy (ISE, one of several organizations around the world that officially certifies energy conversion efficiency measurements in solar cells) in April 2013 under a light-concentrating magnification of 302 times (cell surface: approx. 0.165 cm2)."
Don't be fooled. This is a decent result, on par with the top performers, but this is not going to be any use in phones. The inbuilt Fresnel probably helps a little, but that concentration is mainly produced by the institute's equipment. If you could get anywhere near 300x power with a tiny little lens like that then all solar panels would use them to instantly boost results.
The original limit paper may be found here, for those on an edu connection: http://link.aip.org/link/doi/10.1063/1.1736034
EDIT: Some clarifications
- The 30% example is only for Silicon, you can do better with different materials but the problem is making them with the right bandgap, that is, the photon energy that the material can absorb. With multi junction cells you stack the layers so that light with low energies (small eV) get absorbed first, increasing down to the big layer at the bottom to maximise efficiency.
- I realise that if you integrate over that curve you'd get a lot more than 100%, the calculation is probably something similar but a bit more involved.
- My opinion? Solar panels need to become printable to be viable. There has been some work on this, in making silicon panels more cheaply or the 'spray on' types. In this way you would need to blanket cover buildings which is potentially doable if the panels were cheap enough. That's the only way we'd get enough power in this climate.
Commercially, PV is not economically viable. A friend did some work on this during his degree, looking for a cheap way of bringing solar power to poor nations. Turns out you can't even get close without using concentrating technology and even then you're not using the photovoltaic effect. You just melt something with a large thermal mass, like salt, and use that to - you guessed it - boil water and run a turbine. PV is cool, but too expensive at the moment to be anything more than convenient in rural areas.
Remember that if you buy a solar power system, you're not buying it because you want to make money, you won't. You're buying it to be self-reliant and off the grid. While that energy is definitely not free if you amortise the cost of installation, it is yours and you're somewhat protected from power cuts/brownouts/etc in times of crisis. Solar hot water is a different beast, and does actually save money quite rapidly. Ofgem says that average consumption is 3300kWh/year or around 10kWh a day so you're looking at around a 15-20kWh installation to go totally off grid (during the day!) with a good size battery bank.
Last edited by Whiternoise; 23-06-2013 at 05:50 PM.
watercooled (23-06-2013)
It's roughly double, but I sincerely doubt these will be commercially available. They're expensive and really only worth using on satellites where you can rely on more constant solar power as well as higher efficiency cells allowing for smaller solar panels and thus lower take off weight (and lower launch costs as a result).
In most of the northern hemisphere you won't see much benefit from solar panels on your house, but using cheap solar panels in the Sahara is a serious proposal in order to meet Europe's future energy requirements. Once the infrastructure is in place for energy and maintenance, bits like solar furnaces become cost effective for reduced costs on smelting and so on.
Silicon panels are cheap because silicon is cheap and we know how to manufacture it - it's an offshoot of IC manufacture.
Really interesting post by Whiternoise.
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