HN Gopher Feed (2017-07-12) - page 1 of 10 ___________________________________________________________________
Scientists Design Solar Cell That Captures Nearly All Energy of
Solar Spectrum
135 points by 3eto
https://www.rdmag.com/news/2017/07/scientists-design-solar-cell-...___________________________________________________________________
meri_dian - 5 hours ago
>"This particular solar cell is very expensive, however researchers
believe it was important to show the upper limit of what is
possible in terms of efficiency. Despite the current costs of the
materials involved, the technique used to create the cells shows
much promise. Eventually a similar product may be brought to
market, enabled by cost reductions from very high solar
concentration levels and technology to recycle the expensive growth
substrates."We will end our reliance on fossil fuels not by forcing
masses of people to change their lifestyles and inconveniencing
them, but by developing green energy tech that is simply more
efficient and cost effective than fossil fuels. Once this happens
the transition away from carbon based energy sources will be
swift.Given the rate of progress, I believe we'll see widespread
adoption of renewable energy far before climactic conditions on
earth become dire for humanity.
the8472 - 5 hours ago
Electricity and transportation, which you often see in the
headlines about progress about moving to renewables, are not the
only GHG emitters. Agriculture, deforestation, heating are also
big sources. As far as I have read there has been a lot less
progress in that area.
philipkglass - 4 hours ago
In the US, electricity + transportation makes up 56% of
anthropogenic emissions and agriculture makes up
9%:https://www.epa.gov/ghgemissions/sources-greenhouse-gas-
emis...The European Union reports aggregates a bit differently,
but agriculture is only 10% there too (see Figure
3):http://ec.europa.eu/eurostat/statistics-
explained/index.php/...Neither the USA nor the EU are
undergoing deforestation at present, and electrical heating can
substitute for the vast majority of applications currently
served by fossil-combustion heat. That's why most research and
headlines about GHG reductions in the developed world focus on
transport electrification and electricity decarbonization.In
poorer parts of the world, where automobile use is less common
and/or fewer people have grid tied electrical service,
deforestation and agricultural emissions make up a larger share
of total anthropogenic emissions. But most of the world's
anthropogenic emissions, and most of the low-hanging
mitigations for emissions, come from geographic regions that
commonly have grid tied electrical service and other modern
amenities.
the8472 - 3 hours ago
But those replacements, electrical heating and industrial
processes, are also holes. Basically, if we replaced 100% of
the current electricity production with renewables that
wouldn't even provide the energy needed for electric
vehicles. So we already have to go >100%. And then we need to
overhaul heating and energy-intensive industries too.And even
if we get to that point we still would not be carbon-neutral
due to the remaining sectors. And possibly due to new natural
sources (permafrost) we're already locked into due to the
warming that is already in progress.So the point is that just
inventing our way to replace the current grid with green
sources is insufficient for meeting the climate budget within
a few decades.
philipkglass - 2 hours ago
I think we're all making slightly different points. OP said
"We will end our reliance on fossil fuels ... by developing
green energy tech that is simply more efficient and cost
effective than fossil fuels. Once this happens the
transition away from carbon based energy sources will be
swift."You replied pointing out that electricity and
transportation are not the only sources of emissions -- not
sure if it was intended as a rebuttal because OP didn't say
they were. I noted that electrical heating can generally
substitute fossil heating, that the developed world isn't
undergoing deforestation, and that agriculture is a much
smaller source of developed-world emissions compared with
fossil combustion. Neither I nor OP said or implied that
"just inventing our way to replace the current grid with
green sources is sufficient for meeting the climate
budget."We're obviously going to blow past the "safe" 2
-degree-rise-by-end-of-century cumulative emissions target.
In the long term, if complex civilizations survive, I
expect large scale atmospheric carbon removal efforts
(enhanced silicate weathering and similar). Otherwise
feedback processes and anthropogenic emissions apart from
fossil combustion are probably going to amplify ~4 degrees
of end-of-century warming to more like 7-9 degrees of
warming by end-of-millennium. After that it'd take ~100k
years to restore the pre-industrial atmospheric CO2
concentration status quo by natural sinking mechanisms
alone.
birdmanjeremy - 5 hours ago
I like your optimism, but I think you're wrong. It may already
be too late.
agumonkey - 4 hours ago
This will make a very nice ecological pressure on humans.
pishpash - 5 hours ago
Climactic conditions will always be a problem. The next headache
will be how to deal with a heat bath from uniformly dissipated
waste heat from this energy rather than natural gradients and
storage that drive climactic processes. When greedy humans get
their hands on 'unlimited energy' that is not a panacea, but a
much bigger catastrophe waiting to happen.
vkou - 4 hours ago
Since we're talking about solar power, this is not a huge
concern.
londons_explore - 4 hours ago
If humans really had "unlimited energy", we could air condition
the entire world, and send the waste heat to space with large
infrared (or even visible light) radiators.
Thorncorona - 4 hours ago
Not really. Air conditioning is a heat displacement system,
so you'd still have the same amount of heat. Using infrared
radiators would just accelerate global warming since green
house gases mainly absorb infrared light.Visible light would
probably be a hazard. Would be pretty great for "beam in the
sky" special effects though.
SubiculumCode - 37 minutes ago
I think she was suggesting sending the exchanged heat into
space..you know, up.
Zigurd - 4 hours ago
At some point potentially soon if you want really good
economic growth you have to decouple economic growth from
energy growth. That is a step more fundamental than
decoupling energy growth from coal and oil.
wernercd - 5 hours ago
meh... people have been screaming DHOOOOOOOOOM!!! for
generations upon generation...We'll never make enough food...
we'll never have enough energy... we'll never get
along...Things are always bordering on the end of the world yet
we survive.
michaelmrose - 4 hours ago
Prior returns don't guarantee future results. Have you
considered that people have taken steps to avoid catastrophy.
wernercd - 34 minutes ago
Granted, it only takes one "failure"... but... "people
taking steps" is exactly what I was alluding too...Time and
time again, cries of "Too many people!!!"... how will we
feed 1 billion people?Advances in farming, logistics,
technology, etc...What's being done now? More advances in
farming, vertical farming, AI, etc...
Zigurd - 3 hours ago
That depends on the nature of the threat. Running out of
feedstock for plastic? Not a problem. That's the sort of
thing for which one can assume a technology fix will happen,
and there is probably plenty of time. On the other hand,
missing the population slow-down projections and ending up
with a 20 billion population? That's doom, and there is no
techno-savior.
wernercd - 36 minutes ago
"ending up with 20 Billion Population? That's doom, and
their is no techno-savior"Except for advances in vertical
farming, green energy, advances in urban planning allowing
people to live denser and more packed together...We'll all
be dead because earth can't handle the population...
cira'1968:https://www.nytimes.com/2015/06/01/us/the-
unrealized-horrors..."Dr. Ehrlich was so sure of himself
that he warned in 1970 that ?sometime in the next 15 years,
the end will come.? By ?the end,? he meant ?an utter
breakdown of the capacity of the planet to support
humanity.?So... by 1985, we will all be dead because
DOOM!!!Time and time again...Now... can we all "get along"?
Christians, Muslims, Chinese, Russians, etc? THAT isn't a
technology problem - that's a humanity problem.Can we feed
everyone? We sure can... and advances in tech continue to
push the envelope and there is no reason to believe that we
can support many multiples of what we have now.Is there an
upper limit? Undoubtedly... are we near it? Hardly...
dwringer - 2 hours ago
"Survivorship bias or survival bias is the logical error of
concentrating on the people or things that made it past some
selection process and overlooking those that did not"
hueving - 40 minutes ago
Which human species didn't make it past all of the previous
catastrophes they predicted?
vkou - 5 hours ago
When do you think we will reach 1/10th of our current GHG
emissions?2020? 2030? 2040? 2050? 2100? Plus or minus five years?
Will we have a linear decline to that level? When do you think
that decline will start? Is there a particular model you're
thinking of?What degree of GHG concentrations/temperature
increase will be the limit of what you consider to be 'not dire
for humanity'? Is it compatible with your expected model of GHG
emissions?Are the billion people living in the Indian
subcontinent included in your definition of humanity, or are we
talking about North Americans and Europeans? If yes, will we be
willing to shelter environmental refugees from impacted areas?I'd
really love to believe that everything will turn out fine - but
while I've ran into many optimists, I've yet to run into one that
is willing to quantify the reasons for their optimism.
guimarin - 4 hours ago
10% -> 2025; 20% -> 2030; 50% -> 2040; 95% -> 2050.
India/Africa are included there. I think 95% of potential GHG
emmissions (not just indexed to today but to 'present time')
will be crossed in like 2060 or so. Renewables are going
extremely quickly. we are in the steep part of the s-curve and
there is no reason to believe we wont' get a few doublings due
to battery cost decreases and deployed solar cost efficiencies.
The transition will be a lot faster than ppl believe.
vkou - 26 minutes ago
By that plan, we'd be looking at ~21.6 years of current GHG
emissions.This will add ~777 GT of CO2 to the atmosphere.
Which will put us at ~500 ppm CO2 (We just passed 400 ppm).
That would be warming between 2.5C and 3C.If you want to hit
a 95% reduction in GHG emissions, you're also going to have
to:* Shut down every single fossil fuel power plant over the
next 25 years.* Build enough renewable/nuclear powerplants to
replace all of our fossil fuel power sources, twice over.
(Assuming we switch to electrical transportation.)And, the
elephant in the room:* Halve all current trans-continental
shipping and air travel. It is currently responsible for
~6-7% of our GHG emissions. (And if it were to grow
unconstrained, would likely double in volume in the next 30
years.)* While bringing our other emissions down to nearly
zero.We can clearly do all this, but it would require
significant changes in our lifestyles - something that
optimists tend to not be willing to accept.
Retric - 5 hours ago
My guess is ~2070-2090 will see 20% of current fossil fuel
use.Boats and Aircraft are going to be hardest to transition
and will likely make up a large chunk of that 10+%. Bio fuels
may take some of this, but it really depends on overall demand
for liquid hydrocarbons.Electricity and home heating are going
to change from market forces.Cars have many options, but oil is
going to get expensive (as in 2-3x current price not 10x) which
will push alternatives.Electric trains can take over most long
distance trucking and shorter distance is easier to transition.
This will be a fairly fast transition if oil spikes again in
~2030-2040 combined with some form of carbon tax.PS: Plastics /
fertilizer and other chemical processes are going to be the
wildcard IMO. But, they don't involve burning carbon so they
are also less important.
vkou - 4 hours ago
I was writing up a response to your initial guess of 10% by
2060, which was... Pretty dire. Past-the-Paris agreement,
2.5C to 3C warming dire.20% by 2070-2090, on the other hand,
is a lost cause. That would put atmospheric at 580 PPM by
2080. That's >4C of warming, if we don't hit any positive
feedback loops.I'm not particularly concerned about plastics.
They can be synthesized from biomass.
Zigurd - 4 hours ago
In a few years the question will become "How to do
geoengineering safely relative to the risks of warming?"
The planet may be able to support 9-11 billion people with
mostly renewable energy, but perhaps humanity will not get
there fast enough to avert risk of hitting a positive
feedback level that would commit humanity to far more
massive and therefore far riskier geoengineering.
Retric - 4 hours ago
Sorry, I got into a habit of submit then edit on HN because
we used to get errors if you waited to long. I did not
think we would hit 10% by 2060, but I hope we hit 40%.US
coal use is down to where it was around 1930. Petroleum is
around 1960's usage levels. https://www.eia.gov/todayinene
rgy/detail.php?id=26912Natrual gas has spiked, but it's
realitvly speaking less of a global warming threat due to
C(x) H(x) turning into H20 (x) + C02 (x) which produces
less CO2 per heating vs just C into CO2 from coal.So,
while there are a huge range of predictions. What happens
in the next 20 years is more important than what's going on
40 - 60 years from now.
jamesaross - 3 hours ago
Don't the inevitable methane leaks from natural gas
create more of a GHG effect than the CO2 emitted from
burning it? It's not just the environment disasters like
in California, but everyday minor leaks.
Retric - 2 hours ago
Methane has a short half life in the atmosphere ~10 years
ish and there is already quite a bit of it there. So,
it's only really important when the amount released is
increasing relative to the average released over the last
20 year. AKA if they cut release in 20 years then (ed:
it's contribution to) temperature would drop fairly
quickly.
https://en.wikipedia.org/wiki/Atmospheric_methaneNote it
does break down into more CO2 than the wieght of Methane
because Oxygen molecules are heavy.The real risk is if
warming the arctic starts to release a lot of stored
methane, which would be very bad.
hwillis - 2 hours ago
They are not insignificant (right now, they're just a bit
more than the methane from livestock) but the CO2 is
emitted in much greater amounts.
gene-h - 1 hours ago
As far as planes go, an intriguing option is liquid hydrogen.
Hydrogen has a large energy density by mass, which is why we
use it in rockets. There have been proposals on how current
airliners might be converted to run off of hydrogen in the
near term[0] for short and medium distance travel. If we can
get fuel cell electric propulsion to work at jetliner speeds
there is even more potential, as fuel cells can be made more
efficient than heat engines.[0]http://www.fzt.haw-
hamburg.de/pers/Scholz/dglr/hh/text_2004_...
Gys - 5 hours ago
'The new design converts direct sunlight to electricity with 44.5
percent efficiency, giving it the potential to become the most
efficient solar cell in the world.'
sbierwagen - 5 hours ago
Note careful use of "potential" there. Fraunhofer hit 46% two
years ago with a four-junction cell:
https://www.nrel.gov/pv/assets/images/efficiency-chart.png
londons_explore - 4 hours ago
it's sad that nothing more has been published on that
architecture for 2+ years...One would imagine most of the
research dollars being into how to make multi-junction cells
cheaply, rather than into other much lower efficiency cells.
sbierwagen - 4 hours ago
"The only figure of merit in a PV system is cost per
kilowatt-hour installed". Multijunction cells require
concentrating panels and two-axis tracking. In order for them
to make economic sense, both the panels and the tracking have
to have lower lifetime costs than standard untracked
panels.So far, they don't. Plus, concentrating panels don't
work under cloudy skies, so...
ZenoArrow - 3 hours ago
> "In order for them to make economic sense, both the
panels and the tracking have to have lower lifetime costs
than standard untracked panels."Is this the problem that
Insolight have a potential solution
for?https://insolight.ch/
sbierwagen - 3 hours ago
We'll know as soon as they put product pricing on their
site.
ZenoArrow - 2 hours ago
Fair point, but it does seem to be a solution worth
tracking the progress of.
adamwong246 - 4 hours ago
I always wondered why we did not just use prisms to separate the
different wavelengths, then capturing selections of the spectrum
with a variety of simpler, unstacked panels. Perhaps one could even
deflect the infrared into a more conventional, presumably more
efficient, heat collector while the higher frequencies are directed
to true photovoltaics.
tedsanders - 4 hours ago
As usual, cost is the issue. Both the cost of the optics, the
cost of tracking, the cost of imperfect tracking, and the cost of
the complexity in the design and installation.I know some
academic research labs have looked into arrays of microlenses &
prisms, which sound interesting, but I haven't heard of any
commercial products. Googling for micro prisms and solar cells
will show you some projects.Ultimately, I think it's just much
easier to install a simple rectangular slab with two wires coming
out. And the costs of solar cells are so cheap that they're
probably comparable to the cost of the optics you'd want to lay
above them.I also imagine that balancing the current-voltage
characteristics of the cells could be challenging when light at
different times of the day has different spectra (e.g., you
wouldn't want diminished performance in reddish sunsets).
maxerickson - 4 hours ago
People with excess roof space (and whatever other space) look at
cost before they look at efficiency.Half the roof here would
provide plenty of power, the problem is that it would be
expensive.
gene-h - 1 hours ago
This approach has been tried before and was used to make a solar
cell with record efficiency[0]. This approach might be needed to
get up to 50% efficiency. [0]http://www.electronicproducts.com/Su
stainable/Solar/Prism_de...
klodolph - 4 hours ago
Think of how solar is an investment: you pay money up front, use
up a certain chunk of land, and you get energy over the next 25
years. Imagine panel A which costs $100 and has 22% efficiency,
versus panel B which costs $500 and has 30% efficiency. No point
in buying panel B, since you can buy 5x panel A for the same
price.
jcbrand - 2 hours ago
But then you'd also need to cover 5 times the area, and land
also costs money.
philipkglass - 4 hours ago
The abstract is more informative than the press coverage:http://onl
inelibrary.wiley.com/doi/10.1002/aenm.201700345/ab...The cell is
assembled in a mini-module with a geometric concentration ratio of
744 suns on a two-axis tracking system and demonstrated a combined
module efficiency of 41.2%, measured outdoors in Durham, NC. Taking
into account the measured transmission of the optics gives an
implied cell efficiency of 44.5%.Since this is a concentrating
cell, compare to the concentrator cell records tracked on NREL's PV
efficiency records chart:https://www.nrel.gov/pv/assets/images
/efficiency-chart.pngThe current record for 4-junction-or-more
concentrator cells is 46.0%. This isn't a record-setting cell even
if the implied efficiency holds up under standardized test
conditions.This cell like all high-concentration cells is unlikely
to see mass market acceptance on Earth. The module needs precise
two-axis sun tracking to work effectively even under perfect clear-
sky conditions. That's significantly more expensive than fixed
arrays or single-axis sun tracking as used by conventional large
scale PV. And there's a vicious feedback loop: since two-axis
tracking is significantly more expensive, it doesn't get
developed/scaled, so the cost gap gets even wider over time WRT its
competitors.But that's not actually the worst problem of high-
concentration PV for terrestrial use. The worst problem is that
HCPV can use only direct normal irradiance. Ordinary non-
concentrating PV cells produce very nearly 25% of its rated output
if it receives 25% of test-condition illumination under non-ideal
conditions (due to some combination of clouds, air pollution haze,
dusty glass, etc.) Concentrating cells will produce close to 0% of
rated output under the same non-ideal conditions. Few regions have
clear enough skies to work with HCPV, but those same regions tend
to be dusty, which the concentrating optics cannot tolerate.
Mechanical and optical complications make HCPV higher-maintenance
than ordinary flat PV and more expensive to install
initially.That's why there were a dozen+ companies working on
concentrating PV in 2008 and all of them are now bankrupt or have
exited HCPV manufacturing. Eking out another cell-level improvement
wouldn't have rescued the value proposition of their complete
systems. The refined polysilicon price spike that made exotic
technologies look briefly promising only lasted a few years and
then it became clear again that crystalline silicon is very hard to
beat.
mark-r - 3 hours ago
I wonder if it wouldn't have more luck in outer space
applications? Perhaps not if the optics add much weight for the
amount of power produced.
philipkglass - 3 hours ago
In orbit you wouldn't have to worry about dust or clouds, to be
sure. But keeping pointed exactly at the sun could still be a
pain. As far as I know there are no spacecraft using
concentrating PV for power, though spacecraft do commonly use
multi-junction cells similar to these without concentration.
Space applications are very conservative due to the high cost
of hardware and the small fraction of the total budget
represented by the PV power system. Cutting another 30% from PV
system cost is outstanding if you're building utility-scale PV
projects on Earth, but down in the noise if you're building
communication satellites.
sbierwagen - 5 hours ago
As usual with press releases, this pretends there is no prior art.
Of course, stacking solar cells to increase efficiency has been a
thing for five decades: https://en.wikipedia.org/wiki/Multi-
junction_solar_cell
ndonnellan - 4 hours ago
Yep, see 40% cells used 4 years ago in http://www.businesswire.co
m/news/home/20130426005162/en/Amon...(36% eff in practical
application due to system losses)
k__ - 3 hours ago
Nice.What's the maximum?What's the current standard?
hwillis - 2 hours ago
Max so far is 46%[1], max theoretical is 86.8%[2]Most solar
panels are 15% or better. The best residential cells are
22.2%[3], the commercial cells are 25.3%. The theoretical
maximum efficiency of single-layer silicon PV cells is
~32%.[1]: https://www.nrel.gov/pv/assets/images/efficiency-
chart.png[2]: https://en.wikipedia.org/wiki/Shockley%E2%80%93
Queisser_limi...[3]:
https://us.sunpower.com/sites/sunpower/files/media-
library/d...
schoen - 22 minutes ago
That's awesome. I remember always hearing 10% when I was a
kid, which looks about right on that first chart, assuming
it takes a few years before things are commercialized. It's
terrific to see the march of improvements in efficiency.
philipkglass - 2 hours ago
The current state of the art for commercialized multi-
junction cells, used almost exclusively in space
applications, is 30-32% cell efficiency:http://www.spectrolab
.com/solarcells.htmhttp://www.azurspace.com/index.php/en/prod
ucts/products-spac...https://solaerotech.com/products/space-
solar-cells-coverglas...Multi-junction cells similar to these
have so far reached efficiencies up into the mid-40% range
with optically concentrated sunlight under experimental
conditions, though such high efficiencies have not been
reached in mass production.Multi-junction cells represent
less than 0.01% of annual PV cell production. About 95% of
annual PV cell production is based on different variants of
single-junction crystalline silicon, with current commercial
cell efficiencies in the 16-25% range. The 30% cells for
space use also sell for more than 1000x the price-per-watt of
a simple 16% silicon cell.A theoretical "infinite-junction"
solar cell could achieve up to 68.7% efficiency under full-
power illumination from the sun on a clear day, or up to
86.8% efficiency on a clear day under optically concentrated
sunlight:https://en.wikipedia.org/wiki/Solar_cell_efficiency#
Thermody...The theoretical limit for single-junction silicon
cells is
29.4%:http://ieeexplore.ieee.org/document/6557081/SunPower
has reached just over 25% efficiency industrially for its
best cells, which are single junction silicon using advanced
cell structures.The highest conversion ever achieved
experimentally for single-junction silicon is 26.6%,
announced just a couple of weeks ago:http://www.sciencedirect
.com/science/article/pii/S0927024817...The experimenters
combined two leading industrial techniques for high
efficiency silicon cells (interdigitated back contact
structure, like SunPower uses, and heterojunction cells using
amorphous silicon, like Panasonic/Tesla use) to reach the
26.6% record.
k__ - 2 hours ago
Cool, thanks :DWhat does an increase of 10% mean? That I
could get 10% more Watts from the same area of panels?How
much do we need? Would a houshold in Canada need much more
panels than one in Mexico?Is 15% or 20% already enough to
power a whole 1-family-house?Are batteries or PV panels the
bigger problem here?
philipkglass - 1 hours ago
A household in Canada would typically need more panels
than one in Mexico. Canadian homes tend to consume more
electricity and the Canadian rooftop will get less
sunlight.If you are space-constrained, like on a rooftop,
10% more power from the same area of panels could be
significant. It's a step function. It goes from "not
enough room for desired wattage" to "enough room for
desired wattage" very abruptly. Once you've reached
"enough room for desired wattage," further efficiency
improvements matter much less. You don't care a lot
whether you have 25% or 40% leftover roof space after
installing the panels. Paying for further efficiency
improvement is worthwhile only if it offsets enough costs
elsewhere to lower systemic costs (from using e.g. less
mounting hardware, less connecting wire, less
installation labor.)The higher the industry-average
efficiency, the less of a constrained-space advantage
there is for expensive, higher-efficiency modules. That
is, SunPower had a more compelling advantage when they
were selling expensive 19% panels and cheap Chinese
panels were at 12%. But now that SunPower offers
expensive 22% panels and cheap Chinese panels are at 15%,
more households can now reach their desired wattage-per-
roof targets without paying for premium-efficiency.If you
just want to zero out your household's annualized average
electricity consumption, because e.g. you have a net-
metered grid connection, adding batteries to a PV system
will increase the expected financial time-to-payback. If
you are off-grid you need batteries to use solar power
after dark but should make every effort to cut your non-
daylight power needs before sizing the battery system.
Batteries are currently a lot more expensive per watt-
hour delivered than the instantaneous output of solar
panels. In an intermediate case, where you don't get full
net metering but are still grid connected, there are a
few but not many cases where household batteries yield
positive financial ROI at current prices. You could make
the numbers work for a modest fraction of Hawaiian
households and smaller fractions of households in
Germany, California, and Australia.
[deleted]
matt_wulfeck - 4 hours ago
I just had my panels turned on. I love solar. It's still difficult
to justify it short-term on a cost-basis, but I'm saving about a
dollar a day after all things are said and done.That being said,
I'm generating my own electricity and my panels will run for a very
long time. The best is cranking the AC and still watching the meter
run in reverse during really scorching days.
fred_is_fred - 4 hours ago
What the NPV and pay-off time of your system? I've been unable to
get one bid here that's less than 10 years because electricity is
fairly cheap here.
workerIbe - 4 hours ago
I have built a system that cost just under $2k and should pay
off in about 3-4 years (depending on battery lifetime). 2.4 Kw
(8 panels) of used panels @ $.32/Watt, Charge controller, 3Kw
inverter, transfer switch and 320ah@48v used Golf Cart
Batteries. System is offgrid and supplies all my convenience
outlets, kitchen and 240v circuits are on still on the grid.
Panels are on top of free standing structures and being off
grid permits are not required and only the transfer switch
installation needed to be done by an electrician. Bonus is
being offgrid it acts as a big UPS in a power failure.
matt_wulfeck - 3 hours ago
This is a great plan. PG&E here in California forces solar
customers onto a more expensive plan. If you can avoid that
switch and use solar to dramatically reduce (but not
eliminate) your total kwh load then you'll definitely come
out way ahead, because you'll be on their cheapest tier.
workerIbe - 3 hours ago
Yes, most of the electricity I have generated has been what
would have been tier 2 @ $.26 kWh, with the climate stuff
going thru Sacramento atm I expect the price to go even
higher soon.
grw_ - 7 minutes ago
I've wondered about the 'used panel' market for a while. Do
you know why your seller didn't just increase the price of
the property or move the panels? Does the second-hand price
of panels decrease linearly with the amount of lifetime left,
and how can you verify?
matt_wulfeck - 4 hours ago
Yes it's 10 years for me as well. Most of that is because we
have a 30% efficiency hit because we didn't want to cut down a
tree in our backyard that shades it for 2 hours a day during
about 6 months of the year. Our system is also larger than our
current usage, because we plan to use more (electric car, more
kids, etc).Another benefit to think about is you've effectively
locked in your electricity rate. With some companies that might
not be a big thing, but here in CA PG&E has been relentless
with their rising kwh costs.
fred_is_fred - 4 hours ago
I pay on average about 10.3 cents per kwh and have a newer
home that's very efficient at holding cool air (and live in a
state where we heat more than we cool). For those reaons it's
a tough sell for me. If rates continue to rise and solar
continues to fall, we'll have a cross over that works for me
probably in a few years.
matt_wulfeck - 3 hours ago
It's not cost competitive for you at 10 cents. Why bother?
I'd kill for that kind of price in electricity. Our total
cost with solar is around 13c per kwh over 20 years.
wilwade - 3 hours ago
I also have the same (10.7 cents over the past year). We
have a community solar project in town, but it is ~13
cents over 20 years as well.
fred_is_fred - 2 hours ago
That's also what SolarCity told me...
ianai - 3 hours ago
Any chance some of your energy comes from nuclear?
fred_is_fred - 31 minutes ago
Coal and wind. I live in Colorado.
e40 - 4 hours ago
For the one I'm about to install it is little over 5 years.
lutorm - 3 hours ago
The pay off time for our system here in Hawaii was, if I
recall, about 6 years, even though the price of installations
is really high. The price of electricity is too, though.
matt_wulfeck - 3 hours ago
What do you pay per kwh?
vkou - 3 hours ago
The internet tells me it's 30c/KWH.Hawaii's primary source
of electricity is oil.
fovc - 50 minutes ago
I'm assuming a 10 year payback equates to an annualized return
of ~7%. Would you be paying cash for the panels or using
financing? If the former, do you have other investments paying
that much? If the latter, at what interest rate?
afeezaziz - 5 hours ago
If the process to make this kind of solar cell can be lowered
enough through scale then they should communicate this process to
Chinese solar companies. I am sorry for my poor understanding of
chemical process; if the materials of the solar cell are roughly
the same then it would be quite easy for the existing manufacturers
to actually switch to this solar cell production.I cannot wait for
the era of super cheap electricity!
rini17 - 5 hours ago
Switching manufacturing from silicon would not be easy, likely
this needs whole new process from scratch.Also, as the article
notes, they won't be available in large sheets but only small
milimeter chips - which require light concentration and thus sun-
tracking mechanism.
wavefunction - 5 hours ago
Why should research funded by American taxpayers be transferred
to Chinese solar cell producers, and by whom?I hope an American
firm implements the underlying science into a manufacturing
process, and any Chinese firms that want to use the process pay a
fair and equitable license for the technology.
zAy0LfpBZLC8mAC - 3 hours ago
> Why should research funded by American taxpayers be
transferred to Chinese solar cell producers, and by
whom?Because Americans live in the atmosphere that Chinese CO2
emissions go to?Not saying they should, but that would
obviously be the reason?
wavefunction - 1 hours ago
Well, I'm in favor of technological spread across the world,
especially when it's beneficial to the environment or society
at large.However, Chinese solar cell firms have been dumping
cheap and sub-standard solar panels on America for years in
an attempt to destroy the American industry, so I am less
excited about specifically Chinese solar panel firms gaining
access to this technology.I suppose it marks me as a bit of a
chauvinist in this case but I would prefer if those who
conduct themselves as adversaries do not also enjoy the
benefits accorded a friend.