
France approves 720MW of solar as price falls another 5% - toomuchtodo
https://www.pv-tech.org/news/france-approves-720mw-of-solar-as-price-falls-another-5
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laser
I wonder if it could ever make sense to have ultra-high voltage or
superconductive power transmission lines wrapping around the planet so that we
could take advantage of the fact that it's always daytime somewhere to forgo
much grid-scale storage and instead just get electricity from wherever it's
daylight. Aside from the geopolitical/national security issues, I wonder if
such a thing is feasible or it's ultimately going to be more efficient to
store energy than transmit it half-way around the world.

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freebs
Why use wires when we could possibly concentrate and beam the light across the
ponds?

~~~
pjc50
1) You can't beam round a curved surface and the atmosphere isn't refractive
enough in the visible spectrum (only works for shortwave radio)

2) The death ray is an environmental and safety hazard

3) Atmospheric attenuation would probably be more than electrical attenuation
at that distance

~~~
nielsbot
I know HN is not for humor, but i really got a laugh out of “the death ray is
an environmental and safety hazard”, listed with such seriousness.

~~~
pjc50
Thankyou - that was entirely deliberate, you can only get humour past the HN
voting system if either it's totally deadpan or you explain the joke in the
same comment.

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DoctorOetker
I keep wondering about the Solar Sinter project by Markus Kayser *

What if instead of manufacturing artwork, it manufactured a mechanical energy
storage, large enough to store either daily variations or even yearly
insolation?

Perhaps glass blocks (filled with sand) as weights for storing as potential
energy (how deep would a shaft have to be to store daily or yearly insolation,
assuming the weight is ideally half as tall as the shaft?)

Perhaps storing compressed (even liquified?) air? How airtight is the
resulting sintered glass?

Perhaps making 1 upper reservoir and somehow digging a narrow shaft (making
the walls glass while digging/blowing up the sand through the already
vitrified upper part of the shaft? Then somehow building the lower underground
reservoir from the inside out, and store potential energy in the closed system
containing water (condensed from air?)

Solar panels, wiring, cheap plastic Fresnel lenses, control electronics would
need to keep getting supplied to attach to newly built energy storages. But as
much as possible, especially things that wear out should be renewably built
from glass onsite (for example scoops to move and redistribute sand)

In example consider an NxN square of already completed storage, sites then
there is ~ 4 _N adjacent sites under construction so the project either could
speed up by actually building ~N /4 circumference layers at a time, or start
delivering ~(N-4)_N of renewable on-demand energy (since the storage site
height was chosen to have enough capacity to store daily, weekly or yearly
insolation)

* [https://kayserworks.com/](https://kayserworks.com/)

~~~
DoctorOetker
ok I calculated the height/depth for a shaft housing a glass weight half the
size (which is the optimal height for the weight in any shaft of fixed height,
I assume you understand this is optimum, if you want a derivation I can
provide it upon request)

For clear skies (typical of deserts), we can use the daily insolation at sea
level: 21,6 MJ/m^2

(I will ignore inefficiency of solar panel, the less efficient, the less deep
or tall we need to store the energy generated, and one time construction of
the storage is preferable over reconstructing the weights and shafts once more
efficient panels become available)

So if we want to store it as potential energy of a glass weight under the
solar panel that generated the energy we have for each square meter of panel:

a glass weight with cross section one scquare meter, and height l = L/2 where
L is the height of the shaft.

glass weights 2500 kg/m^3, so we have mass of the weight: m = l * 1 m^2 * 2500
kg/m^3 = l * 2500 kg/m = L/2 * 2500 kg/m

We want the weight to be at all times contained in the shaft so it can be
closed and sand can not blow under the weight or into the mechanisms.

the height difference for the glass weigh at the top -but still completely
inside the shaft- to the bottom -but also still completely inside the shaft-
is h = L - l/2 - l/2 = L -l = L - L/2 = L/2

The potential energy difference for a weight of mass m and vertical travel
distance h is E = m * g * h

Plugging everything together:

E = ( L/2 * 2500 kg/m * 9.81 N/kg * L/2 )

Solving for L = 2 * sqrt ( E / (2500 * 9,81 N/m))

Since the assumed insolation is 21.6 MJ/m^2 then one square meter of (ideal
futuristic) solar panel will simply generate 21.6 MJ = 21,6 MNm

Plugging into the equation for L we get L = 59,35 m

I seeriously underestimated potential energy I guess, I thought it would have
been larger.

If your panels are less efficient (say 10%) or you have a large unused area
you can of course make the structure less tall/deep.

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sdunwoody
Please forgive me if this is a stupid question - but is heavily investing in
solar electricity a good idea in Europe considering the variation in climate
throughout the year?

Energy demand is highest in the Winter, when mean monthly sunshine hours are
at the lowest.

Even in Nice (the very south of France) where I assume this difference would
be smaller, there's still a big gap between 347.5 mean hours in July and 139.3
mean hours in December
([https://en.wikipedia.org/wiki/Nice#Climate](https://en.wikipedia.org/wiki/Nice#Climate)).

Surely we'd need to heavily invest in backup generation capacity that would be
dormant for the vast majority of the summer then heavily in use over the
winter?

Admittedly I have a very limited amount of knowledge in this area - but
wouldn't wind or tidal power generation be a better bet here (well, Europe
anyway)?

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mariushn
One use case would be Air conditioning, most needed when it's sunny/hot.

~~~
sdunwoody
I'm not sure about France, but it's rare to have air con in the UK because the
summers aren't hot enough :) I think a lot of Europe is similar in this regard
(with the exception being the south).

Even if France does have a reasonable number of air con units installed, I
would expect energy consumption to be higher in the winter due to shorter days
etc. It would be good to see statistics though.

~~~
Leherenn
Air con is a bit more common, but nothing like the US.

Consumption is much higher in winter than summer (summer is actually the
period of the year with the lowest consumption).

[https://goo.gl/images/mdRj1r](https://goo.gl/images/mdRj1r)

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wcoenen
Capital must be raises to pay for these projects. Is there a way for Europeans
to invest in that?

Or is this out of reach for the small "retail investors"...

~~~
dalbasal
There are lots of green energy funds. If you ask at most European banks, they
will put you touch with their "wealth" team where you can pick a managed
portfolio or fund to invest in. It may also be a checkbox you can tick on your
pension scheme.

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mikec3010
Could you store renewable energy via electrolysis, and instead of having
storage tanks of dangerous hydrogen at home, pump the gas back into a grid?
Most houses have natural gas lines and those are relatively safe. Would it be
viable to have "hydrogen lines" that just ran in reverse when excess renewable
energy is produced? Then draw off it to a home fuel cell during peak demand?

~~~
pjc50
Why on earth would you do this at home rather than at a central facility where
it's cheaper and easier to handle bulk gases?

You _can_ incorporate hydrogen into the grid but only up to a point:
[https://www.telegraph.co.uk/business/2018/01/06/hydrogen/](https://www.telegraph.co.uk/business/2018/01/06/hydrogen/)
and it has issues
[https://www.nrel.gov/docs/fy13osti/51995.pdf](https://www.nrel.gov/docs/fy13osti/51995.pdf)

~~~
mikec3010
You would do this at home because that is where residential PV is located. Of
course it's more obvious to send the power back down the wire and, as you
said, convert to hydrogen centrally.

My question looks silly now in contrast, but it was thought up considering
that grid buyback isn't going so well in the us, and focusing on a safe way to
store and use hydrogen as a battery competing with flywheels or lithium
battery cells, or centralized pumped hydro, etc. Just a hypothetical.

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nvahalik
Countries are building lots of solar and wind. However, these techs only
operate/run during the daytime or when the wind is blowing... which is not
100% of the time.

If they continue to build out solar/wind and thereby drive FF-production "out
of business" what happens when solar/wind cannot meet demand? Are they
building stored energy reserves as well? What happens then?

~~~
_Codemonkeyism
My guess is that energy will be so cheap, we produce much much more than we
consume in the future. There will be an abundance of energy some decades down.

Also electric cars will create very large storage capcities for energy in the
next decade.

On top of that we get intelligent meters, with machines like my washing
machine pulling power at the best time, my battery chargers using the right
time etc, so (non-industry) demand will flatten out over time with intelligent
metering.

I would have feared about this issue 20y ago, but I think this is no longer of
any importance for the development of solar power.

What is relevant with the ongoing centralization of solar power is power
transmission.

~~~
MrEfficiency
>Also electric cars will create very large storage capcities for energy in the
next decade.

Chem engineer here, battery technology doesnt seem to be a guarantee to
improve.

Batteries are limited by the physics of our universe. The chemistry between
two chemicals will not change, and it feels like we have exhausted every
option.

This is a non trivial problem and I am unsure if I expect a solution.

~~~
mrep
I'm no electrical engineer, but I think we can do some napkin math.

80khw battery in an average model s * 300000000 million cars /
(3,911,000,000,000 kwh energy use in the in all of 2015 [2] / 365 days per
year) = 2.239 times as much storage in cars on the road versus energy usage
which seems pretty doable. Also, it also gets better because as car batteries
age and their storage / weight goes down, you can replace them with new ones
and put the old ones in grid storage locations where weight / storage does not
matter and run them till they are literally dead.

[1]: about a little less than 1 per person (just rough estimating here)

[2]:
[https://en.wikipedia.org/wiki/List_of_countries_by_electrici...](https://en.wikipedia.org/wiki/List_of_countries_by_electricity_consumption)

~~~
mrep
2 big variables I forgot about.

1\. We need to eventually switch our winter gas heaters to electric which
while helping balance summer vs winter electric usage, electric heating isn't
as efficient and we have to increase the outside air a lot more in the winter
than we have to cool it in the summer (for most people at least).

2\. I forgot to add in the extra electric demand needed to power the cars
which is currently powered by oil.

~~~
icebraining
Electric heat pumps are quite efficient, AFAIK.

~~~
amluto
For swimming pools, which are admittedly a special case, heat pumps are
already cheaper to operate than gas heaters in most of the country.

(They’re special for several reasons. A big one is that they have _huge_
thermal mass, so your heat pump can operate at whatever time of day you want.
This means you can optimize for electric rates vs outdoor temperature. Heat
pumps, unlike gas boilers, are considerably more efficient when it’s warm
out.)

