
Tesla deployed over 300 Powerwalls in Hawaiian schools to cool down classrooms - doener
https://electrek.co/2018/02/23/tesla-powerwall-hawaii-school/
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chris_va
This perhaps says a lot more about the state of the Hawaii power grid than the
benefits of the Powerwall.

Due to economies of scale, unless your grid infrastructure is really poor,
grid attached energy storage is going to be cheaper than distributed energy
storage. Tesla just wants to sell batteries, and consumers are easier to
target than utilities.

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kurthr
See my other comment with links down thread, but HELCO (and other Hawaiian
Electric Utilities) no longer support net metering, because it is not
profitable (enough) for them. So they sell retail at $0.30-0.50/kWh and buy at
$0.10/kWh making a lot of people upset and crashing the solar market in the
islands. That makes battery storage cost effective where standard installs are
much less so.

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rebuilder
That's really expensive electricity! I assume there are obstacles to
developing more power plants in Hawaii?

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walrus01
Mostly because each island is its own small grid. Everything is fossil fuel,
no hydro, little wind, no nuclear. Cost of transporting fuel. Environmental
concerns about air pollution (eg: no China style cheap coal power plants).

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neltnerb
It's always been strange to me that an island with abundant solar and
geothermal resources relies on imported oil for most of their power
generation.

[https://www.eia.gov/state/?sid=HI](https://www.eia.gov/state/?sid=HI)

"In 2015, Hawaii imported 91% of the energy it consumed, mostly as petroleum."

They seem to be working hard on it at least, although I'm surprised that only
20% of the _renewable_ energy production is geothermal. I guess it's just more
expensive than solar nowadays.

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BurningFrog
Iceland is exploiting the hell out of it's geothermal energy, attracting
energy intensive industries like aluminium smelters and bitcoin mining.

Doesn't the Big Island have similar levels of available geothermal resources?

Is the difference that Iceland is an independent nation while Hawaii's
decisions are made in Washington DC?

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SerLava
A long time ago they started using geothermal energy but some poisonous gas
was released. So they shut it down permanently.

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cardamomo
Source?

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geertj
Why does this project need battery storage? The power demand for air-
conditioning during the day follows the supply of solar. Is it to cater for
hot but cloudy days?

~~~
walrus01
You can't run air conditioners directly off solar. PV panels natively produce
DC. There are units with microinverters built into the back of the panel that
produce AC. Even in a sunny climate clouds will pass in front of the sun.
Unless you have a _massively_ oversized PV array, you can't just run the DC
array's output into a bank of sinewave inverters and then straight into the
input of multiple 2 to 5kW load air conditioners.

I'm assuming here that a typical AC unit will look something like a 12000,
18000 or 24000 BTU/H LG, Daikin or Samsung split type, ductless, cooling-only
unit.

The cumulative kWh/day and kWh/month produced by your PV is what you should
care about. As compared to what your load will consume in the same time
period.

For off grid, which now economically makes sense in much of Hawaii because
fossil-fuel powered grid power can costs $0.32 to $0.50/kWh.

You need a battery buffer so that your load (the air conditioners) doesn't
brown out and fail when the a few clouds pass in front of your PV panels. At a
given time when it is a little bit cloudy out you might have 12kW of load but
even a very big PV array might only be producing 4kW.

The load is constantly running off the battery and inverter system, while the
PV panels and charge controller are constantly doing their best to keep the
battery full.

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Faaak
Coming from Europe, I've never seen an AC unit expressed in BTU/hour. To me it
seems much more logical to express it in kW.

The only "strange" (but correct) notation was on a french train, the AC was
expressed in kcal/hour

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y4mi
Then you've probably never had to plan cooling for a server room. BTU's are
often the only metric you get from the servers datasheet.

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walrus01
I find that these are occasionally very inaccurate. If possible put a
prototypical server on a watt meter and artificially load cpu, disk and ram to
determine its real world max wattage and thermal values. Then compare to what
its wattage is while idle.

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altcognito
At the scale of a server room, you're estimating over an aggregate and
probably want some overhead/room to expand.

~~~
walrus01
At the scale of a small to medium colocation facility you define W per
cabinet... Such as a typical 44U height cabinet in a row designed for front to
back airflow. 5kW per cabinet would be a normal low range, up to 10-12kW. Then
figure out your floor spacing and sq ft usage to determine how many cabinets.

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bringtheaction
Nowhere did they say what Powerwall actually is, and I’d never heard of them.
Powerwall is a battery made by Tesla to store excess solar energy.

[https://www.tesla.com/powerwall](https://www.tesla.com/powerwall)

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foepys
This "article" reads like an ad.

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thsowers
As a Tesla fan, I dislike the writer for this site. He often makes any Tesla
failure sound like a success, and everything reads as heavily biased

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rory096
Worth noting that the author is /u/FredTesla on reddit, moderator of
/r/TeslaMotors as well as the founder of Electrek. His career is essentially
built on being a Tesla fanboy.

~~~
olivermarks
There are dozens of battery companies creating storage units, but Tesla are
always superb with their marketing efforts to brand...in this case, batteries
as 'powerwalls'.

This is the 'Hoover' logic of making a generic device synonymous with a brand
name.

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pasbesoin
Whatever else you might say about Musk and company and their various ventures,
they are actually solving real problems, with real innovation.

NOT a bunch of talk about "too soon" or "focusing on core competencies".

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ggm
I wonder if the power budget in Hawaii would permit the other kind of air
conditioning, where you soak down a large water thermal mass, and then use it
to do the chiller side. I know nothing is free, but its a model which quite a
lot of places are moving to, in search of a different pattern of energy usage.
Hawaii might be one of the hard cases: I believe it has really high, and until
recently diesel backed power and this kind of off-peak power may simply not
exist.

It's a complementary technology to this use of powerwall. it's not an either-
or thing.

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heartbreak
Isn’t that form of air conditioning a non-starter in humid climates like
Hawaii?

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dubyah
I interpreted the parent post as talking about chilled water thermal energy
storage as opposed to evaporative cooling.

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ggm
Yes. its not evaporative cooling: you have a watermass you chill down with
offpeak power, and then use as the coolth source to chill dry air in the
aircon, rather than using a normal fridge chiller circuit. Its power-shifting.
The total powercost is probably comparable to on-demand chilling but you shift
the power budget to off-peak, or other sources.

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character0
Does anyone know why Hawaii doesn't utilize more geothermal energy? There are
a few hits for geothermal projects, but I would have expected these to be much
more popular.

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mter
It upsets pele. I'm totally serious. Google for why do native hawaiians oppose
geothermal.

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skookumchuck
This sounds odd. When I spent some time in Hawaii, houses had a gap between
the top of the walls and the roof, to let the breeze blow through the house.
While being impossible to air condition such a structure, it was not needed.
The ambient temperature with the breeze was nearly always comfortable.

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pontifk8r
Does it seem unusual that it's costing $100mm for 2300 classrooms, which is
about $43k each?

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wernercd
How many powerwalls per classroom? Solar? Electrical upgrades?

[https://www.tesla.com/powerwall](https://www.tesla.com/powerwall)

"Your final design and pricing will be based on your electrical panel, home
energy usage, number of Powerwalls, and where you’d like your Powerwall
installed. Typical installation cost ranges from $800 to $2,000. This does not
include solar installation, electrical upgrades (if necessary), taxes, permit
fees, or any retailer / connection charges that may apply."

I assume shipping would add a HEAFTY cost in Hawaii as well.

