T-Pain Is On A Boat: Re: [Electric Boats] Shopping For new battery bank

Sunday, February 8, 2015

Re: [Electric Boats] Shopping For new battery bank - economics of electrics

Its a good plan .. and will likely work ok *with a small motor*.

Aim for about 1/2 hp, or 350W, per ton of displacement.
This will get you the 5 knots for a 50 foot or 15 m boat.

At twenty tons displacement, thats only 7 kW (==10 hp).
So a 14 kWhr usable battery, or 17.5 kWhr nominal lithium, would run for
two hours.

An 80 hp motor would be expensive in terms of required battery.
80 hp= 59.6 kW.
59.6 kW / 0.8 = 74.5 kWhr.
For two hours, thats 149 kWhr.
At 300 $ per kWhr, the battery would cost 44.700$.

Going from 7 kW power to 59 kW, 8 times more, would likely get you hull
speed at 9.5 knots.

Going from the standard prop to a large, slower rotating, more
efficient, prop, with the smaller power, would probably get you about
30% more range.
Normal props (and marine gears) are pretty inefficient.

Some data:
Lithium batteries will get you about 80% usable power.
Current lowest cost is about 300$ / kWhr.
Electric cars use batteries in the 10 kWhr to 80 kWhr sizes.

The lower end in electric cars in hybrids, of 10 kWhr, is really not too
useful in range, about 30 km.

As an example:
Over here in europe, of all new taxis, about 1/3 are all hybrids.
I have asked 3 hybrid drivers, and they are all happy with them, and
report about 1/2 fuel costs compared to normal diesel engines.

? Whats up with the comparison with cars:
Battery costs are driven by the amount of batteries made.
Almost all the worlds battery production in terms of energy storage go
into cars (=cars consume almosta all the batteries).
As electric cars are getting more common, and better, and batteries are
getting larger, more batteries are needed.
Thus more are produced, and they are again getting cheaper.

The current cost of 300W / kWhr is going down about 20-30% every year.
Within 3-5 years, electric car batteries will thus be half the cost.
Cube (0.8) = 0.512.
So in six years they will be at 1/4 the current costs, or 4 times the
energy storage for the same cost.
At that point a standard misize car, with current electric range of 200
km, would have a 800 km range.

At that point you only need to charge the battery once or twice per
month, and the electric car will be much cheaper (superior) to a
gasoline model.

The curve is exactly the same as for example hard disk drives, PC
processor speeds, cellular phones, PV or solar panels, and automated
production in general.
The only variables are the speed of cost decline, and where the
breakpoint is at which the curve flattens out.

We are pretty far away from any theoretical hard limit, and new battery
chemistries are being researched heavily.
Its practically certain better batteries will be discovered, and thus
the cost/kWhr will again drop greatly.

A good comparison is PV system and panels costs.
The price/W has dropped 97 times, or to 3% of cost, in 25 years.
Current PV panels cost about 0.5€/W.
The breakeven with normal electricity production was at 1$ / W, and thus
PV is today quite a bit cheaper vs "regular" electricity, unless the
electric company prevents use of PV (laws favoring utilities, and
expensive permits).
These are called "soft costs" in the PV business.

In the US soft costs are about 3/5 to 80% of total system cost.
US current system costs are about 25.000 $ /house (3-5 kW peak).
In australia, about 4000$ (3-4 kW peak).
In australia there are no soft costs, as small scale personal install
are permitted.
About 30.000 install are done per year in austrlia.

Fact checks are easily done using your google fu.

On 05/02/2015 16:33, Scott Isbell isbell1s@yahoo.com [electricboats] wrote:
> I was looking at the 80hp motor, but am looking at doing it as
> economically as possible. I am a mechanic and electrician so can
> probably do most of the work my self. My end goal is to use solar and
> wind turbin to charge my system and not rely on marinas. Do you have
> recomendations on solar panel suppliers and batteries.
>
> Thanks,
> Scott Isbell

--
-hanermo (cnc designs)