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Old 06-11-2019, 00:33   #1
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Playing with some numbers - Generation Cost

Cost to generate power seems to be $.75-$8 / kw/hr depending on how you do your math. Size your generator to run AC units, then run it for just watching TV and you'll be sad.
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Old 06-11-2019, 00:36   #2
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Re: Playing with some numbers - Generation Cost

Cost to generate from Solar works out at $0.15 / KWHr, assuming rigid panels.
Space seems to the be the challenge.
If you can use your solar at time of generation, rather than cycle through batteries, will save money. Therefore oversized solar is not necessarily a waste.
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Old 06-11-2019, 00:38   #3
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Re: Playing with some numbers - Generation Cost

Cost to time shift generation capacity using batteries - Solar or Generator adds a lot of cost
This ignores some hardware costs like inverters. Too many variables.

So if you charge your batteries from generator, and then watch TV or cook or whatever, this is what your battery use adds to your generator cost.

$0.41-0.66 / KWHr
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Old 06-11-2019, 00:40   #4
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Re: Playing with some numbers - Generation Cost

So - as a rough comparison

Cheapest power is solar.
Batteries cost a lot
Time shifting your generator capacity may make sense, depending on your generator. You need to do the math based on your load.

This is all assuming new kit and some rough estimates for fitout. Also assumes self maintained. Easy for costs to change if you hire mechanics often.

Slightly ugly excel attached so as to find errors in my math, or play with variables.
eg. Battery cycle life at different discharge patterns.
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Old 06-11-2019, 00:44   #5
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Re: Playing with some numbers - Generation Cost

Next is trying to calculate three questions

1. What is the cheapest way to make fresh water, including the cost of the watermaker.

2. What is the cheapest way to run a boat with AC.

3. Is going to a single diesel engine cost effective in a used catamaran. And if so, how.
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Old 06-11-2019, 09:29   #6
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Re: Playing with some numbers - Generation Cost

NFR, some good brainstorming there. Hope this discussion develops
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Old 06-11-2019, 09:42   #7
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Re: Playing with some numbers - Generation Cost

Quote:
Originally Posted by nfbr View Post
Next is trying to calculate three questions

1. What is the cheapest way to make fresh water, including the cost of the watermaker.

2. What is the cheapest way to run a boat with AC.

3. Is going to a single diesel engine cost effective in a used catamaran. And if so, how.
1. Solar via 12 v water maker or Solar via inverter for mains this is on the assumption you have enough solar to power both and do not need a shower every 2 hours (your question does not have consumption, or amount made per hour against diesel generator or 12v batteries via solar so I will leave that out for the seriously bored people to work out in my mind set as long as you can have enough to drink and a shower a day the rest is expendable energy and a waste )
2. Solar via an inverter again if you have enough solar , and are willing to switch of the AC when the sun dont shine.
3. No why would you . were would you put the single motor to effective drive the boat without truly upsetting performance , thus using more fuel .

Solar is free panels are cheap if you have enough space you can run a modest house with Solar why not your boat
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Old 06-11-2019, 13:24   #8
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Re: Playing with some numbers - Generation Cost

Quote:
Originally Posted by tarian View Post
1. ...
3. No why would you . were would you put the single motor to effective drive the boat without truly upsetting performance , thus using more fuel .

Solar is free panels are cheap if you have enough space you can run a modest house with Solar why not your boat

3. Why not run one engine / generator in one hull and put a large Lithium battery bank in the other hull. Use electric motors to drive the 2 props and a large solar array to help charge the batteries. You wouldn't even need to start the engine for short pulling anchor/drop anchor evolutions! You can buy a decent battery bank for the savings of a $15,000 engine.
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Old 06-11-2019, 14:10   #9
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Re: Playing with some numbers - Generation Cost

Quote:
Originally Posted by nfbr View Post
Cost to generate from Solar works out at $0.15 / KWHr, assuming rigid panels.
Space seems to the be the challenge.
If you can use your solar at time of generation, rather than cycle through batteries, will save money. Therefore oversized solar is not necessarily a waste.
I believe people severely underestimate the cost of solar per kWh on a boat. Here is my calculation, which I believe is realistic for my type of use:

Over 10 years, 100W panel:
$200 initial panel cost (flexible)
$600 install, including arch, controller, etc.
$400 flexible panel is replaced every 3 years due to cracking, etc.
Total investment: $1,200

Max energy that the panel can theoretically generate will be 100W x 5 hrs x 365 x 10 years = 1,825 kWh. However, we need to reduce this to usable energy:
80% due to cloudy days, seasonal variation
50% since we are not cruising all the time (this will vary on lifestyle)
70% due to energy not needed (i.e. batteries full but panel working)
Net usable energy is only 28% of 1,825 kWh or 511 kWh.

Realistic cost per kWh = $2.5

So, this is the major problem with solar as the main power generation source on a boat. You cannot connect it to the grid to increase utilization to 100%. It is difficult to size properly, because on one hand you want more to account for cloudy days, on the other hand, the more you have, the more excess capacity. It looks ugly and needs a lot of space. It is more practical in the trade winds vs close-hauled when the boat is not straight up. As a result of this, it is expensive.

Now compare this to the Honda 2000i or in my case, a $250, 700W invertor generator that you can replace every year if so desired.

Clearly, it depends on the cruising habits but full time cruisers are a relatively smaller portion of the overall community. So, my preferred energy generation solution would be:

- Small solar for emergency/backup and to charge the batteries/fans/cameras while not on the boat. I believe 80-100W is enough.

- Main engine alternator as the primary charging method (tried and proven)

- If on a small boat, cruising occasionally, take a small inverter generator with you for longer trips. Replace every year. If on a larger boat, get a diesel generator for the convenience, not for the money saving.

SV Pizzazz
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Old 06-11-2019, 20:04   #10
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Re: Playing with some numbers - Generation Cost

Quote:
Originally Posted by Pizzazz View Post
I believe people severely underestimate the cost of solar per kWh on a boat. Here is my calculation, which I believe is realistic for my type of use:

Over 10 years, 100W panel:
$200 initial panel cost (flexible)
$600 install, including arch, controller, etc.
$400 flexible panel is replaced every 3 years due to cracking, etc.
Total investment: $1,200

Max energy that the panel can theoretically generate will be 100W x 5 hrs x 365 x 10 years = 1,825 kWh. However, we need to reduce this to usable energy:
80% due to cloudy days, seasonal variation
50% since we are not cruising all the time (this will vary on lifestyle)
70% due to energy not needed (i.e. batteries full but panel working)
Net usable energy is only 28% of 1,825 kWh or 511 kWh.

Realistic cost per kWh = $2.5

So, this is the major problem with solar as the main power generation source on a boat. You cannot connect it to the grid to increase utilization to 100%. It is difficult to size properly, because on one hand you want more to account for cloudy days, on the other hand, the more you have, the more excess capacity. It looks ugly and needs a lot of space. It is more practical in the trade winds vs close-hauled when the boat is not straight up. As a result of this, it is expensive.

Now compare this to the Honda 2000i or in my case, a $250, 700W invertor generator that you can replace every year if so desired.

Clearly, it depends on the cruising habits but full time cruisers are a relatively smaller portion of the overall community. So, my preferred energy generation solution would be:

- Small solar for emergency/backup and to charge the batteries/fans/cameras while not on the boat. I believe 80-100W is enough.

- Main engine alternator as the primary charging method (tried and proven)

- If on a small boat, cruising occasionally, take a small inverter generator with you for longer trips. Replace every year. If on a larger boat, get a diesel generator for the convenience, not for the money saving.

SV Pizzazz

Well, you can hardly include the cost of failures and questionable decisions. Why would you replace a flex panel again and again with the same junk that fails? Can't include that cost. Why would you spend $600 to mount a $100 panel? Why build an arch and put a flex panel on it?


My build:
panels $500 - I bought two 260watt hard panels 520W total (altestore)
arch $300 - I bought a 4 bow bimini frame for SS tube from Mystic consignment for $225 and $75 from home depot for some AL and screws
Controller - $330 from amazon victron 100/50 mppt
Breaker and wiring - $50 ish

$1180 for 520W

So, even if I accept your 28% yield (way low for live aboard) and the 10 year life (I expect 20), I'm at $0.44/kWh = ((0.28*520*5*365*10)/1000)/$1180 (I think the real cost is more like half that, and as for space, I'm on an old 1975 tartan with a skinny aft end so anything built this century has way more space.)

I have had no issues for the 5 years installed, including 15months live aboard in the tropics. There's NO WAY a generator would have been cheaper or more convenient schlepping gas and changing oil and who knows what may fail with all those moving parts. And let's not completely ignore the fact that solar is the socially responsible power source!
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Old 06-11-2019, 20:10   #11
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Re: Playing with some numbers - Generation Cost

FYI. 5Hr Insolation Value includes weather variance.
Reducing for weather is double impacting. Adjust insolation for location
https://www.altestore.com/howto/sola...map-world-a43/

These are all ballpark numbers
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Old 06-11-2019, 20:38   #12
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Re: Playing with some numbers - Generation Cost

To bad we always ignore the real total cost of of Gas Generators. We put nothing in the budget for cleaning up pollution and down down stream impacts. Irma damage est $50 billion, $90 billion for Maria.. $140billion cost for just 2 Caribbean hurricanes that happened in the same year. Think of the world wide cost of catastrophic storms and floods. Half a Trillion maybe a Trillion per year world wide. I don't know, but it is a big number. And some percent of that damage must be contributed to climate change. Nobody knows what that number is, But even 0.1% of a Trillion is $1 Billion dollars! And unfortunately, the cost is unevenly (unfairly) distributed to those who live in hurricane belts and flood zones.

So, Remember that when you buy a Gas or Diesel generator, to some extent you are forcing other people to pay to clean up after your mess.


Rant over, sorry
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Old 06-11-2019, 21:53   #13
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Re: Playing with some numbers - Generation Cost

$7000 for panels, shipping, wiring, controllers, custom frame, a few tools I didn't have, etc.

We make 6.5 kwh per day on average.

6.5kwh x 365 x 10 = 23725 kwh in 10 years.
$7000/23725 = $0.30 per kwh

I suspect they will last much longer than 10 years.

$0.20 per kwh if they last 15 years.
$0.15 per kwh if they last 20 years.
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Old 07-11-2019, 00:20   #14
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Re: Playing with some numbers - Generation Cost

Zstine, I do agree partially with your assessment of engines polluting the air with exhaust gases. But you can’t alleviate the fact that it took engines to mine the minerals to build the solar panels. It took engines to fabricate the panels in a factory. It took engines to get people to work on the manufacturing process. It took engines to deliver panels to market places. Everything has a carbon footprint.

I have solar panels on my roof. California wildfires left me without heat in the house, hot water, or electricity for refrigerators for 3 days. So, I had to buy a couple of generators ( Honda). If the rainy season is delayed and winds cause pg&e to shut power again we could see lows in the house of mid 40’s. By next wildfire season I will have all the electrical wiring in place to just fire up and flip a couple of breakers.

I learned a big lesson about being solar dependent. You have to cover your bases with fossil fuel and solar and have all your ducks lined up.
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Old 07-11-2019, 02:22   #15
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Re: Playing with some numbers - Generation Cost

I am still not convinced that solar energy is less expensive in a typical usage scenario. You need to look at the problem conceptually. Sailing vessels are used for cruising which be definition involves moving from one place to another. When you move you often use the engine which generates power more or less for free. Solar produces energy at fixed times during the day and is impacted by shading, boat position and weather. Energy consumption follows a different pattern based on our boating lifestyles. In order to balance the two one needs to either i) invest in more battery capacity; ii) oversize your solar panel capacity; or iii) rely on additional power generation sources such as the engine or a generator. You can't multiply by 365 because no one spends 100% of time on the boat. You have to subtract the time when you are moving under engine power, etc. If you have an over-sized battery bank or panels, you will often be generating more power than the batteries can take (this is why people say solar works well with lithium but that is mega expensive).

When you take all of this into account, the price of solar will be closer to the price of ICE generation (which I calculate at $1/kwh. Thus, we all need a mixture of power sources and I see solar as complimentary. Some will see solar as the primary power generation source. It is a trade-off between type of sailing, tolerance to noise vs. clean boat lines, etc. But be realistic about the cost of solar generation. It is not $0.15 cents per kwh unless living on the hook for 10 months of the year.
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