fresh meat

Re: fresh meat

Welcome Morpho!

You don't need to duplicate your post... I think everyone here pretty much hits the "New Posts" link--and having multiple threads on the same subject just confuses people where to reply.

Regarding what is a "Watt"... It is not a bad question at all.

How much electrical math have you had? The basic equations are:

V=I*R=Voltage=Current (Amperes) * Resistance (Ohms)

W=V*I=volts*amps=Power in Watts...
W=V^2 / R = I^2 * R

Watts is a "rate" -- basically like Miles Per Gallon is a rate.

A 100 Watt Light bulb tells us how much power the light is burning--but not how much energy is needed to run the bulb for a period of time (a 20 MPG gallon car -- how much gas do we need to make the "trip).

So, in physics (and chemistry and such), there are other units (Joules, Erg, and such) that are used in the MKS (metric system)--however these are very small numbers. So, for residential and commercial use, they made up a unit called a Watt*Hour. Basically, run a 1 watt load for 1 hour, you have used 1 watt*hour of energy (like 20 MPG car, run it on 1 gallon of fuel, and it will go for 20 miles).

So, a 100 watt light bulb running for 2 hours:

100 Watt * 2 Hours = 200 Watt*Hours

Or, run a 400 watt light for 1/2 an hour:

400 watt*1/2 hour = 200 Watt*Hours

Or--the same amount of energy was used.

The related unit is the kWatt*hour (kilo-watt-hour). That is:

1 kWatt*Hour = 1,000 Watt*Hours

For our homes, the utility bills in kWhrs (again--an easier number to deal with on the bills--200 kWhrs @ $0.10 per kWhr = $20.00 is my monthly power bill, is easier than 200,000 Watt*hours * $0.00010 per Whr = $20.00).

The biggest confusion for most people--me included at times--is the difference between Watt and Watt*Hour. You need to know both for designing a solar system...

Watts is like the Horsepower of the generator (peak power needed to run everything at once).

And the Watt*Hours is like the fuel tank--on average, running some lights, microwave, fridge over 24 hours--how big of storage tank (battery) are you going to need, and how much solar panel (plus sun) is going to be needed to fill up the tank at the end of the day.

Either you will need to study basic electricity--or ask a few basic questions at a time--until you get a hold of the whole thing. It is not hard, but you can drown if tossed in the deep end of solar.

Lastly, we normally stress conservation here before throwing up solar panels all over the property and stuffing batteries in the basement.

Typically solar electric power is 2-10+ times the cost of utility power ("Grid Tied" to "Off Grid" application range of cost).

It is almost always cheaper to send money on conservation than to spend money on generating your own power (and typically, a lot less frustrating).

-Bill

Re: fresh meat

Actually, no--I do not.

All "freshly baked" (or half-baked) for your pleasure.

We try not to give "canned" answers here... Everyone has a slightly different question and level of experience.

And, especially, with new users--the WARNING:

Off Grid systems with lead acid batteries are more dangerous to work than regular 120/240 VAC household wiring.

Batteries will output more current into a short circuit than 120 VAC home plug can--welding a dropped wrench on to the terminals.

Also, batteries are filled with hydrogen/oxygen gas--very explosive.

And batteries are full of very strong sulfuric acid. Also, batteries have no off switch / breaker to make them "safe" to work on--they are always "hot" and ready to "bite". Wearing safety glasses, removing rings, covering the battery bank with a board/plastic/rubber mat when working near them, and wrapping electrical tape around your tools are all common safety tasks when working on these systems.

Make any one mistake--and frequently it will cascade into a worst situation.

Do not work on, or design/install any electrical system unless you are 100% sure of what you are doing (or have a knowledgeable friend to help).

Regarding help from this forum, I can point to the "search tool" to try and find common questions--and I have also had good luck with Google and a custom search:

Google: key words site:www.wind-sun.com/ForumVB

The "site:" limits your searches to a particular website/path. Sometimes the "natural language questions" get me closer than the "Search" button above (and sometimes, not).

Have fun!

-Bill :roll:

Re: fresh meat

OK, once more from the top... You want to run a 1,800 Watt*Hour load in Lindale, Alberta, Canada... So a "city" so small, that in Google Maps the only feature that stands out is a stack billowing steam.

Using the PV Calculator, picking Edmonton Alberta (a small suburb 50 miles east of the Metroplex of Lindale)... Use default settings for everything, start with 1kW of solar panels (easy to scale) and 0.52 derate factor--because you are off-grid:

Results

Month
Solar Radiation(kWh/m2/day)
AC Energy (kWh)
Energy Value(Can$0.0862 per kWhr)
1      2.94          50     4.31 
2      4.36          66     5.69 
3      5.82          94     8.10 
4      5.26          78     6.72 
5      5.47          80     6.90 
6      5.56          77     6.64 
7      5.35          74     6.38 
8      5.40          77     6.64 
9      4.45          63     5.43 
10      3.94          60     5.17 
11      2.63          41     3.53 
12      1.79          28     2.41 
=====================================
Year      4.41          789     $68.01

In February, you will, for typical weather patterns, generate an average of 28 kWhrs per month or just under 1kWhr per day of useful 120 VAC energy.

Depending on your needs, you may try running your panel at 80-90 degrees vertical (help clear snow during the winter)--run as above with 90 (vertical) panel--you will get about the same amount of power--but if you have snow, it will probably be easier to clean, and you might gain some from white snow reflecting sun into the panel...

OK, next assumption, lets assume that you will need to use a generator (or other alternate energy source) during the worst 3 months of the year. So the minimum 30 day average is now 60 kWhrs per month, or 2 kWhrs per day (2,000 Watt*Hours per day).

With this assumption, a 1 kW solar panel system would seem to meet your minimum needs for 9 months out of the year.

I, however, agree with Tony's (Icarus) suggestion of taking your "guestimated" load and multiply it by two... So, 1.8 kWhr*2=3.6 kWhr planned system.

Using our 1kW PV Calculation Results we can figure:

(3.6 kWhrs per day needed / 2kWhrs per day)*1kW ref panels = 1.8 kWatts of solar panels

1.8kW (1,800 watts) of solar panels will give you more than enough power for reasonable growth. And, if you keep your loads down in the winter--your daily average available power needs are almost covered too (especially if you don't need an electric fridge/freezer during this time--another reason to watch seasonal loads).

So ~1,000 to 1,800 watts of solar panels.

Next, battery sizing... Normally recommend 6x your daily load. And, unless you need 12 volts DC, recommend 24 volt battery bank--will support a 2,000+ watt inverter quite nicely--if needed.

Assume inverter is 85% efficient, 3 days of no sun, and 50% maximum discharge:

1,800 Watt*Hours * 1/0.85 * 1/24 volt battery bank * 3 days * 1/50% dischrg = 529 amp*hours at 24 volts

This battery is sized based on 1,800 watt daily load... With 1,000 watt of solar panels, which works out to round 5-7% ratio of solar charging current to battery capacity (recommended is ~5% to ~13%).

This 529AH battery bank is on the "large" size of the range... You could choose to just double the solar panels and leave the batteries alone--or double the panels too (from ~1,000 watts to ~1,800 watts of solar panels). Your choice.

Picking a generator--you don't want to oversize the unit. A 529AH battery bank would probaby be OK with a 650-1,000 watt charger--which may run on a 2,000 watt generator. If you go with a larger battery bank, you may need to step up to a larger unit:

529AH * 5% = ~26.5 amps min
529AH * 13% = ~69 amps max

If you make the battery bank larger (or smaller), size the charger/genset appropriately. Try to avoid running a 600 watt charger on 6kW genset... Generally, generators drop in fuel efficiency once they are under 50% load (some are pretty good down to 25% load)--You may end up "buy" 3kWatt of fuel flow and only using 600 watts of electricity. On the other hand, you will usually be able to run a charger at 90% of generator output--so the genset does have to be larger...

Many folks run the genset in the morning to bulk/quick charge the battery bank and run other loads (like washer, vacuum, etc.)... Then shut down once the battery is about 85%+/-5% full, and let the solar panels bring it back to full power.

I will stop here... Our Host is a good place to start looking for components--but being in Canada, you may wish to purchase local (in country) based on shipping and duties.

Outback and Xantrex make good Solar Charge Controllers (60-80 amp controllers). Get the Remote Battery Temperature Sensor.

For solar panels, look at the 100 watt and larger units--less wiring and generally lower $$$/watt. As long as you look at good brands of mono/poly crystalline panels--buy "$ per watt" delivered cost.

For an inverter, highly recommend a TSW (True Sine Wave) inverter for running your home. More efficient and "electrically" compatible with anything out there. If you are tight on money--get a smaller TSW for your electronic loads and fridge (1,000 watt max or so, less if not running the freezer). Get a big, cheap, MSW (modified square wave) to run your well pump, vacuum, and table saw.

Lastly, I would high recommend a Battery Monitor... Something like the Trimetric is a good low cost unit. I really like the Xantrex Linklite and Linkpro units as they have a progamable output that can be set to warn/turn off inverter if you get below XX% battery capacity... If you save running your batteries dead just one time, you probably will have paid for the unit.

And while you are on the Battery Monitor Page, look at the Kill-A-Watt meter--great way to measure your 120 VAC loads in Watt*hours to better estimate the needs of your computer, fridge, etc.

The above is a first guess based on commonly used rules of thumb and assuming flooded cell batteries (cheap and rugged). Other options like AGM batteries and such are available depending on your needs. Any questions?

-Bill

Re: fresh meat

$8,000 for 100'? Wow--sounds like SF Bay Area--a few years ago my brother-in-law had to spend $10,000 for a buried run from the pole to his home (over $xx,000 remodel, they make you bury your feed).

Morpho--I don't think you got anyone upset here... It is that, even though though this is a Renewable Energy Forum (attached to a RE wholesaler/retailer)--we are all a very practical bunch here.

If you have utility power nearby--it almost never makes sense to go off-grid solar.

Most people don't realize how good they have it (with utility power) until we tell them that their RE power costs them $1-$2 per kWhr (using "cheap" US supplied materials--can be much more for non-US installations).

Yes, it is nice to "go green"--but most times, going green really means conservation and utility power. Just substituting a on-grid live style with off-grid technology is usually neither green or cost effective.

For Icarus/Tony--I have the feeling that he would install a utility feed to his cabin if it where available. However, I am sure he would not be running a 1,000 kWhr per month bill when connected.

The issues of generating your own power are many. And unless you have lived the off-grid life and all of the issues (old inverter is obsolete, can't repair and need a new one, plus new support equipment because the old equipment won't interface with the new; hail storm takes out panels, kids with baseball, etc.).

I can't say I have lived that life--I am just Grid Tied in a large metropolitan area. But we here try to talk people out of the idea that off-grid is cheap and idyllic . It is neither. But it is better than not having any electricity or heat at all (and usually better than 24/7 generators and fossil fuel space/water heating).

-Bill

Re: fresh meat

Well, sort of true...

The most efficient coal and natural gas fired generators are probably in the 40-50%+ range for heat to electric conversion.

Another 25-50% energy loss in distribution (transmission lines, transformers, local distribution).

For my electric company--very roughly 50% of my "retail cost of electricity" is for "power" from the generator and the other 50% is for the costs of distribution and transmission (distribution in the larger cost factor).

Morpho, what are your power rates? I assume they are still much less that we pay "on the coasts" of the US metro areas.

Mine run from $0.09 to $0.58 per kWhr (I have Time Of Use pricing; depending on time of day, season, and amount of power used--the more I use, the higher the rates--me, I am always at the $0.09 rate effectively because of conservation and Grid Tied solar--during the summer I "sell" power at $0.29 per kWhr in the afternoons and "buy" it back at $0.09--1 year net metering).

If you keep your usage low (~300 kWhrs per month or less), then the power costs are around $0.12 per kWhr (for flat rate pricing). Over 1,000 kWhrs per month, those go upward of $0.40 per kwhr (again for flat rate residential).

In the end, spend your bucks on design and conservation first (second, and third ). Solar hot water / heating can be a better deal than Solar PV too. For cold areas, that gets a bit more complex to prevent freezing.

-Bill