Small is beautiful !

Re: Small is beautiful !

Welcome to the Forum THC!

Sounds like a neat place.

THCanada wrote: »

My only concern is the well pump (150 ft deep)...investigating on a manual pump...

There are some nice water pumps out here that can work with solar panels, battery bank, and/or AC genset/utility power--All with the same pump in the case of the Grundfos SQ Flex series--Although they are not cheap (probably around $2,000 or more these days).

You can go another way--A big old AC genset and standard well pump into a cistern--Then use a small AC or DC pump from your battery bank to pressurize the home (and run a Ozone Generator to keep the tank bug free).

There are also VFD (variable frequency drives) which can be a nice cross between a $2,000 in-well German engineered pump and a standard AC pump that is "nicer" to an off grid power system.

This thread has lots of information and random links to information on Solar RE, conservation, and other home related energy projects.

a small windmill 600W (12V AC)...(we live on top of a hill which have 4.1 m/s average wind annually)
four 110W solar panels (12V DC)
one Solarwind Hybrid 40A Charge Controller (12V AC / DC)

I don't know anything about the SolarWind controller--Go ahead and try it to see how well it works for you--But watch your battery bank voltage/state of charge to see if it is keeping your bank charged or not. I am a bit leery of it. I think it will prove to be too small for your needs (only 150 watt rated for 12 volt solar array???) and will not properly/fully recharge the battery bank (if 14.5 volts is maximum charging voltage, that is usually too low for flooded cell battery banks).

Wires to go from panels and turbine to inside Charge Controler .....What size ?..is 8 AWG OK for a 40 ft run without too much lost.

Using a basic voltage drop calculator and 1% to 3% maximum voltage drop, 14.5 volts and 50 amp current down two wires (three phase wiring can be a size smaller wire gauge):

• 40', 50 amps, 8 awg => 3 volt drop

For a wind turbine, you can probably stand a higher voltage drop is a ~23% drop--One of the big problems with 12 volt systems--You need very expensive copper wire to send power any distance with "reasonable" voltage drop.

Also--you have a 40' run from the turbine to the home/battery bank--But you also should have a minimum of 60' tall tower (30' above obstructions, ~300-500 feet or more from those obstructions) for turbulence free air to run your turbine (which also adds to the wire length).

Note that I am not a big fan of small wind--So take my opinion with a grain of salt.

The 4.1 M/S (~9.2 MPH) is just at the floor of "enough wind" to get useful power from a typical wind turbine (usually need around 10-12 MPH minimum). And, many times, those measurements from wind maps are at 120 Feet or higher elevation--A 20-30 foot tower is not going to see those numbers (on average).

Also, it is difficult to find a reliable "small wind" turbine (make sure it is installed a fair distance from the home/where kids play--There are enough examples of shedding blades and falling turbines that I would not want one next to the home--let alone the issues with noise in heavy winds).

Anyway, if you need wind and it makes sense for your home--We can talk more about that later.

maybe one rectifier 1000V/50A (to save one wire trip from turbine to controller which accept both AC and DC )

In your case, I would stay with the three cables for the longer wire run--Will help reduce voltage drop a bit.

two (225Ah) or four (450Ah) TrojanT-105 batteries ( is car booster cables cut to size ok for inter-connecting batteries ? )

Car booster cables are questionable--Many in our area are just 8 awg cables. With a 300 watt 12 volt inverter, you need around 6 awg minimum. You have to go through the voltage drop calculator to find the right minimum AWG for your needs (wire length is important, as well as charging/discharging/surge current--you only have a about 0.5 to 1.0 volt maximum voltage drop from inverter to battery bank--And you want around 0.05 to 0.10 volt drop from charge controllers to battery bank).

A lot of people use welding cable for battery connections--But the very find wire of welding cables makes it difficult to properly/securelly/safely terminate the cable ends. You might check with a battery distributor if they can make up cables for your needs. See this site for paralleling battery strings.

I like to size the battery bank to the loads--Too large of battery bank is almost as much pain as too small of battery bank. A Kill-a-Watt type power meter can help you here a bunch.

For example, sizing a solar array for the battery bank using the rule of thumb of 5% to 13% rate of charge for a 450 AH @ 12 volt battery bank:

• 450 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 424 Watt array minimum
• 450 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 847 Watt array nominal
• 450 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,102 Watt array "cost effective" maximum

Note--the larger the battery bank, the larger the suggested solar array would be. In your case, since you are using this for backup power, you can probably get away with the 5% rate of charge as you have utility power to normally keep the batteries charged.

However, you need to also size the array for the amount of sun you get in your region... Using PV Watts for Ottawa, fixed array tilted to latitude 45 degrees) (you can pick a site closer to your home):

Month      Solar Radiation (kWh/m2/day)
1      2.86     
2      4.70     
3      5.27     
4      5.01     
5      5.21     
6      5.47     
7      5.53     
8      4.99     
9      4.56     
10      3.54     
11      2.27     
12      2.60     
Year      4.33

Tossing out the bottom three months, we get a minimum of 3.54 hours of sun for October--For an 847 watt "nominal" array:

• 847 watt array * 0.52 end to end system eff * 3.54 hours of sun = 1,559 Watt*Hours per day...

A 300 Watt AC load would last about:

• 1,559 Watt*Hours per day * 0.85 inverter eff * 1/300 watts = 4.4 hours of "solar power" per average October day

On a 450 AH battery bank, assuming 2 days of "no sun" and 50% maximum discharge for longer battery life (basically 1/4 of battery discharge per day):

• 450 AH * 12 volt battery bank * 1/4 level of discharge * 0.85 inverter eff * 1/300 watts = 3.8 hours per day of "battery power"

As you can see--when we add all of of the basic rules of thumb, it takes a fairly large system to power even a "nominal" of 300 watts * 6 hours per day. Accurate measurements and "extreme" conservation will be your friend.

A good inverter ( not decided yet ).

Hands down, a MorningStar TSW 12 volt 300 watt (600 watts for 10 minutes) AC inverter is ideal for your needs as stated.

....maybe more solar panels ?

It depends--For emergency/backup power for a few days at a time--An small/efficient genset may be a better (more cost effective) option. A Honda eu2000i (1,600 watt) with an 120 VAC 40 amp or so battery charger (pull start) to a Honda EM4000SX (electric start/auto start compatible) or similar would be a good match for your home/loads (gasoline may be your best option for cold weather operation).

If you decide to run other appliances (fridge/well pump/etc.) from your battery system--Then we are talking about a much larger system (24 or 48 volt battery bank, a much more expensive inverter, etc.).

-Bill