Vanity: I need advice on a backup generator

4/25/11 | me

[spacejunkie01]

I need advice on the best backup generator to buy, particularly non gas run. I like solar but not sure who deals in them besides mysolarbackup.com and they're not cheap.

If I want to run my freezer/fridge for an extended period of time, what would be best?

[Graybeard58]

Run your generator on propane, use synthetic oil and change it once a year; twice a year if that makes you feel better.

Should be addressed to the O.P. I'm not in the market for any of those things.

[upchuck]

LOL!!

[GOPJ]

bump for later

[upchuck]

Gas powered generators are very similar to lawn mover engines

Think what would happen to your lawn mower if you ran it for 12 or 18 hours straight

You oil would be mud in no time at all

I have a Yamaha EF2400iS generator. Great machine. Super quiet. On page 20 of the owner's manual it says to replace the oil initially after 20 hours run time. Then every 100 hours run time.

The generator is three years old. I use it a lot. I change the oil every 50-75 hours run time. I use synthetic oil. No problems so far.

[PA Engineer]

If I want to run my freezer/fridge for an extended period of time, what would be best?

I'm a little late to the discussion and agree that propane is the way to go for fuel. If you are only concerned about keeping your refrigerator going, then let me suggest a different option.

Using a small batter bank of 2-Trojan L16 batteries and a small inverter, you can run your refrigerator (depending on the wattage of say 1.6KW day) with only a couple hours of generator time required per day. You can use the generator to charge the batteries for a couple hours each day rather than letting it run 24 hours. With a 10 circuit generac transfer switch (you can wire yourself) you can do your other chores and laundry during the charge time. This option will allow you to go with a much smaller and cheaper generator without the worry of burning it out.

If you are interested I could explain more and provide links.

[DB]

The air cooled ones suck.

The generator maintenance company (their primary business is cell towers) in my area is pretty happy with mine. But as I said, it uses a common Chrysler V6 engine running at 1800 RPM’s and is water cooled. That makes a lot of the common Generac oddball engine problems go away...

As far as noise, it sounds like a typical car when running.

[DB]

Yamaha and Honda make great small generators.

[DB]

Just as a note...

A/C using 50A @ 240V is 12kW.

Around here we get about 1kW of sun per square meter. At 15% efficiency that’s 150W per square meter. Therefore you would need about 80 square meters of panels to power the A/C. Throw some more losses in there and say 100 square meters. That’s 10 meters by 10 meters or 33 feet by 33 feet of solar panels. That’s a long, long way from “acres of panels to run one” even if you tripled the size of it to run the A/C well into the night...

There are plenty of arguments about the cost effectiveness of it all, but area is not that big of an issue.

[DB]

Earthquakes are our big issue.

Continuous gas delivery is very debatable then.

[chuckles]

Does the Square meter of panels make AC or DC? How many volts? I understand watts, but in the real world he would have to have enough panels to make enough amps to convert to 240v AC to run the air conditioner. Using the term "acres" I admit was a flip remark, but a few square meters wont get it either. You have to charge a large bank of batteries to make the current steady and then convert it to AC with very expensive converters that run hot( eg waste energy). I haven't done the math, but am willing to bet you couldn't get 50 amps of 240 AC from 20 8 x10 panels. Just think of the batteries and the converter. Phone company batteries and a converter the size of a refrigerator might get it done. The idea of an absorption AC was a better plan.

If solar worked even close,it would already be on every house. It is a tax credit that runs some light bulbs is about it. Real horsepower still comes off the pole.

There was a self sufficient house experiment in the North East somewhere that got government grants to completely live off the grid and run everything, not just survival type appliances. He took $500k of our tax money and did it, but he had every square inch of roof covered and then went to the yard with more panels. I don't know if it was more than an acre, but it sure looked close. The upkeep on the batteries and converters was enormous. He did however create enough juice to turn the meter backwards much of the night which made him technically "off the grid". IN the real world, however, there was always the rainy overcast snowy days that made him sweat for a few sunny days. All for the low low price of $500K.

[DB]

The panels produce DC voltage/current. The voltage depends on the panel and how many cells are wired in series. Inverters can be very efficient. Typically around the 96% range. Maintenance on the inverter should be low if designed properly. They have no moving parts other than perhaps a fan and some relays.

http://www.solarelectricalsystems.com/documents/kyocera-kd135gx-lp.pdf

The above panel (a quick Google search) has an area of about 1 meter squared (10.89 square feet) and produces 95W with 800W/m^2 of sunlight. So with 20 8 x 10 panels worth of area (1600 square feet) that would produce just under 14kW with typical direct sun light. To convert that to AC using a 96% efficient inverter the inverter would output about 13.4kW. And yes their are other losses, but you'd have to lose another 10% to get to 12kW AC. You don't need batteries if you don't go off grid.

A typical house can nearly zero out its electricity usage for about $40k of solar equipment. But that's only because of all the subsidies and tax giveaways. Typically those subsidies and tax giveaways amount to about 30% of the cost of the project...

Without those subsidies and tax giveaways the economics of it is very debatable.

[DB]

“And yes their are” should be “And yes there are”...

[WVKayaker]

Your calculations may seem good to you, but do not reflect reality, IMHO. The panels almost NEVER realize their full capacity, and begin degrading as soon as installed. Dust (and anything else) accumulations also take their toll.

...Example: in 2009, Germany’s actual national PV solar CF was 6,578 GWh/(7,890 MW x 8,760 hr/yr) = 0.095 out of a national theoretical maximum of 0.115. The actual CF indicates the PV solar panels are aging, dusty, partially shaded by trees, partially snow-covered, roofs are not be true-south-facing and the panels are not correctly angled; about 80% of the PV solar systems are roof-mounted. Germany could raise its average CF, if it installed more field-mounted suntracking PV systems that would have CFs of about 0.16 - http://bifuel.net/starter-homes-get-solar-panels-as-standard-equipment/

The rated capacity is at noon, in full sunlight, and that MAY only happen once each day... and anything less....is less! I hope your air conditioning doesn't draw many AMPS!

The biggest fraud currently (other than the pResident) is the guy on TV talking about a "solar generator" for times when your power goes out. "Just hook it up in the middle of the storm..."

http://www.mysolarbackup.com/?gclid=COPIxcjtuagCFQXu7QodA3wqCA

[Hillarys Gate Cult]

Some underground gas was interrupted here by Hurricane Hugo. It seems that millions of falling tree branches caused by the storm can puncture underground lines. Such a thing even wiped out my sewer.

[Hillarys Gate Cult]

I’m working on a quantum generator. Or maybe I already did.

[DB]

Dude, it wasn’t intended to be super accurate calculation... Nor did I ever suggest it was a good idea for use as a standby generator... In fact I wasn’t suggesting it was good idea at all economically... The only point was it doesn’t take a huge area to generate a decent amount of power. Far less than the poster I was responding to thought.

In short it was just a basic example.

In my original example I tripled the panel area to add lots of margin for his 12kW A/C example...

And 0.095 is 82.6% of the theoretical 0.115 performance in the German study you site. That actually is pretty good...

And, the solar panel manufacturer link I provide earlier has a 20 year warranty stating the power output won’t degrade below 80% of its original rated value. So the drop off over time isn’t nearly as bad as you make out.

And yes, you have to clean the panels from time to time... Duh...

And staying on the grid makes it much more practical because you don’t need batteries with all the cost and efficiency losses they cause. And during the periods the A/C is cycling off the solar power is feeding the grid reversing the spin on your power meter. So the solar system doesn’t have to provide 12kW continuously during a hot day, it has to average what the A/C uses over the day to balance the energy use as long as you stay on the grid.

And most people don’t use A/C to cool their house with snow outside... Where I live it is only hot when the sun is shining... At night it normally cools off quickly.

So chill out...

[meyer]

Continuous gas delivery is very debatable then.

A lot of the gas pumping stations use electric pumps, so a widespread power outage may affect the availability of natural gas as well. IIRC, during the rolling blackouts in Texas last winter, there were a couple of isolated areas in New Mexico that couldn't get gas for heating their homes due to inadequate pumping capability on some of the gas transmission pipelines.

[MomwithHope]

I could use some advice too. I got the info in the mail from mysolarbackup. My hubby just isn’t there yet. All we really need to survive if it really hits the fan is water - we have a well and pump. We can heat with wood and have an lp tank so we could use our stove, but water is the challenge. Hubby tends to think big as far as how to run the whole house but I just care about the water. Aby advice would be appreciated. Thanks!!

[ClockDoc]

re: Water pumping.
A lot depends on your situation.

A shallow well (<20 foot lift) is quite doable. A 12 VDC RV pump might well do the trick here. Another alternative would be a standard agricultural windmill to keep a storage tank topped off.

Deep wells usually require 240VAC and lots of startup current. You will encounter basically 2 types of pumps in this situation. 1. Jet pump (A return line assists the pump with the lift) 2. Submersible (Pump is in the well and does a direct lift on the pressure side.) These present more of a challenge. One might consider establishing a storage tank, where a generator supported pump fills it occasionally with gravity and/or a 12VDC RV pump to supply the house.

[MomwithHope]

Thanks for the advice. It is a deep well 170 feet I think and our pump is submersible as you described. Would a solar backup generator be enough to power it?? We are really looking at a non-gas solution and we don’t have room for a storage tank anywhere, house is on a hilltop with very little room around it.
Thanks!!