Oil Lamp compared to batteries

[lkruper]

I am in the process of trying to figure out my minimum power requirements for my cabin if the grid fails during an emergency. I have been reading posts about people reducing their needs by using led lighting, etc. However a quick calculation of the power needed to keep a 60w light bulb on for 8 hours per night was "illuminating." Please check my numbers as I am not yet a solar fanatic! I am only factoring in the cost of the batteries, not everything else.

• 60 watt light for 8 hours/day
• 60 * 8 = 480 w
• 480 * 5 (5 day autonomy) = 2400
• Inverter inefficiency @ 90% = 2640
• 2640 / 12 = 220 ah battery needed

====================================

2 T105 = $280 (I have not looked for best prices yet)

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Lifetime of battery based on warranty. Could be more or less.
2 years = $140/year = 0.38 / day

==================================

Cost of operating oil lamp.

1/2 oz per hour

Walmart cost of oil = 64 oz for $5.97 = 0.09 / oz * 4 = 0.36 / day

====================================

So I come up with a little bit less cost with an oil lamp. One could burn cooking oil for free.
Also, a case of this oil would add up to quite a bit of autonomy. For my purposes, only
using off-grid for emergencies this makes sense as I already have 8-10 oil lamps in my cabin
and a bottle of oil. I don't think it would be much fun to live like this every day.


Without 5 day autonomy, the batteries come out way on top. How many ppl really subscribe
to 5 day autonomy in practice?


### edit ###############################################
After looking at another recent post it occurred to me that a 60w equivalent led takes
much less than 60w as a 50w equivalent was taking 8 w.
################################################## ####
Can lower the price of lamp burning by using kerosene... $4.00 / gal at the pump if you
can find it.
################################################## #####

[Sunking]

So why would you use 60 watt incandescent lighting on a battery lighting system? Incandescent has its place, but not for what you want.

You want T5, CFL, or LED. Yes it is a bit expensive, but a lot less expensive than the panels and batteries required to run equivalent incandescent lighting.

Second point why 12 volts?

[lkruper]

So why would you use 60 watt incandescent lighting on a battery lighting system? Incandescent has its place, but not for what you want.

You want T5, CFL, or LED. Yes it is a bit expensive, but a lot less expensive than the panels and batteries required to run equivalent incandescent lighting.

I was adding my note while you were replying. I had just read the other thread. And they last 25000 hours which is negligible for $28.

[Sunking]

Why are you hung up on 12 volts?

[lkruper]

Why are you hung up on 12 volts?

I know the advantages of 24v and would certainly employ it. However in my mind the 12v calculations are easier because I am more used to it, and I use that for mock-ups. In the example I just used, I suppose I could have used two 100ah 12v batteries to get 24v but I also always use the T 105s because I know their specs better.

[Mike90250]

I love these LED's for 2.2w

https://www.wiredco.com/10_LED_SMT_SMD_Warm_White_G4_Disc_LED_Module_12VAC_p/10ledwarmwhiteled.htm

10 - 30v w/ onboard driver 160 lumens

[lkruper]

So why would you use 60 watt incandescent lighting on a battery lighting system? Incandescent has its place, but not for what you want.

You want T5, CFL, or LED. Yes it is a bit expensive, but a lot less expensive than the panels and batteries required to run equivalent incandescent lighting.

Second point why 12 volts?

I keep forgetting to factor in that this is an emergency system for me. I have had the cabin for 5 years and have never needed to use emergency supplies. If I use them 2 weeks in one year, that would be extraordinary. And yet it is like insurance and potentially life saving. I wish charged batteries could be stored up like lamp oil.

It might be more cost effective for me to purchase a propane generator and store two weeks of propane indefinitely.

[Living Large]

I keep forgetting to factor in that this is an emergency system for me. I have had the cabin for 5 years and have never needed to use emergency supplies. If I use them 2 weeks in one year, that would be extraordinary. And yet it is like insurance and potentially life saving. I wish charged batteries could be stored up like lamp oil.

It might be more cost effective for me to purchase a propane generator and store two weeks of propane indefinitely.

Now you're talking - propane may be the way to go. I am wondering if Dereck's question takes into account that you appear to be powering a single light bulb, unless I missed something. For a low power system, is it worth going above 12V?

[lkruper]

Now you're talking - propane may be the way to go. I am wondering if Dereck's question takes into account that you appear to be powering a single light bulb, unless I missed something. For a low power system, is it worth going above 12V?

Well he also knows my history. I already have posted a list of things I want to power such as my DSL modem, Satellite TV, low wattage fridge, etc....

My example was to see if it was cost effective to power lights from fuel instead of expensive electricity.... I cannot power a modem with oil, but lights are doable.

Also, the power at my cabin is quite good and stable. I am trying to prepare for the possibility that next year is high precipitation and I could be stranded there due to flash floods on the road out with power outages.

That is why my first priority is to find a way to easily hook up my existing portable 1600w inverter generator without putting a cord through the window or open door.

[Sunking]

Well he also knows my history.
That is why my first priority is to find a way to easily hook up my existing portable 1600w inverter generator without putting a cord through the window or open door.

Well don't count on me remembering everything. I need reminded what the objectives are. I get folks mixed up sometimes.

Don't get confused with 12,24, or 48 volt systems. That is why you want to work with Watt Hours. Battery voltage and capacity is just a result of watt hours required. Based on that you then select the best voltage. 12 volt systems is for pretty dang small stuff.

Question to you is does all your stuff run off 12 volts? If so then 12 volts is a good option if the daily demand can be met. Otherwise do not get married to 12 volts. But do not and I repeat DO NOT get trapped into 12 volt batteries. Even if your system is 12 volts, 12 volt batteries are not likely a solution. You woul dbe looking at 6 or 4 volt batteries.

My take is:

If Inverter requirement have exceeded 500-600 watts continuous rating, you have exceeded 12 volts.
If panel wattage exceeds 500 watts, you have exceeded 12 volts.
If your daily Watt Hour consumption has exceeded 1 Kwh, you have exceeded 12 volts

Going above those limits and cost skyrockets, and safety becomes compromised. There is no reason to do that. RV's are an exception.

[Living Large]

Well he also knows my history. I already have posted a list of things I want to power such as my DSL modem, Satellite TV, low wattage fridge, etc....

My example was to see if it was cost effective to power lights from fuel instead of expensive electricity.... I cannot power a modem with oil, but lights are doable.

Also, the power at my cabin is quite good and stable. I am trying to prepare for the possibility that next year is high precipitation and I could be stranded there due to flash floods on the road out with power outages.

That is why my first priority is to find a way to easily hook up my existing portable 1600w inverter generator without putting a cord through the window or open door.

I know you posted elsewhere, but you went through all the calculations including days of autonomy above for a single light bulb, including buying batteries - so it was a bit confusing.

[lkruper]

Well don't count on me remembering everything. I need reminded what the objectives are. I get folks mixed up sometimes.

Don't get confused with 12,24, or 48 volt systems. That is why you want to work with Watt Hours. Battery voltage and capacity is just a result of watt hours required. Based on that you then select the best voltage. 12 volt systems is for pretty dang small stuff.

Question to you is does all your stuff run off 12 volts? If so then 12 volts is a good option if the daily demand can be met. Otherwise do not get married to 12 volts. But do not and I repeat DO NOT get trapped into 12 volt batteries. Even if your system is 12 volts, 12 volt batteries are not likely a solution. You woul dbe looking at 6 or 4 volt batteries.

My take is:

If Inverter requirement have exceeded 500-600 watts continuous rating, you have exceeded 12 volts.
If panel wattage exceeds 500 watts, you have exceeded 12 volts.
If your daily Watt Hour consumption has exceeded 1 Kwh, you have exceeded 12 volts

Going above those limits and cost skyrockets, and safety becomes compromised. There is no reason to do that. RV's are an exception.

Thanks, I will keep that in mind. My current analysis of what would run off of solar is:

109 AH per day @12v
1 300w panel
1 300w inverter
All devices on at the same time = 150w

Does the 109AH per day X 12v = 1308wh per day mean I have exceeded your 1Kwh daily limit?

[lkruper]

I know you posted elsewhere, but you went through all the calculations including days of autonomy above for a single light bulb, including buying batteries - so it was a bit confusing.

Sorry for the confusion and in the context that it was presented, your question was valid. In fact the requirements for my total emergency system as currently planned is pretty tiny.

[Sunking]

109 AH per day @12v
1 300w panel
1 300w inverter
All devices on at the same time = 150w

Does the 109AH per day X 12v = 1308wh per day mean I have exceeded your 1Kwh daily limit?

For Emergency, no it works out. But I do see something that catches my eye with a 300 watt panel being able to generate 1.3 Kwh of usable energy per day. If you are talking about Emergency power for just a day or two that is fine. But if you are talking extended outages not likely to work.

1.3 Kwh/day using MPPT requires 6.5 Sun Hours in a day. No place in the USA gets that much a day except for a few places in Summer months. In Winter depending on where you live Sun Hours can drop to less than 2 or 3 sun hours. That being the case a 300 watt panel can only generate 400 to 600 watt hours.

As for battery capacity again it depends on how many actual days of autonomy you want. For just emergency 2 days will require a minimum 270 AH. 1 day is 200 AH.

[lkruper]

For Emergency, no it works out. But I do see something that catches my eye with a 300 watt panel being able to generate 1.3 Kwh of usable energy per day. If you are talking about Emergency power for just a day or two that is fine. But if you are talking extended outages not likely to work.

1.3 Kwh/day using MPPT requires 6.5 Sun Hours in a day. No place in the USA gets that much a day except for a few places in Summer months. In Winter depending on where you live Sun Hours can drop to less than 2 or 3 sun hours. That being the case a 300 watt panel can only generate 400 to 600 watt hours.

As for battery capacity again it depends on how many actual days of autonomy you want. For just emergency 2 days will require a minimum 270 AH. 1 day is 200 AH.

Thanks for the analysis. I also already own a gas 1600w inverter generator that will be deployed first and have one APC ups set up on my DSL modem. The solar is needed if an emergency would exceed my gasoline reserves and the generator can supplement solar for charging.

I agree that my solar capacity is shaky with just one 300w panel, particularly since I get good South-West exposure from late morning but may lose a bit in the early morning due to trees... need to measure that better. And winter is a known risk. I could add another panel if necessary.

One thing I really don't understand. Why would a 300w inverter not be sufficient when my peak load can never get above 150w?

I was considering the Morningstar 300 SureSine because if it is in the cabin it does not have a fan and would not be distracting. (http://www.amazon.com/Morningstar-SI...gstar+inverter)