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JohnSurrey: Estimated Power Needs


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JohnSurrey

 

 

You haven't read enough of the solar / alternative energy threads on this site.

 

I haven't read any of them either and, looking at the above, I doubt very much I'd understand them if I did... Out of interest how much would I be looking at to install solar here - we have a small house with plenty of sun - 1 led TV, 1 average size fridge, 1 small window air con, rice cooker, kettle, lights inside and outside... I saw a big box and a panel in the local mall here with Aegis on it - 35,000 peso but I have no idea what it would support - our electric bill is 3,000 to 4,000 peso /month?

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Actual costs, I cannot tell you. Too many variables here. But, I can tell you how to get the figure you need in order to determine the size of your array, which would tell you what size your battery b

Plus take into account how 'dirty' your power is. If you're losing televisions and appliances due to power surges, brownouts, etc..., it might be best to just remain totally off-grid (my plan). I'm to

I don't know squat about technicalities or the math behind things but ... I spent a few years living on a boat using mainly solar power while at anchor in North Queensland and Darwin so the climate is

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Paul

I haven't read any of them either and, looking at the above, I doubt very much I'd understand them if I did... Out of interest how much would I be looking at to install solar here - we have a small house with plenty of sun - 1 led TV, 1 average size fridge, 1 small window air con, rice cooker, kettle, lights inside and outside... I saw a big box and a panel in the local mall here with Aegis on it - 35,000 peso but I have no idea what it would support - our electric bill is 3,000 to 4,000 peso /month?

 

Actual costs, I cannot tell you. Too many variables here. But, I can tell you how to get the figure you need in order to determine the size of your array, which would tell you what size your battery bank would need to be, and the size and type of the best controller suited for you.

 

Firstly, the best way to determine loads is not by reading the specs label on appliances, but to check the actual usage of necessary appliances with a power meter.

 

If you do an internet search, you will end up with a useful meter that looks something like this: 

 

main_p4400.jpg

 

Plug each appliance into the meter, and the meter into a power point in your home. Over any time period, you can calculate usage of said appliance. Typically, this would be anywhere from 24 to 48 hours. Many of these power meters will show low and high power usage, current voltage, estimated cost of running the appliance, cycles (frequency of the power coming into your home), etc. 

 

Secondly, I will give you some examples, based on appliances you listed above, to estimate your particular power usage. Let's assume the following are the actual ratings for each appliance listed.

 

1 - LED television. 50 watts

1 - Refrigerator* - 120 watts

1 - 1/2 hp air con* - 370 watts

1 - Rice cooker - 400 watts

1 - Water kettle - 1,800 watts

? - Lights - ??

 

So, if the above figures are what each appliance, on average, would use - then multiply the wattage rating by each appliance's usage, in hours, to get total watt hours used over the course of a day. 

 

So, the formula is: (watts used) X (hours powered) = (watt hours consumed per day)

 

Now, let's assume you use each appliance for the time lengths listed, below. I will list total watt hours of each appliance, consumed.

 

1 - LED television - powered 5 hours per day - 250 watt hours

1 - Refrigerator* - powered 14 hours per day - 1,680 watt hours

1 - 1/2 hp air con* - powered 02 hours per day - 740 watt hours

1 - Rice cookerǂ - powered 15 minutes per day - 100 watt hours

1 - Water kettleǂ - powered 15 minutes per day - 450 watt hours

 

Add the total watt hours each appliance has consumed to get the total watt hours your home consumes in a 24 hours period.

 

The total watt hours consumed for this day, is 3,020. Or, it could be called 3.02 kWh.

 

 

* If these appliances have inverter compressor technology, they will run significantly more efficient than typical appliances using the old style compressors. Refrigerators using the older style compressors, average about 14 hours per day, cooling.

 

ǂ Take a few moments to look at the labels on each of these appliances. You will be surprised as to how many watts they are actually rated for, regarding power consumption.

 

Anyway, once you have the total watt hours, you can then start calculating for your specific system needs.

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easydrifter

I have about P50,000. Wrapped up in a starter kit with only 2 panels and 2 batteries (and other associated components).

This allows me to run fans and lights during brownouts. I figure if I spend another P50,000. I can get a few more 140 watt panels, a couple more 150ah batteries, and a nice inverter, then I could power my refrigerator (my personal goal), then I'll be up to P100,000. As far as running an AC; fugettaboutit. I would not buy one of those box style solar power generators, not much power for the money there. Better to piece your own system together. Disclaimer: "I don't know jack shit about electricity but I'm just doing it" We're lucky to have Paul and some others here who can answer some of the more technical issues.

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AussieLex

I don't know squat about technicalities or the math behind things but ... I spent a few years living on a boat using mainly solar power while at anchor in North Queensland and Darwin so the climate is kinda similar to here.

 

Bear in mind my system was 12 volt but I kinda think something similar is doable here in a house just not sure what it would take to power household fridge fridge... I had 4 x 100 watt solar panels, 450 amp hour deep cycle batteries, (3 x 150 amp hour), a 40 amp charge controller, a  2000 watt 12 volt to 240 volt inverter and a honda 1000 watt generator.

 

I was powering: a 240 volt TV, 2 laptop computers, 3 or 4 lights, a 12 volt macerating toilet, an 80 litre engel 12 volt fridge, 12 volt water supply and sump pumps and a 240 volt fan, ... I sold the boat in 2014 and cant remember for sure what the total draw of power was but I remember at peak performance the 400 watts of panels produced 25 to 28 amps ... but that was only for an hour or two a day ... mostly they produced 15 to 20 amps ... with a daily average of about 140 to 150 amp hours ... my usage was not quite balanced  and I ran my generator for battery charging maybe once a week.. one tank full of gas, 1.2 litres for about 7.5 hours running and battery charging ... I also had a seatec 25 amp smart battery charger ... I feel that 600 watts of solar panels would have had my usage balanced pretty well and i would have liked to add an extra 150 amp hour battery, mind you then I would also need to upgrade the charge controller ..

 

I think this kind of system would work ok in a house but if I was going to do it i would want 1000 watts of solar panels, 900 amp hours in batteries.... (6 x 150 amp) a 4 - 5000 watt inverter and a 100 amp charge controller and still the backup generator and battery charger ... I have no idea about local costs for components but am going to begin checking things out for when I get my own place ...

 

Remember i don't know much about electrical things ...only know what worked for me in the past ... 

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Paul

I sold the boat in 2014 and cant remember for sure what the total draw of power was but I remember at peak performance the 400 watts of panels produced 25 to 28 amps

 

I think I have addressed this in the past. 

 

It is mathematically and electrically impossible for 4 - 100 watts solar panels to produce 25 to 28 amperes, even in 100% full sun, with the panels perpendicular to the sun, on a cloudless day.

 

The absolute maximum amperes they can generate, is called their Isc, or short circuit current. This is when both ends - positive and negative - of the panel are connected together to create a closed loop, charging no connected load. The Isc, as well as other characteristics of the panel, are printed on the label on the back of any given (100 watts) solar panel.

 

As you can see by the specifications for my Just Solar panels (image attached below), that magic number is 5.69 amperes. Times four, that would be 22.76 amperes. Under an actual load, and directly connected through a charge controller, that would be less.

 

The maximum power current, or Imp, is 5.54 amperes. This would be 22.16 amperes, for four panels. But, considering panels are no where near 100% efficient, that number would be even less than 5.54 amperes, realistically. This is why I use 77% in calculations, to be more realistic about actual output of a panel.

 

IMG_0204r.jpg

The only thing I can figure is, your controller, or other meter that was showing charging amperes, was not calibrated very well?

 

 

We're lucky to have Paul and some others here who can answer some of the more technical issues.

 

I do not claim to be any sort of electrical guru here. I am only going by what I have learned, from others who have been in alternative energy for many years, and from what I have experienced, personally, over the past few years. 

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AussieLex

Paul I was talking about a 12 volt system and 400 watts mathematically could produce 33  amps ... watts divided by volts equals amps ..that much I did learn from my 12 volt bible ... There was nothing wrong with my digital charge controller and I regularly saw 25+ amps ... during the "heat of the day"   now right or wrong thats what I have experienced ...

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Paul

 

 

Better to piece your own system together.

 

I agree, 100%. In today's market, panels are so cheap (by comparison over previous years) now, that there is no reason to not "over panel" your system, especially if running an MPPT controller. Batteries, however, are still hanging up there in price, not allowing off-grid systems to be cost effective. 


 

 

Paul I was talking about a 12 volt system and 400 watts mathematically could produce 33  amps

 

While that is certainly true, Lex, if your system only produced 12vdc, you would never charge a single battery. That's why 12vdc panels actually produce a voltage of around 22vdc unloaded, and around 17-18vdc loaded.


And, the hotter it is, believe it or not, the less your panels will generate.

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AussieLex

 

 

That's why 12vdc panels actually produce a voltage of around 22vdc unloaded, and around 17-18vdc loaded.

 

You are correct  ... my 12vdc solar panels had a terminal voltage of 17vdc, the charge controller/regulator took care of the charging of the batteries ... I lived entirely on solar and generator power for about 4 years and what I said comes from personal experience... My only reference is a book called the 12 volt bible for boats. 

 

My wife and I will be looking to buy a little place of our own in the southern provinces in Cebu or Negros hopefully next year and i intend to set up a solar back up power system something like what I said 

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musingloudly

Just to add information here that I hope would be useful...

 

When using an inverter to drive anything with a motor the computation should be different. THis is because of the initial spike or draw that's required to turn the motor on... I discovered this the hard way when I was trying to figure out why my 300 watt inverter could not support my 90watt ref... It turns out that upon initial turn on, the power draw can multiply significantly.... So now, my 300 watt inverter is used for my fans, tv and cable box (all running at the same time) with no issues as long as the sun is shining... Given the limits of my system, I never use it for anything with a motor...  I hope that helps...

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Mikala

 

 

When using an inverter to drive anything with a motor the computation should be different. THis is because of the initial spike or draw that's required to turn the motor on...

 

You could always install a soft-start for the refrigerator. There's a circuit diagram available on www.homemade-circuits.com for just that purpose... :)

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Paul

 

 

I discovered this the hard way when I was trying to figure out why my 300 watt inverter could not support my 90watt ref.

 

You could always install a soft-start for the refrigerator. There's a circuit diagram available on www.homemade-circuits.com for just that purpose... :)

 

I imagine refrigerator inverter compressors would probably start if connected to a 300 watts inverter? But, this is only a guess on my part.

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Mikala

I imagine refrigerator inverter compressors would probably start if connected to a 300 watts inverter? But, this is only a guess on my part.

 

Inverter driven motors generally have lower starting currents than regular induction motors. How much lower is based on each manufacturer, so it would behoove the end-user to read the startup currents carefully to ensure they meet their limitations (needs).

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Nice info. I have a question - is it better to have a grid-tie or off-grid system?

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Paul

Nice info. I have a question - is it better to have a grid-tie or off-grid system?

 

By far, the best choice would be a grid-tied system, especially if living in a country where tax credits and discounts are granted to home owners. This would be for a grid-tied system only. This means that, during the day, you would use the power generated by your solar array. If not used, it would go back into the grid, where you would be given credit for the power your array generated. The draw back is, when the grid goes down, so does YOUR power. But, you don't have the cost of the batteries. Most people, especially those living in cities in the US, go with this choice. It provides them with substantial savings on their electric bills. 

 

For those living in areas where there is no grid, or where it would not be financially feasible to have power connected to their homes, would have to go with off-grid solar systems, to provide most, if not all of their power needs. Alternatives are wind or hydro, and back up generators.

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Mikala

 

 

For those living in areas where there is no grid, or where it would not be financially feasible to have power connected to their homes, would have to go with off-grid solar systems, to provide most, if not all of their power needs. Alternatives are wind or hydro, and back up generators.

 

Plus take into account how 'dirty' your power is. If you're losing televisions and appliances due to power surges, brownouts, etc..., it might be best to just remain totally off-grid (my plan). I'm totally off-grid at my ranch in Hawaii, but not because of the power. It's because the cost to bring electricity to my place was last estimated around $120,000. I love having lights and power to everything though when I see the town of Hilo go dark from a storm or electrical disturbance! :)

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