I'm an Electricity Retard, please help

[greenrootsmama]

I must have missed class the day they went over energy conversions and what it all means because electricity just baffles me. The extent of my knowledge in that department is that a 100 watt light bulb uses more power than a 25 watt bulb. I have no idea what this means in terms of cost or energy used. I've looked it up but I just get more confused. I like to consider myself to be pretty intelligent but this is where I make up for it. LOL.

So, I'm trying to figure out what I would need in terms of a solar set up if I want to run a full size refrigerator, a couple of fans, 1/2 a dozen or so lights, a couple of laptop computers and have a little left over to charge some small batteries for flashlights, power tools and such.

Does anyone know how I might find out what I need based on my energy demands? I would need it spelled out s-l-o-w-l-y in 3rd grader terms that my electricity-challenged mind could understand.

 

[inchworm]

Actually, I think you need to add up how many amps you need, but I really have no idea

 

[justusnak]

Amps?? whatts??? Voltage??? SHOCKING!!! I dont get it either. Sorry, wish I could help ya there.

 

[patandchickens]

First comment, you may need to consider a new fridge if you want it run off solar... most people who are living off of solar are VERY careful about using minimal and smaller appliances and the absolute most efficient ones available, otherwise the system gets ridiculously expensive, and the fridge is a *big* load. (Obviously it can be done but most people would incorporate careful fridge choice into the design.)

Second comment, is this grid-connected solar or independant solar that will have a bank of batteries. It makes a big difference I think, because if the latter you have to plan enough extra capacity to charge extra battery storage against periods of cloudy weather.

Here is a page on calculating load requirements, scroll down the page to "1. Load Calculation Work Form":
http://www.solar4power.com/solar-power-sizing.html#loads

Here is another, possibly a bit too simplistic, page on the same sort of calculations:
http://diy-renewable-energy.com/articles/calculating-basic-solar-panel-watt-requirements-and-costs/

and from http://www.offgrid-desert-living.com/offgrid-solar-battery-storage.html :

Amp hours are calculated multiplying the current drawn by the load by the length of time it will operate. Watts-to-amps To calculate amps when the power consumption is expressed in watts, use the following equation: A = W/V (where W = watts and V = volts DC) For example: A 100 watt light bulb will draw approximately 8.33 amps DC (8.33 Adc = 100 watts/12 Vdc) If the light runs for three hours it will consume (8.33 Adc x 3) or 25 Ah of power. For these calculations, do not use the AC amp rating of a device. AC amps are measured on a different scale and will not give correct results. Time and power The length of time a load is operated will affect the power draw. In some cases, an appliance which draws a large wattage may not consume as many amp hours as a load drawing fewer watts but running for a longer period of time.

For Example: A circular saw draws 1500 watts or 125 amps DC. It takes 5 seconds to complete a cross cut. Twelve such cuts would take a minute and you would consume 125 Adc x 0.016* hour = 2 Ah (*1/60 = 0.016) Observation The circular saw, while it draws more power, consumed fewer amp hours of electricity because it ran for a short period of time.

Good luck, have fun,

Pat

 

[greenrootsmama]

Wow, Pat, I think that's the simplest explanation I've heard/read yet. LOL. That makes a lot of sense. I am considering a new fridge purchase but I had no idea what I need to look for. All of the websites that have the stats on refrigerators express energy consumption in kwh per year. I have no idea how that equates to the wattage I will require from a solar panel. If I buy a fridge that uses 510 kwh per year then how big does my solar panel need to be? How to I convert that to watts per hour?

 

[patandchickens]

All of the websites that have the stats on refrigerators express energy consumption in kwh per year. I have no idea how that equates to the wattage I will require from a solar panel. If I buy a fridge that uses 510 kwh per year then how big does my solar panel need to be? How to I convert that to watts per hour?

According to the first link that I posted,

For total home systems that have a grid-connected electrical history you can simply use the kWh per month from your bill and convert this into a weekly figure, where the monthly kWh (X) divided by 4.3 times 1000 equals your average weekly watt-hours per week.

Does that help any? (kWh/month should be approx kWh/yr divided by 12). I think once you calculate that you can proceed thru the worksheet in that link, to estimate total amp hours per day you will need.

I am SO not up on the whole electricity thing myself, so I am not sure how directly this will tell you what you want, but I think it is a necessary step.

Probably once you have established whether a system is ballpark-plausible the best thing to do would be to contact a few companies and say 'hey, this is what I want to do, can you give me an estimate'

Good luck, have fun,

Pat

 

[sylvie]

A friend has a frig that looks like a chest freezer and the lid opens up, leaving the cold inside instead of pouring out like an upright frig.
He runs his entire small home's electrical needs on 2 solar panels and a bank of batteries and inverter. That includes a computer, lights, radio, tv and the frig.

 

[greenrootsmama]

A friend has a frig that looks like a chest freezer and the lid opens up, leaving the cold inside instead of pouring out like an upright frig.
He runs his entire small home's electrical needs on 2 solar panels and a bank of batteries and inverter. That includes a computer, lights, radio, tv and the frig.

Do you know how many watts the solar panels are? That's a great idea about the fridge. Makes a lot of sense, I'm definitely going to look into it. Thanks.

 

[philpatton]

greenrootsmama patandchickens did a very good job of explaining how everything is measured.

You will find the requirements for each appliance somewhere on the appliance or in its owners manual, you know the book that is supplied with every appliance, computer, TV etc that everyone never reads.

Write down what each appliance claims to require and add the numbers to find the total energy usage for you home. In the case of light bulbs this will vary from manufacturer to manufacturer but you should be able to find the information either on the box that they came in or on the companies website.

Then start checking to see how many solar panels that you would need. You can do the research on line or by talking to the local solar panel companies. That will also allow you to determine how many batteries that you need.

Remember you have to take precautions when storing batteries. You need to store them in such a way that they are vented outside the house, that is if you are planning on storing them inside your house. Hydrogen gas can really be nasty.

Theres an old technology that you might look into. Its called icy ball refrigeration. Here are a couple of links that will explain the concept. By the way it doesnt require the use of any electric. http://en.wikipedia.org/wiki/Icy_Ball
http://crosleyautoclub.com/IcyBall/HomeBuilt/HomeBuilt.html