Your Questions About Solar Power

Thomas asks…

What is the maximum amount of energy that can be collected from solar power?

I was wondering what the upper limits of solar power is (If we had 100% efficient solar panels, how much power would they generate in full sunlight). I know that it's impossible to achieve 100% efficiency but as I said before I'm interested in how much energy is theoretically available from solar power.

ssadmin answers:

The Earth receives 174 petawatts (PW) of incoming solar radiation (insolation) at the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses. The spectrum of solar light at the Earth's surface is mostly spread across the visible and near-infrared ranges with a small part in the near-ultraviolet.

Average over the entire earth = 164 Watts per square meter over a 24 hour day

8 hour summer day, 40 degree latitude 600 Watts per sq. Meter for those 8 hours

2000 Watts per sq. Meter in the tropics with the sun directly overhead.

Daniel asks…

How can I use Solar Power in my home?

I am wanting to power just a couple household items with a small solar panel. What will I need? I know I need a solar panel, and some kind of AC-DC converter, and a battery perhaps? How would I wire it up?

I do NOT want to spend a fortune doing this, I am only in an apartment, so it needs to be small and self-contained.


ssadmin answers:

Good luck without spending a fortune. 100 watt panel is over 400 bucks. Inverter for a junk one is 50 (200 if its good) another 20-40 for a regulator, another 100-200 for some batterers.

You're looking at around 800 bucks for something that might power your tv for few hours each day.

At this points after you have all that all you do is wire it up.It's very easy.
Two wires comes from the panel into the regulator.
Two wires goes from the regulator to the battery.
Two wires from from the battery to the inverter.
Inverter powers what ever you want. Most time they come with normal ac plugs.

Nancy asks…

What is capacity hour rate for solar power batteries?

I'm looking a battery for use with solar power and it has the following specs.

Volts 12
Capacity @ 20-hr rate 120
Capacity @ 100-hr rate 145

How does this translate into running a 1000 watt appliance and how long you can run it with this battery.

ssadmin answers:

Watts = Volts * Amps.
So a 12 volt battery supplying 10 Amps is producing 120 Watts of power.
Batteries are rated in Amp-Hours. For example one battery might be rated at 100 Amp-Hours. That would mean it could supply 1 Amp for 100 hours or 2 Amps for 50 hours. But it could probably not supply 100 Amps for 1 hour. Batteries work better at low rates of use. Your examples are 20 hour rate gives 120 Amp-Hours, meaning it can supply 6 Amps for 20 hours (6 Amps times 20 hours = 120 Amp-Hours), but if you drain it more slowly, taking 100 hours instead of 20, it will give you 145 Amp-Hours, which would be 1.45 Amps for 100 hours.

To get Watt-Hours, multiply by the number of volts. Most such batteries are 12 volt (but not all are so check). So a 12 volt battery that has a 120 Amp Hour capacity has a 12 * 120 = 1,440 Watt-Hour capacity. Since one kilowatt (kW) is 1,000 Watts, that would be a 1.44 kilowatt-Hour (kWh) battery. You electric bill is usually in units of kWh. Check your electric bill to see how many kWh a month you use, then divide by 30 to get the number per day. That will give you an idea of how many batteries you need to store enough energy to make it through the night if you are off grid and relying on solar panels for all your power. I suspect you will be shocked at the number of batteries needed.

Donald asks…

Anyone help me to know what to consider when designing solar power for the home?

I know little on solar power for the home. I understand that it is possible to convert power to chemical form then use it as electricity. My question is, what elements are involved and how is the sizing being done?
I need the power design to power lights (say 10), TV and radio.

ssadmin answers:

First of all, the conversion is chemical to electricity, as in the chemistry of a car battery which provides an output voltage.
To meet your needs, you need to figure how much useful sunlight you will have per day. Such sources as the Weather Channel, or National Climatology office can supply that to you. You need to determine the total load. Just add everything up, and that is the load you need to have sufficient energy to provide power for. If this works out to be, let's say 200 watts, then you need at least a 200 watt solar panel, provided that you have enough sunlight from the time that you get up in the morning, until you go to bed at night. Count on it, you won't have enough sunlight for your needs, unless you live up in Alaska. Even then, there is part of the year where there will not be enough light at any time of the day. What you need, for full 24 hour coverage is a battery bank, and unless everything will run on 12 or 24 volts, then you need 1 or more inverters. With inverters, you lose 10% in conversion loss from DC to AC. Batteries should be RV, Trolling motor, or best yet, electric fork lift batteries, or the reasonable equivalent of such as these. I would recomment at least double to quadruple the total energy need for the solar panels, and to multiply the battery capacity by the total load supply that you have figured out, for at least a 24 hour run time. All of that, then multiplied by 90% to know how long the system will provide power, IF you use any DC to AC inverters. Within reason, the larger the battery bank, the better. Do NOT use regular car batteries, they will not last as long as you need them to last, unless you understand the difference between cranking amps, and reserve amps. Another point is that auto batteries are simply not designed for this kind of service.

Mandy asks…

How to run 15 kW motor from solar power system?

I want to design solar power system to run 15 kW, 3 phase motor, 50 Hz for pumping purpose. I will be using batteries for back up supply from Grid supply to charge battery during solar power failure. Please suggest me the capacity of inverter that is needed to use as power supply to the motor?

I request necessary circuit diagram and equipment capacity to use for this purpose from all the members please please?

ssadmin answers:

It sounds like the site has grid power, so I would stay with that.

You could then supplement the power with solar, using grid-tied inverters. There are 3-phase inverters, but you might find it simpler to just use several single-phase inverters, one or more on each leg. I see no point in using batteries, that would only add to the cost. In fact, you would only go with grid-tied solar for water pumping if you were in one of those rare places in the world where grid electricity is very expensive.

With grid tied, you will also not have to worry much about under-sizing your solar array. If you put in a 1 kW array, it won't save as much money as a 5 kW or 10 kW, but the system will still work.

Also, if you have a choice of when to do the pumping, you can set up your controller to pump when sun is abundant. For example, if you're filling a reservoir, fill it between 10 am and 3 pm.

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