## Designing a Solar Panel System to Meet Your Needs

**Author: Maureen Smith**

To correctly size your solar system, you must ensure that over a period of time (taking into consideration the seasons and average weather and light conditions), your solar panels produce at least as much energy as your loads (laptop, TV, lighting, etc) consume.

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In the UK, northern Europe and north America, a conservative estimate allows for four hours of peak sunshine in summer and one hour in winter.

The power produced by a solar panel in one hour is its power rating (Watts).

The estimated power produced in a day by the panel is obtained from multiplying the power produced in one hour by the number of hours of peak sunshine.

Thus, in the UK, a 30W panel will produce around 120 Watt-hours (30W x 4 hours) of power on an average day in summer.

1. Estimate the Total Power Usage (wattage) of Your Appliances

List all the 12V electrical appliances you intend to power from your solar system and find out how many watts each consumes (from the appliance, power adaptor or instruction booklet).

2. Calculate Your Total Daily Watt-hour Requirement

Estimate how many hours you expect to use each appliance each day. Multiply each appliance’s wattage by its estimated daily hours’ usage to calculate the daily Watt-hour requirement for that appliance. Add up the daily Watt-hour requirements of all your appliances to determine your total daily Watt-hour requirement.

3. Calculate Your Solar Panel Size

Take the total daily Watt-hour requirement you calculated in 3, and divide by the number of hours of usable light you expect in an average day (eg, four hours in summer and one hour in winter for the UK, northern Europe and north America). This will give you the minimum wattage of your solar panel.

4. Calculate Your Battery Size

Battery capacity is measured in Amp-hours (Ahrs). To calculate how large a battery you need, take the total daily Watt-hour requirement calculated in 3, and divide this by the battery voltage (12V or 24V) to convert back to Amp-hours.

You shouldn’t discharge a battery beyond half-level, so you must then multiply this figure by two to give the correct battery size.

The calculation thus far assumes you will be recharging your battery daily. If you wish to be power-autonomous for n days (ie you will only solar-charge your battery every n days), multiply the above figure by n to give you your final battery size.

5. Worked Example

You wish to run a 30W laptop for 2 hours a day and a 10W light for 4 hours a day. The daily Watt-hour requirement of the laptop is 30 x 2 = 60 Watt-hours. The daily Watt-hour requirement of the light is 10 x 4 = 40 Watt-hours. Thus, the total daily Watt-hour requirement is 60 + 40 = 100 Watt-hours. You will be using the system in summer in a location that provides 4 hours of daily sunlight. Thus, your panel needs to have a wattage of at least 100 / 4 = 25W.

Your 12V battery needs to be able to power your laptop and light for five days between charges. Thus, your battery size needs to be at least (25/12) x 2 x 5 = 20.83 Ahrs.

Article Source: http://www.articlesbase.com/diy-articles/designing-a-solar-panel-system-to-meet-your-needs-1432315.html

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Amount of water which can be undergone in photoelectrolysis one day by using 100 watt power solar ??

In our project we should produce Oxygen from water by Solar power. In one day how much amount of water can be undergone photo electrolysis by using a 100watt solar panel? And how much oxygen can be produced from it. I am really in need of answer, plz help..

can 1 solar panel of 100 watt charge 2 or more batteries at one time.?

i am trying to design back up power system of 1000 watt but i am confused, do i need a solar inverter (charger) or i can use a regular 230 volt inverter( charger) while i can use a charge controller with solar panel .

ok i will try to explain more clearly. my family in pakistan is having difficult time becuase of power outages so i am thinking about building a solar back up system in which i can have two 80 watt 12-17 volt panels which will give me 160 watt with around 9 amp and hook them with two batteries of 12 volt 200ah each now i want the inverter to have a charge function as well so at night if the power is gone for along time and batteries are drained( which i doubt) since all what will work at night will be ceiling fans and few energy saver lights out side the house. I want to know that would that system will be enough to run like 4 celing fans and 7-8 energy saver lights for few hours. on the inverter my question is that would it be feasible to use a regular inverter or should i get a inverter with charging function aswell. if i get a charging function inverter would it effect the solar panels in anyway when it will try to charge batteries when ac power is avalible.

If a solar panel creates 100 watts does it mean 100w a day, hour, or sec?

Does this mean 100 watts, would = 500 Watts in 5 Sec?

Does this mean a 100 watts soloar panel, would = 6,000 Watts in 60 sec?

solar panel help needed!!!!?

if i have a 100 watt solar panel and it collects 100 watts and i dont use it does it store it in the solar panel or just go away?

How does a solar panel system store energy?

In specific, can a 40 watt solar panel store 100 watts in a battery. Also what is the difference between volts and watts. Another question was that can I was a cigarette lighter power adapter from a car to change the voltage from DC to AC.

Will a 100-watt solar panel (measured at 1000 w/sq m/d) produce 600 watts at 6000 w/sq m/d insolation?

How many hours would it take for this solar panel to fill this battery?

I need to know how long it would take to fill this battery http://www.apexbattery.com/8g8d-itp-solar-battery-8d-solar-batteries.html with this solar panel http://store.altenergystore.com/solar-panels/100-to-149-watts-solar-panels/kyocera-kd135gx-lp-135w-12v-solar-panel/p6172/

battery website http://www.apexbattery.com/8g8d-ltp-solar-battery-group-8d-solar-batteries.html

Can I connect a solar panel directly to an inverter?

I’m working on a small project where I can connect low voltage/watts equipment using an inverter connected directly to my solar panels. I know you can connect them directly to each other but what is the power ratio to run the inverter and its load….meaning. If i want to run a 100 watt 12V inverter, what solar panel(wattage/amps/voltage) do i need. How much amps/voltage do i need from the solar panels to make the inverter work, with and without load?

Is it possible for my Solar panel to supply half the energy for my fridge?

I’m planning on installing a few 100 watt solar panel to harness some energy I’ld then like to use the energy on my fridge, im aware that this amount of energy will not be enough to supply the whole fridge so i was wondering if I could hook up the solar panels to the fridge, but also have the electricity from the electrical companies be able to supply the rest of the energy. Is this possible?

If so would I need to hire an electrician or be able to do it myself?

I’m also curious to know a rough estimate of how much money per month would i save if i had three 100 watt solar panels? ( my eletrical company is PSE&G)

( and my fridge is a Kenmore Coldspot, with no ice maker or water dispenser)

Thank you so much

I’m building a solar panel (70-100 Watts) and i don’t know what size battery makes sense to use?

Please recomend one of these batteries in which to store the power generated by my solar panel.

http://search.greenbatteries.com/search/Category-Rechargeable_Batteries–SubCategory-rechargeable_lead_acid_batteries_-_SLA%2C_AGM%2C_deep_cycle–_autodone-http%3A%2F%2Fstore.yahoo.com%2Fgreenbatteries-store%2F–catalog-greenbatteries-store–keywords-deep_cycle_12V–x-0–y-0

PS the panel is 12V

If I installed 20, 100 watt solar panels and 20 12v batteries for power storage?

how much of my power needs would this generate? This system would be not be tied to the grid unless there’s a benefit. We use about 600kw monthly and receive 5.5 hours of sun light daily. Thank you for any help. Chris

What is the total cost for a solar panel and accessories to generate a 100 watts power?

How long will it take a 100 Watt solar panel to charge a 55 Amp hour car battery?

I’m doing physics homework and am really stumped.

How many kwH does a 100 watt solar panel produce each day?

I am looking at a 100-watt solar panel and inverter that plugs into an electrical socket and feeds energy back into the house. It runs about $600 and want to figure out how much kwH of energy it will produce and how long it would take to pay back the cost of the solar panel.

here is an ebay link to what I am looking at

http://cgi.ebay.com/400-Watt-Grid-Tie-Inverter-12V-110-W-Solar-Panel-System-/200497883572?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item2eae9ae9b4#ht_12422wt_1139

How long would it take a 100 watt Solar panel to charge a 12 volt Battery ?

* A regular car battery

Mike, I’m assuming the solar panel in question is wired for 12 volt battery charging, which means it actually peaks out at 18 volts if the circuit is open. Panels are rated in watts, which is found by multiplying the panels open circuit voltage by it’s short circuit current, or amps. A 100 amp panel wired for 18 volts would have a short circuit current of 5.5 amps. My guess is the question is using a 55 amp hour battery because it is exactly 10 times the amp rating on such a panel.

You might see the answer already, but I’ll explain further anyway. If a battery holds 55 amp hours, that means you can start out fully charged, and draw 55 amps out for an hour before it is dead. Or you could draw out 1 amp for 55 hours, and end up at the same place. So if the panel can feed in 5.5 amps for 10 hours, then it would replace 5.5 X 10 = 55 amp hours.

In the real world, the panel would actually put out a bit less than 5.5 amps, since it would not actually be at short circuit amps with a 12 volt battery in front of it. The battery is not 100% efficient, so each 10 amp hours you feed in might yield 8 amp hours of storage, and so on. But I’m guessing the question you are trying to answer is theoretical, so they are probably looking for 10 hours, in direct sunlight that is. Good luck, and take care, Rudydoo

if you live in the lower 48 states, you get about 12 hours of daylight on average over the course of a year. 100 watts is 0.1 kwh. there are 8,760 hours in a year, so there are about 4,400 hours of daylight a year.

equation is,

4400 hours x 0.1 kwh x (days of sunlight/365) x cost /kwh x panel unit efficiency = $ produced

then,

$600/$ produced = simple payback

you may then do a net present value analysis (which makes the payback worse)

notes:

days of sunlight may be obtained locally from your weather bureau

cost/kwh can be obtained from your utility bill

panel efficiency can be obtained from the manufacturer data

equation does NOT include any cost for equipment upkeep or repair.

solar energy is NOT economically viable without extensive government subsidy. i think you will find your payback to be over 10, closer to 20 years, depending on utility cost (vary in the us between about $0.07 and $0.25 per kwh).

No. Increasing the insolation by a factor of six will heat the standard solar panel, increasing its internal resistance and decreasing its efficiency. At some point there is a maximum amount of power that you can derive from a panel, but that depends on the technology.

Seems like your watts, volts and amps confusion has been handled. I’ll tackle the headline question.

Some solar panel systems store energy and some don’t.

One type of system has no storage capacity at all, hooks up directly to your meter (and the power grid) and delivers power to your house as long as it is generating electricity. Extra capacity is sent to the utility and the home owner’s account usually gets credited.

The second type takes any excess capacity and stores it on site. This is done in a battery array. Although one university professor in NJ is doing it with hydrogen.

Location, weather, shading, and de-rating would be factors, but a rough estimate would be about 230 kWh per month, or just over 35% of your usage. There are benefits to being tied to the grid, but it really depends on what your motivations are for doing solar. Contact me at the E-mail below if you would like a detailed list of pros and cons.

Be advised you will also need racking, a charge controller, a combiner box, an inverter, fuses, disconnects, switchgear, and properly-sized wiring. Please do not try to do this project alone unless you are comfortable and familiar with these items.

The panel puts out 11.25 amps, if the battery is clear dead, then it will take about 24 hour to a full charge.

A watt is a unit of power, which represents one joule per second. This means a watt is already a rate of energy per unit of time. So a 100 watt solar panel produces 100 watts, meaning 100 joules per second.

Energy can also be measured in kilowatt hours, which represents the production of 1000 watts for 1 hour. So over the course of an hour, this panel would produce 0.1 Kilowatt Hours of energy, or 360,000 Joules.

Generally, the larger the battery, ie, the amp-hour rating is higher, the better you are, as you can store more energy. So it’s a trade-off of capacity versus price and size. You have to decide that trade-off, you know the parameters, I don’t.

You may want to get a battery rated for deep discharge. Most lead acid batteries (auto type) cannot be completely discharged without damaging it. These are sometimes referred to as “marine batteries”.

100 amp-hour is about the biggest, and your 100 watt panel will take about 12 hours to charge it.

You will need a panel output of 15 volts in order to charge a 12 volt battery, 12 volts is not enough.

You will also need a charge controller of some sort to avoid overcharging the battery and damaging it. A good one will use a DC-DC converter to increase the voltage to that needed to charge the battery.

.

I don’t know but I’m sure it’s very little. The biggest mistake people make when working with solar panels is to not concider that solar panel do not make electricity at house current flow levels. House current is 120 volts ac. The best solar panels are 17 volts dc.

100 watts of 17 volt dc is a small fraction of 100 watts, 120 volt ac.

Solar generators simply are not practical. Wind turbines have proven themselves to be the only practical means of generating “free” electricity with cold fusion perhaps the trump card.

Depends on what you are trying to do. Are you looking for a stand alone system with batteries? Is the load AC (plugging into the wall) or DC (running directly off the battery). If it is AC, you’ll need an inverter. Is the load you are trying to power 100W, or do you want a 100W panel? There are system losses, so it’s not a 1:1 ratio. You would need to know the load and how many hours it runs to correctly size the system.

Here’s a really nice cabin package that includes 130W of panels, charge controller, batteries, inverter, racking, safety equipment, the works. http://www.altestore.com/store/Kits-and-Package-Deals/Off-Grid-Cabin-Systems/Off-Grid-Cabin-Package-A-130W-PV/p39/

It depends. If you are off the grid what you don’t use or store goes away. I live in the suburbs and my electric company will buy what I don’t use. So during the day when I’m generating electricity it goes into my home, all my extra electricity goes out to the grid and my meter runs backwards. Other homes are using what I generate. At night when I’m not generating any electricity my meter runs forward. My system isn’t large enough to zero out my bill, so I always use a little bit more from the city than what I sell back. My electric bill went from around $200 a month to about $20.

You can install a small grid-tied system that provides a small amount of power into your general pool of electricity. You can’t easily direct it to just your fridge, it will just be available power for your home. There is a minimum voltage that grid-tied inverters need, so a very small system is tough to do. (A new inverter that can be used with one panel is available, but they are sold out until next year). Here is the smallest kit we sell, it has four 60W panels for 240W, http://www.altestore.com/store/Kits-and-Package-Deals/Grid-Tied-Systems/Alt-E-Designed-Grid-Tie-Packages/AltE-Micro1-Grid-Tied-Residential-Package/p5642/. Depending on where you are, it can generate about 25kwh a month. I’m not sure what you pay per kwh, but if I guess $.15, it can save you $3.75 a month. Even if you get the 30% tax credit from the federal gov’t and the state rebate, payback on a small system can be years.

Your local electric code may require that an electrician wire part or all of he system, check with your electrical inspector.

Normally it is not connected directly because the voltage and current output from the panel is fluctuating as it is entirely dependent on the sun’s rays.

So the solar panel is therefore connected via a “Charge Controller” to a 12V lead acid battery to charge it.

The battery is then connected to the inverter.