Wednesday, September 13, 2023

How To Calculate Batteries For Solar System

How Much Power Can I Take From A Battery

How To Calculate Battery Capacity Of A Solar System
 Unfortunately, you will never be able to take all the power from a battery. Each battery has a Depth of Discharge rate to prevent them to be damaged. Check here to discover more about DOD For example Lead acid GEL batteries will give you around 50% of their rated power. LiFePO4 batteries will give you around 80% of their rated power.

Where You Live And Your Solar Panels

Where you live has a big impact on how much energy your solar panels are capable of producing. Thats why solar was first put to use in sunny places like the U.S. Southwest.

The more access to sun your solar panels have, the more they can produce. While some states in northern latitudes get less than 4 hours of sunlight per day on average, others can get more than 7.5 hours.

Obviously, the more sun, the better. But its still possible to enjoy the benefits of solar even in places up north.

How To Use A Calculator To Calculate How Many Solar Panels You Need

Our solar calculator can estimate the number of panels needed for your home. The tool works by taking your average monthly energy usage in kilowatt hours .

• Calculators that use kilowatt hours are more accurate because they consider your exact energy needs
• Those that ask for home area must assume the electricity consumption

Each electric company has a different power bill format, but they all display your electricity consumption for the billing period. The exact description will vary, but you should look for a term such as kWh used or kWh consumed.

Solar calculators also ask for your home location to determine how much sunshine is available. Based on those two values, they can estimate the system size in kilowatts. Some solar calculators assume a wattage for panels, while others ask you directly. Based on the total kilowatts and the rated watts per panel, the calculator can determine how many are needed.

It is important to understand the difference between kWh savings and dollar savings. kWh savings refer to the amount of energy that your panels produce. On the other hand, dollar savings are obtained when the solar electricity production is multiplied by the kWh price.

Also Check: Is Solar Really Worth It

How To Calculate Battery Capacity For Solar System Off

 Last year during holiday period with some friends we planned to go to 5 days trekking in the wilderness. No food or water was available during the trip. So we had to figure out how much we had to carry with us. Not carrying enough food and water could be risky because we could run out of supplies. Carrying too much food and water would put too much weight in our backpack. It was not an easy decision. Finally, we decided to take high energy bars that would help us to have enough food with less weight. Maria and Paul decided to take canned food because they only planned to stay with us for 3 days.

A similar problem can arise when you design a solar system. Your battery must be big enough to supply your power needs but also small enough to reduce the total cost of the system.

How to calculate battery capacity for your solar system? You need two key pieces of information: energy consumption and days of autonomy

Follow these procedures when calculating the required battery capacity of your solar system.

The sunlight available to produce electricity varies greatly throughout the United States. Southwest states like California and Arizona get the most sunshine, while northeast states like New York and Massachusetts get the least.

However, you should not discard solar power just because you live in a state that isnt sunny. For example, New York only gets moderate sunshine, but it has very high electricity prices. Solar panels are worth it in this case, since they achieve high savings even with reduced production. Saving 750 kWh when you are charged 25 cents/kWh is better than saving 1,000 kWh at 12 cents.

After estimating how many panels are needed in your home, you can make better purchasing decisions. Keep in mind that you dont have to pay the full system cost upfront. Many banks finance for solar panels, and you can pay off the loan with the electricity savings achieved. Leasing solar panels is also a viable option, where you pay a monthly price instead of purchasing the system. Your local solar installer may offer several purchasing options, adapting to your needs.

Read Also: How Much Power Does A 5kw Solar System Produce

How Do You Calculate A Battery For A Solar Panel

There is a simple formula for deducing what panel size you need for your battery, but this depends on how many hours of sunlight youre getting per day, which, for most cases, we can average out at around six. This simple formula is:

Battery amp hours multiplied by voltage and then divided by daylight hours.

For example, a 100ah, 12v battery would be 100×12=1,200. This divided by 6 hours equals 200. So, if you want to charge a 100ah battery from flat to full in a day, a 200-watt panel in ideal conditions would do it.

Now that weve got a better idea of what to consider when matching a solar panel and batteries, lets take a look at the best panel size for particular battery setups.

Ideally, youll want slightly more power coming from your panel than you need from your batteries, as this will reduce the chance of running out of power and help during overcast days.

Remember, these are rough estimates, like your location and your energy needs will also play a part in the battery and panel size you need. Here are the best panel sizes in general for most common battery specifications.

Picking The Right Battery

So, which solar battery is right for you? There are a few different battery types commonly used for off-grid storage systems:

• No maintenance, no venting
• Highest efficiency, faster charging, more usable capacity

The two main battery chemistries for off-grid are Lead Acid and Lithium. These two chemistries have unique characteristics. Lithium batteries are more efficient, which means less power is wasted in the charge/discharge process. They also have a greater discharge depth allowing you to fully utilize all of your battery capacity.

Lead acid batteries are sensitive and need to be fully recharged every day, where Lithium batteries can stay at a partial charge without any adverse effect. Lead acid batteries also have a more limited amount of usable capacity and are typically discharged only 50%.

Because of the better efficiency and deeper discharge depth, Lithium battery banks tend to be only 50-60% of the size of a comparable lead acid bank! The Lithium batteries we use are purpose-built for off-grid solar, and utilize a special Lithium chemistry called Lithium Ferro Phosphate .

This type of Lithium battery is engineered to provide a long service life while also being safe, with a stable chemistry and sophisticated electronic protection features.

 55.2kWh: 1150ah 48v Sealed LA 57.6kWh: 1200ah 48v Flooded LA

This is not intended to be a comprehensive guide on off-grid design.

Read Also: What Is A Solar Heated Pool

How Much Are You Prepared To Pay For A Battery

If you are not prepared to pay over \$10,000 for a battery storage solution, there arent many batteries available to you that will be a suitable size for your electricity use. Solar batteries cost roughly \$1,000 per kWh, for a 10kWh battery, youre looking at around \$10,000.

If you are a low energy user, you could get a small battery less than 5kWh to serve your needs.

So Is It Beneficial To Have Solar Panels

How to Size your Solar Power System

Taking the example from the previous paragraph, we can see right away that a solar installation, once profitable, will be financially advantageous throughout its lifetime. Solar installations are most of the time guaranteed to operate at 80% of their initial value after 20 years, and can even exceed these lifetimes.

The price of electricity from your supplier on the power grid is made up of 3 separate “costs”:

• The cost of the electricity itself – about 40%
• The network fees – around 40%
• The VAT – 20% .
• Generating your own electricity on site therefore avoids paying grid costs and VAT on the electricity that was self-consumed. In addition, having your own energy source allows you to be partially independent of the grid and therefore self-sufficient in case of a power outage or natural disaster.

How Does Irradiance Affect Solar Panels

Although there are several factors impacting solar panel power output, irradiance or the suns energy, is by far the biggest.

Irradiance is measured in kilowatt-hours per square meter per day or year and varies considerably depending on your geographic location.

Irradiance values in kWh/m2/day are also known as peak-sun-hours and this is used by solar installers to work out how much energy a solar installation can generate.

It can be found from historical data using database lookups on sites like GlobalSolarAtlas. Simply enter your city and note your local peak-sun-hours see image below:

Chicago peak-sun-hours is almost the US average

The table below shows the irradiance values for 5 cities, both in the US and abroad:

Table Irradiance in 5 different locations

 City 4.253 5.699

Incidentally, the peak-sun-hours for Chicago is about the US average , so Ill use that in my calculations.

How Many Solar Panels Do You Need For 1000 Kwh Per Month

A family with several siblings can easily reach a monthly consumption of 1,000 kWh. In places with expensive electricity, this results in monthly electric bills of over \$200. However, solar power is an effective solution to reduce energy expenses.

As explained above, the number of panels needed to reach 1,000 kWh per month changes depending on local sunshine and panel wattage. To simplify calculations, solar radiation is specified in peak sun-hours per day. Weather scientists calculate this value by measuring the total sunshine in a location and converting it to equivalent hours of peak sunshine.

• Peak sun hours should not be confused with daylight hours
• Since sunlight is moderate in the early morning and late afternoon, these hours do not count as complete peak sun hours
• You may find a site that gets 12 hours of average daylight, and 6 peak sun hours per day

There are many online databases that provide peak sun hours based on site coordinates, including the Atmospheric Science Data Center from NASA. Once you know the peak sun hours, estimating the number of solar panels needed for 1,000 kWh is simple.

• The first step is calculating the kilowatts needed. You must simply divide the average daily kWh by the peak sun hours
• Assuming a 30-day month, an electricity generation of 1,000 kWh is equivalent to 33.33 kWh per day
• If the site gets 6 peak sun hours per day, you need 5.56 kilowatts

Also Check: Where Are Rec Solar Panels Manufactured

Solar Battery Calculation: How To Size The Battery For Solar Street Lights

In the course of designing solar led street lights,

just like many,

youd often encounter the problem of accurately sizing the battery.

This is because,

when the battery is undersized, the street light wont be able to sustain for up to 3 rainy or cloudy days.

Also, if the battery is oversized, youd face the problem of sulfation, especially if its a flooded battery bank.

Well, we have decided to completely solve the challenge of accurately sizing your battery.

Weve compiled a detailed breakdown and a step-by-step guide to sizing the battery for your solar-led street light.

The cost of increasing the size of the system to 5kW is only \$657 per kW. If we assume that you receive a feed-in tariff of 11.1c for every kWh you export back to the grid, it will only take 4 years to pay back the extra 2kW this is assuming that all of the additional solar power output is exported back to the grid. If you self-consume the power, it will pay back much faster. You can expect the panels to continue generating solar power for another 20 years.

Read Also: How Much Does The Average Solar Panel System Cost

Calculate A Solar Energy System Requirement

You need to match the kilowatt hours of your solar PV system to the kilowatt hours that your appliances will use. To approximately estimate the energy requirement for a period of time, we need to multiply the hourly power consumption by the number of hours of intended use. An example for the same would be a 40W appliance in domestic use that will be used for 2 hours per day. The daily energy consumption for it would be 40*2 = 80 Wh.

Repeat that exercise for every appliance individually to calculate the daily energy requirement for your solar energy system. Add in any appliance that will use power while connected to the solar panel. The result will give you an indicative total energy requirement for the solar panel to produce for the day. You can work out the number of panels needed a few ways.

You calculate how many solar panels you may need by dividing the maximum hourly solar energy system output by the wattage output of one single panel. The number of solar panels of the size used in the calculation will theoretically meet that energy demand during a sunny day.

Another way is to multiply the households hourly energy requirement by the peak sunlight hours for the area. Then divide that answer by the wattage of the solar panel intended to be used.

How Large Should The Battery Be

The battery storage capacity should slightly exceed the power generation potential of your system to ensure batteries are not stressed too much.

Ideally the battery should store enough usable power to supply energy for one full 24 hour period. The next day there should be a power source to fully recharge it. The battery bank should be large enough to support the power and load maximum requirement safely and without damaging or shortening the life.

For more in-depth information on battery sizing, read How to size an off-grid solar power system. It will help you decide how much energy you are likely to need in your off-grid solar power installation.

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How To Calculate The Area Required For Off Grid Solar Power System

• Xindun

how to calculate off grid solar system ? When purchasing a off grid solar power system, many customers have this question: How much area do I need to reserve for off grid solar power system?

1. Solar panels are installed on the roof

The installation area of one piece solar panel is estimated to be 2.1-2.2.

The solar panel installation area calculation method of the whole solar power system: the number of solar panels x 2.1/2.2.

2. Solar panels are installed on the ground

The installation area of a solar panel on the ground needs to be calculated as 2.5 .

The calculation method of the solar panel installation area of the entire solar power system: the number of solar panels × 2.5 .

The solar inverter, solar controller and battery are recommended to be placed in a ventilated and dry room.

For example:

The Climate Of The Area And Peak Sunlight Hours Calculation

How Much Solar Power Do I Need? How to Calculate Your Needs

The sunlight hours available to your location will directly impact the watts generated from the solar set up.

The more hours of sunlight available the less number of panels required to generate a given output.

Inversely, with lesser sunlight hours, more solar panels will be required. By dividing this average hourly wattage requirement by the number of sunlight hours daily at the location, you calculate the watts your panels need to produce every hour. Using this figure you can select the panels required. The sunlight hours and sun angles vary by season. This will also be a factor for calculating the number of available sunlight hours and thus the panels required.

Lets look at a simple calculation to understand this concept better.

Lets say the summer season sunlight at the location is available for 6 hours and for mid winter it is 4 hours. Then in mid winter a 10w panel will provide 10w * 4h = 40watt-hours of DC power into your battery. In summer the amount would be 10w*6= 60watt-hours. There would be a little energy lost due to resistance through the regulators, cables, and batteries chosen. In calculating the solar power system you would built some assumption of loss into the final calculation.

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How To Use Pv

The previous section assumed that you can mount solar panels at an ideal location: Perfectly south facing, with a great tilt-angle, and without any shading. What if your roof, or other location, is not quite that good? In most cases we can still accurately figure out what it will take to produce the kWhs needed. All we need is a little help from the US tax payers!

The US government, and NREL in particular, has created a very handy online tool that can calculate solar PV yield for any place on earth, taking orientation, angle, and even the local weather patterns such as cloud cover into account. It is called PV-Watts and clicking this link should open it up in a separate window. First we enter the location of the solar panels, or Ottawa to stick with our previous example. PV-Watts now finds the nearest location that it has weather data for, and displays that. Go to the next screen, and for our example we need to change a few parameters. The DC system size is how much solar PV you have, in kW. We want to know what each kW of panels will produce so change this to 1. The module type of Standard should be fine for most, we can also leave Array type to the default of Fixed . The system losses of 14.08% are fine too. For the Tilt we will change this to 45 degrees, the latitude of Ottawa, just like our earlier example, and the Azimuth is fine at 180 degrees .

Correction factor = PV-Watts reported yield per kW of panels / Actual yield per kW of panels

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