Sunday, March 19, 2023

How To Size An Off Grid Solar System

Stop Waiting On Solar Car Try Something Else Instead

How to Size My Off-Grid Solar System & How Much Does it Cost?

If we want to put solar on EV, solar-powered cars, let’s do it now. But not the way of the Solar Car idea by gluing solar cells all over our EV. Solar requires a flat surface, and the surface area available on the vehicle we drive nowadays is minimal. I mean, lets keep researching the technology until its more ready for the market. And lets focus on more practical research/solutions for putting solar on EVs, particularly “Solar Recharging System for Electric Car”, or Deployable Solar Systems for Electric Car.

Deployable Solar. I think this is a topic we should dig into further.

Build Your Own Off Grid Solar System

Before considering building an off grid power system yourself, its a great idea to fully understand how they work and most importantly how to size the components. This is crucial.

There are many resources, such as this site DIYSolarShack, to help in off grid design, but it can save a lot of time and thinking power if you simply hire a professional installer to do the calculations for you.

Take The Stress Out Of Off Grid

Make the most of Commodores latest innovation, our updated Off Grid Calculator. This webpage has been designed to make life easier for you. We understand how difficult it is to choose the right solar system and also how difficult it is to calculate Off Grid. So, we thought why not turn the complicated equations, and worrying decisions associated with going Off Grid into a positive experience, where you simply tick the boxes applicable to you!As the video above displays, all you have to do is:Select which products you use around the houseHow long you will use them for per dayBy you doing this, our off grid calculator can quickly calculate the:Potential Load KWAverage KWh Per DayWhich systems will be suitable to your power usageThe Winter average daily effective solar section is set at 3 hours per day. This is a conservative estimate based off the average number of effective solar PV input hours in Winter. Our research confirms that the national average annually is between 4 to 5 hours per day. This means 1kW of solar panels will produce between 4kWh to 5kWh per average day. In Winter our research indicates 3 hours of effective solar PV input to be the national average, and 6 hours of effective solar PV input to be the Summer average for Australia. Follow this link below to find the average for your area on a map.PV Performance Map AustraliaWith our tool, you can adjust the amount of effective solar hours to suit your location.

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How To Solar Sizing An Ev

If you can put solar on your EV, where would you put it? On the car’s roof, maybe the bonnet too. OK.

How much space have you got? What power level do you get with that space? Does it worth the money? Does it provide a good return on investment? Or just good for the environment?

That is a lot of questions, just for sizing the solar system for your EV.

Designing A Battery Bank

Off grid solarClean Connect Solar

Battery banks are essential for off-grid solar systems, as theyll keep your home running when the sun goes down. Youll want to ensure you have enough battery storage to power your home throughout the day, too, for those days when its cloudy. Calculate the total watt-hours you can get from a battery by multiplying its voltage and amp-hours . It would help if you then subtracted any battery percentage that cannot be discharged all batteries will have a maximum depth of discharge rating.

If you have a 12V with 50Ah capacity, that battery would have a maximum capacity of 600Wh. If it has a maximum DOD of 50%, its maximum discharge is 300Wh or 3 hours of run time. Use these calculations to find the most efficient batteries and the correct number of batteries for your home.

If youre looking for components for your off-grid system, like the Sol-Ark inverter, lithium batteries, solar panels, and more, check out our catalog of wholesale solar equipment. And if you need assistance with designing your system, contact The PowerStore, Inc., today!

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Selecting A Solar Inverter

There are two primary types of inverters: modified sine wave and true sine wave inverters. Modified sine wave inverters are cheaper but may cause some operation issues with modern devices like stereo systems and computers. Actual sine waves cost more but dont have the problems mentioned above and are more efficient.

Youll also need to ensure that the solar inverter you choose is rated to provide for your peak load calculation mentioned above.

How Many Solar Panels Do I Need For Off Grid

Solar panels, solar battery charger, batteries and an inverter are needed for an off-grid solar system

Basic solar panel sizing uses the same process for off grid or on grid solar systems. The process is driven by the load i.e. how much energy does your home consume per day?

Home energy consumption can be found from last years utility bill and its the average daily value were looking for. The average US home consumes about 30kWh per day.

With an irradiance value of 4kWh/day or peak-sun-hours, the amount of solar power required is:

30kWh / 4 = 7600 watt-hours solar power.

If using 200 watt solar panels, it would take 7600 watts / 200 = 38 solar panels.

However, a solar power system has losses, so it will generally produce much less than the calculation indicates.

Losses can be up to 23% of the solar system rating. For a 7600 watt system, the rating needs to be multipled by 1.44 to make up for the possible losses.

Realistic power rating needed = 7600 x 1.44 = 10800 watts, or 36 solar panels.

Off-grid solar systems need to have enough solar capacity to charge up a battery bank , as well as run the home in the daytime.

I would normally allow up to 30% of the total daily energy consumption for night-time running.

Although this would mean installing 30% more solar, or 48 panels in total, its better to have too much power capacity than not enough when youre off-grid.

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How Realistic Is The Result

Of course, those calculations were based on several assumptions:

  • Daily driving over the year of 35km

  • 5 hours average of solar charging under the sun per day over the year

  • 200W per m2, plus 20% of extra space for covering the area, efficiency about 23-24%

  • Recharging frequency and mileage calculate until the battery is depleted .

There will be variations on factors that are affecting the results. Some may do better and others for worse, but achievable.

Find The Right Installer For Off

Sizing your off grid solar system

Off-grid system installation is a specialty craft and not a service that most solar companies provide. The quality of the installation is paramount to the ongoing operation of the system. We can put you in touch with specialist off-grid installers. All you need to do is complete our off-grid quote request.

Also Check: Are Solar Panels Harmful To Your Health

Calculate The Off Grid Power Generator Components’ Size

After that you can calculate the size of the components

  • calculate your average daily consumption
  • divide the daily consumption by the average number of useful daylight to get the size of the off grid solar power panels in watts
  • In case the main generator is an off grid residential wind turbine, divide the number from 1. by the average number of wind hours to get the size for the wind turbine.
  • The size of the inverter and the charge controller should fit the size of the solar panels OR the size of the residential wind turbine
  • Think of the batteries as a pool of water that is filled during the day and drained over nights .. You canât however discharge the batteries bellow the 20% line . The capacity in KWh of the batteries when fully charged is the Ah rating multiplied by the voltage multiplied by 1-0.2=0.8 . This should suffice for your consumption during the no production hours. So you calculate backwards from your night consumption to get the batteries size in Ah .
  • I wonât be surprised if you find out that you need many batteries, and that you need a battery rack
  • Building Your Solar Battery House Or Compartment

    Once you have the components ordered, you would be ready to build your battery house, which may be a room in your existing home, part of the garage, or a separate shed. Batteries take up a fair amount of room, they need to be protected from kids or critters that might hurt themselves by touching the contacts or might accidentally damage the battery and release the acids inside.

    Additionally, most types of batteries need some amount of temperature control, and dont do well with freezing weather. However, if you go with less expensive unsealed batteries, you will have to build in some ventilation in to your battery house in order to prevent buildup of explosive hydrogen gas, which these types of batteries release in small amounts when charging.

    In order to reduce costs, most solar setups have their main power electronics the charge controller and inverter as well as safety shutoffs, fuses, and breakers in the battery room as well.

    We talk about this in part 3 of this series.

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    Determining How Much Energy Solar Panels Produce

    As you might have guessed, the amount of power that your solar panel produces depends on how much sun they gets. That means during the shorter days of winter you will get less power. Also, cloudy days will give you much less power than sunny days.

    Again, the best way to know how much power your solar panels will produce is to measure it. Buy one solar panel and measure how much energy you can produce throughout the year. Not every year is the same, so you will need to oversize your system just a little bit in order to account for usually dark or cloudy years.

    However, you may just want to get a rough estimate of how much solar power your panels were produce. Luckily the US government has produced solar power availability data for the entire United States.

    The map above shows on average how much power your solar panels will produce per day. The number depends on the color of your area it ranges from about two to eight. This number can be multiplied by the power rating of your solar panels to determine how much power they would produce. So if you live in an area labeled as three on the map and you bought a 1 kW Solar panel array then you would get 3 kWh of energy produced per day on average.

    This assumes that you have full access to the sun so long as it is up. If location of your solar panels is partially shaded, especially during mid day, then you will get less power than the map shows.

    Calculate The Amount Of Batteries You Need

    UTL Off Grid Solar System

    Now that you know how much power you need, you need to figure out how many batteries you need to store it.

    • Do you need only enough storage for a day or two or do you need to have enough batteries to store 3 or 4 days, or more, worth of power?
    • Do you have another power source, like a generator or turbine, that will kick in if the sun doesnt shine?
    • Will you be storing the batteries in a warm room or will they be in a cold location?

    Batteries are rated for storage at around 80 degrees Fahrenheit. The colder the room, the bigger the battery bank you need by over 50% more for below freezing. Each of these answers affects the size, and cost, of your battery bank.

    What voltage battery bank do you need 12V, 24V, or 48V? Generally, the larger the system, the higher voltage battery banks are used to keep the number of parallel strings to a minimum and reduce the amount of current between the battery bank and the inverter. If you are just having a small system, and want to be able to charge your cell phone and power 12V DC appliances in your RV, then a basic 12V battery bank makes sense. But if you need to power much over 2000 watts at a time, youll want to consider 24 volt and 48 volt systems. Besides reducing how many parallel strings of batteries youll have, itll allow you to use thinner and less expensive copper cabling between the batteries and the inverter.

    Use our off-grid calculator to calculate what size battery bank you need based on these answers.

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    Best Place To Find Turnkey Solar Installers

    If youre looking for a company to handle the complete installation process for an off-grid solar system – from system design and procurement to installation and permitting and inspection – then check out the SolarReviews solar companies database.

    Itll show you the best local solar companies in your area based on consumer reviews.

    For A Bit More Space You’re Off

    Tesla Model 3 infinite driving. It is totally Off-Grid no more recharging from a 32% increase of surface area.

    Cybertruck recharge only twice per year, not far from Off-Grid. A 30% increase in surface area will make it Off-Grid.

    Wuling Hongguang Mini EV infinite driving. It is totally Off-Grid no more recharging from a 20% increase of surface area.

    Read Also: How Much Do The Tesla Solar Panels Cost

    Avoid Solar Panel Shading At All Costs

    Secondarily, solar panel suffer greatly when they are even partially shaded by trees, building, and any obstructions that might be present. You might think that having your panels only 10% shaded we just reduce the power output by 10%. Yet in most cases it will reduce the total power output by at least 1/3. And depending on how your panels are wired, it could reduce the total array output by 1/3, not just the one panel. So, unless your home is completely free from shading, especially in the winter, it is frequently cheaper overall to put your panels a little distance away from the house where they will receive full sun all your long.

    What Size Off Grid Solar System Do I Need

    Battery Bank Sizing: Off Grid Solar Power System Design – Step 2

    Solar system sizing depends on you estimated annual energy usage. If your home was connected to the grid, then this is easy to find as it appears on your utility bill.

    Simply read the previous years energy consumption in kilowatt-hours . An average value for the US is 11000kWh per year or 30kWh/day.

    If its a new build, then you need to estimate your average energy needs from the appliance ratings. This is fairly easy, but fridges, freezers and AC need special consideration more later.

    On of the most common mistakes when designing off-grid solar systems is to undersize the installation, either by under-estimating the energy needs or over-estimating the annual energy a system will realistically generate.

    The table below shows average power ratings for common household appliances:


    1200 *

    The starred items pull more power at startup so extra battery capacity should be added at the design stage to make sure these demands can be met.

    Many appliances will give an average annual energy consumption on their labels, which is mostly the case for appliances with compressors on board, and also washing machines.

    For the rest of your appliances, add up the power ratings in watts and estimate how many hours per day/month/year they will be used. Multiply the total watts by annual hours to find the estimated energy needs of your home.

    Its a good idea to add 20% to account for any future expansion.

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    What Size Battery Charger Do I Need

    As a general rule, lead acid batteries need a solar charger with output in amps 20% of the battery bank amp-hour capacity.

    For my example off grid installation that would be:

    Battery capacity 1041 x 20% = charger output size = 208 amps

    The input volts should be matched to the solar panel output volts and output volts to the battery volts.

    For lithium batteries output current of 30% battery capacity is recommended.

    Important: All batteries have a Maximum Charge Voltage and Maximum Charge Current, which can be found in the specifications. These should not be exceeded ot the battery life may be significantly reduced.

    Most good quality chargers used in off grid solar power installations can be set for voltage and also have variable current output.

    Solar Cells Efficiency Increase Gives The Same Mileage Gains

    If solar cells’ efficiency increase by the same percentage as surface area, it gives the same results, Off-Grid. At a 25% solar cell efficiency, an 20% increase is 25% x 1.2 = 30% solar efficiency, a 30% increase is 25% x 1.3 = 32.5% solar efficiency. Such levels of solar cells are already on the market. Were just waiting for the price to come down to more suitable for residential / vehicles use.

    If we can have a more extensive coverage area for solar, a deployable system spans over Area C. The surface area increases vastly. It does not affect the vehicles aesthetics because it is put away when not used. It does not require gluing solar cells on the surface. It does not block out the beautiful panoramic roof. We can get valuable benefits while contributing to the climate.

    Have you noticed that we didnt include any trunk cover surface for calculations? Mainly windows and the roof.

    Also Check: How Much Solar Panels Do I Need

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