What You Should Know About Stand-Alone PV System
Disconnecting from the local grid gives you energy independence. It’s the freedom to live remotely away from overpopulated areas and stop handing your hard-earned money over to utility providers.
Whether you’re looking to save money, live remotely, or travel cross-country, off-grid solar systems are strongly worth considering.
Going off-grid doesn’t have to be complicated.
We’ve distilled the essentials of off-grid solar systems. Here’s everything you need to know to build an independent DIY off-grid solar power system and whether going off-grid or staying grid-tied is the right solution for your energy needs and budget.
What Is an Off-Grid Solar System?
An off-grid solar system satisfies your electrical requirements by harnessing the sun’s power without relying on the electrical grid. Without a direct connection to a utility grid, your off-grid solar system provides an independent power supply to your home, RV or trailer.
The off-grid solar system comprises the following components:
- Solar panels
- Charge controllers
- Battery banks (sometimes called portable power stations or, when combined with solar panels, portable solar generators)
These components all work together to provide energy for your home’s electrical appliances and devices.
- Solar panels capture sunlight. Most homeowners and businesses set up these panels on a rooftop system or an open yard for direct sunlight.
- The solar panels transfer the captured sunlight to the charge controllers.
- Charge controllers act as the ‘delivery man’ between the solar panels, the battery bank, and the inverters. The charge controller regulates the amount of power received, preventing battery overload. It keeps the battery fully charged and tops off the power levels when needed.
- The energy passes through the charge controllers to the solar battery bank, the heart of the off-grid solar system.
- The battery bank stores energy until it comes time for you to use it.
- Inverters convert the direct current (DC) energy into alternate current (AC) power to power your appliances.
Grid-Tied vs. Off-Grid Solar Systems
Grid-tied solar systems connect to the utility grid, while off-grid systems don’t. The difference between grid-tied and off-grid solar power systems centers around where you store the energy you generate.
Every system requires a place to store energy. Solar panels only capture energy when the sun is out, but you’ll still need a way to power your home in the evening.
With grid-tied systems, your panels transport the electricity generated to the utility grid. The utility provider distributes this energy to other residents in the community. In return, you can earn credits for the excess energy you generate through a net-metering program.
Off-grid power is different. Without the utility grid to keep your energy in reserve, you’ll need to find alternative storage. A solar battery or portable power station offers dedicated energy storage, allowing you to access stored energy during cloudy weather, nights, or blackouts.
Pros and Cons of Solar-Powered Off-Grid Systems
A solar-powered off-grid system has numerous benefits, but it’s not without its challenges. Here are the factors to consider:
Pros of solar-powered off-grid systems:
- Energy independence: Going off-grid gives you complete freedom from the utility company. You’re no longer subject to their terms and conditions, and rising utility costs won’t affect you.
- Power remote locations: Off-grid solar lets you access power in remote areas where utility power might be too expensive to run power lines or otherwise unavailable.
- Energy-conscious: Off-grid systems reduce carbon footprint and pollution for cleaner air quality and a healthier environment.
- No more blackouts: Off-grid solar means your power stays on even when the rest of your neighborhood experiences a blackout.
- Saving money long-term: While initial costs for an off-grid solar system are high, it pays itself off eventually, letting you live with zero electricity bills. Some people offset their costs in as little as five years.
Cons of solar-powered off-grid systems:
- Higher initial investment: Off-grid solar requires a more substantial initial investment to purchase and install the equipment. While solar energy eliminates your monthly electricity bill, it’ll take some time before the savings offset the cost in full.
- Limited energy storage: Off-grid solutions have a limited storage capacity, which depends on solar battery capacity. Knowing how much energy storage you need to meet your electricity requirements is essential when choosing your solar-powered system.
- Battery maintenance: Batteries have a costly initial investment and require maintenance. Batteries also eventually need to be replaced, but newer battery technologies like LiFePO4 last for many years.
How to Build a DIY Off-Grid Solar Power System
Installation costs for off-grid power solutions can increase the upfront investment. The good news is that you can get around paying labor and installation fees by doing it yourself. It’s a multi-step process but feasible for DIY enthusiasts.
Follow these steps to build your simple off-grid solar power system and save.
Determining How Much Power You Will Need
Start by calculating your daily power consumption for running your appliances and devices. Knowing your power consumption will let you determine your solar panel and battery storage requirements.
You can calculate your energy requirement using the following steps:
- Check the power rating for each appliance and device.
- Estimate the runtime for each appliance and device.
- Calculate the Watt Hour (Wh) by multiplying the power rating in watts (W) by the time you plan on running the appliance in hours (h).
For example, a TV may require 80W. If you plan on using your TV for five hours daily, the total energy consumption required for running your TV is 400 Wh.
Add up all of your appliances and devices. Examples include refrigerators, lights, water heaters, electric fans, grills, coffee makers, power tools, laptops, Wi-Fi routers… anything in your home that requires electricity.
You can also look at your previous electric bills, which should list your monthly kilowatt-hour (kWh) output. Divide the monthly kWh by 30 days to estimate your daily electricity usage.
Calculating the Amount of Battery Storage Required
Your battery storage should have at least enough capacity to accommodate your daily energy usage in kilowatt-hours. However, that’s only part of the equation.
You also have to estimate how many days your system will be without the sun. You can search for your area’s annual average of cloudy or sunny days online. A smaller solar battery capacity may be sufficient in areas with lots of sunlight, while larger solar battery banks are best in regions with more cloudy days. When in doubt, it’s best to size up rather than down.
Each battery has a Depth of Discharge (DoD) rate, meaning you can’t take all the power from the battery. Lead acid gel batteries typically give around 50% of the total rated power, meaning a 100Ah battery delivers 50Ah of usable energy. LiFePO4 batteries distribute 80% of the rated power capacity.
Let’s say you’re total daily energy consumption is 3,000 Wh, and you need two days of backup for potentially cloudy days. And assuming that you use LiFePO4 batteries, it has a DoD of 80%.
Here’s the formula for calculating battery storage capacity taking into account times when you may not be able to generate much solar power due to Cloud cover:
Daily Energy Consumption x Number of Cloudy Days / Depth of Discharge = Solar Battery Storage Capacity
3,000 Wh x 2 (backup cloudy days) / 0.8 (DoD) = 7,500 Wh of battery storage capacity.
You can be extra cautious by accounting for the annual correction factor. Batteries lose their capacity over time, meaning they won’t hold the same amount of power after a certain number of life cycles.
Here’s what it would look like in the above example:
3,000 Wh x 2 (backup cloudy days) x 1.15 (annual correction factor) / 0.8 (DoD) = 8,625 Wh of battery storage capacity.
Calculating the Number of Solar Panels Needed for Your Location
Before rushing out and purchasing solar panels, find out if your location can accommodate solar. You’ll need to calculate your energy usage and find the solar panels with the best conversion efficiency rating.
First, you need to understand the number of peak hours of sunlight your area receives every month. Then divide your monthly electrical usage by your monthly sunlight hours.
If you’re installing solar panels on the roof, you’ll need to account for the roof direction and shading, in which case, a solar calculator can provide a more accurate estimate.
Also, the number of solar panels depends on the panel’s power output. Most solar panels produce between 100 and 400 watts of power.
Let’s say you use 3,000 watts of power per day and receive five peak sunlight hours daily.
If you’re buying a 250W panel, each panel produces approximately 1,250 watts daily (250W panel x 5 peak sunlight hours).
As a result, you need at least three 250W panels to generate 3,000 watts of power per day. Three panels will give you approximately 3,750W of power. Excess stored energy can help prepare you for cloudy days when you may not receive maximum output from your solar panels.
Identifying a Solar Charge Controller
Solar charge controllers prevent batteries from overcharging. If the current is too high, it can damage the battery and potentially start a fire. If the battery is running at a dangerously low level, the control disconnects it to prevent harmful usage.
Pulse With Modulation (PWM) and Maximum Power Point Tracking (MPPT) regulars are the two most common types of solar charge controllers. MPPT controllers are more efficient than PWM controllers since they compare the panel’s voltage against the battery’s voltage.
PWM controllers send pulses of power by switching the power flow on and off continuously. It establishes a direct connection between your panels and the bank, making it the most straightforward and affordable option.
MPPT regulators optimize the voltage between the panel and the battery to extract maximum voltage, especially during rough weather conditions. While MPPT controllers are more expensive, they’re also 20% to 30% more efficient. Also, they’re best for high-voltage PV systems like your home.
PWM controllers are ideal when you have a small system and won’t need to maximize efficiency, such as powering an RV.
MPPT controllers are essential for a large-scale system such as powering your home since maximum efficiency is a priority.
Ideally, look for charge controllers that let you monitor and customize the regulator via an app on your mobile device. If you’re living in a rainy region, consider getting a waterproof control to ensure the controller’s safety.
Selecting an Inverter
The inverter manages the power flow between DC and AC energy. It takes the DC power from your panels or batteries and converts it into standard household AC electricity. After conversion, you can use it for your lights, TV, fridge, and other household appliances.
First, consider your off-grid solar inverter size. The size depends on your energy output. Here are general recommendations to help you pick out the proper inverter size:
Next, look at the technical specs of the inverter. We’ve laid out the standard specs and given you metrics to consider:
- Efficiency: Conversion efficiency determines the amount of current lost in converting DC into AC. Aim for a system with a higher conversion efficiency.
- Parameters: Pay attention to the output power, output voltage, and overload capacity. It should be compatible with your electronics and appliances. For example, everyday electronics use 120V, and some major appliances like ovens require 240V.
- Warranty: Warranties range between 1 and 10 years. Most inverters range between 3 and 5 years.
Balance of System (BoS)
The Balance of System (BOS) is all the photovoltaic components except for the module and solar panels. BOS primarily includes charge controllers, batteries, inverters, wiring, switching, junction boxes, and power conditioners.
Other elements within the BOS cover mounting systems, battery chargers, sensors, safety devices, solar concentrators, solar trackers, and lens reflectors.
You’ll have to purchase all these BOS components if you’re putting together your own DIY off-grid solar system. For example, wiring connects the solar panels to all other electrical parts of the off-grid solar system. Opting for dedicated solar cables means they can withstand UV radiation, temperature, and weather variations.
Mounting systems support solar panels. Whether ground-mounted or on the roof, you need to secure the solar panels. A solid mounting system keeps solar panels upright to withstand wind and secures them from physical damage.
Once you’ve calculated your energy use, battery storage, solar panels, and hardware needs, you’re ready to build your DIY off-grid solar system!
Introducing EcoFlow Power Kits
A power kit is a convenient way to switch to off-grid power if you want to skip the complicated installation and save money by bundling the BOS components. The EcoFlow Power Kit is a hassle-free plug-and-play modular power system. It requires less wiring, meaning fewer mistakes, and lets you instantly deploy and use off-grid power.
The power kit contains four components: the power hub, Smart console, solar battery, and Smart AC/DC distribution panel.
Unlike traditional power kits, Ecoflow Power Hub conceals the components in one box, saving space, and is easy to set up. The Power Hub includes:
- Inverter charger
- Two MPPT solar charge controllers
- DC-DC step-down converter
- DC-DC battery charger with MPPT
The console allows you to monitor and control your energy consumption, while the LFP battery (or batteries) stores your energy. The Smart distribution panel regulates your AC and DC loads.
The EcoFlow Power Kits feature stackable batteries, allowing you to add up to three batteries of the same size. The batteries come in two battery sizes: 2kwH and 5kWh. If you’re unsure about your backup power needs, you can start with one or two batteries and add more later.
How Are Power Kits Installed?
EcoFlow Power Kits are designed to be plug-and-play and require no specialist knowledge to install. You or your installer of choice should have no problem installing the Power Kit. If you run into problems, EcoFlow has your back with live chat on EcoFlow App, tutorial videos, and a quick start guide to help you during the installation process.
Here are the basic steps required to install an EcoFlow power kit:
- Mount your solar panels: Choose a good place to mount your solar panels where there won’t be any obstruction to sunlight. Rigid panels work best for solid structures like tiny homes and standard residences, while flexible solar panels work best for RVs, campers, and vans. With the EcoFlow Power Kit, you can mix and match rigid and flexible solar panels to create the most efficient configuration for your build.
- Install the power hub, console, LFP battery, and AC/DC Smart distribution panel: Select the appropriate place to install these components in your home. You’ll need to connect the solar panels to the power hub, so installing the hub on the wall close to the roof is probably best. You’ll also need to charge the power hub to make it entirely off-grid. Investing in an EcoFlow Smart Generator (Dual Fuel) can give you a last line of defense when you’re unable to generate enough power from solar.
- Wire up off-grid solar: Connect all components to your power hub, including the solar panel(s), LFP battery, console, and Smart distribution panel. You’ll also need to connect a power strip to use the electricity with regular plugs.
- Test your solar system: Turn the power on and test your installed solar system. Check your EF Smart app to read the console and monitor charge levels.
Best Off-Grid Solar Systems and Their Costs
The best off-grid solar system for you depends on your energy needs, which often come down to your household size and whether your installation is at a fixed location, like a tiny home, or mobile, like an RV.
EcoFlow’s Power Kit calculator makes it easy to design a custom off-grid solar system that meets your needs.
For reference, here are some common use cases:
Best Solar Power Kits for Vans/Rvs/Trailers
The best solar power kit for vans, RVs, and trailers is EcoFlow’s Get Set 5kWh Kit, a space-saving, plug-and-play system.
A 5kWh battery gives you ample capacity to satisfy the appliances in your RV. With the uncertainty of the weather conditions while on the road, it’s better to be safe than sorry if you run into extended Cloud cover.
Unlike some solar power kits, the Get Set Kit features an LFP or lithium-ion battery. It has a longer lifespan and greater efficiency than older battery technology, lasting up to 20 years. Furthermore, an LFP battery is safe and requires no maintenance.
Depending on your RV’s shape, we recommend combining rigid and flexible solar panels to maximize your solar energy generation potential. Both flexible and rigid solar panels are durable, lightweight, and can endure extreme weather.
For the EcoFlow Get Set 5kWh Kit and the two 100W rigid solar panels (mounting feet included), you could build this whole setup for 226 a month with financing or less than 8000.
Best Solar Power Kits for Tiny Houses
A tiny house is unlikely to have as many appliances as a normal-sized house. It’s why we recommend the EcoFlow 10kWh Prepared Kit. A 10kWh capacity provides substantial power to run your lights and appliances.
The compact size of the power kit lets you save space in your tiny house, and installation is a breeze. It uses a simple parallel connection, meaning you place all the battery units side by side and connect each wire to the Power Hub.
We recommend getting one or two 400W Rigid Solar Panels to give you enough daily electricity to power your tiny house. Rigid solar panels are highly durable under any weather condition and are easy to mount on a flat roof. If you have a slanted roof, flexible solar panels may be a more viable option — or you can consider a combination of the two.
For the EcoFlow 10kWh Prepared Kit along with the 400W Solar Panel, you could expect to pay approximately 14,000. Frequent discounts and sales at the EcoFlow online shop may make that price drop even lower.
Best Solar Power Kits for Full Off-Grid Powered Living
Living in a remote location requires homeowners to prepare for anything. Whether you’ve got tons of power-hungry appliances in your home or want backup power for consecutive cloudy days, choosing a system with sufficient capacity is vital.
We recommend EcoFlow’s 15kWh Independence Kit for DIY off-grid living. With three stackable 5kWh batteries and a Smart distribution panel, it’s a robust solution for fully independent off-grid living.
A 7-inch touchscreen lets you view all critical information and monitor the DC output and battery charging data in real-time. Additionally, you can customize the AC charging and discharging levels, AC input frequency, and 12/24 DC output voltage.
The EcoFlow app allows you to remotely monitor much of the Console’s data. Check the app to view the system’s health and update firmware anytime.
For a high-powered system like the 15kWh Independence Kit, we recommend at least two 400W Solar Panels. Depending on your home’s design, flexible solar panels can also help you maximize solar energy capture. The setup gives you enough power to supply your batteries and keep your home powered on demand.
The cost for the EcoFlow’s 15kWh Independence Kit and the two 400W rigid solar panels (mounting feet included) would average just under 500 a month with financing and less than 20,000 to purchase outright. With EcoFlow sales, you could even pay less than 15,000.
How to Calculate the Correct Size and Power Usage
To get the most out of your off-grid solar system, you must know how to size your system correctly to cover your energy usage.
Take a look at the following steps to size your solar system:
- Type of home: What do you plan on using your off-grid system to power? (RV, off-grid living, tiny house, etc.)
- Size of your home: How big is your home? Size is an essential consideration if you plan on mounting your panels on your roof.
- Appliances: What is your total daily energy consumption? Identify the appliances you need to power and the run time.
- Backup power: How long do you need backup power? If it’s common to experience consecutive days of cloudy weather, you’ll want to prepare accordingly. You may need to increase your storage capacity by adding extra batteries.
- Solar panels: What is the appropriate number of solar panels based on your daily energy consumption? A power-hungry household would need a higher solar panel power output, such as 400W. Take the panel’s watts and multiply that by the Peak Sun Hours in your area to estimate the total watts produced per day for each panel.
Using the EcoFlow Power Kit Calculator, you can accurately determine your usage and correctly size your solar power kit in minutes.
How Much Does an Off-Grid Solar System Cost?
The costs vary depending on the sizes and quality of each component. A significant share of expenses comes from the solar panel’s output, the number of panels you buy, and the solar battery storage capacity.
Here are estimated averages based on the rated power of the solar panels:
- 1kWh: 10,800 to 13,500
- 2kWh: 18,000 to 22,500
- 3kWh: 27,000 to 31,500
- 4kWh: 31,500 to 36,500
- 5kWh: 36,000 to 40,500
- 10kWh: 63,000 to 72,000
Know that the costs will likely be lower when you apply for the 26% federal tax credit and other available tax breaks and incentives.
Also, we’ll break down the cost by the equipment you’ll need:
- Solar panels: Monocrystalline solar panels cost between 1 to 1.50 per watt. Solar panels can cost between 5,000 to 30,000 depending on composition, rated energy output, and the size of your off-grid build.
- Charge controllers: Charge controllers are affordable and range from 50 to 1,000.
- Inverter: Range significantly in price between 3000 to 13,000.
- Solar Batteries: It costs several thousand to 30,000, depending on the battery type and storage capacity.
If you have a tiny home, RV, or trailer or live a minimalistic lifestyle, there’s a good chance your costs will be lower.
How Many Solar Panels Do I Need to Be Fully off the Grid?
The number of solar panels largely depends on the following:
- Your daily electrical usage
- The wattage your solar panel generates
- The number of peak sunlight hours in your area
By following the steps above, you can calculate your daily energy usage. From there, look for rigid, flexible, or portable solar panels that suit your needs. Depending on your region, some areas will have more sunlight hours than others. States like Arizona, California, Nevada, and Mexico have the most sunshine, while states like Alaska, Washington, Ohio, Indiana, and Michigan have the least.
Maintaining Your Off-Grid Solar System
Maintaining your off-grid solar system extends its lifespan. The most critical maintenance aspect is taking great care of your solar batteries.
Follow these guidelines for maintaining your solar battery bank:
- Monitor the charge level: The Depth of Discharge refers to the battery’s discharge levels. A battery bank will gradually lower its depth of discharge, meaning its capacity will decrease over time.
- Don’t mix batteries: Mixing old and new batteries can limit performance since aging batteries can degrade the quality of the new ones.
Besides the batteries, you also want to take care of your solar panels. Keep solar panels clean of dirt, debris, and pollen build-up, which impact the amount of sunlight received. Also, clean your solar panels annually to prevent residue from reducing the amount of power they can produce.
Is Going Off-Grid Right for You?
If you’re still on the fence about off-grid living, let’s consider why most people choose this lifestyle.
As with any renewable energy, solar power is better for the environment than fossil fuel energy. Solar power lets you generate electricity without emitting greenhouse gases, thus reducing your carbon footprint by leveraging the sun’s power.
Going off-grid with solar benefits our planet and helps us reach a net-zero future.
An off-grid solar solution is a practical choice for those living in areas without access to traditional electricity provided by utilities. Off-grid solar systems don’t rely on outside electricity and function independently, making them perfect for remote regions or places prone to blackouts.
Being independent of the grid also is advantageous in areas prone to harsh weather conditions like tornadoes and hurricanes. Whether traveling in an RV or living in a tiny home to reduce living costs, energy independence is why many people switch to off-grid solar power.
Frequently Asked Questions
Below are some common questions about off-grid solar systems:
Yes, you’re typically required to have a permit for off-grid solar. Although you don’t have to submit an interconnection utility agreement, a building permit is still mandatory. Although you won’t connect the system to a local utility grid, it still needs to pass inspection to ensure sound structural engineering and fire safety. Your off-grid solar system must pass various building electrical codes to ensure the power is safe and sufficient. Standard off-grid systems should meet the following regulations: Solar panel placement guidelines Standard domestic wiring requirements Auxiliary power generation requirements Power storage and conversion guidelines DC minimum wiring requirements Code requirements will vary by county and state. Check with your city or county Building Inspector’s office for a complete checklist.
An off-grid cabin typically needs between 5,000 to 7,000 watts per hour of electricity to run optimally. However, you’ll need to add up the running hours on the appliances you use to get the right amount of solar power tailored to your needs.
The number of solar panels needed to run a house off-grid entirely depends on the following factors: Amount of electricity your household uses Amount of direct daily sunlight The type of solar panel you choose Amount of useable roof space (if roof-mounted) The average kilowatts used for a household is around 11,000 kilowatt-hours per year. A 1500 sq. ft. home needs about 20 to 25 300W panels to go entirely free of the grid. RVs and smaller homes require significantly less.
With more people going off-grid than ever before, there’s never been a better time to join the energy independence movement.
It all starts with calculating your energy needs and finding the right size power kit for your RV, tiny home, or home to achieve full-time off-grid living.
Check out the options at EcoFlow today.
EcoFlow is a portable power and renewable energy solutions company. Since its founding in 2017, EcoFlow has provided peace-of-mind power to customers in over 85 markets through its DELTA and RIVER product lines of portable power stations and eco-friendly accessories.
How to Design and Install a Solar PV System?
Today our modern world needs energy for various day to day applications such as industrial manufacturing, heating, transport, agricultural, lightning applications, etc. Most of our energy need is usually satisfied by non-renewable sources of energy such as coal, crude oil, natural gas, etc. But the utilization of such resources has caused a heavy impact on our environment.
Also, this form of energy resource is not uniformly distributed on the earth. There is an uncertainty of market such as in the case of crude oil as it depends on production and extraction from its reserves. Due to the limited availability of non-renewable sources, the demand for renewable sources has grown in recent years.
Solar energy has been at the center of attention when it comes to renewable energy sources. It is readily available in an abundant form and has the potential to meet our entire planet’s energy requirement. The solar standalone PV system as shown in fig 1 is one of the approaches when it comes to fulfilling our energy demand independent of the utility. Hence in the following, we will see briefly the planning, designing, and installation of a standalone PV system for electricity generation.
- : A Complete Guide About Solar Panel Installation. Step by Step Procedure with Calculation Diagrams
Planning of a Standalone PV system
Site assessment, surveying solar energy resource assessment:
Since the output generated by the PV system varies significantly depending on the time and geographical location it becomes of utmost importance to have an appropriate selection of the site for the standalone PV installation. Thus, the following points must be considered for the assessment and selection of locations for installation.
- Minimum Shade: It must be made sure that the selected site either at rooftop or ground should not have shades or should not have any structure that intercepts the solar radiation falling on the panels to be installed. Also, make sure that there won’t be any structural construction soon surrounding the installation that might cause the problem of shading.
- Surface Area: The surface area of the site at which the PV installation is intended should be known, to have an estimation of the size and number of panels required to generate the required power output for the load. This also helps to plan the installation of inverter, converts, and battery banks.
- Rooftop: In the case of the rooftop installation the type of roof and its structure must be known. In the case of tilt roofs, the angle of tilt must be known and necessary mounting must be used to make the panels have more incidents of solar radiation i.e. ideally the radiation angle must be perpendicular to the PV panel and practically as close as to 90 degrees.
- Routes: Possible routes for the cables from an inverter, battery bank, charge controller, and PV array must be planned in a way that would have minimum utilization of cables and lower voltage drop in cables. The designer should choose between the efficiency and the cost of the system.
To estimate the output power the solar energy assessment of the selected site is of foremost significance. Insolation is defined as the measure of the sun’s energy received in a specified area over a period of time. You can find this data using a pyranometer, however, it is not necessary as you can find the insolation data at your nearest meteorological station. While assessing the solar energy the data can be measured in two ways as follows:
- Kilowatt-hours per square meter per day (KWh/m 2 /day): It is a quantity of energy measured in kilowatt-hours, falling on square meter per day.
- Daily Peak Sun Hours (PSH): Number of hours in a day during which irradiance averages to 1000 W/m 2.
Peak sun hours are most commonly used as they simplify the calculations. Do not get confused with the “Mean Sunshine Hours” and “Peak Sun Hours” which you would collect from the meteorological station. The “Mean sunshine hours” indicates the number of hours the sunshine’s were as the “Peak sun hours” is the actual amount of energy received in KWh/m 2 /day. Amongst all months over a period of year use the lowest mean daily insolation value as it will make sure that the system will operate in a more reliable way when the sun is least due to unsuitable weather conditions.
Calculation of Energy Demand
The size of the standalone PV system depends on the load demand. The load and its operating time vary for different appliances, therefore special care must be taken during energy demand calculations. The energy consumption of the load can be determined by multiplying the power rating (W) of the load by its number of hours of operation. Thus, the unit can be written as watt × hour or simply Wh.
Energy demand Watt-hour = Power rating in Watt × Duration of operation in hours.
Thus, the daily total energy demand in Wh is calculated by adding the individual load demand of each appliance per day.
Total energy demand Watt-hour = ∑ (Power rating in Watt × Duration of operation in hours).
A system should be designed for the worst-case scenario i.e. for the day when the energy demand is highest. A system designed for the highest demand will ensure that the system is reliable. If the system meets the peak load demand it will meet the lowest demand. But designing the system for the highest demand will increase the overall cost of the system. On the other hand, the system will be fully utilized only during the peak load demand. So, we have to choose between cost and reliability of the system.
Inverter Converter (Charge Controller) Ratings
For choosing the proper inverter both the input and output voltage and current rating should be specified. The inverter’s output voltage is specified by the system load, it should be able to handle the load current and the current taken from the battery bank. Based on the total connected load to the system the inverter power rating can be specified.
Let’s consider 2.5 kVA in our case, hence an inverter with power handling capacity having a size of 20-30% higher than the power running the load should be chosen from the market. In the case of motor load, it should be 3-5 times higher than the power demand of such an appliance. In the case of the converter, the charge controller is rated in current and voltage. Its current rating is calculated by using the short-circuit current rating of the PV module. The value of voltage is the same as the nominal voltage of batteries.
Converter and Charge Controller Sizing
The charge controller rating should be 125% of the photovoltaic panel short circuit current. In other words, It should be 25% greater than the short circuit current of solar panel.
Size of solar charge controller in amperes = Short-circuit current of PV × 1.25 (Safety factor).
For example, we need a 6 numbers each of 160W solar panels for our system. Following are the related date of PV panel.
Suppose the PV module specification are as follow.
The required rating of solar charge controller is = (4 panels x 10 A) x 1.25 = 50 A
Now, a 50A charge controller is needed for the 12V DC system configuration.
Note: This formula is not applicable on MPPT Solar chargers. Please refer to the user manual or check the nameplate data rating for proper sizing.
The size of Inverter should be 25% bigger than the total load due to losses and efficiency problem in the inverter. In other words, It should be rated 125% than the total load required in watts. For example, if the required wattage is 2400W, than the size of inverter should be:
So we need a 3kW of inverter in case of 2400W load.
Daily Energy Supplied to Inverter
Let us consider in our case the daily energy consumption by the load is 2700 Wh. Note that the inverter has its efficiency, thus the energy supplied to the inverter should be more than the energy used by the load, so the losses in the inverter can be compensated. Assuming 90% efficiency in our case, the total energy supplied by the battery to the inverter would be given as;
Energy supplied by the battery to the inverter input = 2700 / 0.90 = 3000 Wh/per day.
The inverter input voltage is referred to as the system voltage. It is also the overall battery pack voltage. This system voltage is decided by the selected individual battery voltage, line current, maximum allowable voltage drop, and power loss in the cable. Usually, the voltage of the batteries is 12 V so will be the system voltage. But if we need higher voltage it should be multiples of 12 V. i.e. 12 V, 24 V, 36 V, and so on.
By decreasing the current, power loss and voltage drop in the cable can be reduced, this can be done by increasing the system voltage. This will increase the number of batteries in the series. Therefore, one must choose between power loss and system voltage. Now for our case let us consider the system voltage of 24 V.
Sizing of the Batteries
While sizing the battery some parameters are needed to be considered as follows:
- Depth of Discharge (DOD) of the battery.
- Voltage and ampere-hour (Ah) capacity of the battery.
- The number of days of autonomy (It is the number of days required to power up the whole system (backup power) without solar panels in case of full shading or rainy days. We will cover this part in our upcoming article) to get the needed Ah capacity of batteries.
Let us consider we have batteries of 12 V, 100 Ah with DOD of 70%. Thus, the usable capacity of the is 100 Ah × 0.70 = 70 Ah. Therefore, the charged capacity that is required is determined as follows;
Required charge capacity = energy supplied by the battery to the inverter input/system voltage
Required charge capacity = 3000 Wh/ 24 V = 125 Ah
From this, the number of batteries required can be calculated as;
No. of batteries required = Required charge capacity / (100 × 0.7)
No. of batteries required = 125 Ah / (100 × 0.7) = 1.78 (round off 2 batteries)
Thus, 2 batteries of 12 V, 100 Ah are required. But due to round off 140 Ah instead of 125 Ah is required.
Required charge capacity = 2 × 100Ah × 0.7 = 140 Ah
Therefore, two 12 V, 100 Ah batteries in parallel to meet the above charge capacity. But as the individual battery is of 12 V, 100 Ah only and the system voltage requirement is of 24 V we need to connect two batteries in series to get the system voltage of 24 V as shown in figure 2 below:
So, in total there will be four batteries of 12 V, 100 Ah. Two connected in series and two connected in parallel.
Also, the required capacity of batteries can be found by the following formula.
Sizing of the PV Array
Different sizes of PV modules available in the market produce a different level of output power. One of the most common way to determine the sizing of the PV array is to use the lowest mean daily insolation (Solar irradiance) in peak sun hours as follows;
The total size of PV array (W) = (Energy demand per day of a load (Wh) / TPH) × 1.25
Nmodules = Total size of the PV array (W) / Rating of selected panels in peak-watts.
Suppose, in our case the load is 3000 Wh/per day. To know the needed total WPeak of a solar panel capacity, we use PFG factor i.e.
Total WPeak of PV panel capacity = 3000 / 3.2 (PFG)
Now, the required number of PV panels are = 931 / 160W = 5.8.
This way, we need 6 numbers of solar panels each rated for 160W. You can find the exact number of solar panels by dividing the WPeak by other rating i.e. 100W, 120W 150W etc based on the availability.
Note: The value of PFG (Panel Generation Factor) is varying (due to climate and temperature changes) in different regions e.g, PFG in USA = 3.22, EU = 293, Thailand = 3.43 etc.
over, the additional losses should be considered to find the exact panel generation factor (PGF). These losses (in %) occur due to :
- Sunlight not striking the solar panel straight on (5%)
- Not receiving energy at the maximum power point (excluded in case of MPPT charge controller). (10%)
- Dirt on solar panels (5%)
- PV panels aging and below specification (10%)
- Temperature above 25°C (15%)
Sizing of the Cables
The sizing of the cables depends on many factors such as maximum current carrying capacity. It should have a minimum voltage drop and have minimum resistive losses. As the cables would be placed in the outdoor environment it should be water-resistant and ultraviolet.
The cable must behave minimum voltage drop typically less than 2% as there is an issue of voltage drop in low voltage system. Under sizing of the cables will result in energy loss and sometimes can even lead to accidents. whereas the oversizing is not economically affordable. The cross-sectional area of the cable is given as;
- ρ is the resistivity of the conducting wire material (ohm-meters).
- L is the length of cable.
- VD is the maximum permissible voltage drop.
- IM is the maximum current carried by the cable.
Lets have a solved example for the above example.
Suppose we have the following electrical load in watts where we need a 12V, 120W solar panel system design and installation.
- An LED lamp of 40W for 12 Hours per day.
- A refrigerator of 80W for 8 Hours per day.
- A DC Fan of 60W for 6 Hours per day.
Now let’s find the number of solar panels, rating and sizing of charge controller, inverter and batteries etc.
Finding the Total Load
Total Load in Wh / day
= (40W x 12 hours) (80W x 8 hours) (60W x 6 hours)
= 1480 Wh / per day
The required wattage by Solar Panels System
= 1480 Wh x 1.3 … (1.3 is the factor used for energy lost in the system)
= 1924 Wh/day
Finding the Size and No. of Solar Panels
WPeak Capacity of Solar Panel
= 1924 Wh /3.2
Required No of Solar Panels
No of Solar Panels = 5 Solar Panel Modules
This way, the 5 solar panels each of 120W will capable to power up our load requirements.
Find the Rating and Size of Inverter
As there is only AC loads in our system for specific time (i.e. no additional direct DC load connected to the batteries) and our total required wattage is:
Now, the rating of inverter should be 25% greater than the total load due to losses in the inverter.
Inverter Rating Size = 225 W
Find the Size, Rating No of Batteries
Our load wattage and operational time in hours
= (40W x 12 hours) (80W x 8 hours) (60W x 6 hours)
Nominal Voltage of Deep Cycle Battery = 12V
Required Days of Autonomy (Power by batteries without solar panel power) = 2 days.
[(40W x 12 hours) (80W x 8 hours) (60W x 6 hours) / (0.85 x 0.6 x 12V)] x 2 days
The required capacity of batteries in Ampere-hour = 483.6 Ah
This way, we need a 12V 500Ah battery capacity for 2 days of autonomy.
In this case, we may use 4 number of batteries each of 12 V, 125Ah connected in parallel.
If the available battery capacity is 175Ah, 12 V, we may use 3 number of batteries. You can get the exact number of batteries by dividing the required capacity of batteries in Ampere-hour by the available battery Ah rating.
Required Number of batteries = Required capacity of batteries in Ampere-hour / Available battery Ah rating
Find The Rating and Size of Solar Charge Controller
The charge controller should be 125% (or 25% greater) than the solar panel short circuit current.
Size of solar charge controller in Amp = Short circuit current of PV × 1.25
The required rating of solar charge controller is = (5 panels x 8.8 A) x 1.25 = 44 A
So you can use the next nearest rated charge controller which is 45A.
Note that this method can’t be used to find the exact size of MPPT solar chargers. Please refer to the user manual provided by the manufacturer or see the nameplate rating printed on it.
Finding the Cable, CB, Switches Plug Ampacity
Use the following tools and explanatory posts with charts to find the exact amperage rating of wire and cables, switches plugs and circuit breakers.
The standalone PV system is an excellent way to utilize the readily available eco-friendly energy of the sun. Its design and installation are convenient and reliable for small, medium, and large-scale energy requirements. Such a system makes the availability of electricity almost anywhere in the world, especially in remote areas. It makes the energy consumer independent of the utility and other sources of energy such as coal, natural gas, etc.
Such a system can have no negative impact on our environment and can provide energy for long periods after its installation. The above systematic design and installation provide useful guidelines for our need for clean and sustainable energy in the modern world.
Standalone pv system
American Journal of Electrical and Electronic Engineering. 2018. 6(2), 72-76. DOI: 10.12691/ajeee-6-2-4
In this paper a standalone PV system for the electrification of a typical modern average home in Shewa Robit (Longitude and Latitude of 10°00′N, 39°54′E respectively with an elevation of 1280 meters above sea level) that can meet the electricity power demand successfully has been designed. So as to know the daily energy consumption, load estimation has been done by considering the floor plan of the home and the daily power consumption and energy demand of the house at peak hour were found to be 5.048kW/day and 11.619kWh/day respectively. The design result shows that a typical modern average home in Shewa Robit can be electrified by using sixteen sm-130 PV modules, six 6E120-13, 12V, 808Ah batteries, one 3kW inverter, one Schneider (Xantrex) C35, 12/24V charge controller and 20m, 53.5mm 2 copper conductor with the total investment cost of 12,960.36 which gives a unit cost of energy (COE) of 0.058 /kWh.
Smart electrification will allow us to make better use of energy, reduce emissions and ultimately help to mitigate climate change. In Ethiopia there is a huge shortage of electric power which intern affects daily routines and overall performance of people 1, 2. When power is available, it is not free from power quality problems like fluctuations; harmonics, voltage sag and voltage swell 1, 2, 11, 14. Hence utilizing renewable energy resources in an off-grid manner with distributed generation for homes is an imperative solution to overcome this problem 10, 11. To design and implement such systems, the task is started from load estimation and resource potential assessment as described by Figure 1 below.
Here the need is in order to properly size those components of the system indicated in Figure 1 by considering a load on the typical modern average home. A typical modern average home in Shewa Robit contains one salon, two bed rooms, corridor, terrace/veranda, one kitchen, one shower and one toilet. Usually the kitchen, toilet and shower are separated from the main house. So as to estimate the load, efficient household equipment has been selected and lamps used for this study are also compact florescent types (CFLs) with 11 W and 15W rating as presented in 2. Table 1, Table 2 and Table 3 presented below shows the detailed load estimation for this study.
Table 2. Summary of equipment loads in the typical modern average home
Table 3. Summary of overall system load in the typical modern average home
From Table 3 above, we need to have 5.048 kW of power from the inverter output as we have this amount of connected load in to the PV system plant. Therefore; the efficiency of the inverter has to be taken in to account so as to know the adjusted wattage that has to be given by the battery and interred in to the inverter. So that we can have the rated output of 5.048 kW from the inverter output this is equal to the load wattage to be served.
Most literature showed that the inverter efficiency is equal to 85% 5, 6, 7, 8 and we expect the output from the inverter to be 5.048kW. Hence, the input power to the inverter that has to be delivered by the battery is:
Therefore the total wattage expected to be supplied from the Battery is approximately equal to 5.938kW = 5938W.
Design (System Sizing)
Total amp-hour demand per day
Required battery Capacity
Day of Autonomy is days of storage desired and for a design purpose it is three to five days 4, 5, 7, 16. And for this application 4 days is selected.
From the battery specification sheet 6E120-13, 12V, 808Ah battery is selected for this study.
Note that when we are going to select a battery from the data sheets, we have to look for the battery which gives (Battery capacity (Designed))/Capacity of selected battery) near to a whole number.
Therefore; we need to have a total of 2×3 = 6 batteries for the whole system. The two batteries have to be connected in series and then these strings have to be connected in parallel.
3.2. Photovoltaic Array Sizing3.2.1. Calculating the Area Needed by the PV Module/Array
The total annual energy consumption by the house hold is given by 4240.935kWh/year. The worst case (summer) solar radiation in Sehwa Robit (where the house in question is located) is equal to 5.28kWh/m²/day in July 9, 12. Hence, the annual solar power radiation is 5.28kWh/m²/day × 365 days/year = 1927.2 kWh/m²/year.
The area required to generate the required power is:
The PV module of Sm-130 is selected for this work. The efficiency of PV cell ranges from 6%. 30% 13, 16. And in this work 15% efficiency is assumed as it is the efficiency of the selected PV module.
3.2.2. PV Module Number Determination
Required array output / day
Selected PV modules maximum power voltage is then = 17.6 × 0.85= 14.96V
Selected PV modules guaranteed power output = 130 × 0.9 = 117 W and peak sun hour at optimal tilt is equal to 8 hours. Therefore;
For stand-alone systems, the inverter must be large enough to handle the total amount of watts in the system. As a standard design procedure the inverter size should be 25-30 % bigger than total watts of peak wattage from the photovoltaic panels 6, 15.
Since the total peak wattage required from the PV module is 2080 watts or 2.08 kW,
The inverter size should be about 3 kW or greater.
3.4. Solar Charge Controller Sizing
According to standard practice, in any PV system design, the sizing of solar charge controller is to take the short circuit current (Isc) of the PV array, and multiply it by 1.3 2, 3, 18. From the specification data sheet of the selected module, Isc = 8.13A. Hence,
So the solar charge controller should be rated 85A at 24 V or greater.
3.5. Conductor Sizing
VDI is Voltage Drop Index where Amps indicate the nominal current of the PV module; cable length is assumed to be 20m = 65.6 feet as most modules are installed in the roofs of the house it is a reasonable assumption. % Volt drop is the acceptable voltage drop level (10%) and Voltage (DC) is the system DC bus voltage. Then according to VDI result, an appropriate conductor size will be selected from the table.
From the universal cable size data sheet the nearest voltage drop index (VDI) to this value is found to be 49.Therefore; the size of the cable corresponding to this VDI is 53.5 mm 2.
Result Summery and Cost Estimation
The overall system architecture (system sizing result) of a standalone photovoltaic based power supply unit and its cost estimation is presented in table 4 below.
To evaluate the system unit energy cost, an assumption of 10% interest rate (represented by i) and a project life span of 25 years (represented by n) are taken in to consideration from 3, 17. Therefore; the annual total cost and the unit energy cost per year can be calculated as follows.
C I = Capital Cost = 12, 960.36
C OM = Operation and Maintenance Cost
The unit energy cost is determined by dividing the total annual cost by the total energy consumed usefully per year.
In short in this study deign of solar PV system for a modern average home in Shewa Robit is presented in a clear and step by step calculation approach. Hence the work can be used as a good reference material for PV system designers, researchers and for education purpose.
Based on the system sizing and cost estimation result, the author of this work believes that, implementation of such systems may be slightly worrisome when we see from the economy of residents’ perspective. However, considering the shortage of power in the town and country at large (only 27.2 % coverage in the year 2017 1 ), the increment of day to day governmental and non-governmental organization subsidies towards renewable energies, this cost should not be seen as a significant impairment.
over, regarding its role in the protection of vegetation and forestry and therefore the prevention of soil degradation, the improvement to the quality of life of the many people residing in the town, the future situation regarding fossil fuel sources, and its contribution to the reduction of pollutant emissions in to the environment such distributed energy systems are useful.
It should be also noted that free solar energy will also be utilized, load will be satisfied in an optimal way; help is given to the mobilization of investments towards clean energy; and, most of all, the poor will benefit from the electric light provide from the grid.
The author of this work would like to thank National Metrological Service of Ethiopia for their kind response to give some valuable solar data. He also thanks Dr. Getachew Bekele for his knowledge transfer of distributed generation concept.
Conflict of Interests
The author of this work declares that there is no any conflict of interests regarding the publication of this paper.
/kWh: Dollar per kilowatt-hour
CFL: Compact Fluorescent Lamp
C om : Operation and maintenance cost
I sc : Short circuit current
V m : Maximum power voltage
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Published with license by Science and Education Publishing, Copyright © 2018 Mikias Hailu Kebede
This work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
Cite this article:
Mikias Hailu Kebede. Design of Standalone PV System for a Typical Modern Average Home in Shewa Robit Town-Ethiopia. American Journal of Electrical and Electronic Engineering. Vol. 6, No. 2, 2018, pp 72-76. http://pubs.sciepub.com/ajeee/6/2/4
Kebede, Mikias Hailu. Design of Standalone PV System for a Typical Modern Average Home in Shewa Robit Town-Ethiopia. American Journal of Electrical and Electronic Engineering 6.2 (2018): 72-76.
Kebede, M. H. (2018). Design of Standalone PV System for a Typical Modern Average Home in Shewa Robit Town-Ethiopia. American Journal of Electrical and Electronic Engineering, 6(2), 72-76.
Kebede, Mikias Hailu. Design of Standalone PV System for a Typical Modern Average Home in Shewa Robit Town-Ethiopia. American Journal of Electrical and Electronic Engineering 6, no. 2 (2018): 72-76.
What is an Autonomous PV System?
An autonomous PV system is also known as a stand alone PV system. The autonomous System is a hybrid or autonomous photovoltaic system that is not wired into the grid. The majority of standalone systems need batteries or some other kind of storage, while some may or may not have storage.
Why are Autonomous PV Systems Developed?
Due to the growth of solar, wind, energy storage, electric vehicles, and building automation, energy systems have become more heterogeneous. Future energy systems will need to be able to control and communicate securely, autonomously, and reliably with billions of buildings, vehicles, and other things in addition to the millions of distributed generation locations. In order to find clever and reliable solutions for running highly electrified, heterogeneous energy systems, NREL developed the idea of AES (Autonomous Energy Systems) and carried out foundational research.
What Makes Up an Autonomous PV System?
A number of individual photovoltaic modules (or panels), typically 12 volts and with power outputs ranging from 50 to 100 watts each, make up an off-grid or Stand Alone PV System. The desired output of power is then produced by combining these PV modules into a single array.
Where are Standalone PV Systems Used?
In isolated rural areas and for applications where alternative power sources are either impractical or unavailable to supply power for lighting, appliances, and other uses, stand-alone PV systems are perfect. In these situations, installing a single standalone PV system is more affordable than paying for the local power company to attach power lines and cables to the residence as part of a grid-connected PV system.
An electrical system made up of a collection of one or more PV modules, conductors, electrical parts, and one or more loads is called a stand-alone photovoltaic (PV) system. However, for household purposes, a small-scale off-grid solar system does not always need to be tied to a rooftop or building structure. RVs, camper vans, yachts, tents, and other off-grid structures can all be powered by solar energy. Many businesses, including Amazon, now provide portable solar kits that let you generate your own trustworthy, cost-free solar electricity wherever you go, even in remote areas.
Elliot is a passionate environmentalist and blogger who has dedicated his life to spreading awareness about conservation, green energy, and renewable energy. With a background in environmental science, he has a deep understanding of the issues facing our planet and is committed to educating others on how they can make a difference.