If you have decided to install a solar panel system to cover your home power needs, then this tutorial is for you.
I have tried my best to guide you step by step, from buying different components to wiring everything by yourself.
(Want to know about the 13 proven and best ways to generate power off-the-grid? Click to grab
The 13 Proven Ways to Generate Power Off-the-Grid)
You have to know some basic electrical and math for designing the entire system. I have also attached links of my other instructions to make the charge controller and energy meter.
For an off grid solar system you need four basic components
- Solar Panel (PV Panel)
- Charge Controller
- Inverter
- Battery
How the solar system fits together
In the next few steps I will explain in details how you can choose the above components according to your requirement.
Note: In the pictures I have shown a big solar panel of 255W @ 24V, two batteries of 12V @ 100Ah each, 30A @ 12/24V PWM solar charge controller and a 1600 VA pure sine wave inverter. But during the calculation I have taken a smaller solar system example for better understanding.
Step 1: Calculate Your Load
Before choosing the components you have to calculate your power load, how much time it will run, etc. It is very simple to calculate if you know basic math.- Decide what appliances (light,fan,tv etc ) you want to run and how much time (hours).
- See the specification chart in your appliances for power rating.
- Calculate the Watt Hour which is equal to the product of the power rating of your appliances and run time (hours).Load Calculation Example:Lets you want to run a 11W compact fluorescent lamp (CFL) for 5 hours from a solar panel, then the watt hour is equal to: Watt Hour = 11W x 5 hr = 55
- Calculate the total Watt Hour: Just as with the CFL we’ll now
calculate the watt hour for all the appliances and add them together.Example:CFL = 11W x 5 hr = 55Fan = 50 W x 3hr = 150TV = 80W x 2hr = 160
Total Watt Hours = 55+150+160 = 365
If you are not interested in doing the above maths then use a load calculator for this calculation. There are many such load calculators available in the internet, for example this Off Grid Load Calculator.
Step 2: Battery Selection
The batteries I use for my solar system
Top view of the batteries
- Most of the appliances need a constant rated voltage to run efficiently. Solar panel voltage is not constant, it varies according to the sun light.
- If you want to run the appliances during the night then it is impossible.
Video: Battery Selection for Solar Power
There are various kind of batteries. Car and bike batteries are designed for supplying short bursts of high current and then be recharged and are not designed for a deep discharge. But the solar battery is a deep-cycle lead-acid battery that allows for partial discharge and allows for deep slow discharge. Lead acid tubular batteries are perfect for a solar system.Ni-MH batteries and Li-Ion batteries are also used many small power application.
Note: Before going to choose the components decide your system voltage, 12/24 V or 48 V. The higher the voltage, the lesser the current and the lesser the copper loss will be in the conductor. This will also reduce your conductor size. Most of the small home solar systems will have 12 V or 24 V.
In this project I’ve selected the 12 V system.
Rating of Battery:
Batteries capacity are rated in term of Ampere Hour.Power = Voltage X Current
Watt Hour = Voltage (Volts) x Current (Amperes) x Time (Hours)
Battery Voltage = 12V ( as our system is 12V)
Battery capacity = Load / Voltage = 365/12 = 30.42 Ah
But batteries are not 100% efficient, assuming 80% efficiency
Capacity = 30.42/0.8 = 38.02 Ah
By taking some margin you can select a 40Ah deep cycle lead acid battery.
Step 3: Solar Panel Selection
A big 255W solar panel @ 24V
Solar panel ratings for the 255W solar panel
Solar panels are generally rated under standard test conditions (STC): irradiance of 1,000 W/m², solar spectrum of AM 1.5 and module temperature at 25°C.
Rating of Solar Panel:
The solar panel size should be selected in such way that it will charge the battery fully in one sunny day.During the 12hr day time the sunlight is not uniform, and it also differ according to your location on the globe. So we can assume 4 hours of effective sunlight which will generate the rated power.
So total power output of Panels = 12V x 40Ah = 480Wh
Power to be generated per hour = 480 / 4 = 120W
By taking some margin you can choose a 125 W, 12v solar panel.
Step 4: Charge Controller Selection
An example charge controller
Another charge controller
Usually, the solar power systems uses 12 volt batteries, however solar panels can deliver far more voltage than is required to charge the batteries.
By, in essence, converting the excess voltage into amps, the charge voltage can be kept at an optimal level while the time required to fully charge the batteries is reduced. This allows the solar power system to operate optimally at all times.
Types of Charge Controllers:
- ON OFF
- PWM
- MPPT
Among the 3 charge controllers MPPT have the highest efficiency but it is also costly. So you can use either PWM or MPPT.
Rating of Charge Controller:
Since our system is rated at 12V, the charge controller is also 12V.Current rating = Power output of Panels / Voltage = 125 W / 12V = 10.4 A
So choose a Charge Controller of 12 V and more than 10.4 A.
If you like to reduce your system cost you can make your own PWM charge controller. For step by step instructions you can see my instructable on building a PWM Charge Controller.
You may also like my new 3.0 design of an Arduino MPPT Solar Charge Controller.
Step 5: Inverter Selection
My 1600 VA pure sine wave inverter
Video: Why We Need an Inverter in a Solar PV System
Solar panels (PV) receive the sun’s rays and convert them into electricity called direct current (DC). DC is then converted into alternating current (AC) through a device called an Inverter. AC electricity flows through every outlet of your home, powering the appliances.Inverter Types
- Square Wave
- Modified Sine Wave
- Pure Sine Wave
So in my opinion choose a pure sine wave inverter.
It may be grid tie or stand alone. In our case it is obviously stand alone and completely off-the-grid.
Rating of Inverter:
The power rating should be equal or more than the total load in watt at any instant.In our case the maximum load at any instant = Tv (50W) + Fan (80W) + CFL (11W) = 141W
By taking some margin we can choose a 200W inverter.
As our system is 12V we have to select a 12V DC to 230V/50Hz or 110V/60Hz AC pure sine wave inverter.
Note: Appliances like fridge, hair drier, vacuum cleaner, washing machine, etc. likely have a starting power consumption several times greater than their normal working power (typically this is caused by electric motors or capacitors in such appliances). This should be taken into account when choosing the right size of inverter.
Step 6: Mounting the Solar Panel
After designing the solar system, buy all the components with appropriate rating as per the previous steps.Now it is time to mount the solar panel. First choose a suitable location on the roof top, or on the ground, where there is no obstruction of sunlight.
Prepare the mounting stand: You can make it by your own or buy one. In my case I have taken the drawing from the solar panel company and made it at a near by welding shop. The tilt of the stand is nearly equal to the latitude angle of your location.
The stand for my big solar panel
The DIY stand for my 10 watt solar panel
My 10 watt solar panel mounted on the stand
If your latitude is below 25°, use the latitude times 0.87.
If your latitude is between 25° and 50°, use the latitude, times 0.76, plus 3.1 degrees.
For more details on tilting click here
First, place the stand in such a way that the face is directed towards south (or north if you’re in the southern hemisphere. Mark the leg position over the roof.
To get the south / north direction use this compass android app (or even better, a real, physical compass!)
I decided to secure my 255W solar panel mount on my roof with concrete. I roughened up the surface at each leg of the stand by using a sharp object. I made around a 1 square feet size rough surface on the roof at each leg. This is helpful for perfecting the bonding between the roof and concrete.
Prepare concrete mix: Take cement and stones with 1:3 ratio then add water to make a thick mix. Pour concrete mix at each leg of the stand. I made a heap shape concrete mix to give maximum strength.
(You can of course secure it into place using other methods than concrete, this is just an example of a solution for my specific situation)
Mount the panels to the stand: At the back sides the solar panel have inbuilt holes for mounting. Match the solar panel holes with the stand/platform holes and screw them together.
Mounting the solar panel
The junction box
Step 7: Series and Parallel Connection
After calculating the battery capacity and solar panel rating you have to wire them. In many cases the calculated solar panel size or battery is not readily available in the form of a single unit in the market. So you have to add a small solar panel or batteries to match your system requirement. To match the required voltage and current rating we have to use series and parallel connections.1. Series Connection:
To wire any device in series you must connect the positive terminal of one device to the negative terminal of the next device. The device in our case may be solar panel or battery.
In series connection the individual voltages of each device is additive.
Example:
Lets say 4 12V batteries are connected in series, then the combination will produce 12 + 12 + 12 + 12 = 48 volts.
In series combination the current or amperage is same.
So if these devices were batteries and each battery had a rating of 12 Volts and 100 Ah then the total value of this series circuit would be 48 Volt, 100Ah. If they were solar panels and each solar panel had a rating of 17 volts (Osc voltage) and were rated at 5 amps each then the total circuit value would be 68 volts, 5 amps.
2. Parallel Connection:
Parallel Connection
In parallel connection the voltage is remain same but the current rating of the circuit is the sum of all the devices.
Example:
Lets say two batteries of 12v, 100Ah are connected in parallel – then the system voltage remains 12 volts but the current rating is 100 + 100 = 200Ah. Similarly if two solar panels of 17V and 5 amps are connected in parallel then the system will produce 17 Volts, 10 amps.
Step 8: Inverter and Battery Stand
The battery and inverter stand that I built
At the back side I made a big circular hole just behind the inverter fan for fresh air suction from the outside. Later I covered the hole with plastic wire mesh. A few small holes are also made for inserting the wires from the solar panel, charge controller and inverter to the battery and AC output to the appliances. At both sides 3 horizontal holes are provided for sufficient ventilation. A glass window is provided at the front side to view the different led indications on the inverter.
Inside view of the inverter stand
Step 9: Wiring
How to wire the system
Closeup of the charge controller wiring
Wiring of the charge controller
Note: First connect the black / negative wire from the battery to the charge controller’s negative terminal, then connect the positive wire.
After connecting the battery with the charge controller you can see the Charge Controller indicator led lights up to indicate the battery level.
After connecting this, inverter terminals for battery charging is connected to corresponding positive and negative terminals of the battery.
Inverter wiring
Inverter AC output
Solar panel junction box wiring
An MC4 connector
Safety: It is important to note that we are dealing with DC current. So the positive (+) is to be connected to positive (+) and negative (-) with negative (-) from Solar Panel to Charge Controller. If it gets mixed up, the equipment can break and may catch fire. So you need to be extremely careful when connecting these wires. It is recommended to use 2 color wires i.e. red color for positive (+) and black color for negative (-). If you don’t have red and black wire you may wrap red and black tape at the terminals.
Connect the DC load or DC light as the final step.
Additional Protection: Though charge controller and inverter have inbuilt fuses for protection, you can put switches and fuses in the following places for additional protection and isolation.
- In between solar panel and charge controller
- In between charge controller and battery bank
- In between battery and inverter
Metering and Data logging:
If you are interested to know how much energy is produced by your solar panel or how much energy being consumed by your appliances you have to use energy meters.
My DIY energy meter
For a DIY based energy meter you can see my instructable on building an energy meter which have both metering and data logging capability.
Thank you for reading my instructions!
(Want to know about the 13 proven and best ways to generate power off-the-grid? Click to grab The 13 Proven Ways to Generate Power Off-the-Grid)
License: CC BY-NC-SA 2.5
Want more like this?
This is just one aspect of self-reliance. You'll find more in our 100% free online Self-Reliance Catalog, a carefully curated collection of the best in self-reliance & resilience
The goal of The Self-Reliance Catalog is to help you know better what is worth getting and where and how to do the getting, whether that “thing” is a plant, a tool, a book, or even a design for a home or greenhouse.
No comments:
Post a Comment