Solar Energy for Beginners

mank1234

Solar energy is radiant light and heat from the Sun that is harnessed using a range of ever-evolving technologies such as solar heating, photovoltaics, solar thermal energy, solar architecture, molten salt power plants and artificial photosynthesis..

mank1234

The following books are very helpful for the newbies. It takes care of the basics including earthing to avoid damages due to lightening.

solar-energy-handbook.pdf

4MB

currentratings.pdf

154kB

schneider-earthing.pdf

451kB

surge-protection-overvoltage-devices.pdf

1MB

mank1234

Safety is the number one consideration in any installation. What can possibly go wrong if an installation is not done right?

Fire - usually when wrong wire size or equipment is used.
Electric shock - when there is current leakage due to insulation failure or poor earthing.
Damage to equipment - due to improper earthing, overloading, poor installation etc
Dissatisfaction - installation not meeting expectations
Inability to recoup cost (low return)

earthrealm

Chief, na only you waka come😁😁

mank1234

earthrealm
Welcome one of my solar guru and mentor. I sight you. Please join me in sharing from your wealth of experience.

brabus

earthrealm silently following the class

mank1234

How does solar system work
All solar power systems work on the same basic principles. Solar panels first convert solar energy or sunlight into DC power using what is known as the photovoltaic (PV) effect. The DC power can then be stored in a battery or converted by a solar inverter into AC power which can be used to run home appliances. Depending on the type of system, excess solar energy can either be fed into the electricity grid for credits, or stored in a variety of different battery storage systems. For the different battery types, see https://www.kobocity.com/d/36-which-battery-is-the-best-value-for-money-wise/11

DSquare

mank1234

What make up a solar system installation
A typical solar system setup will have the following components.

solar panels: to covert solar energy into electrical energy
DC circuit breaker or fuse , DC surge arrester, DC disconnect switch, blocking diode: disconnect switch is to prevent flow of current to the upstream system in case of maintenance. Breaker or fuse to protect the wiring from excessive current and the protect the solar panel in case of unintended flow of back current. Surge arrester to protect inverter and household appliances from lightening. Blocking diode is necessary when you have more than 2 string of solar in the same circuit.
combiner box: usually houses the DC safety devices above and ensure that 2 or more strings of solar are combined neatly
solar charge controller CC: the voltage and current from the solar panels fluctuates as solar isolation changes through the course to the day. CC converts this fluctuating voltage into a steady voltage that the inverter or battery can accept.
power inverter: coverts the DC voltage from the CC/battery into AC that appliances in the house can use.
battery: stores energy (DC) for later use.
AC breaker and SC disconnect switch and SC surge arrester (functions in similar manner as the DC counterpart)
mounting kit for the solar panel and wire
Note: some inverters have charge controller inbuilt thus eliminating the need to buy them separately.

mank1234

The three main types of solar power systems

On-grid - also known as a grid-tie or grid-feed solar system
Off-grid - also known as a stand-alone power system (SAPS)
Hybrid - grid-connected solar system with battery storage
Second image is an example of grid tie setup.

mank1234

Planning your system
The first step in planning your setup is to do load analysis.

You must find out your daily energy need.
You must also determine how much energy you consume between the hour of 4pm and 8am (usually called night time energy usage).
You must also find out how much power your appliances consume at startup.
Determine if you will be totally off-grid. If you’ll be totally off-grid, you also have to decide to run your power hungry load during the day except you’re very big pocket wise 😂
There may be other things to consider on a personal level (eg is it a rented apartment, can you mount your panel on the roof etc)

mank1234

mank1234 daily consumption
Your solar panel must be able to generate at least this much energy in a day.

If using lead acid battery it should be able to generate, 1.25 of this energy as lead acid battery has efficiency of about 80%.

If you plan to use Lithium, your generation should just be equal to your daily need.

mank1234

mank1234 Night time use
Your battery bank must be able to take care of this energy usage.

If you are going to use lead acid battery, you have to also consider the dept of discharge (DOD) that is acceptable to you since discharging too deep your battery will reduce its lifespan. Assuming 50% DOD, your battery should have capacity of 2 times your night time energy use.

Again, if you are in Southern Nigeria, you must must necessarily oversize your battery bank to take care of 3 days without sunshine. That means your battery bank should be 3 times your night time daily energy usage.

If you don’t want to do the above, you must have standby generator or a connection to the national grid.

mank1234

mank1234 maximum appliance surge power
Your selected inverter must have surge capability above this limit, else it will spoil sooner or later. If more than one appliance has huge startup surge figure, you need to sum them up if the probality of them starting up at the same time is great.

If you intend to use this appliance at night time (see quote mank1234) your battery too would have to be able to handle this surge.

A 12V lead acid battery is made up of 6 cells. Surge power draw is a major cause of premature battery failure where just one out of the 6 cells is destroyed thus causing loose of capacity in a short time.

mank1234

In the coming days, I’ll work through a typical design and planing for a household that consumes 100kWhr of energy from the national grid in a month going completely Off-grid. The household has the following appliances with high surge startup power - 1hp water pumping machine 7kw startup surge, fridge 1.2kw startup surge, freezer 1.5kw startup surge. Other appliances with low startup current requirement are not listed.

mank1234

mank1234
Calculations & Sizing of Equipment

First we have to select a capable inverter. Our starting point is surge capability: our inverter should be able to handle 7kW + 1.2kW + 1.5kW surge (i.e 9.7kW assuming all were to start at once). Most inverters have surge capability of 2 times its power rating, so we go with a 5kW.inverter.
Next we select our working voltage. At 5kW, if we go with 12V setup, maximum current draw by inverter will be 5000/12 = 416.7A, which is too high; at 24V it will be 208.3A; 104.2A at 48V. The higher the current the thicker the wire required. So we settle for a 48V setup.
Next is battery requirement for night time usage. assuming the customer above consumes an average of 2kW each night (4pm to 8am), it means he needs battery of 6kWhr to take care of 2 extra days with inadequate sunshine. If he is going for lead acid battery and he wants 60% DOD, it means he will need 6kWhr/0.6=10kWhr battery storage.
Number of 12V 200AH battery needed =
10000/(200 × 12) = 4.2 = 4 batteries of 12v 200ah connected in series to get 48V 200AH
Next is solar panel required. For a home that consumes 100kWhr a month, daily consumption = monthly consumption divide by number of days in a month, that is 100kWhr/30days = 3.34kWhr a day.
But we have to factor in inefficiencies in the system.
A 5kW inverter will have say 100W self consumption when loaded which in 24hrs will sum up to 2.4kWhr.
Total energy to produce for panel in a day = 3.34kWhr + 2.4kWhr = 5.74kWhr
In Nigeria a watt of solar is capable of producing 2 to 4 watt hour a day. So we will work with the low case scenerio. This is akin to the solar panel producing full power for 2 to 4 hours.
Wattage of solar panel needed = daily consumption divide by a multiple of what the panel can produce in a day.
Total solar panel wattage needed = 5.74kWhr/2hr = 2.87kW.
To enjoy solar energy go for Maximum Power Point Tracking (MPPT) CC rather than Pulse Width Modulation (PWM) CC.
Select your solar panel to closely match this energy requirement. It should be in multiples of two except you’re using high voltage CC (up to 500V)
We need to determine the number of solar panel we need and in what size each. Solar panel comes in different sizes. Common sizes are 100W, 150W, 200W, 225W, 250W, 280W, 300W, 325W 350W etc.
Divide total solar panel wattage by the solar panel you want to select.
Here, I’ll be selecting 300W solar panel,
So 2.87kW/0.3kW = 9.6 = 9 or 10 panels each of 300W, choice will depend on how many panel is in a string.
Note1: The maximum voltage of a string should not exceed the voltage rating of the charge controller below.
Note2: If the string is more than two ensure to use reverse blocking diode in each string to prevent damage to the panel because not all panel have this built in and even those that have are rated to a small current.
Next we choose charge controller. The charge controller should be MPPT as stated above and should be able to handle 3000W and able to charge a 48V battery string. The CC should be able handle a current of 3000W/48V = 62.5A.
Wiring and circuit breaker selection.
1) charge controller to battery: breaker of 1.25 × 62.5A = 78.13, so use 80A breaker. No surge device required
2) Inverter to battery: breaker of 5kW/48v = 104A. Use 100A, you won’t reach this 104A current except during startup for few seconds which isn’t long enough to trip the device and the probability of all 3 starting at the same time is slim. No surge device
3) Inverter to load: use isolation switch from inverter. Use breaker on each individual load circuit separately. AC Surge device required to protect load.
4) solar to CC: use breaker on each string, put an isolator after combining the string, use DC surge to protect CC.

SuleimanKano

Insightful

mank1234

Charge controller
Your charge controller should be matched to your battery bank (12V or 24V or 48 or 96V setup as the case may be) and should be able to handle the power from the solar panel. You can parallel some charge controller (CC) if the power is too much for one CC to handle but you can’t combine two CC on one string of solar.

mank1234

Advantage of an efficient and well calculated setup cannot be overemphasized. I’m still using the same inverter and charge controller I got more than 15 years ago and will only change when I see the need to embrace new technology.

mank1234

An alternative method exist where the household loads are listed and the length of time it will be on use to calculate total energy requirement. If done right one should be able to reach the same conclusion.

mank1234

Major equipment list for the 100kW monthly energy consumption with maximum of 2kWhr daily night time consumption and 9.7kW maximum opportunistic startup surge is (totally Off-grid) :

5kW inverter with 2x surge capability
80A MPPT charge controller
9 to 10 300W solar panels
4 200AH12V lead acid battery (9.6kWhr) or 5kWhr Lithium battery

mank1234

Dijita equipment list is listed here: mank1234
Cost varies depending on your pocket size.
Inverter. You can check one of this verified sites:
https://prag.global/buyright-nigeria/
https://solarshopnigeria.com/
https://www.solardepotng.com/