Off-Grid stand-alone photovoltaic system Basic Design with technical specification.

As we know stand-alone (off grid) photovoltaic system is powering loads that are not connected to the utility grid.

Few main advantages is Gain energy independence & Access to electricity or reduce diesel generator costs for your home. Let’s first we focused on Technical Specifications of BOM.

  1.  PV MODULES – PV modules must conform BIS Standards IEC 61215 / IS14286/IEC 61730. Each PV module must use a RF identification tag (RFID), which must contain the Month and year of the manufacture (separately for solar cells and module), Country of origin (separately for solar cells and module), I-V curve for the module, Peak Wattage, Im, Vm Temp. for the module.
  2. BATTERY BANK – The batteries shall be solar photovoltaic batteries of flooded electrolyte, low maintenance, lead Acid. The Storage batteries should conform IEC 61427 / IS 1651 / IS 13369 as per specifications. There must be Battery protection panel and contain suitable wooden rack, hydrometer, thermometer, cell tester and connecting leads etc.
  3. Power Conditioning Units (PCU) – PCU refers to combination of Solar charge controller and inverter and shall be supplied as integrated unit. PCU should conform IEC 61683, IEC 60068 as per specifications. while selecting PCU we must have to consider Switching device, Input voltage from PV array, Protections eg. (Short circuit protection, Input under voltage / Deep discharge of battery, Input surge voltage protection, Over current,  Battery reverse polarity protection etc.), Cooling, Sine-wave output with THD at full load UPF and nominal input voltage, AC charger input & %Regulation.
  4. Charge Controller Unit (CCU) – The charge controller, controls the output of the solar array and prevents the batteries from being overcharged. There are two basic types available a PWM and a MPPT. Charge Controller Unit shall be dual input type from SPV & Grid Main Supply, however the input is fed from a SPV panel only for battery charging. The charge controller shall be preferably PWM type employing IGBT switching elements. Charge controller should conform IEC 62093 / IEC 60068 as per specification. while selecting CCU we must know following, Protections – (Short Circuit, Deep Discharge, Input Surge Voltage, Over Current (load), Battery Reverse Polarity, Solar array reverse polarity) Also there is requirements of following indication (String ‘ON’, Main ‘ON’, Charging ‘ON’, 80% Charged, 100% Charged, Charger Overload, Battery On Trickle. Battery disconnected / Fault Battery Reverse Polarity, Low Solar Power, System Fault and Charger over Temperature and Input Over / Under Voltage (for AC).
  5. DC DISTRIBUTION BOARD (DCDB) – A DCDB shall be provided in between PCU and Solar Array. It shall have MCCB of Suitable rating for connection and disconnection of array section. It shall have meters for measuring Array voltage and Array current.
  6. Inverters – Inverters shall be of very high quality having high efficiency and shall be completely compatible with the charge controller and distribution panel. Inverter should conform IEC 61683, IEC 60068 as per specifications. while selecting inverter consider following – Nominal Capacity (KVA/Kwp), Input Voltage, Efficiency, Overload Capacity, Regulation, Total Harmonic Distortion may be Less than 3%, Protection – (Over Voltage both at Input & Output, Over Current both at Input & Output, Over Frequency, Surge voltage inducted at output due to external source.)
  7. Cables & Wirings – Cables shall be conforming to IEC 60227/ IS 694 & IEC 60502/ IS 1554 & Voltage rating – ( 1,100V AC, 1,500V DC). For the DC cabling, Solar Cables, XLPE or XLPO insulated and sheathed, UV stabilised single core flexible copper cables shall be used. Multi-core cables shall not be used And For the AC cabling, PVC or XLPE insulated and PVC sheathed single or multi-core flexible copper cables shall be used. Generally above 5kwp system the minimum DC cable size shall be 6.0 mm2 copper. The minimum AC cable size shall be 4.0 mm2 copper. In three phase systems, the size of the neutral wire size shall be equal to the size of the phase wires. The following colour coding shall be used for cable wires: − DC positive: red (the outer PVC sheath can be black with a red line marking)  − DC negative: black  − AC single phase: Phase: red; neutral: black  − AC three phase: Phases: red, yellow, blue; neutral: black  − Earth wires: green.
  8. Earthing and lightning protection – Earthing is essential for the protection of the equipment & manpower. Two main grounds used in the power equipment’s are (System earth & Equipment earth). System earth is earth which is used to ground one leg of the circuit. For example in AC circuits the Neutral is earthed while in DC supply +ve is earthed. And equipment earth all the non-current carrying metal parts are bonded together and connected to earth to prevent shock to the man power & also the protection of the equipment in case of any accidental contact. The Earthing for array and distribution system & Power plant equipment shall be made with GI pipe and GI strip.
  9. MODULE MOUNTING STRUCTURE – Hot dip galvanized iron mounting structures may be used for mounting the modules / panels / arrays. The Mounting structure shall be so designed to withstand the wind speed of 150 km/ hour. The mounting structure steel shall be as per latest IS 2062: 1992 and galvanization of the mounting structure shall be in compliance of latest IS 4759 with thickness of 80 microns as per IS 5905. All fasteners shall be of Stainless steel – SS 304. The foundation for Module Mounting structures shall be 1:2:4 PCC Construction and must take care there shall be minimum necessary clearance between ground level and bottom edge of SPV modules.

Let’s we Look forward about steps to basic design of solar off-grid system.


Step 1 – Determine the Total Load.

As we know the Electrical energy usage is normally expressed in watt hours (Wh) or kilowatt hours ( kWh ).

( power of the appliance – W) x (Number of hours per day it will operate – Hours/day) =                 ( Energy consumed by that appliance per day – WH/day.)

To determine the daily energy usage for an appliance, multiply the power of the appliance by the number of hours per day it will operate. The result is the energy (Wh) consumed by that appliance per day.

Step 2 – Determine the sizing PCU & Battery bank.

  • As we know System voltages are generally 12, 24 or 48 Volts. The actual voltage is determined by the requirements of the system.
  • For example, if the batteries and the inverter are a long way from the energy source then a higher voltage may be required to minimise power loss in the cables. In larger systems 120V or 240V DC could be used, but these are not typical household systems.

Note – The recommended system voltage increases as the total load increases. For small daily loads, a 12V system voltage can be used. For intermediate daily loads, 24V is used and for larger loads 48V is used.

Step 3 – Determine the sizing of SPV needed.

The size of the PV array should be selected considering seasonal variation of  – solar irradiation & the daily energy usage, Battery efficiency etc

The basic formula is Array Size Needed = (Load) x (MPPT Controller Loss) / (Sun Hours).

  • For general calculation to determine number of modules in series, divide the system voltage by the nominal operating voltage of each module.
  • For general calculation to determine the number of strings in parallel, the PV array output current required (in A) is divided by the output of each module (in A). 

Note – Number of modules connected in series & parallel is depending upon system designer.

  • Step 1 – Determine the Total Load.

AC Load Example, 230Vac

Load 1 – 100W x 4 Hours/day = 400 WH/day.

Load 2 – 50W x 6 Hours = 300 WH/day

Load 3 – 100w x 3 Hours/Day = 300 WH/day

Total Load = 1000 WH/day @ 230Vac.

  • Step 2 – Determine the sizing PCU & Battery bank.

Proper battery bank sizing is important for the operation of the SPV. The basic calculation for this step is

Calculation 1

(Load AH/day) = (Load WH/day) / Base Battery Voltage

(Load AH/day) = (1000) / 24V = 41.66 AH/D @ 24V

Calculation 2

(AH Battery Bank Size Needed) = (Load AH/day) x (Days of Autonomy) / (Max DOD)

(AH Battery Bank Size Needed) = (41.66 AH/D) x (2) / (0.80) = 104.16 AH @ 24V of Battery Needed.

Let’s say we have 150AH, 12V Battery, we need two batteries in series connection.

Calculation 3 – Solar charge controller – It’s calculate based on PV module specification. If we consider

Pm = 100Wp, Isc = 6 Amps, Voc = 16.7Vdc.

Solar charge controller = (3 Pv Module * 6A) x 1.3 = 23.4 A i.e we select 30A, 12V charge controller.

Calculation 4Selection of inverter 

Selection of Inverter depends on factors such as cost, surge requirements, power quality and for inverter/chargers, a reduction of the number of system components necessary. The selected inverter should be capable of supplying continuous power to all AC loads AND providing sufficient surge capability to start any loads that may surge when turned ON.

From the Total load  (energy) assessment , a selected inverter must be capable of supplying 400VA continuous with a surge capability.

  • Step 3 – Determine the sizing of SPV needed.

Array Size Needed = (Load) x (MPPT Controller Loss) / (Sun Hours)

Array Size Needed = (1000 x 1.10) / (4) = 275 watts of solar modules is needed.

If we using a 100 watt module we need 3 solar modules.

Conclusion :-

1) SPV – 100wp – 3Nos.

2) Battery required – 150AH, 12V. – 2 Nos.

3)Charge Controller – 12V, 30Amp.

4)Inverter – 400VA or greater. Other BOM as per system requirement.

Note – it’s just a simple design.. For bigger load we also have to consider different parameters as per requirements.



Introduction ~ Concentrating Solar Thermal Technology.

Concentrating Solar Thermal Technology.

  • As we Know Many power plants today use fossil fuels as a heat source to boil water, The steam from the boiling water spins a large turbine, which drives a generator to produce electricity.
  • However, a new generation of power plants with concentrating solar power systems uses the sun as a heat source.
  • The 3 main types of concentrating solar power systems are :- linear concentrator, dish/engine, and power tower systems.
  • ! more Importent Application of CST Technology is ‘solar cooker‘, It is a device which uses the energy of direct sunlight to heat, for cooking or pasteurize food or drink.

Let us we learn basic concept about CST technology.

Please Click Here to download PDF file.

Concentrating Solar Power Basics | NREL

Learn about concentrating solar power systems and the three types are linear concentrator, dish or engine, and power tower systems.

Many power plants today use fossil fuels as a heat source to boil water. The steam from the boiling water spins a large turbine, which drives a generator to produce electricity. However, a new generation of power plants with concentrating solar power systems uses the sun as a heat source. The three main types of concentrating solar power systems are:linear concentrator, dish/engine, and power tower systems.

Linear concentrator systems collect the sun’s energy using long rectangular, curved (U-shaped) mirrors. The mirrors are tilted toward the sun, focusing sunlight on tubes (or receivers) that run the length of the mirrors. The reflected sunlight heats a fluid flowing through the tubes. The hot fluid then is used to boil water in a conventional steam-turbine generator to produce electricity. There are two major types of linear concentrator systems: parabolic trough systems, where receiver tubes are positioned along the focal line of each parabolic mirror; and linear Fresnel reflector systems, where one receiver tube is positioned above several mirrors to allow the mirrors greater mobility in tracking the sun.

Source: Concentrating Solar Power Basics | NREL

Rooftop Solar Technology & Government Policy.

As we know The future is bright for continued PV technology dissemination. Rooftop Solar Technology – RTPV technology fills a significant need in supplying electricity, creating local jobs and promoting economic development in rural areas, avoiding the external environmental costs associated with traditional electrical generation technologies.

i think Major power policy reforms and tax incentives will play a major role.

so let us we focused on Rooftop Solar Technology & Government Policy.

Download ppt ~

Introduction To Rooftop Solar Technology & Government Policy

Note ~ The Given details is not latest please visit MNRE/GOI web site for latest updates.

Canal-top solar power project in West Godavari.

A canal-top solar power project of one mw capacity at a cost of Rs 8 crore will be coming up on Losari Main Canal at Gollavanitippa village of Bhimavaram rural mandal in West Godavari.

The New and Renewable Energy Development Corporation of Andhra Pradesh Limited has carried out a survey on the feasibility of the project recently and sent a report to the Centre for its consent and once the project gets its consent, works are expected to begin in about two months’ time. (more…)

Opportunity in renewable energy (Solar & wind) sector.

” The need for renewable energy resources has never been bigger than today, let’s we look forward to best opportunity in this sector.”

  • Start manufacturing plant of solar cell or module, plug and play small solar kit, mobile windmill etc.
  • To fulfil Electricity demand increased wind and solar or hybrid (wind + solar) small, medium and large scale power plant, or else hybridization of coal based thermal power plants with Cs or CSP technology.
  • let’s we manufacture different tools or machine operate on solar power which used for day to day use as well as swachh bharat mission.
  • Let’s focus on Skill development programme with additional job creation for everyone, ITI/Diploma/Engineering students & professional.
  • Let’s we make integrated approach for Nature inspired Eco village by developing innovative tools and product for farmers by using solar energy for agriculture application and adopting agro-horti-forestry approach.

Many more opportunity are not mention in this list, am request to everyone, must suggest & share much more opportunity with us.

“Convert Today’s innovative opportunity into Tomorrow’s sustainable future.”

Smart Solar Pv Solution.

Smart Solar Pv Solution.


Smart pv solution is combination of modernize digital technology with simple smart & global operation and management techniques.

It’s incorporates power conversion, remote control, data collection, online analysis as well as environment adoption etc.

  • Why we need smart pv solution?

We need smart pv solution to achieve efficient power generation, smart O&M, maximum reliability & safety and maximize ROI.

  • From solar plant construction to O&M we have to optimizes & innovate entire process, how?

To optimizes & innovate entire process, we have to integrate 3 technology, Pv technology, information technology and internet technology.

By using these technologies we can able to reduce the O&M cost, optimize initial investment, raise the energy yield as well as increase ROI.

The smart pv solution also includes high speed interconnected networks to provide real time solar plant information. We may use ANN, cloud storage as well as big data analysis to process the smart information for solar plant management and continuous optimization of solar plant performance.

Smart Pv Technical Solution.

While we designing any project two things we must keep in mind is performance ratio & internal rate of returns (IRR) of our project.

  • How we increased IRR and PR by using Smart Pv Technical Solution?

We increased IRR and PR by using modernizes & advance digital technology as given below,

  • Multi MPPT Controller,
  • Multi peak tracking (ANN),
  • separately dividing Pv module string,
  • By analyzing losses, shading effect, terrain inconsistency etc.

If we use Multi-MPPTs and Multi peak Tracking system we get higher energy yield.

Smart string monitoring with better availability during faulty condition.

Currently we are using DC combiner cabinet with lower MPPT controller, instead of using this technology we have to use smart Pv controller. It’s combination of MPPT & Inverter.  Smart Pv controller is control center in solar power plant. Using smart Pv controller we can detect both current and voltage of each string.

So that it’s increased accuracy for fault detection in minimal time period and increased efficacy of O&M.

For example ~ approximately few year ago we us only two MPPT controller for 1MW, but now we have to used 100 MPPTs controller for a 1MW plant.

The distribution system we connect in series connection, due to this if in any of the component fault occur then whole s/m may fail, Instead of using distributed parallel s/m, the failure rate may reduce because,

  • If we use multiple Pv controller out of this, if one controller fails, no effect on other controller because it’s connected in series.
  • If fault occur it’s easy to reinstall because it’s small and light in weight.
  • As it’s available in spare and easy to reinstall, it’s reduce the chances of failure rate.

The smart pv controller support software, it can remotely upgrade online to adopt changes of component and environment.

Smart & efficient O&M with Expert O&M system and big data analysis.

As we know the only field engineer can’t able to provide accurate & real time data of O&M. there for we need smart technical solution as given below,

  • Use SCADA or Drones to conduct large scale inspection of O&M performance of any particular solar power plant. It’s providing you smart communication or interaction channel with real time data to Field engineer to head office.
  • It’s optimizes the allocation of personnel and improves the mountainous efficiency.
  • Big data mining & expert s/m is an platform based on the cloud stroage, big data mining and expert s/m. this allows user to customize reports and perform secondary development.
  • Expert O&M system and big data analysis also provide maintanance and check-up suggestion to increase ROI.

System safety & PID effect prevention.

As safe DC transmission & protection are key & difficult issue, Smart Pv S/m is free of dc combiner cabinet, the DC power from Pv string s directed to Smart Pv Controller for converting into AC power & long distance transmission.

It measures such ac reducing length of DC power cable & removing  DC combiner and prevents DC transmission safety and protection issue.

To preventing PID effect we use plc based RCD ckt for safety against leakage current and provide highest safety to human being.

Basic Introduction to solar PV System.

Basic introduction to solar PV System Presentation.

The need for renewable energy resources has never been bigger than today and so  is a lot of research going to match this high energy demand.  Solar PV Array technology is one such  technique which can actually make the effective  use of solar energy available to us.

Let’s we take overview of solar PV System.

Solar Overview Urval