Renewable Energy — Intermittency and Storage
Part 7 of blog series on Food and Energy Security. Part 6 is here
These days, public awareness around renewable energy — especially Solar Photovoltaics (PV) — is at an all-time high. Much of this everyday excitement is visible on neighborhood rooftops, driven by the Government of India’s aggressive push for grid-interactive rooftop systems under the PM Surya Ghar: Muft Bijli Yojana. At our rural farm, we have also installed a 5 kW rooftop solar system. Long ago, we had even developed a mini solar lamp, used a box-type solar cooker, and installed a solar water heater with a storage tank.
The renewable energy spectrum spans a diverse array — from Solar Photovoltaics (PV), Solar Thermal, and Concentrated Solar Power (CSP) to onshore and offshore Wind, Ocean Tidal and Wave systems, and Geothermal energy. Yet every one of these resources is fundamentally periodic or intermittent. To transform these variable flows into dependable power, robust storage systems are essential — most notably Battery Energy Storage Systems (BESS), Pumped Storage Hydropower (PSHP), and Green Hydrogen paired with fuel cells. While a village can operate decentralized off-grid gadgets, meeting national energy demand requires high-capacity, dedicated High-Voltage Direct Current (HVDC) transmission corridors — often called “Green Energy Corridors” — to evacuate power from mega solar plants.
There are many articles and detailed annual reports on the Ministry of New and Renewable Energy (MNRE) portal. I have compiled the following eleven focused sections to offer a practical overview of each technology alongside its current installation landscape, bringing wider awareness to the full spectrum of renewables shaping our energy transition.
Indian scenario
India’s clean-energy transition gained decisive momentum after the 2015 Paris Agreement (COP21), where the nation committed to achieving 50% of its cumulative electric power installed capacity from non-fossil sources by 2030 — a milestone crossed well ahead of schedule — anchoring its long-term pledge to reach net-zero carbon emissions by 2070.
Behind this rapid scale-up lies a coordinated institutional ecosystem under the Ministry of New and Renewable Energy (MNRE), Government of India, working alongside state nodal agencies and distribution utilities (DISCOMs) to resolve ground-level bottlenecks in land acquisition, right-of-way, and grid integration:
- Solar Energy Corporation of India (SECI): Procurement & Market Aggregation. A public sector enterprise that pioneered competitive reverse bidding to discover affordable tariffs and aggregate renewable power for state utilities.
- Indian Renewable Energy Development Agency (IREDA): Capital Mobilization. the specialized green financier channeling domestic and multilateral capital into clean energy infrastructure.
- Technology & Quality Benchmarking: Dedicated national institutes guiding sectoral standards — NISE (National Institute of Solar Energy, Gurugram) for solar cell testing and certification, NIWE (National Institute of Wind Energy, Chennai) for wind resource mapping and offshore validation, and NIBE (National institute of Bio Energy, Kapurthala) for bio-energy and advanced biofuels.
Solar Photovoltaics (PV)
Almost every pulse of energy on our planet carries the Sun’s signature. Look around: the crops standing in the fields, the food on our tables, the ancient chemical vaults of coal, crude oil, and natural gas buried deep beneath the earth — all are nothing more than solar radiation captured, transformed, and fossilized across geological periods. Even the rivers that turn our hydroelectric turbines flow only because solar heat evaporates the oceans and drives the great hydrologic engine in the sky.
At its core, the Sun is a titanic cosmic fusion reactor, fusing hundreds of millions of tons of hydrogen into helium every second. In doing so, it unleashes a variety of electromagnetic radiation. The harmful rays are intercepted and stopped by Earth’s unique high stratosphere and fragile ozone layer. Only ultraviolet, infrared, and a narrow band of visible white light reach the Earth.
Solar Panels
Modern human ingenuity probed the solid-state physics of matter itself. Bell Labs developed first practical 6%-efficient silicon solar cell in 1954 which was very expensive only used in space missions. Innovation accelerated in the 2010s with monocrystalline designs pushing efficiencies past 20%, leading into modern high-efficiency architectures like TOPCon (Tunnel Oxide Passivated Contact)and Heterojunction (HJT) that delivers commercial efficiencies beyond 22% to 25%. Intense R&D is going on worldwide to improve efficiencies further. Solar cells generate only DC electricity.
Technology Evolution
- Polycrystalline (Mottled Blue): The early workhorses made from melted silicon fragments. With modest efficiencies (14%–16%), they are now largely obsolete.
- Mono-PERC (Uniform Black): Sliced from single-crystal silicon with a rear reflective layer, lifting efficiency to 20%–21%.
- N-Type TOPCon (Modern Standard): The current benchmark for new plants, using ultra-thin oxide layers to prevent electron losses and pushing commercial efficiency past 22% to 23.5%.
- Bifacial Panels: Glass on both sides lets the panel generate power from direct overhead sun as well as light bouncing off the ground, adding 8% to 15% extra yield on the same footprint.
At peak noon, about 1,000 W/m² of solar energy reaches the earth. Solar panels convert this light into electricity, allowing a 1 kWdc system to generate an average of 4.5 to 5.5 kWh of energy each day. Over the course of a year, designers typically plan for around 300 productive days, leaving margin for cloudy skies when generation falls to near zero. A typical 5kW rooftop solar needs about 300 Sq.ft area whereas about 3.5 to 4 acres are required for one megawatt or 1000kW solar PV ground-mounted utility parks.
Solar power plant comprises of:
- PV Panels and its mounting steel structure
- Inverter: that converts raw panel DC into grid-synchronized 50 Hz Alternating Current (AC).
- DC and AC Cabling
- Earthing and lightening arresters
- A large Transformer to raise voltage (11 or 33kV) to grid level for evacuation along with metering and safety switchgear Generally the panels have about 25 yrs of life. However panels loose efficiency due to heat and dust. Over the years they also degrade reducing output.
Following two Infographics show (i) Basic ingot and silicon wafers making and (ii) solar panel making from wafers.
Indian Deployment of Solar
India has deployed over 168 GW of solar capacity in three distinct models:
- Ultra-Mega Solar Parks: Centralized desert giants (such as Bhadla and Khavda) evacuating bulk power over high-voltage Green Energy Corridors.
- PM Surya Ghar (Rooftop Revolution): Subsidized rooftop installations that generate daytime power on terraces and offset utility bills via bidirectional net metering.
- PM-KUSUM (Agricultural Solar): (i) Standalone solar pumps and solarized rural 11 kV feeders that replace expensive diesel and supply reliable daytime irrigation and (ii) Up to 2MW solar power plants on farmers barren lands by willing farmers.
Mega Solar PV power plants installation in India
5-kW Roof Top Solar PV system at a glance
3-HP motor-pump set for irrigation at a glance
2-MW solar PV power plant on farmland under PM Kusum scheme
Solar Thermal
Small domestic solar thermal applications in India include box-type cookers, Fresnel concentrators , and rooftop solar water heaters with storage tanks. Despite their utility, widespread household adoption remains limited, primarily due to rooftop and outdoor space constraints.
Concentrated Solar Power (CSP): Unlike standard Solar PV panels that turn sunlight straight into electricity, Concentrated Solar Power (CSP) uses heat. Giant mirrors track the sun and focus its rays to boil water, create high-pressure steam, and spin a traditional turbine-generator to produce power. It works in 3 Steps: (a) Focusing Sunlight: Curved or flat mirrors concentrate direct sunrays onto a central pipe or a tall tower receiver. (b) Heating Fluid: An oil or molten-salt fluid absorbs this concentrated heat, reaching 400°C to 565°C. (c ) Spinning Turbines: The hot fluid boils water into high-pressure steam, driving a standard turbine hooked up to the power grid.
Grid-Scale Plants in the Thar Desert: Under Phase-1 of the National Solar Mission, utility plants were set up in Rajasthan notably the Godawari Green Energy 50 MW Parabolic Trough plant (Naukh, Jaisalmer) and the Reliance Rajasthan Sun Technique 100 MW CLFR (Compact Linear Fresnel Reflector) plant at Dhursar, Jaisalmer.
Industrial Process Heat & Community Kitchens: Concentrating Solar Thermal (CST) has seen widespread, practical success in offsetting furnace oil, LPG, and diesel:
- Community Steam Cooking: The Shirdi Saibaba Sansthan in Maharashtra operates 73 solar dishes generating pressurized steam to prepare over 40,000 meals daily; a similar large setup operates at Shri Thirupathi Balaji temple complex,Tirumala.
- Dairy and Textiles: Parabolic concentrators supply 120°C–180°C clean process steam for milk pasteurization at Amul dairies and boiler pre-heating in textile and chemical plants across Gujarat, Maharashtra, and Tamil Nadu.
Wind Energy
WEG (Wind Energy Generator)
While solar panels sit quietly under the sun, wind turbines are heavy mechanical machines. They do not work by wind “pushing” the blades like an old paddle wheel; they work on the principle of aerodynamic lift, much like an airplane wing.
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The WEG works like this
- Aerofoil Action: As moving air flows over the curved cross-section of the composite blade, it creates low pressure above the blade and high pressure below it, producing rotational lift.
- Torque and Gearbox: The massive rotor turns slowly (roughly 10 to 18 RPM). Inside the housing atop the tower, a multi-stage planetary gearbox speeds this up to around 1,500 RPM to drive a conventional copper-wound generator. Modern “direct-drive” turbines eliminate the heavy gearbox altogether.
- Electronic Grid Coupling: Power output is conditioned via advanced power electronics (converters) that feed frequency-synchronized, clean 50 Hz AC power into the high-voltage evacuation lines.
Technology evolution
The Pioneer Era (1990s–2000s): Small 250 kW to 500 kW turbines mounted on short steel lattice towers. Modern Onshore Standard: 3.0 MW to 4.2 MW giants with modular glass-fiber/carbon-fiber composite blades and variable-pitch controls that feather the blades to survive cyclonic storms.
India’s Installed Base
India stands 4th globally in cumulative wind installations, trailing only China, the United States, and Germany. The country’s total installed wind capacity has crossed 57.4 GW (generating over 106 billion units of electricity annually), concentrated primarily across seven wind-rich states.
- Gujarat : Propelled by the windy coastal corridors of Saurashtra and the vast salt flats of Kutch, Gujarat has surpassed 16 GW, housing massive installations including 5.2 MW multi-megawatt turbines.
- Tamil Nadu: Home to the iconic Muppandal Wind Farm in Kanyakumari district — one of the largest contiguous wind corridors in the world — leveraging strong seasonal jet streams blowing through gaps in the Western Ghats (Palakkad and Shencottah passes).
Emerging Frontiers
Offshore Wind; India possesses a 7,500 km coastline with an estimated 70 GW of offshore potential off Tamil Nadu and Gujarat. Key Challenges: Wind generation remains heavily seasonal, producing nearly 60% to 70% of its annual electricity during the four monsoon months (May to August). Balancing this surge requires responsive grid scheduling, dynamic transmission corridors, and pumped storage backstops.
Ocean Tidal and Wave Energy
Tides vs. Waves
Two Different Mechanics
- Tidal Power (Celestial Gravity): Driven by the gravitational pull of the Moon and Sun. Seawater rushes into bays and estuaries twice a day. We tap it via tidal barrages (coastal dams) or underwater stream turbines (submerged rotors turned by the current).
- Wave Power (Wind Friction): Driven by winds blowing across open water, creating surface kinetic motion harvested by floating buoys or air-column pistons.
India’s Footprint & Pilot Setups
India has an estimated 12,400 MW of tidal potential and 40,000 MW of wave potential, primarily explored through pilot research projects:
- Gulf of Khambhat & Gulf of Kutch (Gujarat): India’s tidal hotspots with tidal ranges up to 8–11 meters. Early proposals (like a 50 MW tidal stream plant in Kutch) were shelved due to high capital costs compared to cheap solar.
- Durgaduani Creek (Sunderbans, WB): A proposed 3.75 MW tidal barrage aimed at powering remote delta islands, eventually dropped over environmental concerns for local mudflats.
- Vizhinjam Wave Plant (Kerala): A landmark 150 kW Oscillating Water Column (OWC) pilot built by IIT Madras and NIOT. Waves pushed air through an onshore concrete chamber to turn a bidirectional Wells air turbine.
- Sindhuja-I (Tuticorin, Tamil Nadu): Deployed 6 km offshore by IIT Madras, this floating point-absorber wave converter bobs with surface swells to drive an onboard generator, aimed at providing clean power to remote navigation buoys and offshore sensors.
Geothermal Energy
Unlike solar and wind that harvest energy circulating above the crust, geothermal energy taps the primordial heat trapped beneath it — generated by the planet’s original gravitational formation and the continuous radioactive decay of minerals in the deep mantle.
Extraction
Deep wells (typically 1 to 3 km deep) tap into natural pressurized subterranean hot water or steam reservoirs. The Geological Survey of India (GSI) has mapped roughly 340 hot springs across seven geothermal provinces, with an estimated theoretical potential of ~10,000 MW (10 GW).
Indian scenario
Because India sits primarily on an older, stable continental shield rather than active volcanic plate boundaries, most Indian reservoirs are low-to-medium enthalpy best suited for binary-cycle power and direct heat utilization. Some installation include:
- Puga Valley (Ladakh) located at an altitude of over 14,000 feet near the Himalayan collision zone.
- ONGC Energy Centre successfully drilled and completed deep exploratory geothermal wells here to establish India’s first 1 MW demonstration-scale geothermal power plant. Beyond electricity, it offers clean space-heating for extreme Ladakh winters, greenhouse farming, and hot-spring tourism.
Energy Storage: Managing the intermittency
Solar panels produce their surge of power at solar noon; wind turbines spin vigorously during seasonal monsoon nights. Yet, modern society demands reliable electricity at 8:00 PM when families switch on lights and cook dinner, and throughout the night when industrial assembly lines run uninterrupted. Because electricity on the grid must be consumed at the exact millisecond it is generated to prevent frequency collapse, variable renewables cannot power an industrial nation without energy storage.
- Pumped Hydropower Plants. Most promising energy storage worldwide. We have elaborated this in a dedicated blog; Hydropower -The silent Giant.
- Lithium Iron Phosphate (LFP) Storing electrical energy directly in batteries like LFP batteries for short-to-medium duration (Minutes to Hours):
- Green Hydrogen Converting excess electricity into Green Hydrogen and synthetic clean molecules to power heavy industry, long-haul transport, and seasonal grid reserves where batteries are physically too heavy or expensive.
Pumped Storage Hydropower (PSP)
Often called a water battery. The principle is simple: store electricity in the form of water at height, and recover it when required. I have given details in my earlier blog on Hydropower.
Lithium Iron Phosphate (LFP) batteries
While early electronics and electric vehicles favored Nickel Manganese Cobalt (NMC) chemistries for maximum volumetric energy density, stationary utility grids have overwhelmingly standardized on Lithium Iron Phosphate ( LFP): They offer:
- thermal and chemical stability ensuring fire safety in large megawatt-scale battery parks.
- Exceptional Cycle Life: Commercial LFP cells routinely deliver 6,000 to 10,000 full charge-discharge cycles at 80% Depth of Discharge (DoD), translating to a 15- to 20-year operational life on daily grid cycling.
- Non-Toxic Materials: LFP eliminates expensive, ethically compromised cobalt and scarce nickel, relying instead on iron and phosphate.
The Emerging Horizon (Sodium-Ion)
For stationary power where physical weight is not a constraint, Sodium-Ion (Na-ion) batteries are entering commercial pilot phases. By substituting lithium with abundant, inexpensive sodium (table salt chemistry) and using aluminum current collectors instead of copper, Na-ion promises even lower levelized storage costs for 4-to-8-hour grid shifting.
Green Hydrogen: Storing Clean Energy in Chemical Bonds.
Green Hydrogen (It’s called “Green” since its produced by electrolysis using only non-fossil fuels like Solar and Hydroplants) acts as the clean chemical bridge.
Electrolysys — the Core Splitting Process: Pure demineralized water is fed into an electrolyzer. Direct electric current breaks the molecular bond, producing pure hydrogen gas at the cathode and oxygen at the anode.
Hydrogen is not a source of energy. Hydrogen is a way to store and transport renewable energy, not a source of free energy. Electrolysis followed by compression and fuel-cell conversion can return only a fraction of the original electricity. To produce 1 kg of hydrogen needs 55 kWh of electricity, that hydrogen gives only 20 kWh through a fuelcell. For heavy long haul transport hydrogen is suitable (and not batteries) .
The Electrolyzer Technologies:
Alkaline Electrolyzers (AEL): The mature, low-cost industrial workhorse utilizing a liquid potassium hydroxide (KOH) electrolyte and nickel-based electrodes. Ideal for steady baseload operations.
Proton Exchange Membrane (PEM): Employs a solid polymer electrolyte membrane with platinum/iridium catalysts. PEM responds in fractions of a second, making it ideal for directly tracking fluctuating solar and wind inputs.
Solid Oxide Electrolyzers (SOEC): Runs at high temperatures using ceramic membranes. When integrated with industrial waste heat, SOEC achieves the Beyond
High-Temperature Nuclear Hydrogen (Beyond Electrolysis)
- Most current discussions on green hydrogen focus on low-temperature water electrolysis — using renewable electricity from solar or wind to drive Alkaline or Proton Exchange Membrane (PEM) electrolyzers at ambient temperatures (around 60°C to 80°C). While clean, this process is an energy-intensive brute-force route: it requires roughly 50 to 55 kWh of electrical energy to produce a single kilogram of hydrogen.
- To unlock large-scale, economical hydrogen production without straining the electric grid, researchers are turning toward thermochemical water-splitting and high-temperature (850–1000oC) steam electrolysis (HTSE) powered directly by high-temperature nuclear reactors.
- Operational testbeds like the Fast Breeder Test Reactor (FBTR) at Kalpakkam, which utilize liquid sodium coolant and produce core outlet temperatures around 500°C to 550°C, can serve as a critical proving ground. The ultimate goal of this research is linking thermochemical and HTSE loops to dedicated High-Temperature Gas-Cooled Reactors (HTGRs) or Compact High-Temperature Reactors (CHTRs) delivering outlet temperatures above 850°C to 1000°C.
Fuel Cells
Turning Clean Molecules Back into Watts. A Fuel Cell is simply electrolyzer running in reverse. Instead of burning hydrogen to make mechanical motion through a noisy, hot heat engine, it combines hydrogen and oxygen electrochemically:
- No Combustion, Zero Harmful Emissions: The only physical byproducts leaving the tailpipe or exhaust stack are warm water vapor and heat.
- High Thermodynamic Efficiency: Fuel cells convert 50% to 60% of the chemical energy directly into electricity — far surpassing the Carnot thermodynamic limits of traditional internal combustion engines.
- PEM Fuel Cells: Compact and quick-starting, PEM ( Proton Exchange Membrane fuel cells are the global standard for heavy zero-emission transit: city buses, regional mining haul trucks, and prototype railway trains.
Green Hydrogen for Green Ammonia to produce Urea fertiliser
While green hydrogen serves as a vital clean fuel, its most profound contribution to India’s sovereignty lies in national food security through Green Ammonia. Conventional nitrogen fertilizers like urea rely heavily on the Haber-Bosch process fed by fossil natural gas — leaving domestic agriculture vulnerable to volatile international gas prices and import disruptions.
By combining electrolytic green hydrogen produced from desert sunshine with atmospheric nitrogen, plants synthesize green ammonia, which is then reacted with captured carbon dioxide to manufacture Green Urea. SECI’s strategic green ammonia off-take tenders with fertilizer majors (including IFFCO, KRIBHCO, and NFL) represent more than an industrial decarbonization drive; they anchor a resilient agricultural supply chain, transforming clean domestic electrons directly into affordable plant nutrients that nourish millions of farm acres.
Projects and Industrial Deployments
India has launched an aggressive public framework backed by the National Green Hydrogen Mission and massive utility battery tenders managed by SECI:
- Utility-Scale Battery Parks (BESS): Tata Power 120 MWh Utility BESS (Chhattisgarh): One of India’s largest grid-scale operational LFP battery storage installations, co-located with a 100 MW solar plant to provide sub-second frequency control and peak shifting.
- Green Hydrogen in Refining & Mobility: IOCL Mathura & Panipat Green Hydrogen Plants: Indian Oil Corporation has established megawatt-scale electrolyzer facilities at its northern refineries, replacing fossil-methane grey hydrogen with green hydrogen to desulfurize diesel and petroleum fuels.
- NTPC Leh Green Hydrogen Mobility Project (Ladakh): Located at 11,500 feet, NTPC built an extreme-altitude solar-powered green hydrogen dispensing station and a fleet of 5 zero-emission fuel-cell passenger buses operating in Leh’s sub-zero climate.
- SECI Green Ammonia Fertilizer Off-take: SECI has awarded long-term production and procurement tenders for over 7 lakh tonnes per annum of green ammonia, establishing a domestic demand sink across public-sector fertilizer plants (IFFCO, KRIBHCO, NFL) to replace imported fossil-based ammonia.
- Clean Rail Transit (Indian Railways): Indian Railways launched trials for hydrogen fuel-cell retrofitted passenger trains under the “Hydrogen for Heritage” initiative on historic non-electrified mountain routes (like the Jind-Sonipat section and the Kalka-Shimla line), proving the feasibility of fuel-cell locomotives.
Green Energy Corridors (GEC)
Generating gigawatts of clean electricity in the sunny deserts of Rajasthan or along the windy coastlines of Gujarat and Tamil Nadu is only half the battle. Because the largest renewable resource zones are situated far away from major urban cities, industrial belts, and agricultural load centers, the power must be transported across thousands of kilometers without choking local networks.
The country launched an all-out expansion of critical transmission highways — the Green Energy Corridors (GEC), featuring dedicated high-voltage inter-state lines (including 400 kV and 765 kV corridors and HVDC links) engineered to evacuate variable power from massive desert solar parks in Rajasthan.
The Missing Link — Upstream Technology and Integration.
Deploying vast solar parks, wind farms, and battery banks creates impressive headlines, but the core engineering beneath them tells a sobering story: India remains primarily an assembler rather than an indigenous manufacturer.
We rely heavily on imported crystal pullers and wafer-slicing tools for solar manufacturing, and foreign refining for active battery chemicals. Just as critically, the crucial power electronics that control modern grids — high-power IGBT semiconductor modules, fast-switching converters, central solar inverters, and heavy-duty Wind Electric Generator (WEG) induction and synchronous machines — are overwhelmingly designed and fabricated overseas.
A genuinely self-reliant energy transition cannot stop at bolting together imported sub-assemblies. The essential next step is mastering these upstream technologies at home: building the heavy engineering, precision metallurgy, and power electronics that actually keep the grid running on Indian terms.
Post Script
India’s ambition to move rapidly towards net-zero carbon emissions is laudable, but it also underlines the scale of the challenge ahead. Solar PV and wind energy are clean and increasingly affordable, yet their output is naturally variable.
A dependable low-carbon energy system will therefore require effective storage at many levels: LFP batteries for shorter-duration needs, pumped-hydro projects for bulk storage, and green hydrogen for longer-duration and industrial applications. Achieving this transition will demand sustained effort in technology upgradation, domestic sourcing of critical materials, higher efficiency across generation, storage and transmission, and careful planning of the entire power system.
The renewable-energy journey is not only about adding more solar panels and wind turbines; it is about building a resilient, reliable and largely self-reliant energy ecosystem for the future.
DISCLAIMER: The information presented in this blog series has been compiled using AI-assisted research based on my structured topic outlines and subsequently reviewed and edited by me. I do not claim original ownership of the underlying technical data and literature, and I fully respect all original authors, institutions, and their copyrights. While every effort has been made to ensure accuracy and context, inadvertent errors or omissions in data and technical details may remain. Readers are kindly requested to bear with these limitations and refer to official statutory publications for verified regulatory or commercial citations.
