Chemistry Grade 12 STEM - Notes on ENERGY and BATTERY TECHNOLOGY

Energy

Energy is the ability to do work and exists in various forms such as potential, kinetic, thermal, electrical, chemical, and nuclear. Chemical energy, stored in the bonds of chemical compounds, is a key focus, particularly how it's released or absorbed during chemical reactions.

Exothermic reactions release energy, often as heat, while endothermic reactions require energy from the surroundings to proceed. Energy can be transferred without being destroyed, as seen in food conversion to mechanical energy, coal to electrical energy, and chemical energy in batteries powering electrolysis.

The transition from fossil fuels is crucial due to environmental pollution and the eventual exhaustion of these sources. Renewable energy sources must be utilized. Potential career pathways in the energy industry include civil engineer, solar photovoltaic installer, petroleum engineer, environmental scientist, financial analyst, electrical power line installer, electrical engineer, geoscientist, oil and gas service unit operators, wind turbine technician, and power plant operator.

Green Hydrogen Energy Economy

Green Hydrogen Energy Economy is considered a promising renewable energy technology. Hydrogen, an energy carrier, can be converted into various forms of energy, like electricity or heat, to meet power demands and address energy problems.

The current hydrocarbon-based economy, reliant on burning fossil fuels, leads to environmental pollution. Many countries are transitioning to a hydrogen-based energy economy, which promises carbon neutrality and net-zero pollution. A Green Hydrogen Energy Economy integrates hydrogen with other renewable sources.

Papua New Guinea (PNG) has the potential to contribute to solving energy problems nationally and globally due to its rich energy resources. Adopting hydrogen energy technology will diversify energy options.

Andrew Forrest's plan to establish a green energy manufacturing complex in Queensland, Australia, focuses on hydrogen electrolyzers, wind turbine equipment, solar PV cells, and electrical wiring, demonstrating a move towards green industry manufacturing and energy production.

The government of Papua New Guinea has signed an agreement with Fortescue Metals Group (FMG) to collaborate on Green Energy, which is expected to transform power generation and distribution. This partnership will explore renewable energy sources like hydro, solar, wind, and geothermal power. FMG is capable of producing over 25 gigawatts of sustainable "green hydrogen and green ammonia" energy from PNG for both internal use and export.

PNG has the potential to use Hydrogen Energy to help adapt and meet its energy needs, aiming to meet 32% of their national power demand with renewable energy sources by 2030 and provide electricity to 70% of the country's dispersed population by 2030.

The key elements of the Hydrogen Economy are:

• Production of Hydrogen
• Packaging of Hydrogen
• Transportation of Hydrogen
• Storage of Hydrogen
• Transfer of Hydrogen

Introduction to Hydrogen Energy Economy

Hydrogen is an energy carrier with the potential to power economies. It's found in $H_2$ carriers (molecules or compounds containing high-energy-density hydrogen).

Hydrogen as Fuel

Hydrogen (H) has 1 proton and 1 electron. As $H<em>2$, it's highly combustible with oxygen but not poisonous. It's abundant but rarely found in pure form due to its reactivity. It combines with elements in water ($H</em>2O$), hydrocarbons, carbohydrates, and proteins. It's also light, escaping into space.

Hydrogen requires separation from other elements to be used, needing significant energy. Therefore, it's an energy carrier like electricity, not a primary source like coal or petroleum. An energy carrier is a substance or phenomenon holding energy that can be transferred.

In the Hydrogen Combustion Reaction, pure $H<em>2(g)$ combines with pure $O</em>2(g)$ to produce water vapor ($H_2O$) and energy:

$2H<em>2 (g) + O</em>2 (g) \rightarrow 2H_2O (g) + energy$

When used in combustion, hydrogen produces only water and energy/heat. It's used to propel space shuttles. In atmospheric air, it may produce nitrogen oxides and water vapor.

Hydrogen carries and stores vast energy quantities. $H_2$ Carriers are sources of hydrogen with high energy density, like methanol, ethanol, oil, coal, natural gas, biogas, biofuels, ammonia, carbohydrates, hydrocarbons, and water.

Introduction to Hydrogen Economy

Rationale

The world currently relies on a "Fossil Fuel Economy" or "Hydrocarbon-based Energy Economy," with cars and power plants fueled by petroleum products and fossil fuels. This reliance has four major issues:

1. Air Pollution
2. Environmental Pollution
3. Global Warming
4. Dependence

Most countries import oil, leading to economic dependency. Transitioning to a hydrogen-based economy helps reduce environmental degradation and economic dependence on fossil fuels.

Hydrogen-based Economy

A "Hydrogen Economy" refers to a hydrogen-based ($H_2$) energy distribution system. Pure hydrogen doesn't occur naturally in large quantities but can be produced. It acts as an energy carrier, influenced by fossil fuel use, sustainable energy generation, and energy sourcing.

Elements of a Hydrogen Economy

The key elements are:

• Production of Hydrogen
• Packaging of Hydrogen
• Transportation of Hydrogen
• Storage of Hydrogen
• Transfer of Hydrogen
• End-users

Considerations include:

• How to produce hydrogen.
• Methods of production.
• Using renewable or non-renewable resources.
• Safe storage and packaging.
• Transportation to end-users.
• Integration into existing energy delivery systems.

Comparison between Hydrogen Energy to Others

A hydrogen-based economy offers several advantages:

• Eliminates pollution from fossil fuels, producing only water as a byproduct.
• No greenhouse gas emissions if produced by water electrolysis.
• Eliminates economic dependency on oil.
• Enables distributed production wherever energy and water are available.

Technological Hurdles include hydrogen sourcing, transportation, distribution, and storage due to its bulky gaseous state.

Summary

• A functional hydrogen economy includes production, storage, packaging, and distribution.
• PNG can adopt a hydrogen economy to diversify energy resources.
• Hydrogen is abundant but found in compounds.
• The hydrocarbon economy is becoming unsustainable.
• Hydrogen is a fuel/energy carrier with higher energy density and lower environmental impact.
• The hydrogen economy faces challenges in transportation and storage.
• Risks associated with hydrogen limit its practical implementation.
• The most common production method involves reforming fossil fuels, requiring significant energy and emitting hazardous substances.

Methods of Producing Hydrogen

Key elements of a hydrogen economy:

• Production of Hydrogen
• Packaging of Hydrogen
• Transportation of Hydrogen
• Storage of Hydrogen
• Transfer of Hydrogen
• End-users

Color-coding Hydrogen Production Methods

Scientific color-coding represents various hydrogen production methods:

• Green Hydrogen: Produced by electrolysis using renewable energy sources like hydro, solar, or wind, resulting in no greenhouse gases and carbon-free fuel.
• Blue Hydrogen: Produced by technologies like Steam Methane Reforming (SMR) with CO2 capture and storage.
• Turquoise hydrogen: uses methane pyrolysis to produce hydrogen and solid carbon.
• Grey Hydrogen: Produced from natural gas using Steam Methane Reforming (SMR), emitting significant CO2.
• Brown (or Black) Hydrogen: Produced via Coal Gasification from coal or lignite burning, emitting large amounts of CO2.

Blue, Turquoise, Grey, Brown, or Black Hydrogen contribute to pollution, while Green hydrogen utilizes renewable energy sources.

Thermochemical Processes

Thermal processes release hydrogen from its molecular structure using energy from natural gas, coal, or biomass. Heat is combined with closed-chemical cycles to produce hydrogen from feedstocks like water.

Natural Gas Reforming

Natural gas reforming is an industrial technology using existing natural gas pipeline infrastructure, with methane ($CH_4$) transformed to hydrogen using steam-methane reformation and partial oxidation.

Steam Methane Reforming (SMR)

SMR uses high-temperature steam ($700^oC$-$1000^oC$) to produce hydrogen from methane, reacting methane with steam at 3-25 pressure (1 bar = 14.5 psi) in the presence of a catalyst, creating hydrogen (H), carbon monoxide (CO), and carbon dioxide (CO2). It is an endothermic reaction.

SMR Reaction: $CH<em>4 + H</em>2O (+heat) \rightarrow CO + 3H_2$

Water-gas Shift Reaction: $CO + H<em>2O \rightarrow CO</em>2 + H_2 (+ small amount of heat)$

Partial Oxidation

Methane and hydrocarbons in natural gas react with a small amount of oxygen, producing carbon dioxide and water. Limited oxygen results in hydrogen and carbon monoxide. In a water-gas shift process, CO is combined with water to produce CO2 and extra hydrogen. It is an exothermic process, faster than steam reforming.

Partial Oxidation of Methane Reaction: $CH<em>4 + \frac{1}{2}O</em>2 \rightarrow CO + 2H_2 (+heat)$

Water-gas Shift Reaction: $CO + H<em>2O \rightarrow CO</em>2 + H_2 (+small amount of heat)$

Biomass Gasification

Biomass gasification involves heat, steam, and oxygen to transform biomass into hydrogen without burning. Net carbon emissions can be minimal, especially with long-term carbon collection, utilization, and storage.

Biomass

Biomass includes agriculture crop residues, forest residues, specially designed energy crops, organic municipal solid trash, and animal wastes.

How Biomass Gasification Works

Gasification converts organic materials into carbon monoxide, hydrogen, and carbon dioxide at high temperatures (>700^oC) with controlled oxygen and/or steam.

Simplified example Reaction: $C<em>6H</em>{12}O<em>6 + O</em>2 + H<em>2O \rightarrow CO + CO</em>2 + H_2 + other species$

Water-gas Shift Reaction: $CO + H<em>2O \rightarrow CO</em>2 + H_2 (+small amount of heat)$

Biomass-derived Liquid Reforming

Liquids derived from biomass resources, such as ethanol and bio-oils, can be reformed to produce hydrogen in a process similar to natural gas reforming. Biomass-derived liquids are more transportable than biomass feedstocks, allowing enabling semi-central or even distributed hydrogen generation at filling stations.

How Does it Work?

Biomass resources are converted into cellulosic ethanol, bio-oils, and other liquid biofuels. Some liquids are transported, where they are reformed into hydrogen:

1. Liquid fuel is mixed with steam at high temperatures to produce reformate gas (hydrogen, carbon monoxide, carbon dioxide).
2. Carbon monoxide combines with high-temperature steam for more hydrogen and carbon dioxide.
3. The hydrogen is purified and separated.

Steam Reforming Reaction (Ethanol): $C<em>2H</em>5OH + H<em>2O (+heat) \rightarrow 2CO + 4H</em>2$

Water-gas Shift Reaction: $CO + H<em>2O \rightarrow CO</em>2 + H_2 (+ small amount of heat)$

Thermochemical Water Splitting

Thermochemical water splitting uses high temperatures (from concentrated solar power or waste heat from nuclear power operations) with chemical processes to produce hydrogen and oxygen from water.

What is the Process?

High-temperature heat ($500^o$–$2,000^oC$) powers a series of chemical processes that produce hydrogen and oxygen from water, recycling chemicals in a closed loop.

Electrolytic Processes

Electrolysis is a method for producing carbon-free hydrogen from renewable and nuclear energy, using electricity to split water into hydrogen and oxygen in an electrolyzer.

How does it work?

An electrical current splits water into its components.

Types of Electrolyzers

Electrolyzers have an anode, a cathode, and an electrolyte.

• Polymer Electrolyte Membrane Electrolyzers use a solid plastic substance as the electrolyte. Water reacts at the anode, and hydrogen ions flow through to the cathode.

Anode Reaction: $2H<em>2O \rightarrow O</em>2 + 4H^+ + 4e^-$

Cathode Reaction: $4H^+ + 4e^- \rightarrow 2H_2$

• Alkaline Electrolyzers transport hydroxide ions (OH-) from the cathode to the anode. Electrolyzers can use a liquid alkaline solution or solid alkaline exchange membranes (AEM).
• Solid Oxide Electrolyzers use a solid ceramic material as the electrolyte, conducting oxygen ions (O2-) at high temperatures ($700^o$–$800^oC$).

Direct Solar-Water Splitting Processes

Photolytic techniques use light energy to split water into hydrogen and oxygen, potentially producing sustainable hydrogen with minimal environmental impact.

Photoelectrochemical (PEC)

PEC water splitting utilizes sunlight and specialized semiconductors to separate water molecules directly. It is a long-term technology with low or no greenhouse gas emissions.

How does it work?

Semiconductor materials immersed in water energize the water-splitting process using solar energy

Why is this Pathway Being Considered?

PEC water splitting is a promising solar-to-hydrogen method with high conversion efficiency and cost-effective materials.

Where does the hydrogen come from?

Two possible hydrogen sources:

• Electrolysis of Water: Splitting water molecules using electricity to produce pure hydrogen and oxygen and may be done anywhere.
• Reforming Fossil Fuels: Splitting hydrogen from carbon in hydrocarbon molecules, using a