CHY 583 Chapter 4 – Energy Storage

Vocabulary flashcards covering energy storage concepts, thermodynamic processes, mechanical and thermal systems, electrochemical batteries, and synthetic fuel production based on Chapter 4 of CHY 583.

Intermittent Energy Sources

Alternative energy sources such as wind, solar, tidal, and wave energy that do not provide a constant supply of power.

Exothermic Reaction

A process where energy is released, and the potential energy of the products is lower than that of the reactants.

Endothermic Reaction

A process where energy is absorbed, and the potential energy of the products is higher than that of the reactants.

Exergonic Process

An energy production process where there is a net release of free energy.

Endergonic Process

An energy storage process that requires an input of energy to proceed.

Pumped Water Storage

A mechanical storage method where water is pumped to a height to store potential energy; for example, $1\,m^3$ of water at $360\,m$ stores $3.6 \times 10^6\,J$ or $1\,kWh$.

Thermal Energy Storage

The storage of energy in the form of sensible heat or latent heat (vaporization or fusion) for later use in heating or cooling.

Sodium Sulfite Decahydrate ($Na_2SO_4 \times 10H_2O$)

A material that exhibits temperature hysteresis, making it suitable for storing heat in winter and coolness in summer.

Chemical Storage Energy Density

The amount of energy released per unit mass; for example, coal releases $32,770\,kJ/kg$, octane $49,010\,kJ/kg$, and methane $55,510\,kJ/kg$.

Anode

The electrical conductor in an electrochemical cell that serves as the site for oxidation reactions.

Cathode

The electrical conductor in an electrochemical cell that serves as the site for reduction reactions.

Voltage

The difference in electrochemical potential between the two electrodes in an electrical circuit, measured in volts ($V$).

Lithium-ion Battery Anode Reaction (Discharge)

$$Li_xC_6(s) \rightarrow 6C(s) + xLi^+ + xe^-$$

Lithium-ion Battery Cathode Reaction (Discharge)

$$Li_{1-x}CoO_2(s) + xLi^+ + xe^- \rightarrow LiCoO_2(s)$$

Gravimetric Energy Density

A measure of battery energy capacity relative to weight, expressed in units of $Wh/kg$.

Volumetric Energy Density

A measure of battery energy capacity relative to volume, expressed in units of $Wh/L$.

Battery Energy Density Formula

$$\frac{\text{Voltage} \times \text{Number of movable } Li^+ \text{ ions in electrodes}}{\text{Total battery weight or volume}}$$

Hydrogen Energy Storage

An environmentally friendly medium with a high chemical energy density of $142,700\,kJ/kg$ that combines with oxygen to form water.

Fuel Cell

A device that converts $H_2$ and $O_2$ into water and electricity with higher efficiency and no flame compared to combustion.

Solid Oxide Electrolyser Cells (SOEC)

A technology that uses excess energy and $CO_2$ to produce syngas for synthetic diesel production.

Syngas

A mixture of hydrogen ($H_2$) and carbon monoxide ($CO$) produced during gasification or electrolysis processes.

Fischer-Tropsch (FT) Process

A chemical process used to convert syngas into liquid hydrocarbons like diesel.