Energy Systems

Energy, Work and Power

• Energy: Capacity of a system to do work. It is the stored amount. $\boxed{E=P\ast t}$
  • Unit for Energy
  $$1\mathrm{J}=1\mathrm{kg}{\mathrm{m}}^2/{\mathrm{s}}^2=1\mathrm{Ws}=1\mathrm{Nm}=\frac{1}{3600}\mathrm{Wh}$$
• Work: It is the transfer of energy via force over a distance.
• Power: is the rate of Energy transfer $\boxed{P=\frac{W}{t}}$
  • Unit for Power

$$1\mathrm{W}=1\mathrm{J}/\mathrm{s}=1\mathrm{VA}=1\mathrm{kg}{\mathrm{m}}^2/{\mathrm{s}}^3$$

Types of Systems

Systems are arrangement of elements that together exhibit a behaviour or function that the individual elements cannot accomplish by themselves. The three ways to analyse of think of systems are:

• Functional: Here the relationship between different functions and behaviours are considered. The components are treated like a black box: Example electricity is the input, resulting in heat and products.
• Structural: The system is described as a set of individual parts that are interconnected.
• Hierarchical: The system on the whole is defined as a Supersystem, constituting of many Subsystems.

Energy System

The energy system value chain consists of Generation, Transportation and Use. Note: Conversion and Storage occur across the whole chain.

Generation of energy

It is the extraction or production of energy carriers from fossil, natural or renewable sources.

• Centralized systems: large power plants, central gas networks etc that is responsible for delivering power to a huge network of targets. Very common in for solid, liquid and gaseous energy carriers.
• Decentralized systems: several point sources that generate energy contributing to the energy grid allowing for bi-directional electricity flows.

Note

Centralized systems usually have import dependencies whereas decentralized systems are independent of global supply chains.

Energy Conversion Chain

Storage of Energy

• The purpose of energy storage is to temporally decouple the energy generation with the energy demand. They enable:

  • stability and reliability (against fluctuations, diverse sources)
  • mobility
  • energy cost optimization (off loading, arbitrage)
  • resilience and back-up (natural disasters, supply chain disruptions)

• Energy storage vs energy carrier: energy storage refers to the whole infrastructure that is responsible for charging, storing and discharging. An energy carrier is a substance (wind, coal, sun light etc) that can converted to obtain energy. Example: Fuel tank vs petrol, battery vs Lithium chemistry etc.

Usage of Energy

It is characterized by the metric Primary energy demand.