From 45dedfd1ecffcd56d1c5632f4de771aa5525a4fb Mon Sep 17 00:00:00 2001 From: eggy Date: Sat, 20 Mar 2021 15:39:49 -0400 Subject: [PATCH] phys: add energy production --- docs/sph4u7.md | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/docs/sph4u7.md b/docs/sph4u7.md index babcb15..f9bed0c 100644 --- a/docs/sph4u7.md +++ b/docs/sph4u7.md @@ -349,6 +349,47 @@ Contents of hadrons must be shown. (See the last example for an example.) Some weak interaction that violates strangeness: (Source: Kognity) +## Energy sources + +!!! definition + - A **primary** energy source is one that is not transformed and used directly by the consumer, such as burning wood for heat. + - A **secondary** energy source is one that is converted from a primary source, such as electricity. + - **Proved reserves** are the resources that are known to be obtainable. + - **Production** are the actual reserves and placed in the market in a certain time interval. + - The **expectancy** of a product is the estimated time its proved reserves will last given its production (proved reserves ÷ production). + - The **specific energy** ($E_{SP}$) of a source is the energy obtained per unit mass of fuel (J/kg). + - The **energy density** ($E_D$) of a source is the energy obtained per unit volume (J/m3). + +If a fuel source can be replenished with a "reasonable" amount of time — one human generation, or 50–100 years — it is considered to be **renewable**. The world still largely uses non-renewable energy sources. + +(Source: Kognity) + +Electricity is the most common secondary energy source due to its convenience and ease of transport. + +### Sankey diagrams + +Sankey diagrams show the transfer of energy in a system via directed lines proportional to quantity of energy. Arrows pointing away indicate energy **degradation** — losses in energy transformation. + +(Source: Kognity) + +### Power generation + +A moving magnetic field produces an electromotive force as alternating current via **induction** and is how the large majority of power generation is handled. + +(Source: Kognity) + +In a nutshell, a source of thermal energy such as burning fossil fuels is used to boil water whose steam is then used to turn a turbine to generate power before condensing and repeating the cycle. + +Coal and oil-powered power plants have efficiencies of around 40% while natural gas is slightly higher at 50% as the gas itself can be used to turn a turbine. + +In **nuclear** power plants, the coolant fluid is instead used to turn a turbine. + +(Source: Kognity) + +As only uranium-235 is fissile, but uranium-238 is significantly more common (99.3% U-238 to 0.7% U-235), uranium must first be enriched until the concentration of U-235 is ~3%. **Gaseous diffusion** is a form of enrichment by forming uranium hexafluoride gas and then spinning it in a centrifuge to force separation of U-238 and U-235 based on mass. The energy used in enriching uranium is substantial and should be included in Sankey diagrams. + +Moderators are used to encourage fission as they slow down neutrons that are going too fast to fission (most) to a speed more suitable for fission. + ## Resources - [IB Physics Data Booklet](/resources/g11/ib-physics-data-booklet.pdf)