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# System prepended metadata

title: 5.3 Energy Consumption & Ecology
tags: [Blockchain]

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# 5.3 Energy Consumption & Ecology
###### tags: `Blockchain`
The following notes are taken from [Coursera](https://www.coursera.org/learn/cryptocurrency/home/week/2)

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### Thermodynamic Limits
:::success
- **Landauer's Principle:** Any non-reversible computation must consume a min amount of energy
- Specificaly, each bit changed requires (kT in 2) joules
:::
- **SHA-256 is not reversible**
:::danger
Energy consumption is inevitable
:::

### Energy Aspects of Bitcoin Mining
- **Embodied energy:** used to manufacture mining chips & other equipment
    - should decrease over time
    - returns to scale
- **Electricity:** used to perform computation 
    - should increase over time 
    - returns to scale
- **Cooling:** required to protect equipment
    - costs more with increased scale

### Estimating Energy Usage: Top-down
- Each block worth approximately $15, 000
- Approximately $25/s generated
- Industrial electricity: $0.03/MJ
    - $0.10/kWh
:::success
Upper bound on electricity consumed:
900 MJ/s = 900 MW
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### Estimating Energy Usage: Bottom-up
- Best claimed efficiency: 1 GHz/W
- Network hash rate: 150,000,00 GHz
- (excludes cooling, embodied energy)
:::success
Lower bound on electricity consumed: 
150 MW 
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### Data Furnaces
- **Observation:** in the limit, computing devices produce heat almost as well as electric heaters
- Why not install mining rigs as home heaters?
- Challenges
    - Ownership/maintenance model
    - Gas heaters still at least 10x more efficient
    - What happens in summer?

### Open Questions
- Will Bitcoin drive out electricty subsidies
- Will Bitcoin require guarding power outlets?
- Can we make a currency with no proof-of-work?