Energy Harvesting Cycle Animation

Energy Harvesting Cycle Animation

Interactive Visualization of IoT Energy Harvesting Systems

Energy Harvesting Cycle Animation

AnimationEnergy and powerHarvest • store • duty cycle

Energy Harvesting Cycle Animation

This interactive animation demonstrates how IoT devices can operate indefinitely by harvesting energy from environmental sources. The system shows the complete energy flow: harvest from source, store in capacitor/battery, regulate voltage, and power the load.

36.0 J

Harvested in one hour

3.8 J

Load energy in one hour

+31.3 J

Net reserve after loss

0.28%

Active duty cycle

TryUse Check balance for the worked 10 mW source over one hour. Recompute the reserve after adding the active, sleep, and storage-loss energy terms shown in the chapter.

ObserveThe source supplies 36 J in one hour. The reserve is positive only when that converted input is at least the combined load and storage loss over the identical interval.

ExplainEnergy balance compares like time windows: harvested power times duration supplies energy, while active and sleep power weighted by their durations determine consumption.

Technical boundariesThe arithmetic is a steady energy ledger; harvester I-V curves, MPPT dynamics, converter cold start, battery ageing, temperature dependence, stochastic sunlight, and brownout transients are outside it.

Colour keyenergy-power identityharvested/currentstored/referencesustainableloss/cautionenergy deficit

Source, storage, and duty cycle

Harvesting sourceSolarVibrationThermalRFCustom source

Available source power (mW)

10.00

Budget window (hours)

Source availability (%)

100%

Conversion efficiency (%)

100%

Storage capacity (J)

Initial storage (%)

50%

Active power (mW)

Active duration per wake (s)

Wake interval (s)

Sleep power (mW)

Storage loss in window (%)

0.5%

Harvesting budget results

36.0 JConverted harvested energy

2.0 JActive-mode energy

1.8 JSleep-mode energy

0.9 JStorage loss

+31.3 JNet energy reserve

93.9 hStored-energy autonomy without harvest

Energy flow and storage

1. Harvest

10.00 mW

available ambient input

2. Convert

100%

power-path efficiency

3. Store

211.3 J

end-of-window state

4. Load

3.8 J

active plus sleep demand

empty

58.7% stored

full

Energy budget comparison

Sustainable for this one-hour window.Harvested energy exceeds the active, sleep, and storage-loss terms.

Worked check

For 10 mW harvested over one hour, the available energy is 36 J. Compare that with the active, sleep, and storage-loss terms over the same hour; the reserve is their difference.

Understanding Energy Harvesting

The Promise of Energy Harvesting

Energy harvesting enables IoT devices to operate indefinitely without battery replacement by capturing ambient energy from the environment. This is crucial for:

• Remote deployments where battery replacement is impractical
• Sustainable IoT reducing battery waste
• Maintenance-free sensor networks
• Perpetual operation for monitoring applications

Energy Harvesting Cycle

The energy harvesting cycle consists of four key stages:

Alternative View: Energy Source Selection Decision Tree

This decision tree guides energy source selection based on deployment environment. Solar provides highest power density for outdoor applications. Vibration harvesting suits machinery environments. Thermal harvesting works for body-worn devices or industrial heat sources. RF harvesting enables indoor applications near transmitters but provides very low power.

Energy Sources Comparison

Comparison of Energy Harvesting Sources

Source	Power Density	Typical Power	Advantages	Challenges
Solar	10-100 mW/cm2	1-100 mW	High power, predictable	Light dependent, large area
Vibration	0.1-1 mW/cm2	0.1-10 mW	Always available (machinery)	Motion dependent, resonance
Thermal	10-50 uW/cm2	0.1-30 mW	Body heat, industrial	Low efficiency, needs gradient
RF	0.1-1 uW/cm2	0.001-1 mW	Works indoors	Very low power, distance

Energy Balance Equation

For sustainable operation, the energy balance must be positive or zero:

\[E_{harvested} \geq E_{consumed} + E_{storage\_loss}\]

Average power requirement:

\[P_{avg} = \frac{E_{active} \times t_{active} + E_{sleep} \times t_{sleep}}{t_{total}}\]

Where:

• \(E_{harvested}\) = Energy captured from environment
• \(E_{consumed}\) = Energy used by the IoT device
• \(E_{active}\) = Power during active mode
• \(t_{active}\) = Time in active mode
• \(E_{sleep}\) = Power during sleep mode
• \(t_{sleep}\) = Time in sleep mode

Storage Element Selection

Design Guidelines

Energy Harvesting Best Practices

1. Oversize the harvester by 2-3x expected load for margin
2. Use MPPT (Maximum Power Point Tracking) for solar to maximize efficiency
3. Implement duty cycling to reduce average power consumption
4. Size storage for expected periods without harvesting (night, calm weather)
5. Add brownout protection to gracefully handle energy depletion
6. Monitor energy budget in firmware to adapt behavior

Common Pitfalls

• Undersized storage: Not enough buffer for consumption spikes
• Ignoring leakage: Storage elements lose charge over time
• No energy awareness: Software doesn’t adapt to energy availability
• Wrong harvester for environment: Using solar indoors, RF in rural areas

What’s Next

Now that you understand energy harvesting systems, explore these related topics:

• Energy-Aware Design Considerations - Comprehensive energy optimization
• Context-Aware Energy Management - Adaptive power strategies
• Duty Cycle Animation - Sleep-wake power management
• Power Budget Calculator - Interactive power analysis
• Prototyping Hardware - Energy-efficient hardware selection

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Animation created for the IoT Class Textbook - ENERGY-001