Energy Harvesting Calculator

Size an energy-harvesting IoT node by balancing harvested power, load power, storage energy, and outage autonomy.

A beginner-first energy harvesting workbench with solar, vibration, thermal, and RF source models, synchronized energy-flow animation, storage sizing, daily balance, and practical design warnings.

Animation Beginner First Energy Harvesting Power Budget

Energy Harvesting Calculator

Balance ambient energy, converter losses, storage capacity, and node duty cycle. The goal is not only positive average power, but enough stored energy to survive cloudy, quiet, cool, or RF-poor periods.

3.15 mW average harvested power

1.01 mW average load power

+51.4 mWh/day daily energy balance

8.3 h storage-only autonomy

Goal

Convert a source estimate into a practical self-powered node decision.

Try First

Switch to RF, then compare harvested power against the same sensor duty cycle.

Watch

The energy token, storage level, daily balance, and warnings update together.

Why It Matters

Average power can look positive while storage is still too small for the expected outage.

Controls

Select a source, then tune the environment, node load, and storage reserve.

Source outdoor light

View energy flow

Playback manual

Light density 12 mW/cm2 Outdoor light level on the panel during useful sun hours.

Panel area 35 cm2 Active harvesting area or equivalent coupling scale.

Availability 5 h/day Hours per day when the source is available.

Harvest efficiency 18% Source and converter efficiency used by the classroom model.

Node voltage 3.30 V Regulated voltage used by the sensor node.

Active current 15.0 mA Current while sensing, transmitting, or processing.

Active time 72 s/h Seconds active per hour. This controls the duty cycle.

Sleep current 8.0 uA Current while the node waits between measurements.

Supercapacitor 10 F Usable storage is calculated from the high and low voltage window.

Outage target 8 h Expected period without useful harvested energy.

1. Source Estimate how much ambient energy reaches the harvester.

2. Converter Apply realistic conversion and power-management losses.

3. Storage Store enough energy for periods with little or no harvesting.

4. Load Calculate average sensor-node power from duty cycle.

5. Decision Check daily surplus and reserve before calling the design sustainable.

75.6 mW harvested peak power

2.0% node active duty cycle

8.4 mWh usable storage energy

Sustainable design result

Energy Flow

The moving token follows energy from the ambient source through conversion, storage, and the node load.

Converter loss

Reading: Harvested peak power only happens while the source is available. Average harvested power is lower.

Live Design Decision

Outdoor solar can support periodic sensing if panel area, sun hours, and storage reserve match the load.

Harvest side

Source modelSolar panel

Peak harvested75.6 mW

Average harvested15.8 mW

Daily harvested378 mWh/day

Load and storage

Average load1.01 mW

Daily load24.3 mWh/day

Storage energy8.4 mWh

Reserve target8 h

Design flags

The average energy balance is positive and storage covers the selected outage target.

Harvest Equation

Peak source power is reduced by efficiency and availability.

Pavg = Ppeak x hours/24

Load Equation

Average current combines active and sleep current using duty cycle.

Pload = V x Iavg

Storage Check

Supercapacitor energy depends on the usable voltage window.

E = 0.5 C (Vhi^2 - Vlo^2)

Beginner Ramp

Energy harvesting is a balance problem: source energy in, converter losses, storage reserve, and load energy out.

• Power is the rate of energy flow.
• Energy is power accumulated over time.
• Autonomy is how long storage can run the node without harvesting.

Core Formulas

Average harvest: Pavg = Ppeak x available hours / 24.

Average load: Iavg = Iactive x duty + Isleep x (1 - duty).

Storage: E = 0.5 C (Vhigh^2 - Vlow^2).

Quick Reference

• Positive daily balance means the average system can recharge.
• Storage reserve handles night, still machines, low temperature gradient, or poor RF exposure.
• RF harvesting usually supports only very low duty-cycle tags or sensors.

Solar Note

Solar design must use realistic useful sun hours, orientation, dirt, shade, aging, and seasonal variation. Outdoor peak values should not be treated as all-day values.

Thermal Note

Thermal generators need a sustained temperature difference and a heat path. If both sides warm together, the usable delta-T collapses.

Storage Note

Supercapacitors have leakage, voltage limits, and converter start-up constraints. The classroom calculation shows first-order usable energy, not a full hardware qualification.

Practice 1

Select RF and keep the default load. Explain why the daily balance becomes difficult.

Practice 2

Select Solar, reduce availability to 2 h/day, and increase outage target. Decide whether storage or load duty cycle should change first.

Practice 3

Select Thermal and vary delta-T. Notice that a small temperature difference gives much less usable power.

Related Study

Energy Harvesting Calculator Tool Use the detailed companion calculator for additional configuration. Power Consumption Calculator Refine active, sleep, and transmit load assumptions. Battery Life Calculator Compare harvested operation with primary battery operation.