Slobodna Energija

The New Site Is Live: A Lean Showcase for Open Hardware & Community Engineering

2026-08-29T18:00:00+02:00

The previous iteration of our website was a single-page React application—dark, flashy, and full of startup aesthetic clichés. It looked like a venture-funded tech startup trying to sell an app. But we are not a startup, we do not sell cloud subscriptions, and we have no corporate board.

Slobodna Energija is an open project hub, a community workshop, and a digital laboratory dedicated to practical energy sovereignty, open-hardware experimentation, and local-language speech tools. The website now completely reflects that mission: lean, fast, static, and transparent.

Static by Design, Git-Driven to the Core

The new platform is built with Pelican, generating pure, standards-compliant static HTML and CSS: - Plain Text in Git: Every project blueprint, sprout idea, dataset, and news dispatch lives as an ordinary Markdown file in our git repository. Proposing a technical correction or submitting a new experiment is as simple as opening a pull request. - Zero Database Vulnerabilities: There is no SQL database, no dynamic CMS to patch, no administrative logins, and no servers to crash under traffic. - Speed & Efficiency: The entire site renders in milliseconds on any browser, consumes negligible server resources, and can be hosted reliably from any static web server or a low-power off-grid Raspberry Pi.

Zero Third-Party Surveillance & Full Sovereignty

We practice the digital autonomy we advocate for in our hardware: - Self-Hosted Typography: Clean, beautifully rendered Manrope and Playfair Display typefaces (covering both Latin and Macedonian Cyrillic) are served directly from our own static server—clocking in at just 368 KB. Not a single request is made to Google Fonts. - Zero Tracking: No Google Analytics, no tracking pixels, no advertising beacons, and zero surveillance cookies. You do not need to click through cookie consent banners because we do not track you. - Transparent Targets: Every figure and indicator on our front page carries an explicit "TARGET" badge. We are focused on building tangible prototypes from the ground up, and we refuse to disguise forward-looking engineering roadmaps as completed results.

Interactive Demos Without Bloated Frameworks

Our interactive Macedonian voice synthesis and Whisper transcription demonstrations remain front and center, but they have been liberated from bulky framework dependencies: - Rebuilt using minimal, vanilla JavaScript, the demo widgets connect smoothly to local and demo endpoints. - No-Script Resilience: If JavaScript is turned off in your browser, the site remains 100% readable, accessible, and functional. You still receive the complete project story and technical specifications—just without interactive audio player buttons.

What Lies Ahead

Over the coming months, we will be replacing striped photo placeholders with real workbench photography, publishing open CAD files and circuit schematics, and streaming live telemetry from our first solar edge prototypes.

Explore the projects, clone the repository, and join us in building open community engineering for everyone.

Open Speech Transcription (Whisper)

2026-08-01T11:00:00+02:00

Every community workshop, technical presentation, panel discussion, and open lecture produces valuable spoken knowledge. Yet raw audio recordings remain closed, opaque data silos: they cannot be indexed by search engines, skimmed quickly, cross-referenced, or easily cited. This project delivers a high-speed, local-first speech-to-text pipeline for the Macedonian language, utilizing OpenAI's Whisper models accelerated by CTranslate2 to execute smoothly on accessible consumer hardware without sending audio to corporate cloud surveillance pipelines.

Transformer Acceleration via CTranslate2 & faster-whisper

Standard PyTorch implementations of Whisper suffer from heavy memory allocation overhead and slow execution loops. We achieve production-grade performance by executing models through the CTranslate2 engine and faster-whisper: - Dedicated Tensor Computation Kernels: CTranslate2 replaces Python-level interpreter overhead with custom C++ tensor execution kernels optimized for NVIDIA CUDA/cuDNN on GPUs and SIMD vector extensions (AVX-512, AVX2, ARM NEON) on modern CPUs. - 4x Throughput Multiplier: Transcribes Macedonian audio streams up to four times faster than vanilla PyTorch implementations while preserving identical word error rates and acoustic precision.

Local GPU & CPU Quantization (INT8 / FP16)

The breakthrough enabling local community deployment without multi-thousand-euro GPU clusters is neural weight quantization: - 8-Bit Integer Quantization (INT8): By mapping 32-bit floating-point weights to 8-bit integers with dynamic per-tensor scaling, the memory footprint of the flagship Whisper large-v3 model drops by over 65%—from 6.2 GB down to just ~2.1 GB. - Consumer GPU Execution: The full large-v3 model runs effortlessly on entry-level consumer GPUs equipped with 6GB or 8GB VRAM (such as NVIDIA GTX 1660 Ti, RTX 3060, or refurbished workstations). - Efficient Multi-Core CPU Inference: On consumer laptops powered by modern multi-core processors (AMD Ryzen, Intel Core i5/i7, or Apple Silicon ARM), the engine utilizes 4 to 8 parallel compute threads with int8_float16 hybrid kernels, executing faster than real-time speech (RTF < 0.6).

Open Ingestion Pipeline: Silero VAD & Word Timestamps

To suppress hallucination artifacts and produce synchronized transcripts, audio passes through a modular automated pipeline: 1. Voice Activity Detection (Silero VAD): Audio is segmented using a 30ms sliding analysis window. Background silence, HVAC fan hum, room reverberation, and applause are pruned before reaching the transformer encoder, preventing degenerative token looping. 2. Batched Beam Search Decoding: Utilizes a 5-candidate beam search with an adaptive temperature fallback schedule (0.0, 0.2, 0.4, 0.6, 0.8) triggered whenever repetition thresholds are detected. 3. Word-Level Timestamp Alignment: Inspecting cross-attention weight matrices within the decoder maps precise start and end millisecond timestamps to every recognized word. 4. Automated Multi-Format Export: Directly outputs time-aligned SRT and WebVTT subtitle files for video platforms, alongside structured Markdown transcripts tagged by speaker.

Preserving Public Knowledge & Open Archives

Open transcription transforms fleeting spoken words into an enduring digital commons: - Searchable Audio Archives: Public lectures on DIY solar installations, community microgrids, and open hardware become instantly searchable by local search engines and web crawlers. - Offline Kiwix Integration: Transcripts are bundled directly into local knowledge mirrors served by our off-grid solar edge stations, making critical documentation available even in remote rural mountain hubs. - Regional Linguistic Inclusion: Lowering barriers for cross-Balkan collaboration by providing accurate source transcripts for downstream open translation models. All pipeline scripts, CLI utilities, and Docker containers are open source and freely available in our git repository.

Voice Synthesis for Macedonian

2026-08-01T10:00:00+02:00

Neural speech synthesis (Text-to-Speech) is a foundational technology for digital accessibility and human-machine interaction. Yet low-resource languages like Macedonian are routinely neglected by major commercial tech vendors or trapped behind expensive proprietary cloud APIs that bill per character, impose network round-trip latency, and log user telemetry. This project delivers an open-source, local-first text-to-speech engine for Macedonian engineered to execute on affordable edge hardware with zero external dependencies.

Piper TTS & VITS End-to-End Neural Architecture

Rather than relying on legacy two-stage pipelines (which generate intermediate mel-spectrograms before feeding a computationally heavy vocoder), our system builds upon Piper TTS and the VITS (Variational Inference with adversarial learning for end-to-end Text-to-Speech) architecture: - Unified Differentiable Network: VITS unifies a Variational Autoencoder (VAE), normalizing flows, and an adversarial HiFi-GAN based vocoder into a single end-to-end differentiable model. - Monotonic Alignment Search (MAS): During training, MAS discovers the alignment between input phonemes and target speech representations automatically, removing the need for labor-intensive, millisecond-level manual audio segment labeling. - ONNX Runtime & INT8 Quantization: Trained checkpoints are exported to ONNX format and quantized using 8-bit integer weights. The model footprint is compressed to under 48 MB, allowing it to be pinned in RAM even on low-cost embedded systems without swapping.

Algorithmic Phonetic IPA Rules for Macedonian

Acoustic models trained on multilingual corpora fail when presented with raw Macedonian Cyrillic text without an explicit phonetic bridge. We developed an open, deterministic grapheme-to-phoneme (G2P) transpiler mapping Cyrillic orthography to the International Phonetic Alphabet (IPA):

Palatal Stops & Affricates:
Accurate discrimination of palatal plosives /ɟ/ (ѓ) and /c/ (ќ) rather than softening dental consonants.
Clean synthesis of complex affricates: /t͡s/ (ц), /t͡ʃ/ (ч), /d͡ʒ/ (џ), and the distinctive Macedonian voiced alveolar affricate /d͡z/ (ѕ).
Palatal sonorants: dedicated modeling for /ʎ/ (љ) and /ɲ/ (њ).
Vocalic Syllabic 'r' (/r̩/):
Macedonian syllabic 'r' governs distinct phonological contexts: when occurring word-initially before a consonant (e.g. ’рбет, ’рѓа, ’ржи) or inter-consonantally (e.g. прст, дрво, крв, брзо), the engine tags the phoneme as syllabic /r̩/, preventing the neural vocoder from introducing synthetic schwa vowels.
Antepenultimate Stress Rule (Третосложен акцент):
Standard Macedonian features fixed antepenultimate word stress: on trisyllabic and polysyllabic words, stress consistently falls on the third syllable from the word ending (e.g., пла́нината, воде́ница, рабо́тилница), while on disyllabic words it falls on the penultimate syllable (e.g., ку́ќа, ри́дот).
The transpiler performs syllabification and injects IPA primary stress markers (ˈ), ensuring speech preserves correct natural cadence and melodic prosody.

Zero-Cloud Local Edge Inference

The defining engineering achievement of this pipeline is its speed and total network independence: - Real-Time Factor (RTF): Running on a stock quad-core Raspberry Pi 4 (ARM Cortex-A72 at 1.5 GHz), the engine achieves a Real-Time Factor (RTF) of ~0.15. A 5-second sentence is synthesized in just 750 milliseconds. On modern x86/ARM laptop CPUs, RTF drops below 0.04. - Sub-180ms Time-to-First-Audio: The pipeline streams synthesized PCM audio chunks to playback hardware within 180 ms of receiving text input. - Total Privacy & Zero SaaS Overhead: The daemon runs locally over a UNIX domain socket or a lightweight localhost REST endpoint. Text never leaves the edge device, providing ironclad privacy for sensitive documentation or off-grid field deployments.

Real-World Applications in the Open Lab

We integrate the voice engine directly into our physical and civic projects: - Spoken Solar Telemetry: Off-grid solar stations and mountain mesh repeaters announce battery reserves, energy harvest figures, and severe weather warnings aloud to visitors and hikers. - Accessible Open Education: Automatically transforming open technical handbooks, civic documents, and workshop tutorials into audiobooks for visually impaired community members. - Open Codebase: All training pipelines, phonetic dictionary tables, and quantized ONNX checkpoints are freely accessible in our git repository under open-source licenses.

Cross-Border Sensor Network

2026-07-17T01:02:00+02:00

Problem Statement

Toxic winter air pollution inversions, summer wildfire smoke plumes, and severe alpine weather fronts do not recognize national borders across the Balkan peninsula. At the same time, high border ridges (Šar Mountain, Korab, Belasica, Osogovo) offer exceptional Line-of-Sight spanning 80 to over 140 km across frontiers. Yet, state environmental monitoring remains fractured across slow bureaucratic silos, while commercial data transmission is crippled by expensive cellular roaming. This sprout builds an autonomous, open-hardware cross-border sensor mesh operating on the license-free 868 MHz LoRa/Meshtastic spectrum to relay vital environmental telemetry freely across borders.

Open Hardware Bill of Materials (BOM Hints)

Radio Node & Repeater: Semtech SX1262 LoRa transceiver on 868 MHz (+22 dBm PA output) mated with a 5.8 dBi omnidirectional fiberglass collinear antenna; ultra-low-power RAK Wireless WisBlock (Nordic nRF52840) or Heltec Wireless Tracker core.
Power Subsystem for Sub-Zero Extremes: 30W glass-laminated monocrystalline solar panel; 12.8V 15Ah LiFePO4 battery pack equipped with an active BMS featuring a hardware-enforced 0°C low-temperature charge cutoff and a self-heating silicone pad powered strictly by excess solar input down to -25°C.
Ruggedized Enclosure: UV-resistant IP67 polycarbonate enclosure fitted with a Gore-Tex hydrophobic membrane vent for internal pressure equalization without condensation buildup; stainless steel mast mounting hardware.
Sensor Instrumentation Suite: Sensirion SPS30 laser optical particulate matter sensor (PM1.0, PM2.5, PM4, PM10); Bosch BME280 (temperature, relative humidity, pressure); Figaro TGS2600 / Sensirion SGP41 sensor for early wildfire smoke, CO, and volatile organic compounds.

Schematics & Experiment Notes

Mountain Line-of-Sight Radio Propagation: Stationed at 1800m to 2200m ASL, repeaters command optical Line-of-Sight into neighboring valleys in Kosovo, Serbia, Bulgaria, and Greece. Configured with Spreading Factor 11 (SF11) and 125 kHz bandwidth, the link budget achieves 148 dB, enabling reliable packet exchange beyond 100 km without cellular towers.
Early Wildfire Detection Heuristic: Firmware evaluates a dynamic combustion anomaly score ($S_{\text{fire}} = k_1 \frac{d(\text{PM2.5})}{dt} + k_2 \frac{d(\text{VOC})}{dt} - k_3 \cdot RH$). A sudden rise in particulate density and reducing gases accompanied by low humidity immediately shifts the node into alarm mode, flooding high-priority LoRa alert packets across the regional mesh.
Zero Cellular Roaming Expense: Packets travel peer-to-peer over license-free ISM spectrum, bypassing cellular telecom providers, foreign roaming fees, and centralized infrastructure completely.

Call for Contribution (How to Join)

Mountaineers & Hikers: Help carry and deploy solar repeater pods at alpine huts, mountain shelters, and summits along international border ridges.
Developers & Web Analysts: Join the development of an open regional web dashboard visualizing real-time transboundary air quality and wildfire hazard telemetry.
Firmware Optimizers: Assist in tuning solar power management and packet collision mitigation algorithms during multi-week winter blizzards.

Open Solar Alliance

2026-07-17T01:01:00+02:00

Problem Statement

Commercial solar equipment is increasingly locked down by artificial software barriers: hybrid inverters requiring mandatory account creation on remote corporate cloud servers that brick during internet outages, battery packs with obfuscated communications that forbid user repair, and ad-infested mobile apps. Furthermore, the Balkan regional market is plagued by counterfeit Grade-B LiFePO4 cells relabeled as Grade-A and solar modules with inflated power ratings. This sprout unites an open alliance of hackerspaces, electrical engineers, and solar installers to engineer open-hardware alternatives, reverse-engineer proprietary protocols, and conduct rigorous, independent lab testing.

Open Hardware Bill of Materials (BOM Hints)

Open EDA Circuit Repository (KiCad): Public repositories hosting CERN-OHL v2 licensed schematics for DIY MPPT charge controllers, active flying-capacitor cell balancers, and smart DIN-rail DC disconnects.
Protocol Sniffing Rig: USB-to-CAN bus adapters (Candlelight / Waveshare) and galvanically isolated USB-to-RS485 converters featuring authentic FTDI chipsets, paired with open digital logic analyzers (Sigrok / PulseView).
Battery Testing Workstation: EBC-A40L high-precision battery capacity tester (up to 40A discharge current with 4-wire Kelvin sense leads), YR1035+ AC milliohm meter ($1\text{ kHz}$ test signal for internal resistance), and a FLIR thermal camera.
Open Hardware Inverter Gateway: Dedicated ESP32 board interfacing directly with inverter Modbus/RS485 service ports, permanently replacing proprietary cloud-dependent Wi-Fi dongles.

Schematics & Experiment Notes

Inverter Protocol Reverse-Engineering: Decoded register tables for prevalent regional hybrid inverters (Deye, Growatt, Easun, Must, Victron VE.Direct). Yields 100% local, offline telemetry for voltages, currents, power flows, and battery state-of-charge directly into Home Assistant via MQTT.
Independent LiFePO4 Torture Benchmarking: Conducting standardized 0.5C charge/discharge lifecycle tests on prismatic cells purchased from regional vendors. Actual capacity curves (Ah), DC internal resistance ($R_{\text{int}}$), and thermal degradation plots are published to a public Git repository, exposing fraudulent supplier specs.
Standardized DIY Mounting Hardware: Open-source FreeCAD parametric models and DXF vector files for structural aluminum and galvanized steel racking tailored for flat roofs, pitched tiles, and balcony railings, cut locally on CNC sheet-metal lasers.

Call for Contribution (How to Join)

Protocol Reverse-Engineers: Assist with logging and decoding unknown CAN bus frames and handshake packets from new inverter models and commercial BMS modules.
Hardware Designers: Contribute modular KiCad schematics for solid-state DC contactors, high-current shunt monitors, and open BMS controller designs.
Solar Installers & Regional Labs: Send suspect cells and gear to our test bench and share field-failure reports in our open collaborative knowledge base.

Local Energy Community Model

2026-07-17T01:00:00+02:00

Problem Statement

When a rooftop solar array produces peak surplus at midday, the energy is back-fed to the distribution utility at a fraction of its retail value, while a neighbor across the street pays full commercial tariff for that exact electricity. Centralized distribution grids penalize micro-producers and experience severe phase imbalance and over-voltage trips when multiple solar inverters inject power simultaneously into the same low-voltage substation feeder. This sprout develops an open-source peer-to-peer (P2P) local microgrid simulation engine and smart meter telemetry gateway for neighborhood energy cooperatives.

Open Hardware Bill of Materials (BOM Hints)

Smart Meter Optical Interface: ESP32 optical probe (IEC 62056-21) or galvanically isolated RS-485 Modbus-RTU converter capturing granular 15-minute OBIS load curves directly from residential and commercial meters.
Local Simulation Server: Low-power edge mini-PC (refurbished HP T630 x86 thin client or Raspberry Pi 4 drawing <15W).
Software Simulation Stack: Discrete-event simulation daemon written in Python utilizing pandapower for AC power-flow and voltage-drop calculations; embedded SQLite / DuckDB local time-series database.
Secure Mesh Networking: WireGuard peer-to-peer encrypted mesh connecting neighborhood nodes to exchange telemetry securely without any centralized cloud dependency.

Schematics & Experiment Notes

15-Minute P2P Settlement Algorithm: The simulator matches local micro-producers with active consumers in 15-minute intervals. Surplus solar power is routed virtually to neighbors at an equitable mid-market rate ($Tariff_{\text{P2P}} = \frac{Tariff_{\text{import}} + Tariff_{\text{export}}}{2}$), maximizing economic savings for both producer and consumer.
Substation Feeder Constraint Modeling: Using low-voltage electrical distribution network impedance models, the simulator verifies that concurrent solar injection does not breach statutory $\pm 10\%$ voltage envelopes on $230\text{V}$ lines, preventing inverter trips.
Automated Demand-Side Flexibility: Dispatches local MQTT control signals to trigger flexible residential loads (heat pumps, hot water thermal stores, home battery storage, EV chargers) precisely during peak midday solar surplus.
Zero-Cloud Privacy Architecture: Highly sensitive high-resolution household consumption profiles never leave the local neighborhood perimeter; the engine exposes only cryptographically aggregated net-settlement values.

Call for Contribution (How to Join)

Power Systems Engineers: Provide real-world wire impedance parameters and low-voltage topology models typical of Balkan residential distribution grids.
Python / Data Science Developers: Contribute to our pandapower optimization routines and machine-learning load forecasting pipelines.
Citizen Energy Collectives: Share anonymized 15-minute smart-meter profile logs to benchmark and validate our open simulation algorithms.

Airborne Wind Turbine

2026-07-17T00:10:00+02:00

Problem Statement

Surface-level winds in valley basins and urban valleys are turbulent, unpredictable, and sluggish (averaging below 3.5 m/s)—well below the threshold for viable turbine generation. However, at altitudes of 100 to 300 metres, wind speeds regularly double or triple. Because wind kinetic power density scales with the cube of velocity ($P/A = \frac{1}{2}\rho v^3$), doubling wind speed delivers an eight-fold increase in harvestable energy. Erecting 150-metre steel-and-concrete towers is environmentally invasive and financially prohibitive for local communities. This sprout investigates open Airborne Wind Energy (AWE) tethered wing systems that tap persistent winds aloft with lightweight ground generators.

Open Hardware Bill of Materials (BOM Hints)

Aerodynamic Wing: Ram-air parafoil wing (3.5–5.0 $m^2$ canopy area) stitched from high-tenacity 40D ripstop nylon with braided Kevlar bridle lines.
High-Tensile Tether Line: 200 metres of ultra-high-molecular-weight polyethylene line (UHMWPE / Dyneema SK78, 2.5 mm diameter, 650 kg breaking strain, linear weight under 3.5 g/m).
Ground Winch & Generator: High-power brushless DC outrunner motor (5065 270KV or repurposed hoverboard hub motor) functioning as a regenerative brake and generator; open ODrive or VESC 6 motor controller supporting Field-Oriented Control (FOC) torque regulation.
Ground Station Instrumentation: S-type industrial load cell paired with an HX711 24-bit ADC for continuous tether tension monitoring (up to 200 kg); AS5600 magnetic rotary encoder mounted on the winch drum shaft to track reel-out distance and speed.
Flight Avionics: Espressif ESP32-S3 module featuring an ICM-20948 6-DOF IMU, BMP280 barometric altimeter, LoRa 868MHz telemetry link, and a thermal nichrome wire wire-cutter for emergency tether severance.

Schematics & Experiment Notes

Ground-Gen Pumping Cycle (Yo-Yo Mode):
Traction Generation Phase (Reel-out): The parafoil wing executes autonomous crosswind figure-8 patterns at speeds up to three times ambient wind velocity, exerting intense aerodynamic line pull ($F_{\text{pull}} > 800\text{ N}$). The unwinding tether spins the ground winch generator, outputting 300–600W into a 48V bus.
Recovery Phase (Reel-in): At the 200m limit, the wing pitches forward to dump aerodynamic lift, allowing the motor to rapidly reel the tether back using under 10% of the energy produced during the generation cycle.
Dynamic Strain Telemetry: Continuous strain-gauge logging monitors line tension in real time. If gust peaks exceed the safe threshold ($1200\text{ N}$), the controller actively depowers the kite's angle of attack to prevent mechanical structural failure.
Emergency Parachute Recovery: If LoRa communication fails for more than 3 seconds or tether tension collapses abruptly, a spring-deployed drogue parachute deploys automatically to bring the wing down in a controlled glide.

Call for Contribution (How to Join)

Kite Makers & Sail designers: Help us tailor and flight-test ram-air foil profiles boasting high lift-to-drag performance ($L/D > 5$) on mountain saddles.
Power Electronics Hackers: Assist in designing bidirectional regenerative DC/DC converter circuitry to efficiently buffer wildly fluctuating generator voltages into LiFePO4 storage.
Autonomous Flight Developers: Collaborate on porting crosswind flight trajectory control to ArduPilot or embedded ROS2 nodes.

3D-Printed Solar Tracking Robotic Arm

2026-07-17T00:09:00+02:00

Problem Statement

Fixed-mount solar panels lose up to 35% of daily insolation because sunlight strikes at oblique angles during morning and late afternoon hours (Lambert's cosine law: $P = P_{\text{peak}} \cos \theta$). Industrial commercial trackers are cost-prohibitive for small off-grid setups, excessively heavy, and frequently consume more parasitic power on heavy motors than the actual energy harvested from tracking. This sprout develops an accessible, 3D-printed dual-axis kinematic mechanism (azimuth and elevation) featuring self-locking worm gears, stepped actuation, and negligible parasitic consumption under 3Wh per day.

Open Hardware Bill of Materials (BOM Hints)

Microcontroller & Energy Monitoring: Raspberry Pi RP2040 or ESP32 dual-core microcontroller; Adafruit INA219 high-side I2C voltage and current monitor to accurately log net harvested energy; DS3231 high-precision real-time clock (RTC).
Motors & Actuation Mechanics: Two NEMA 17 stepper motors geared with 51:1 reduction or heavy-duty waterproof metal-gear servos (RDS3225 25kg-cm / MG996R); Trinamic TMC2209 silent stepper drivers with microstepping.
Sensor Array: 4-quadrant photodetector array built with matched Light Dependent Resistors (LDRs) partitioned by a 3D-printed cross baffle for differential light tracking.
Printed Structure & Bearings: All gears, clevis mounts, and structural housings modeled in FreeCAD and optimized for FDM printing in UV-resistant ASA or PETG with 40% gyroid infill; standard 608RS sealed ball bearings and M4/M5 stainless steel fasteners.

Schematics & Experiment Notes

Self-Locking Worm Gear Kinematics: A 40:1 worm-and-wheel reduction prevents wind-induced back-driving. Motors are energized strictly during active micro-adjustments; in idle state, motor driver rails are completely severed via high-side MOSFETs, reducing quiescent motor draw to zero.
Hybrid Dual-Mode Tracking Algorithm:
Astronomical Solar Position Algorithm (SPA): The controller calculates the exact solar azimuth and zenith based on date, time, and GPS coordinates, ensuring accurate positioning even through thick cloud cover.
Differential Photodetector Calibration: When global irradiance exceeds $200\text{ W/m}^2$, the 4-quadrant sensor fine-tunes alignment directly to the sky's brightest focal point.
Energy Balance & Stepped Duty Cycle: The panel moves in 3.75° increments every 15 minutes. Daily motor operating time totals under 80 seconds, consuming less than 3Wh per day. On a 50W solar module, this delivers an additional 90Wh to 130Wh net harvest compared to a fixed angle.

Call for Contribution (How to Join)

FreeCAD & Mechanical Engineers: Assist with refining weatherproof bearing seals and stress-testing gear teeth against severe gust shear forces.
STEM Educators & Makerspaces: Help us create open visual assembly manuals and workshop curricula for technical high schools and youth maker clubs.
Software Developers: Port our hybrid tracking state machine into standalone modules for ESPHome and MicroPython.

Crypto Micro-Donations for Hardware

2026-07-17T00:08:00+02:00

Problem Statement

Procuring electronic components, precision sensors, solar cells, and lab test instruments from global suppliers is frequently hamstrung by punitive international bank wire charges, SWIFT fees, and credit card gateways that devour 30% to 50% of small donations (€1 to €10). Furthermore, traditional crowdfunding platforms pool money into opaque, non-itemized buckets with zero visibility into how donations translate into actual parts. This sprout builds a sovereign, self-hosted micro-donation infrastructure dedicated to direct line-item sponsorship from open Bill of Materials (BOM) specs.

Open Hardware Bill of Materials (BOM Hints)

Host Server Hardware: Low-power single-board computer (ODROID-C4 or Raspberry Pi 4 with 4GB RAM) equipped with an external 500GB NVMe SSD over USB 3.0 for sustained node operations.
Software Stack: Self-hosted BTCPay Server instance orchestrating Dockerized daemons; Core Lightning (CLN) / LND node with local liquidity management; pruned Monero node for donor privacy.
Interactive Lab Terminal: Espressif ESP32 with a 3.5-inch SPI capacitive touch display (ILI9488) rendering instant on-counter QR payment invoices and triggering addressable LEDs on the matching physical parts drawers.
Cryptographic Cold Storage: SeedSigner or Coldcard hardware wallet for air-gapped signing of liquidity rebalances; zero private treasury keys reside on the internet-facing server.

Schematics & Experiment Notes

Zero-Fee Lightning Micropayments: Leveraging the Bitcoin Lightning Network to process payments under €1.00 with sub-2-second settlement and network routing fees below €0.001. A supporter can directly sponsor a single €0.50 connector or €6 transceiver without bank fees eroding the contribution.
Itemized BOM Sponsorship Targets: Each component from our open KiCad schematics is mapped to an interactive sponsorship target:
Connectors, TVS diodes, and passives: €0.50 – €2.00
Semtech SX1262 LoRa module: ~€6.00
Synchronous MPPT controller IC: ~€12.00
3.2V 100Ah LiFePO4 battery cell: ~€38.00
1kg UV-resistant PETG/ASA filament spool: ~€18.00
Automated Public Accounting (Git-backed Ledger): BTCPay Server webhooks automatically push cryptographically signed commits to a public Git repository (ledger.git), updating inventory levels in real time and publishing scanned supplier receipts immediately after procurement.
Zero Intermediary Dependency: No commercial merchant accounts, zero commission cuts to Stripe or PayPal, and zero risk of arbitrary financial freezes during international solidarity campaigns.

Call for Contribution (How to Join)

Frontend Developers: Help us build a zero-dependency, ultra-lightweight JavaScript widget to render dynamic BOM items and invoice QR codes without external bloat.
Lightning Node Operators: Open direct liquidity channels with our lab node to enhance routing connectivity across the South-Eastern European mesh.
Open Hardware Makers: Connect your local open-source hardware projects to our platform to enable itemized component micro-funding for your prototypes.

Open Green Points

2026-07-17T00:07:00+02:00

Problem Statement

Environmental incentives and energy conservation programs too often devolve into corporate greenwashing, bureaucratic subsidy red-tape, or predatory Web3 schemes based on speculative tokens that crash and attract rent-seekers. Concurrently, citizens who tangibly curtail electricity consumption during peak grid stress hours (peak shaving), deploy balcony micro-solar panels, or volunteer manual labour in local maker labs have no transparent, tamper-proof mechanism to verify their real-world contribution. This sprout investigates a decentralized, non-financialized reputation protocol rooted in cryptographic transparency logs rather than speculative cryptocurrency tokens.

Open Hardware Bill of Materials (BOM Hints)

Optical Smart Meter Read Head: 3D-printed magnetic optical probe equipped with an infrared phototransistor (SFH309) and IR emitter LED, built strictly to the physical IEC 62056-21 / IEC 61107 specification.
Readout Microcontroller: Espressif ESP32-C3 featuring hardware UART and an open OBIS telegram parser running on ESPHome, enabling completely local meter parsing with zero cloud reliance.
Secondary Lab Energy Meter: Eastron SDM120 Modbus-RTU or PZEM-004T v3.0 single-phase digital DIN-rail power meter coupled with a split-core current transformer (CT, 100A).
Hardware Cryptographic Token: Hardware security key (Nitrokey 3, SoloKey, or on-board ATECC608A secure element) generating and protecting the node's Ed25519 device signing keys.
Local SBC Node / Ledger: Ultra-low-power single-board computer (Raspberry Pi Zero 2W or similar) running an open append-only transparency log daemon powered by Merkle tree primitives (Trillian / RFC 6962 architecture).

Schematics & Experiment Notes

OBIS Code Extraction from Smart Meters: The optical probe interrogates standard utility meters (such as Iskraemeco MT880 and Landis+Gyr) at 300 to 9600 baud, parsing official tariff registers: total active imported energy (1.8.0, 1.8.1, 1.8.2) and active exported solar energy (2.8.0).
Cryptographic Proof of Curtailment: The local node models the household's baseline consumption. During grid peak-demand alert windows, verified reductions in active power ($P_{\text{saved}} = P_{\text{baseline}} - P_{\text{actual}}$) are cryptographically signed with the user's Ed25519 key and appended to the local Merkle log.
Non-Transferable (Soulbound) Reputation: Reputation records are irrevocably bound to the participant's self-sovereign public key. They are not tradeable tokens, hold no financial market price, cannot be transferred or sold, and require zero blockchain transaction fees—eliminating financial speculation entirely.
Physical Hacker-Lab Redemption Value: Verified points grant immediate access to shared community infrastructure: reserved machining hours on 3D printers and CNC mills, checkout privileges for high-end test instruments (FLIR thermal cameras, spectrum analyzers, Rigol digital oscilloscopes), and seats in advanced hardware workshops.

Call for Contribution (How to Join)

Cryptographers & Backend Engineers: Help develop lightweight Rust / Go libraries for client-side cryptographic Merkle audit path verification on resource-constrained devices.
Firmware Hackers: Expand our open repository of OBIS protocol parsers to support diverse multi-tariff smart meters deployed throughout the Balkan region.
Makerspaces & Community Labs: Join our testbed federation to integrate automatic lab equipment checkout workflows driven by cryptographic green points.

Microclimate Cooling Mister

2026-07-17T00:06:00+02:00

Problem Statement

Urban asphalt, concrete, and the lack of tree canopy in our cities create brutal urban heat islands, where summer ambient temperatures frequently exceed 40°C and ground surfaces radiate past 55°C. Standard commercial misting systems operate at low pressures, producing oversized water droplets (>30 microns) that drench park benches and passersby instead of cooling the air. Far more critically, using open holding tanks with warm, stagnant water poses an unacceptable biohazard: the aerosolization of lethal Legionella pneumophila bacteria. This sprout develops an autonomous, solar-powered high-pressure microclimate cooling mister featuring psychrometric activation, zero-cloud control, and uncompromising biological safety.

Open Hardware Bill of Materials (BOM Hints)

High-Pressure Booster Pump: 12V/24V DC positive displacement plunger pump (operating at 70 bar / 1000 PSI, flow rate 0.5–1.0 L/min, ~60–80W power draw under full load).
Misting Nozzles & Plumbing: Brass or stainless steel misting nozzles with 0.15mm ceramic orifices and integrated spring-loaded anti-drip check valves; polyamide (PA12) high-pressure tubing rated to 100 bar burst resistance.
Filtration Subsystem: Dual-stage inline filter assembly: 5-micron spun polypropylene sediment filter + 10-inch extruded activated carbon block (CTO) to strip particulates and chlorine that cause limescale clogging.
Sensors & Presence Detection: Bosch BME280 precision sensor for ambient temperature, relative humidity, and barometric pressure; Panasonic AMN31111 / HC-SR501 passive infrared (PIR) motion sensor with a 120° wide detection cone; analog industrial pressure transducer (0–100 bar, 0.5–4.5V output).
Controller & Power: Espressif ESP32-S3 microcontroller; 50W monocrystalline solar panel; 12.8V 12Ah LiFePO4 battery pack with integrated 4S BMS; heavy-duty MOSFET switching module (BTS7960 or IRF4905) featuring PWM soft-start to eliminate inductive inrush current.

Schematics & Experiment Notes

Flash Evaporation Thermodynamics: At 70 bar through 0.15mm ceramic orifices, atomized droplet diameters range between 5 and 10 microns. These microscopic droplets flash-evaporate instantaneously in mid-air before hitting the ground or skin, absorbing latent heat of vaporization ($2260\text{ kJ/kg}$) and slashing localized air temperatures by 5°C to 9°C.
Psychrometric Activation Logic: The microcontroller continuously calculates the wet-bulb depression. Misting is enabled strictly when $T > 32^\circ\text{C}$ AND relative humidity $RH < 45\%$. If the ambient air is already muggy or saturated, misting would create an unbearable greenhouse effect and is automatically locked out.
PIR Presence Gating: The pump fires in disciplined cycles: 15 seconds of misting followed by a 45-second resting interval, and only when the PIR sensor detects human presence within the canopy footprint.
Strict Anti-Legionella Safety Protocol: The system connects directly and exclusively to certified municipal pressurized potable tap water—the use of rainwater storage tanks or recycled cisterns is strictly prohibited. After every operating cycle, a normally-open solenoid drain valve vents line pressure and purges residual water, preventing warm stagnation under direct sun.
Telemetry & Open Data: Local logging of duty cycles, water consumption (litres), ambient $\Delta T$ achieved, and battery status, broadcast across the regional LoRa mesh to inform urban heat island research.

Call for Contribution (How to Join)

Hydraulics & Filtration Makers: Help us torture-test nozzle longevity in areas with extreme calcium carbonate water hardness and prototype an automated mild acetic acid descaling cycle.
Electronics & PCB Engineers: We are designing a compact, DIN-rail mountable PCB with galvanic isolation and flyback clamp diodes for the inductive pump load.
Urban Advocates & Municipalities: Partner with us to map the most heat-stressed bus stops and pedestrian plazas for initial pilot field deployments.

Solar Smart Fountain

2026-07-17T00:05:00+02:00

Problem Statement

Municipal drinking fountains in city parks and public squares frequently sit neglected for weeks when a mechanical tap or valve breaks, wasting thousands of cubic metres of treated drinking water before anyone responds. In addition, early winter frosts freeze standing water inside the pipework, bursting fittings and causing expensive infrastructure damage. Commercial telemetry systems are cost-prohibitive, demand mains grid connections, and run on closed proprietary clouds. This sprout delivers an open hardware retrofit kit that transforms any standard public fountain into an intelligent, autonomous solar node for conservation, leak alerting, and automated maintenance.

Open Hardware Bill of Materials (BOM Hints)

Controller & Radio: Espressif ESP32-C3 RISC-V mini module (with deep-sleep power draw of $15\mu\text{A}$) paired with a Semtech SX1262 LoRa transceiver operating on 868 MHz.
Power Subsystem: 10W monocrystalline photovoltaic canopy panel; single 3.2V 6000mAh LiFePO4 cylindrical cell (32700 form factor) with TP5000 / CN3791 MPPT-like solar charger and ultra-low quiescent current buck-boost converter (TPS63020).
Valving & Contactless Activation: 1/2" brass bistable (latching) solenoid valve requiring only a momentary current pulse (50–100 ms) to open and close, drawing zero quiescent holding current; digital infrared Time-of-Flight (ToF, VL53L0X) or waterproof capacitive sensor for touchless water dispensing.
Metering & Sub-Freezing Protection: Food-grade brass Hall-effect flow meter (YF-B1, 1–25 L/min, ~450 pulses/litre); digital waterproof temperature probe (DS18B20) clamped directly to the incoming riser pipe; secondary gravity-drain electromagnetic valve at the lowest plumbing point.

Schematics & Experiment Notes

Pulsed Solenoid Driver: The bistable latching solenoid is driven via a miniature H-bridge (TI DRV8837). To open the valve, a +12V 60 ms pulse is delivered from a boosted reservoir capacitor; to close, an inverted polarity pulse is applied. The total average electronic power draw remains below 0.8 mW.
Anti-Tamper & Leak Mitigation Algorithm: The firmware measures cumulative flow in real time. If the tap flows continuously for longer than 90 seconds (indicating vandalism, a stuck sensor, or an obstructed basin), the valve closes automatically and a high-priority LoRa alert beacon is dispatched.
Automated Winter Freeze Drain: When the DS18B20 probe registers incoming water temperatures dropping below +2°C, the controller locks out the main intake valve and energizes the lowest drain valve to evacuate standing water via gravity, preventing burst pipes without costly heating tapes.
Sanitary & Potable Water Integrity: The system connects strictly to certified municipal drinking water mains. Rainwater harvesting is deliberately separated and diverted purely to sub-surface soil irrigation for nearby trees.
LoRa Telemetry Payload: Every 60 minutes (or immediately on leak/freeze alarm), a compact 12-byte CBOR packet is broadcast: total volume dispensed ($m^3$), current flow rate ($\text{L/min}$), pipe temperature ($^\circ\text{C}$), and battery voltage ($\text{V}$).

Call for Contribution (How to Join)

Firmware Developers: Help us optimize the ESPHome / Zephyr RTOS state machine for sub-$10\mu\text{A}$ sleep states and resilient LoRaWAN/Meshtastic reconnects.
Mechanical & CAD Designers: We need rugged, vandal-resistant enclosures 3D-printed in UV-stable PETG/ASA or cast aluminium to mount seamlessly onto municipal fountain fixtures.
Field Testers: If you are interested in deploying a pilot fountain kit at your local community centre, schoolyard, or mountain hut, get in touch or open an issue on our community tracker.

Solar Charging Station & Edge Node

2026-07-17T00:04:00+02:00

Clean energy generation and local digital infrastructure should be visible, touchable, and freely accessible in everyday public spaces. Rather than commercial "smart benches" that hide closed electronics behind proprietary vendor NDAs and expensive recurring service contracts, we build an open-hardware public hub and microgrid where every screw, cable, circuit schematic, and line of code is completely transparent, repairable, and free for community replication.

Portable Open-Hardware Structure & Synchronous MPPT Controller

The station is engineered using modular aluminum structural extrusion (2020/2040 profiles) and weather-treated timber, making it reproducible in any community maker workshop using basic hand tools: - High-Efficiency PV Array: An adjustable 120W monocrystalline photovoltaic canopy (22.5% module efficiency) designed to capture direct and diffuse solar irradiance while serving as a rain awning. - Synchronous Buck MPPT Regulator: An open Maximum Power Point Tracking buck regulator switching at 20 kHz with conversion efficiencies exceeding 98%. Utilizing an adaptive Perturb & Observe (P&O) tracking loop, the controller dynamically locates the maximum power operating point ($P = V \times I$) across changing irradiance, temperature swings, and partial cloud cover. - USB-C Power Delivery (PD) & Fast Charging: Four independent, short-circuit-protected DC-DC buck-boost regulators delivering standard USB-PD voltage rails (5V, 9V, 12V, 15V, 20V) at up to 65W per port to cleanly power laptops, handheld transceivers, medical devices, and smartphones.

Safe LiFePO4 Storage Architecture (12V / 24V Modular Banks)

For electrical energy storage, we use Lithium Iron Phosphate (LiFePO4) cells arranged in a 4S configuration (12.8V nominal, 20Ah / 256Wh) or an expandable 8S topology (25.6V 100Ah) for larger stationary deployments: - Intrinsic Thermal Safety & Lifespan: LiFePO4 exhibits outstanding chemical stability with an elevated thermal runaway threshold (>270°C) and zero risk of self-sustaining combustion, delivering over 3,500 full depth-of-discharge cycles (80% DoD) without notable capacity fade. - Smart BMS with Active Balancing: Integrated Battery Management System with cell-level voltage monitoring (HVD: 3.65V, LVD: 2.50V) and a 1.2A flying-capacitor active balancing module that equalizes cell charges without resistive heat generation. - Hardware Low-Temperature Charge Lockout: Dual NTC thermistor probes strictly disconnect charging current when ambient cell temperature drops below 0°C, eliminating catastrophic metallic lithium plating on the graphite anode, while safely permitting discharge down to -20°C.

Industrial RS485 / Modbus Telemetry

Unlike consumer devices that rely on proprietary mobile apps, the charging node interfaces using the robust industrial standard Modbus-RTU over a galvanically isolated RS485 bus: - Real-Time Register Polling: The edge computer queries the solar charge controller via RS485 at 9600 baud, reading live holding registers: PV array voltage ($V_{\text{pv}}$), solar current ($I_{\text{pv}}$), battery charge/discharge current, battery state-of-charge (SoC%), daily cumulative kWh yield, and heatsink thermal status. - Per-Port Current Shunt Monitoring: High-side I2C digital power monitors (INA226) log delivered power across each USB-C charging channel with 16-bit resolution. - Zero-Cloud Local Storage: Time-series telemetry is recorded into a local InfluxDB instance on the node and rendered via a lightweight local Grafana dashboard. - Long-Range LoRa Beacons: Every 15 minutes, the node serializes a compact 32-byte binary telemetry packet and broadcasts it over the 868 MHz Meshtastic / LoRaWAN mesh, feeding live stats to the community map.

Raspberry Pi 4 Edge Server & Local Offline Services

Housed in an IP65 weather-tight vented compartment sits an energy-efficient single-board computer (Raspberry Pi 4 Model B, 4GB RAM) powered directly from the solar DC bus via a dedicated 5.1V / 3.5A buck regulator: - Brownout Immunity (Read-Only Root Filesystem): The OS (DietPi / Alpine Linux) runs with root on a read-only overlay (overlayfs). Abrupt power drops or low-voltage disconnects never corrupt the storage medium or operating system. - Autonomous Wi-Fi Portal: Standalone local Wi-Fi provided by hostapd and dnsmasq, offering digital services to any visitor within a 50-metre radius without requiring an upstream internet uplink. - Kiwix Knowledge Mirror: Offline copies of Wikipedia, open medical handbooks, DIY repair manuals, and full OpenStreetMap vector tiles for North Macedonia. - Microclimate & Soil Ecology: Integrated Bosch BME280 sensor logging barometric pressure, temperature, and relative humidity, combined with capacitive soil probes in surrounding planters. - Open Schematics: All KiCad PCB layouts, structural CAD designs, and Modbus ingestion scripts are maintained in our public git repository.

Local Cryptography & Digital Signatures

2026-07-17T00:03:00+02:00

Digital sovereignty begins with holding exclusive custody of your cryptographic keys. Today, digital signatures, identity verification, and TLS certificates have been largely captured by commercial SaaS platforms and closed Certificate Authorities (CAs) that charge expensive annual fees, log sensitive document metadata on corporate servers, and lock users into proprietary formats. This project proves how independent hackerspaces, engineering teams, and civic labs can operate their own mathematically verifiable cryptographic infrastructure with zero reliance on corporate cloud intermediaries.

Self-Sovereign Identity & Ed25519 Cryptography

Cryptographic sovereignty means that private keys never leave local physical possession: - Modern Edwards-Curve Signatures (Ed25519): We prioritize the Ed25519 signature algorithm (RFC 8032) based on Curve25519. Offering a robust 128-bit security level, Ed25519 delivers blindingly fast signing speeds, compact 64-byte signatures, and constant-time arithmetic that is inherently immune to cache-timing side-channel vulnerabilities. - Open Hardware Security Keys: Native integration with open-hardware security tokens (Nitrokey 3, SoloKey) and smartcards running open-source OpenPGP and PIV applets. Private keys are generated and isolated directly on the secure microcontroller; cryptographic signing operations execute inside the chip, making physical key exfiltration impossible. - Elimination of SaaS Middlemen: Document signatures are verified using pure mathematics and public key cryptography, eliminating the need for vendor accounts, subscription tiers, or proprietary PDF plugins.

Local PKI with step-ca & Automated Local ACME

To manage the certificate lifecycle across our hardware lab, solar stations, and mesh servers, we deploy step-ca (Smallstep Certificate Authority)—a lightweight, open-source PKI daemon: - Trust Hierarchy: An air-gapped, offline Root CA whose private key resides on an encrypted hardware token, paired with an active Intermediate CA running as a systemd daemon on an independent edge server. - Local ACME Protocol Engine: An embedded ACME provisioner enabling automatic issuance and continuous renewal of TLS certificates for internal IoT nodes, charge controllers, and local mesh domains (*.lab.internal, *.solar.mesh) via Caddy or Nginx without exposing nodes to the public internet. - Short-Lived X.509 Certificates: Certificates are provisioned with short 8-hour to 24-hour lifespans using OIDC single-use tokens or SSH certificates. This architecture drastically reduces the threat window of compromised keys and eliminates the latency and failure modes of traditional Certificate Revocation Lists (CRLs). - Certificate-Based SSH Authentication: Replacing static, fragile authorized_keys files with step ssh, which issues ephemeral, cryptographically signed SSH certificates linked to authenticated contributor identities.

Cryptographic PDF Document Signing with pyHanko (PAdES-LT / LTA)

To produce legally unambiguous and archive-grade digitally signed documents, we employ pyHanko—an open-source Python library and CLI engine: - European PAdES Standard (ETSI EN 319 142): Authoring signatures compliant with European PAdES Baseline-LT (Long-Term) and Baseline-LTA (Long-Term Archival) profiles, embedding complete certificate validation material and revocation status so that signatures remain verifiable decades into the future. - Cryptographic Timestamping (RFC 3161 TSA): Integrating an independent Time-Stamping Authority token that provides mathematical, tamper-evident proof that the document existed in that precise bitwise state at that exact second. - Vector Visual Signatures: Embedding clean, SVG-rendered signature blocks containing cryptographic fingerprint hashes, QR verification links, and signer metadata without proprietary formatting.

Zero-Cloud Offline Verification

The defining architectural principle of our stack is strict zero-cloud data containment: 1. 100% Client-Side Processing: The document is digested (SHA-256 / SHA-512) directly in local memory. Not a single byte of document text, title, or metadata ever leaves the machine. 2. Offline Verification: Any collaborator or recipient can verify document integrity and signatures offline using standard PDF readers (such as Adobe Reader or PDF-XChange) or via the open-source CLI command pyhanko sign validate --fps, validating against the locally imported root CA trust anchor. 3. Open Project Governance: We use this pipeline to sign maker collaboration agreements, lab hardware handovers, firmware release manifests, and electrical schematics. All CA bootstrapping automation and pyHanko signing scripts are open source and published in our git repository.

Open Workshops & Education

2026-07-17T00:02:00+02:00

Technological sovereignty is not earned by sitting through slide decks—it is built with a soldering iron, a multimeter, and wire strippers in hand. Instead of passive theoretical lectures, we organize intensive, hands-on maker laboratories where every participant learns how to dimension their own standalone solar array, assemble custom LiFePO4 battery packs safely, and configure edge computing nodes that run completely independent of the commercial electrical grid and internet infrastructure.

Hands-On Hardware Hacking Labs

Our laboratory workshops take place on fully equipped maker benches featuring professional bench instruments: - Diagnostic & Measurement Equipment: Participants work with digital true-RMS multimeters, dual-channel digital storage oscilloscopes (Rigol DS1054Z), current-limiting CC/CV bench power supplies, and radiometric thermal imaging cameras (InfiRay P2 Pro) to identify trace hotspots, parasitic resistances, and thermal bottlenecks on custom PCBs. - Real-World PV Benchmarking: Measuring monocrystalline, polycrystalline, and flexible ETFE solar panels under direct sunlight, overcast skies, and deliberate partial shading angles to trace empirical Current-Voltage ($I-V$) and Power-Voltage ($P-V$) curves. - MPPT vs PWM in Practice: Live bench demonstrations illustrating why conventional PWM regulators forfeit up to 30% of harvestable solar energy (by dragging the PV panel down to the battery voltage), and dissecting how true Maximum Power Point Tracking (MPPT) uses synchronous buck topology to dynamically harvest peak wattage. - Ultra-Low Quiescent Current Conversion: Selecting and tuning DC-DC buck regulators with quiescent current ($I_q$) below $15\mu\text{A}$, ensuring microcontrollers and IoT sensors can idle for months without draining backup storage.

Safe DIY LiFePO4 Battery Pack Assembly

Lithium storage is the critical foundation of off-grid engineering, demanding strict chemical understanding and meticulous safety protocols: - LiFePO4 Chemistry & Intrinsic Safety: We build exclusively with Lithium Iron Phosphate ($\text{LiFePO}_4$). Thanks to its robust olivine crystal structure with strong covalent $\text{P-O}$ bonds, LiFePO4 does not release oxygen upon overcharging and exhibits a thermal runaway threshold exceeding $270^\circ\text{C}$ (contrasted with standard NMC/LCO Li-ion cells where violent runaway can trigger at just $150^\circ\text{C}$). Each cell operates at a nominal 3.2V, with a strict operating window from 2.50V (low-voltage cutoff) to 3.65V (high-voltage charge limit) and a resting float voltage of 3.35V–3.40V, delivering 3,000 to 5,000 deep cycles at 80% DoD. - Cell Sorting & 4-Wire Kelvin AC IR Testing: Every incoming cell (cylindrical 32700s or prismatic EVE 105Ah/280Ah units) is matched using a 1 kHz 4-wire AC milliohm meter (YR1035+) to ensure internal resistance variance remains within 2% across the pack. - Precision Capacitive Spot Welding: Fabricating battery packs using dual-pulse capacitive discharge spot welders (kWeld) generating 800A–1200A pulses for 10–20 ms. We use verified pure nickel strips (0.15 mm – 0.20 mm thickness, validated by spark grinding and saline corrosion tests to exclude counterfeit nickel-plated steel). For larger prismatic cells, we demonstrate solderless modular compression holders with solid copper busbars.

BMS Architectures & Active Balancing

An unmanaged lithium battery is an unacceptable hazard. The lab teaches rigorous integration of Battery Management Systems (BMS): - 4S (12.8V) and 8S (25.6V) Topologies: Wiring and configuring smart BMS boards (Daly, JBD, Ant-BMS) equipped with digital telemetry (UART/Bluetooth/RS485 Modbus). - Active vs Passive Balancing: Installing inductive and flying-capacitor active balancers capable of transferring 1A–2A of charge between adjacent cells without generating destructive heat, completely superseding inefficient 35mA passive resistive bleeders. - Low-Temperature Charge Invalidation: Calibrating NTC thermistor cutoffs to enforce a strict 0°C charging lockout. Charging a LiFePO4 cell below freezing causes permanent metallic lithium plating on the anode, resulting in micro-dendrite growth and catastrophic internal shorts. The BMS firmware is configured to allow cold discharging while strictly blocking charging until the pack reaches safe ambient temperatures.

Building Resilient Off-Grid Computing Nodes

We connect power electronics and computational hardware into an autonomous field node: - Low-Power SBC Integration: Interfacing PV panels, MPPT controllers, and LiFePO4 packs with efficient single-board computers (Raspberry Pi Zero 2W, Orange Pi, ESP32). - Self-Hosted Offline Services: Deploying zero-internet server stacks: local captive-portal Wi-Fi, Kiwix offline Wikipedia and medical libraries, SQLite sensor dataloggers, and Meshtastic LoRa repeaters. - Power Budgets & Deep Sleep: Implementing RTC-based hardware watchdog timers and OS power governors allowing edge nodes to enter timed hibernation and survive multi-day winter overcast stretches.

Freely Accessible Open Educational Materials

All Slobodna Energija workshop curriculum is shared freely without intellectual property barriers: - Comprehensive lab manuals, wiring schematics, and slide-free workshop outlines released under Creative Commons CC-BY-SA 4.0. - Complete circuit schematics and PCB Gerber files developed in KiCad, ready for rapid fabrication. - Open Bills of Materials (BOM) with transparent supplier part numbers and 3D-printable CAD files (STL/STEP) for modular battery trays and sensor brackets. Any student, teacher, or hackerspace collective is encouraged to take these materials and replicate hands-on workshops in their own community.

Airborne Communications

2026-07-17T00:01:00+02:00

Raising lightweight radio equipment just a few dozen metres above the ground fundamentally transforms the geometry and propagation physics of wireless communications. In mountain-rimmed valley basins like Skopje, dense urban reinforced concrete and rugged topographical obstacles attenuate ground-level signals within two to three kilometres. By lofting an autonomous LoRa repeater on a tethered aerodynamic kite or sounding balloon, direct optical Line-of-Sight (LoS) expands across tens of kilometres—establishing an ultra-resilient communication umbrella free from commercial cellular carriers or the electrical grid.

LoRa 868 MHz & Meshtastic Protocol

At the core of the airborne system is LoRa (Long Range) chirp spread spectrum modulation operating within the license-exempt European 868 MHz ISM band, adhering to CEPT/ETSI regulations: - Frequency Channels & Duty Cycle Compliance: For standard community packet traffic, we utilize channels in the 868.0–868.6 MHz sub-band with a maximum effective radiated power of 14 dBm (25 mW) and a 1% duty cycle. For elevated infrastructure repeater nodes, we take advantage of the 869.4–869.65 MHz sub-band, which permits up to 27 dBm (500 mW ERP) and a 10% duty cycle, ensuring superior signal penetration across valley terrain. - Open Meshtastic Protocol: Nodes run a decentralized ad-hoc mesh protocol using managed flood routing with configurable hop limits (typically 3 to 5 hops). Packets carry encrypted text messages, GPS coordinates, and sensor telemetry, with each node maintaining an in-memory deduplication hash table to suppress broadcast storms. - Cryptographic Channel Security: The protocol supports AES-256-CTR/GCM channel encryption for private responder groups (e.g., rescue squads and field teams), while broadcasting open distress beacons and public telemetry over the default primary channel.

The aloft airborne node acts as a dominant sky repeater (Router_Client or Client_Mute role), capturing weak micro-watt transmissions from handheld units down in urban street canyons and bridging them directly across mountain ridges to distant municipalities.

Aerodynamics: Kites and Tethered Balloons

To maintain the radio payload aloft in varying weather conditions, we employ two complementary flight platforms: 1. Aerodynamic Parafoil Lifter Kites (Flowform 16 & Rokkaku): Ideal for moderate to stiff breezes between 12 and 45 km/h (Beaufort 3–6). Flowform kites are completely frameless (no rigid carbon or fiberglass spars to snap upon ground contact); their aerodynamic wing profile and stability are maintained entirely by internal ram-air pressure cells with self-balancing vents. With an angle of attack trimmed between 15° and 20° and a high lift-to-drag ratio ($L/D \approx 4$), a Flowform 16 stably holds a 200–350g payload at altitudes between 80 and 120 metres for hours. The tether is braided Kevlar/Dyneema line (60–90 kg breaking strength)—ultralight, low-stretch, and non-conductive to eliminate static shock hazards. 2. Tethered Helium Sounding Balloons: Used during dead calm or light winds under 10 km/h. High-grade 100g–150g latex meteorological sounding balloons filled with 99.9% pure helium provide ~250–350g of gross lift, generating 100–150g of net free lift above the payload mass to keep the transceiver stationed directly above deployment ground zero.

The airborne payload is enclosed in a weather-sealed, 3D-printed PETG aeropod weighing under 115 grams, housing a Semtech SX1262 transceiver, an ESP32 dual-core MCU, a 3.2V 1500mAh LiFePO4 cell, a miniature MPPT solar trickle board (CN3791), and an omnidirectional half-wave coaxial sleeve dipole tuned to 868 MHz (VSWR < 1.25:1).

Line-of-Sight Calculations & Link Budget

Our field deployments are grounded in rigorous radio frequency physics and mathematical modeling:

Radio Horizon & Geometric Line-of-Sight:
Accounting for standard atmospheric refraction using the 4/3 effective Earth radius model ($k = 4/3$), the maximum line-of-sight radio horizon distance is calculated as: $$d_{\text{max}} \approx 4.12 \times \left(\sqrt{h_{\text{tx}}} + \sqrt{h_{\text{rx}}}\right) \text{ km}$$ For an airborne transceiver elevated to $h_{\text{tx}} = 100\text{ m}$ transmitting to a high-elevation ground node on Mount Vodno ($h_{\text{rx}} = 1060\text{ m}$): $$d_{\text{max}} \approx 4.12 \times (\sqrt{100} + \sqrt{1060}) = 4.12 \times (10 + 32.56) \approx 175.3\text{ km}$$ This geometry unlocks uninterrupted radio visibility across the entire Vardar valley, Kumanovo basin, and northern Pelagonia.
Free-Space Path Loss (FSPL): $$\text{FSPL (dB)} = 20\log_{10}(d) + 20\log_{10}(f) + 32.44$$ For a link distance of $d = 100\text{ km}$ at $f = 868\text{ MHz}$: $$\text{FSPL} \approx 20(2) + 20(2.938) + 32.44 \approx 40 + 58.77 + 32.44 = 131.2\text{ dB}$$
Link Budget & Margin:
With transmitter power $P_{\text{tx}} = +22\text{ dBm}$ (160 mW), transmit antenna gain $G_{\text{tx}} = +2.15\text{ dBi}$, receive antenna gain $G_{\text{rx}} = +3.0\text{ dBi}$, and connector losses of $0.5\text{ dB}$: $$P_{\text{rx}} = 22 + 2.15 + 3.0 - 0.5 - 131.2 = -104.55\text{ dBm}$$ Because the Semtech SX1262 has a receiver sensitivity of $-130\text{ dBm}$ at Meshtastic's LongFast preset (SF11, BW 250 kHz) and down to $-137\text{ dBm}$ at SF12/BW 125 kHz, the resulting link margin is greater than 25 dB. This generous margin guarantees successful packet decoding even through atmospheric rain attenuation and urban RF noise.
First Fresnel Zone Clearance:
The radius of the 1st Fresnel zone at mid-path ($d_1 = d_2 = 50\text{ km}$) is $r_1 \approx 8.656 \sqrt{100 / (4 \times 0.868)} \approx 46.5\text{ m}$. Lofting the node to 100 m clears well over 60% of the first Fresnel zone above intermediate valley ridges and obstacles.

Disaster Resilience & Open Telemetry

During natural disasters (earthquakes, summer wildfires, or electrical blackout cascades), commercial cellular base stations typically fail within two hours once backup batteries exhaust. An airborne LoRa mesh repeater can be launched in under 10 minutes directly from a vehicle trunk or hiker's backpack.

Simultaneously, the airborne pod carries open micro-sensors for barometric pressure, temperature, relative humidity (BME280), and optical particulate smoke counters. Telemetry packets are broadcast unencrypted over open frequencies, logged by community ground stations, and archived into public datasets. All CAD models, PCB schematics, and firmware repositories are free and open source under CC-BY-SA and CERN-OHL licenses.