DGTE is a double-gravity heat engine. The name says what it does: gravity acts twice per cycle. When a sealed capsule is heated, its density drops below the surrounding fluid — gravity pulls the fluid down, displacing the capsule upward. When the capsule cools, its density rises above the fluid — gravity pulls the capsule down directly. Same force, two directions, two power strokes. Segmented linear coils harvest electromagnetic energy from both strokes — no turbines, no pistons, no refrigerants. A full-height annular counter-current recuperator couples the HOT and COLD columns with target effectiveness ε ≥ 0.90, recovering heat that would otherwise be lost.
Two crossover variants are formalised: V1 (rotary airlocks, baseline — proven mechanics, 9/10 confidence) and V2 (magnetic coupling, R&D — higher long-term upside, 5/10 confidence). The architecture accepts both as swappable cartridges. Pilot acceptance targets: net efficiency η = 4–8% at 90–120/20–30 °C, duty factor φ ≥ 0.85, availability ≥ 99% over 30 days, parasitics ≤ 100W, zero crossover-attributable jams.
Best-fit sources: industrial waste heat (compressor oil coolers, CIP/pasteurisation), low-enthalpy geothermal, solar-thermal, district heat. FOAK economics: €40–80k/kWₑ with 12–18 year payback at €0.20/kWh; volume targets €10–15k/kWₑ with 3–5 year payback at high tariffs. The system trades peak thermodynamic efficiency for simplicity, safety, availability, and direct DC output.
Conceived, designed, and authored by Bojan Dobrečevič with AI teamwork (ChatGPT, Claude, Gemini, DeepSeek). The recuperation architecture was seeded by a human insight — "capsules don't traverse the exchanger; fluid does" — and elaborated through multi-LLM iteration into the co-axial annular design adopted as baseline.
Pure DGTE remains alive but hard. The current bench planner says not to build the full machine first. The useful next move is to attack transfer, crossover, pressure balance, and thermal closure as separate bench tests.
P_net = min(P_thermal_gross, P_PTO_path) − transfer losses − auxiliaries
DGTE uses gravity twice as a motion-conversion mechanism, not as a free energy source. A capsule heated in the HOT column becomes less dense than the bath fluid — the fluid sinks under gravity, and the capsule is displaced upward. At the top, it crosses to the COLD column, cools, becomes denser than the fluid — and gravity pulls it straight down. Both motions pass through segmented coils that generate electricity, but net output must be closed against real thermal input, transfer losses, and auxiliary loads.
Central HOT riser and annular COLD downcomer separated by a full-height annular recuperator wall. Crossovers at top and bottom complete the capsule loop. The recuperator is not a separate unit — it IS the wall between the columns, transferring heat continuously via counter-current flow.
| Aspect | V1 Rotary (baseline) | V2 Magnetic (R&D) | V3 Dry-Porch |
|---|---|---|---|
| Confidence | 9/10 | 5/10 | contextual |
| Crossover | Fully-wetted rotary airlocks | Wet-tolerant magnetic coupling | Gas-phase dry tunnels + N₂ puffs |
| Moving parts | Rotating seals/bearings | None through pressure boundary | Valves + pneumatics |
| Parasitics | 5–15W per airlock | Potentially lower | N₂ + ventilation |
| Recuperator ε | ≥ 0.90 (counter-current) | ≥ 0.90 (counter-current) | ≈ 0.70 (regenerative) |
| Dev risk | Low (COTS mechanics) | High (novel physics) | Medium |
| Long-term upside | 7/10 | 9/10 | Limited |
Ideal ceiling: η_C = 1 − T_c/T_h. Net efficiency accounts for recuperator effectiveness, duty factor, generation efficiency, geometry, and parasitics:
Where α ≈ 0.30 captures non-HX irreversibilities, η_gen ≈ 0.8–0.9, P_par/Q̇_in ≈ 0.2–0.35%.
| Parameter | Value |
|---|---|
| Carnot efficiency η_C | 22.17% |
| Usable fraction f_hx (ε=0.90) | 0.96 |
| Duty factor φ | 0.86 |
| Generation efficiency η_gen | 0.85 |
| Irreversibility factor α | 0.30 |
| Gross η | ~4.9% |
| Parasitic deduction | −0.25% |
| Net η | ~4.6% |
With ε → 0.92 and geometry factor χ = 1.02, net approaches 5.5–6.0%.
Most sensitive: ε → f_hx (strongest lever), then φ_duty, then η_gen, then P_par. A 2%-point improvement in ε yields +0.2–0.3 %-point η_net.
Rule: t_inv ≤ 0.10 · t_s and t_× ≤ 0.05 · t_s → φ_duty ≥ 0.85
COLD_START → WARM_THROUGH → RAMP → STEADY ↔ PART_LOAD → CIP/SERVICE. Fault path: FAULT_LATCHED ↔ JAM_CLEAR → RAMP. Transitions tied to ε, φ, Δp, STO, carry-over.
| Level | Loop | Actuator | Rate |
|---|---|---|---|
| Inner | Spacing PI (sensorless back-EMF) | Throughput & crossover rate | ≤5% /s |
| Middle | Δp PID with feedforward | Pump VFD | ~3 t_h |
| Outer | ε guard + ΔT ladder monotonicity | Maldistribution routine | Minutes |
Back-EMF zero-crossing and peak timing from each coil segment provides capsule position and velocity without physical sensors. Controller maintains target spacing t_s and φ_duty. This is the same principle as DCC — the system reads its own electrical signature.
| Test | Goal | Acceptance |
|---|---|---|
| D2 — ε-Ladder | Verify recuperator performance | ε ≥ 0.90 at design; ≥ 0.88 at −20% throughput; ladder monotone |
| D3 — Duty & Dwell | φ_duty ≥ 0.85 | 4h continuous; t_inv ≤ 0.10·t_s; jitter σ < 0.2·t_× |
| D4 — Carry-Over | Bound cross-contamination | < 0.5% per transfer (dye-trace) |
| D5 — Parasitics | Confirm P_par/Q̇_in | 0.2–0.35% (V1/V2); DC cross-check ±1% |
| D6 — Availability | 30-day continuous | ≥ 99%; faults recover within 10 min to ≥95% baseline |
| D8 — V1 Rotary | Rotor performance | Torque map; jam-clear ≤ 3 cycles; carry-over across ±20% throughput |
| D9 — V2 Magnetic | Coupling & EMI | Slip ≤ 20°; spur < −60 dBV; equivalence to V1 on all KPIs |
| D10 — CIP Recovery | Fouling recovery | Post-CIP ε within −1 %-pt; Δp within +5% |
Pressure: ASME BPVC VIII / EN 13445. Piping: B31.3 / EN 13480. Relief: API 520/521. Machinery: ISO 12100, EN 60204-1. Electrical: IEC 60204-1, IEC 61439. EMC: IEC 61000. Functional safety: IEC 61508/61511 or ISO 13849.
| Hazard | Mitigation |
|---|---|
| Over-temperature | Hi-temp trip; redundant RTDs; relief path |
| Over-pressure | Relief + rupture; expansion volume; proof 1.5× |
| Oil leak/spill | Containment pan; leak detect; spill plan |
| Crossover jam (V1) | Screens; torque limit; STO; quick-swap cartridge |
| Recuperator fouling | Filtration; CIP manifolds; ε-ladder monitoring |
| Electrical fault | OCPD; SPD; thermal sensors per segment |
| Block | Share | Learning |
|---|---|---|
| Vessel + annular HX | 28–36% | ↓ with volume |
| Recuperator inserts | 18–24% | ↓ with tooling |
| Crossovers | 10–16% (V1) | V2 falls if standardised |
| Coils + power electronics | 10–15% | ↓ PCB panelisation |
| Pumps/piping | 6–10% | Stable |
| I&C + enclosure | 16–24% | ↓ after FOAK |
| Scale | CAPEX/kWₑ | Payback @ €0.20 | Payback @ €0.40 |
|---|---|---|---|
| FOAK pilot | €40–80k | 12–18 yr | 6–9 yr |
| NOAK volume | €10–15k | 5–7 yr | 3–5 yr |
V1, η_net = 5.5%, Q̇_in = 60 kW_th → P_net ≈ 3.3 kWₑ. CF = 0.9 → E_yr ≈ 26 MWh. FOAK CAPEX €85k → LCOE ≈ €475/MWh. With replication (CAPEX → €55k, η → 6.2%) → LCOE ≈ €295/MWh.
Wright's law on replicable blocks (coils, rectifiers, rotor cartridges, HX inserts): C(N) = C₁(N/N₁)^(−β), β ∈ [0.15, 0.25]. Engineering/commissioning overheads drop ≥50% after FOAK.
| Attribute | DGTE | Micro-ORC | Stirling | TEG |
|---|---|---|---|---|
| Working fluid | Thermal oil | Refrigerants/HFOs | Gas | Solid-state |
| Turbomachinery | None | Turbine + pump | Pistons + seals | None |
| η @ 90–120/20–30°C | 4–8% net | Often off-design | Needs higher ΔT | <3% |
| Maintenance | Low (few wear points) | Turbine/pump/valves | Seals/clearances | Very low |
| Direct DC | Yes | Inverter path | Variable | Yes |
| Refrigerants | None | Yes (HFOs) | No | No |
| Prototype | Goal | Output | CAPEX |
|---|---|---|---|
| C — Physics Demo | Demonstrate dual gravity, crossovers, φ_duty, DC on both strokes | 0.2–0.6 kWₑ (no recuperator) | €20–50k |
| A — Mini w/ Recuperator | Prove ε ≥ 0.90, low Δp, stable φ, crossover reliability | 0.3–0.8 kWₑ | €35–60k |
| B — Pilot (near-product) | Full performance validation, 30-day run | 2–3 kWₑ | €100–200k |
Design C as a platform: flanged ports for future recuperator cartridges; pre-route manifolds and CIP tees; install RTD ladders, Δp ports, and flowmeters from day one; modular coils/rectifiers; same capsule geometry throughout.
| Upgrade | Incremental CAPEX | What Changes |
|---|---|---|
| C → A | €15–30k | Add recuperator cartridge + instrumentation |
| C → B | €70–120k | Full recuperator + production crossovers + enclosure |
| Contributor | Role | Share |
|---|---|---|
| Bojan Dobrečevič | Conception, regeneration lineage, decisive recuperation seed & selection, requirements, final authority | 55% |
| ChatGPT 5 Thinking | Synthesis, models, controls, testing, drafting, integration | 18% |
| GPT-o5 | Extended recuperation from human seed, crossovers, targets | 12% |
| Claude | Safety/regulatory drafting, clarity edits, glossary | 8% |
| Gemini | Re/Pr/Nu references, sensitivity grid, annular corrections | 5% |
| DeepSeek | Slip detection nuances, control-aware perturbations | 2% |
The recuperation architecture was seeded by a human insight: "capsules don't traverse the exchanger; fluid does." This reframing — from regenerative (capsules carry heat) to recuperative (fluid carries heat through a wall) — was the decisive architectural pivot. GPT-o5 elaborated the seed into the co-axial annular counter-current design; multi-LLM review confirmed it as baseline.