High-temperature heat and hot tap water. Air as the working fluid. Keep the existing radiators.
01 / The technology
A jet engine, running backwards.
The reversed Brayton cycle turns aerospace engineering into heat and hot tap water for existing homes.
In the home
Nothing has to be changed.
Two air ducts through the roof or façade, the size of a flue. No unit on the wall, no permit.
Where the boiler was. Floor-standing, 74 × 66.5 × 158 cm and 320 kg. Utility room or attic, not the living room.
Existing radiators and pipes, at up to 80°C. No insulation upgrade needed first.
Heating and hot tap water from one unit: CW3 comfort class, 10 litres a minute at 40°C.
15 to 20 years design life.
Go deeper into the technology
02 / Our innovation
The product.
Older homes need high-temperature heat. Tarnoc reuses their radiators and pipework, reducing the disruption of going electric.
Combi Max · turbine unit + outdoor unit
The efficiency extension
High heat. With outdoor efficiency.
Pairs the turbine with an outdoor unit for larger homes. The outdoor unit carries the base load efficiently; the turbine delivers the 80°C peaks and the hot tap water.
20+ systems installed. From occupied homes to a hospital and a listed monument: hardware working where the heat is needed.
Residential
Inside a Dutch home.
Nootdorp, NL · Staedion housing
Commercial
Hot tap water for a hospital.
Delft, NL · Reinier de Graaf
Heritage
Keep the building’s character.
Arnhem, NL · Gemeente Arnhem
Monument · 1610
Three winters in a house from 1610.
Middelburg, NL · De Vergulde Schoe
13 projects with municipalities, housing corporations and a hospital
“I can see in broad strokes how far the development has come: more efficient, quieter and more professional.”
Bernard Vercouteren, resident of De Vergulde Schoe, Middelburg. A prototype heated the 1610 monument for three years; it now runs the first commercial Turbine Heat Pump.
Go deeper into the pilots
04 / Why customers buy
Calculate the ROI.
Compare the machine, home adaptations, energy and maintenance for a homeowner or a housing portfolio.
Total cost of ownership over 20 years
Gas boilerkeep burning gas
—
Conventional heat pump+ home upgrade
—
Tarnoc Turbine Heat Pumpindoor unit
—
Tarnoc Combi Maxturbine + outdoor unit · scenario
—
—
Combi Max payback vs. gas
—
Saved vs. gas over the horizon
—
CO2 avoided vs. gas
Adjust the assumptions+
Who is paying?
Efficiency scenario
Combi Max subsidy
Want to run the model on your own assumptions, together?
05 / The market
Who is buying the product.
Pre-1980, ≥150 m², over 1,500 m³ of gas a year, its own boiler. Inside that box we are the only machine that fits. Outside it, we tell people to buy something else.
Market sizing, bottom-up
Why it matters
About 175,000 addressable boiler replacements a year in the Netherlands alone. Nobody replaces a working boiler, so the annual replacement flow is the market we sell into.
TAM4.6M homes€46bn
Dutch homes heated by an individual gas boiler, apartments excluded.
SAM2.1M homes€17.7bn
Built before 2000 and needing water above 45°C, not yet on a heat pump, technically installable and economically reachable.
SOM~30,000 homes by 2031€400M
Cumulative capture 2027–2031, growing from 0.5% to 7% of the annual replacement flow.
Bottom-up from Eurostat, BPIE, IEA, EHPA, CBS and RVO housing statistics. Each home valued at one installed Turbine Heat Pump, ex VAT.
Same housing stock, same problem, bigger. Most wave 2 and 3 markets have a worse gas-to-electricity price ratio, which is precisely the problem the Combi Max solves.
Go deeper into the market
06 / The scale path
Sell through installers. Scale through distributors.
Each channel builds the evidence and capability needed for the next.
01
Installer-led B2B
Growth phase · now
Equip installers and housing partners with surveys, training, commissioning tools and service support. Partners bring customer relationships and repeat projects; Tarnoc keeps the product, the standards and the service contract.
Why this makes sense
A repeatable installation offer lets the same product reach many more homes without scaling a direct sales team at the same rate.
Milestone15 local installation companies joined
02
International distribution
Scaling phase · from 2028
Enter through regional distributors and installers that understand local buildings, customer acquisition and service. Wave 2 is Germany, Austria, Italy and Belgium; wave 3 the United Kingdom, Ireland and France.
Why this makes sense
Partners provide local reach while Tarnoc retains the core technology, product standards and training. Dutch field experience becomes the starting playbook.
MilestoneMarket entry into Germany, Austria, Italy and Belgium
Consumers
Tarnoc also sells directly to a limited number of homeowners. These early adopters keep a short feedback loop on home fit, installation and comfort, and pay a deposit before the unit is built.
Go deeper into the sales process
07 / Production
Supply chain.
Own the technology. Scale through partners.
Engineering in Delft · the turbine unit in CAD
→→→
Tarnoc owns the system.
Product design, IP, control software, specifications and acceptance tests remain the core of the business.
Target gross margin at high production volume
>38%
Turbine Heat Pumpindoor unit
>49%
Combi Maxturbine + outdoor unit
More value in every machine as production scales.
Volume purchasing for the compressor and components
Design for manufacture and simpler assembly
Repeatable testing, quality and service
Recurring yearly service revenue on every installed system
08 / Financials
From launch to €70M in three years.
A base case built bottom-up from leads, installer partners and build capacity. The Combi Max carries most of the volume; the Turbine Heat Pump opens the homes nothing else can serve.
€70MRevenue in 2029, base case
EBITDA positive from 2028 · Netherlands only
2027
2028
2029
Turbine Heat PumpCombi Max
Relative revenue per year. About one in five systems sold is a Turbine Heat Pump; the Combi Max carries the rest.
The full model runs monthly to 2030: units, margin steps, headcount and cash. We walk through it in a call.
Tarnoc · Confidential investor presentation · September 2026
01 / 15
The thesis
The Turbine Heat Pump runs an open, air-based reversed Brayton cycle, also known as the reverse Joule or Bell–Coleman cycle. Ambient air is the working fluid; there is no refrigerant and no phase change. Four processes close the loop.
1 → 2, compression. A centrifugal compressor on the 100,000 rpm shaft raises the air to a pressure ratio π of roughly 1.4 to 2.3. For an ideal gas the outlet temperature follows T₂ = T₁·π^((γ−1)/γ), so a modest pressure ratio already takes winter air from around 10°C to 80–100°C at the compressor outlet.
2 → 3, isobaric heat rejection. The hot air gives up sensible heat to the water of the heating circuit in a counter-flow air-to-water exchanger. Because air cools along a temperature glide rather than at a fixed condensing temperature, the exchanger can follow the 60 → 80°C rise of the radiator water with a small mean temperature difference.
3 → 4, expansion. The still-pressurised air expands through a radial turbine on the same shaft. The expansion work is returned directly to the compressor, and the air leaves well below ambient, at about −20°C.
4 → 1, heat uptake. The cold air is exhausted outside and fresh ambient air is drawn in. In an open cycle the atmosphere itself is the cold-side heat exchanger.
Coefficient of performance
For the ideal cycle the heating COP depends on the pressure ratio only: COP = 1 / (1 − π^(−(γ−1)/γ)). With γ = 1.4 this gives 5.5 at π = 2 and 7.9 at π = 1.6. The real machine is governed by its work ratio: the net work is the small difference between a large compressor work and a large turbine work, so the isentropic efficiencies of both machines and the pressure losses in the exchanger enter almost undamped. That is why the air cycle is exacting on turbomachinery, and why the current unit settles at a COP of 1.6 to 1.8 at 80°C supply rather than the ideal value.
Why this is the right cycle for 80°C
Vapour-compression cycles lose efficiency as the condensing temperature approaches the refrigerant’s critical point. Air has no critical point in this range: 80°C is a design point, not a limit.
Sensible-heat release with a temperature glide matches counter-flow water heating (the Lorenz cycle argument); a condensing refrigerant cannot.
No refrigerant means no leakage, no flammability class and a global-warming potential of zero. Air is R-729.
The single shaft removes the electrical conversion losses of a separate expander generator; a proprietary recuperator lowers the compression work for a given supply temperature; the patented enclosure returns motor and electronics heat to the air stream.
The honest trade
At low supply temperatures a vapour-compression heat pump will always be more efficient. The Turbine Heat Pump exists for the 1.6 million Dutch homes that need 65 to 80°C water. The Combi Max pairs both cycles: the outdoor unit carries the efficient base load, the turbine carries the high-temperature peaks and the hot tap water.
Further reading
White, A.J. (2009). Thermodynamic analysis of the reverse Joule–Brayton cycle heat pump for domestic heating. Applied Energy 86(11), 2443–2450.
Angelino, G. & Invernizzi, C. (1995). Prospects for real-gas reversed Brayton cycle heat pumps. International Journal of Refrigeration 18(4), 272–280.
Fleming, J.S., Van der Wekken, B.J.C., McGovern, J.A. & Van Gerwen, R.J.M. (1998). Air cycle cooling and heating, Part 1: a realistic appraisal and a chosen application. International Journal of Energy Research 22(7), 639–655.
Wang, S., Li, S., Jiang, S. & Wu, X. (2022). Analysis of the air-reversed Brayton heat pump with different layouts of turbochargers for space heating. Buildings 12(7), 870.
Zühlsdorf, B., Bühler, F., Bantle, M. & Elmegaard, B. (2019). Analysis of technologies and potentials for heat pump-based process heat supply above 150 °C. Energy Conversion and Management: X 2, 100011.
Yücel, F.C., Oehler, J., Kriese, M., Jende, E., Setzepfand, N. & Stathopoulos, P. (2025). Design, commissioning and closed-loop operation of a high-temperature Brayton heat pump — CoBra. Applied Thermal Engineering 279, 127947.
Field data: measured COP 1.65–1.98 in three occupied homes over the 2025 heating season (MOOI TUNES end report, public, March 2026).
Seven ways to make heat above 65°C, placed by how mature they are and how well they replace a gas boiler in an existing home. Tap a technology.
Technological maturityRetrofit suitability for gas boiler replacement
+−−+
Reversed Brayton cycle · Tarnoc
An open air cycle: compress, transfer heat, expand, exhaust. Four properties set it apart from vapour compression. The compressor inlet is at atmospheric pressure and does not fall as the outside gets colder, so output holds exactly when demand peaks. Pressure ratio and mass flow are free variables, independent of the source and sink temperatures. The optimal pressure ratio is low, roughly 1.4 to 2.3, which is the range where centrifugal compressors and turbine expanders are at their most efficient and where positive-displacement machines cannot follow. And there is no refrigerant circuit: nothing to leak, no phase change, no ceiling at 80°C. Validated in homes, a hospital and monuments; the first commercial systems are sold and installed.
Vapour compression cycle
The workhorse of every fridge, air conditioner and heat pump for over a century. A refrigerant circulates in a closed loop: at high pressure it condenses hot, at low pressure it evaporates cold, and the pressure ratio is dictated by the source and sink temperatures. The compressor consumes nearly all of the input power, so it sets the efficiency. Residential units (1–30 kW) use positive-displacement compressors, rotary or scroll: the pressure ratios required, roughly 3 to 15, are too high for a simple centrifugal machine, which also cannot run at a high pressure ratio with low output. Positive displacement brings contact friction and oil-lubrication losses, and a fixed swept volume per revolution caps the volumetric flow. That cap bites when it hurts most: as the ambient temperature falls, the evaporating pressure and gas density fall with it, so mass flow and heating output drop while the house needs more. Pushed to 80°C the efficiency collapses; propane-based units add flammability limits and outdoor noise.
CO₂ heat pumps
A vapour-compression cycle in which the high-pressure side runs supercritical, the transcritical cycle. That suits large single-pass temperature lifts, such as heating tap water from 10°C to 65°C, but at ordinary space-heating conditions the efficiency is below a regular vapour-compression unit. Design pressures reach 200 bar, which drives cost through pressure-rated components. CO₂ is non-flammable and relatively non-toxic compared with propane or ammonia, though a leak in a closed room is still a safety risk. Its home today is supermarket refrigeration and tap water, not the boiler cupboard.
Gas adsorption
The technology behind Cooll / Thermyo. Ammonia adsorbs onto activated carbon in a batch process rather than a continuous one. The decisive difference is the input: thermal instead of electrical, which in practice means a natural-gas or biogas burner, in theory hydrogen. The COP is low, likely 1.3 to 1.4, and verified data are scarce. Gas-driven heat pumps make sense where electricity is expensive relative to gas; they do not fit countries such as the Netherlands that are decarbonising through electrification, and they keep the gas connection the customer wants to cancel.
Rotation heat pump
Another route to the reversed Brayton cycle. Two heat exchangers spin at high speed inside a vacuum chamber; the high-pressure side sits at the larger radius, centrifugal force on the gas creates the pressure difference, and a fan circulates the gas. No compressor, turbine or acoustic driver. The rotating assembly and vacuum vessel make it an industrial-scale machine, not something that fits where a domestic boiler was.
Magnetocaloric
Certain materials warm up when placed in a magnetic field and cool when it is removed. The effect is small, a few degrees, so usable temperature lifts require stacks of materials in layers and a batch-wise process rather than a continuous flow. Research and early-prototype stage. Low efficiency and low power density make it unlikely to compete with existing heat pumps in a home.
Thermoacoustic
A recuperated reversed Brayton cycle with a twist: instead of a compressor and turbine, a driver much like a subwoofer sets up a standing pressure wave in compressed helium, which compresses and expands the gas more efficiently than turbomachinery can. The catch is amplitude. A useful pressure ratio needs particle velocities above Mach 0.1, where non-linear effects appear: shock formation and flow separation in the heat exchangers. Developers such as Blue Heart Energy therefore run at low pressure amplitudes, which pushes extreme performance demands onto the heat exchangers to reach an adequate COP. We do not expect thermoacoustic heat pumps to match vapour compression on COP, and no consumer product is available yet.
Side by side
Technology
Drive
Working fluid
Where it stands
Reversed Brayton · Tarnoc
Electric · centrifugal compressor + turbine
Air, open cycle
Validated, first systems sold
Vapour compression
Electric · rotary or scroll compressor
Refrigerant (propane, R32…)
Mature, 100+ years; struggles above 65°C
CO₂ transcritical
Electric · positive-displacement compressor
CO₂ up to 200 bar
Supermarkets and tap water
Gas adsorption
Thermal · gas burner
Ammonia on activated carbon
Niche, keeps the gas connection
Thermoacoustic
Electric · acoustic driver
Compressed helium
Pre-commercial
Rotation heat pump
Electric · rotating exchangers
Gas in a vacuum chamber
Industrial demonstrations
Magnetocaloric
Electric · magnetic field
Solid-state stacks
Research
WO2023275784A1 · single-shaft direct drive, as filed
Granted and pending
NL2028575B1 — granted, Netherlands, sets priority
WO2023275784A1 — PCT, published
EP4363780A1 · US20240271798A1 · CN117545969A — pending in Europe, the US and China
Held in full by Tarnoc Holding B.V. with both founders as named inventors. No university, subsidy body or third party holds ownership, joint ownership or a licence. The technology was not co-developed with TU Delft.
The strongest claim
Not the shaft: the enclosure. Using the unit’s own casing as part of the air ducting, so waste heat from the power electronics and motor is captured and returned to the cycle. A competitor who cannot use that trick throws that heat away.
Freedom to operate
An open air cycle with no refrigerant circuit sits outside the dense vapour-compression patent landscape; the closest prior art is in aerospace and rail air conditioning.
Patent registers of the EPO, WIPO, USPTO and CNIPA. Status verified June 2026.
Choose the configuration with a site survey: available space, heating demand, radiators, air routes and electrical connection determine the fit. Specifications below are as published on tarnoc.nl.
Turbine Heat Pump
Combi Max
Heating power
20 kW (Pmax at −10°C)
24 kW nominal · 30 kW max
Supply temperature
up to 80°C
up to 80°C
COP
1.6–1.8
up to 4.3
Outdoor unit
None · no permit, no outdoor noise
Yes · 1,290 × 450 × 900 mm
Working fluid
R-729 (air), no refrigerant
Air cycle + outdoor unit
Cooling
—
11 kW, up to 4 rooms
Hot tap water
CW3 · 10 L/min at 40°C · XL profile
CW3 via the turbine unit
Indoor unit
1,580 × 740 × 665 mm · 320 kg
Same turbine unit
Sound
47.3 dB(A) indoors at 0.9 m
50 dB(A) outdoor unit at 1 m
Energy label
A++
A++
Installation
1 day · existing radiators and pipes
Within 2 days
Price
from €12,600 incl. VAT and installation
from €14,150 incl. VAT after ISDE
Subsidy
Not ISDE-eligible
ISDE-eligible
Best for
Terraced to large homes and monuments where no outdoor unit is possible
Large detached and semi-detached homes, 700–4,500 m³ gas a year
Status
Turbine Heat Pump. CE-marked in December 2025; quotes open, production starts in 2026 with first installations by the end of 2026.
Combi Max. Certification tests completed; documentation in progress.
tarnoc.nl/en/turbineketel and tarnoc.nl/en/combi-max, read 8 September 2026.
Staedion, a social housing association from The Hague, let Tarnoc replace the gas boilers in three occupied 1950s homes in Nootdorp and meter everything for about ten months, across the 2025 heating season. Residents stayed in place throughout.
Home
Electricity
Heat
COP
Saving
A
3,267 kWh
5,385 kWh
1.65
€196
B
1,814 kWh
3,530 kWh
1.95
€342
C
3,341 kWh
6,616 kWh
1.98
€367
Average
2,807 kWh
5,177 kWh
1.86
€301
What went wrong, on the record
Installation took 3–4 days against a 1–2 day target.
A buffer leak, control-system faults and an installation gas leak all required return visits residents had to be home for.
The residents’ overall verdict in the consortium’s end report was critical, and a rent compensation of roughly €100/month was considered necessary.
Households B and C believed they were financially worse off; households have very little insight into their own energy use, and the report says so.
What it feeds
Installation experience and field data feed directly into product development and installer training: installation time, commissioning checks, control software and standby losses were all changed as a result.
MOOI TUNES project end report (public, 20 March 2026).
De Vergulde Schoe in Middelburg is a national monument from 1610. Bernard Vercouteren lives there himself and knows the Turbine Heat Pump inside out: a prototype ran here from 2023, heating the monument for three years without problems or faults. It now houses the first commercial Turbine Heat Pump. Bernard did not just switch to the new version; he watched the technology develop over three years, from close by.
Heating without touching the monument
The house has a high heat demand, and keeping the existing heating system was essential. The Turbine Heat Pump connects to the existing radiators and delivers water temperatures up to 80°C, and the hot tap water. Nothing on the façade, no permit.
From prototype to a quieter installation
In the commercial version the compressor, heat exchanger and enclosure were developed further. Where the previous unit still had a clearly audible whistle, the new Turbine Heat Pump is quiet enough to stand next to and hold a normal conversation.
Built
Experience
Flow temperature
1610
3 years with the Turbine Heat Pump
80°C on the existing radiators
Tarnoc brochure 2026, “Een pand uit 1610, comfortabel warm”. Quote translated from Dutch.
Eight steps, and at every step the customer knows where they stand. Only after the home survey is it certain the system fits, and only then does the customer commit.
1 · Home scan, 5 minutes. A few questions about the year of construction, floor area, radiators and electrical connection.
2 · Online advice call, 30 minutes. Someone from the team walks through the options.
3 · Quote, within a week. A price for that home, including the electrical work and any extras. Everything is in it before signing.
4 · Reservation, €400. The survey is scheduled after this.
5 · Home survey. Walking through the situation together to heat the house 100% electrically; the installation plan becomes final.
6 · Planning the date. 30% is paid at the latest four weeks before installation, with the deposit deducted.
7 · Installation, 1 to 2 days. Old boiler out, Turbine Heat Pump in. The target is always one day.
8 · Warm house, gas off. The gas connection can go. The remaining 70% is paid within fourteen days of delivery.
Why it matters for the business
Cash arrives before the machine is built: €400 at reservation, 30% four weeks before installation, 70% within fourteen days after.
The deposit is safe for the customer: fully refunded if the survey shows the home does not fit, half refunded if the customer withdraws after the survey.
Financing through the Nationaal Warmtefonds removes the upfront-capital objection; the monthly saving covers the repayment from month one.
Tarnoc brochure 2026, “Van reservering tot warm huis” and “Besparen vanaf maand 1”.
Bottom-up, from public housing statistics. Revenue figures value each home at the installed price of one Turbine Heat Pump, ex VAT.
Netherlands
8.0M dwellings, 88% on the gas grid, apartments excluded = 4.6M gas-heated homes (TAM, €46bn)
63% built before 1992 and needing water above 65°C = 2.9M
Near-term capture is modelled for the Netherlands only. Germany, Austria, Italy and Belgium (wave 2) and the United Kingdom, Ireland and France (wave 3) are not yet in the obtainable figure.
Where it bends
The share of the annual replacement flow is the most sensitive input. For scale: Quatt sold 3,000 hybrid units in 2025 (8.1% share) and WeHeat 4,100 (11.1%), both after years of trading.
Economic reach moves with the gas-to-electricity price ratio; every ten points of reach is about 230,000 Dutch homes.
Our own lead data points the same way: households burning over 2,000 m³ a year convert to a paid deposit roughly six times better than households under 1,500 m³.
Eurostat Housing Statistics 2023 · BPIE, Europe’s Buildings Under the Microscope 2023 · IEA, Heating in Buildings 2022 · EHPA Market Data 2023 · CBS Statline 2024 · RVO 2024. Quatt and WeHeat volumes: BRG Building Solutions, NL 2026 edition.
Tarnoc owns the system design, controls and acceptance standards. The best HVAC suppliers in the world provide the critical components, an HVAC OEM industrialises assembly, and certified installers put the machines in homes.
The four steps
Design. Product design, IP, control software, specifications and acceptance tests remain the core of the business.
Source. Tarnoc works with the best HVAC suppliers in the world through an international supply chain, built on the team’s deep market connections and knowledge. Volume commitments and lead times determine the cash requirement.
Assemble. Tarnoc is building a production line together with Technical Heating Platform, an existing HVAC OEM in Türkiye. The line is designed specifically for the turbine heat pump; volume is released only after agreements, end-of-line tests and yield are demonstrated.
Installation. Installation and service are done by external certified installers with deep knowledge of how to service heat pump systems. Every system is sold with a service contract: Basic (2-year warranty, maintenance every 36 months, €60 a year for the Turbine Heat Pump and €110 for the Combi Max) or Premium (7-year warranty, maintenance every 24 months, repairs up to €250 and call-outs included, €99 and €149 a year). Commissioning and field feedback improve the next production batch.
What the margin targets depend on
Qualification, contracted lead times and a repeatable end-of-line test underpin the plan. The >38% Turbine Heat Pump and >49% Combi Max targets assume volume purchasing for the compressor and components, design-for-manufacture savings and a stable product mix. Service contracts add recurring revenue on every installed system from year one.
Service contract terms as published in the Tarnoc brochure 2026.
Concept · a compact indoor unit at the size of a boiler. Early engineering; no specifications published.
The Turbine Heat Pump and the Combi Max are the first two machines on one platform. The next generation folds them into one product: the reversed Brayton turbine and a vapour-compression cycle, together in a single indoor unit. We call it the TwinCycle.
The best of both worlds
80°C and hot tap water from the turbine, so the existing radiators and pipework stay.
The efficient base load from the second cycle, so the running cost of a Combi Max comes without an outdoor unit.
Nothing outside. Two air ducts, no unit on the façade, no permit, no outdoor noise. It goes where the boiler is.
Lighter, smaller, more homes
The TwinCycle is designed to be light enough to carry in and install at any location, and compact enough to go where the current range cannot: a cupboard, a landing, the wall where the boiler hangs. That opens the homes the current range does not serve yet: smaller houses and homes with a lower heat demand, in particular the terraced stock of the housing associations.
Same installers, same one-day installation, same radiators.
A product for the housing-association channel, where Tarnoc already works with eleven housing corporations.
Turbine core, controls and the installer network carry over from the Turbine Heat Pump and the Combi Max.
Also on the drawing board
A boiler-size turbine. The Turbine Heat Pump engineered down to wall-mounted size, for the utility cupboard rather than the attic.
Beyond the single home. The same cycle for apartment blocks and commercial buildings, where the hospital pilot in Delft already points.
Vision, not plan. The TwinCycle is at concept stage and is not in the base-case financial model. This round funds the Turbine Heat Pump and the Combi Max; the TwinCycle is where the platform goes after that.
Tarnoc product roadmap, September 2026. Concept stage; no specifications published.
Netherlands
Germany
Austria
Italy
Belgium
United Kingdom
Ireland
France
Engineering in Delft · the turbine unit in CAD
Founded in Delft · 2019
