TPTS water heater element
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Two Phase Thermo-Syphon
Water Heater Technology Development

TPTS Development Company, formed by Altas Corporation and EcoSystems, has developed a two phase thermosyphon ("TPTS") water heater technology which can be used to produce gas-fired domestic hot water (DHW) heaters of long life and of very high efficiency. This technology is available in systems for water heating which use natural gas (NG), liquefied petroleum gas (LPG) burners, or other combustible fuels, as well as in systems which use solar energy or heat pump heating in conjunction with fossil fuel burners or electric resistance heaters in a backup function. A program is under way to commercialize this technology with a major manufacturer in the USA. Licensees are sought in Europe and other parts of the world.

TPTS Heater
Three hot showers now for every two before!
Typically as high as 4% per hrTypically as low as 0.6% per hr


About 4 million natural gas-fired water heaters and over 3 million electric water heaters are sold per year in the USA alone. The total US sales are probably US$1-US$2 Billion per year at retail, and the markets elsewhere are also large. The market is highly fragmented, offering old technology, involving glass-lined steel tanks of a limited lifetime, and very primitive natural gas-fired water heater design concepts. (The central chimney in gas-fired DHW heaters was a very useful design concept 80 years ago, but currently the energy losses produced by a central chimney have a low average efficiency or "energy factor," barely over 55% for most models. This is simply unacceptable.) The TPTS eliminates these heat losses, it can be easily used with a power burner, and it makes it easy to use the heat of condensation of the water vapor contained in the flue gases. Using TPTS, the average annual thermal efficiency (or "energy factor") can be above 77% in small (single family) water heaters which do not use solar energy. With a power burner and condensation provisions, a TPTS design can achieve energy factors between 87% and 94%, depending on the size of the DHW heater. Combining the TPTS design with the solar DHW technology of Altas, solar fractions of over 80% and even over 90% can be achieved, using a novel coupling system between the solar storage tank and the backup heater, and using TPTS for the backup heater. The TPTS technology is patented in the USA by the Gas Research Institute (GRI) of Chicago, and in Europe by Altas. The development of this TPTS technology started with US Department of Energy (US DOE) and internal R&D funding, and has had external US DOE and GRI support with R&D contracts totaling far over US$1 Million to date.


Frank de Winter at Prototype

TPTS Development Company has recently completed fabricatiion of a pre-production prototype. Engineering prototypes have been made covering a large range of interest, from the 40 gallon (151 liter) unit with a firing rate of 40,000 Btu/hour (11.7 kW), up to 120 gallons (450 liters) in tank size and up to 200,000 Btu/hour (59 kW) in firing rate.


Preliminary cost estimates, made in conjunction with the Copper Development Association in the USA, suggest that the OEM cost for a TPTS unit of a firing rate of 40,000 Btu/hour (11.7 kW) will be between $35 and $40, at annual water heater production levels of significance (say 50,000 units or so).


Assuming natural gas priced at $.75/therm, typical family hot water consumption at 63.5 gal/day, and a retail price differential of $100 for the TPTS heater, and energy factors of 77% for TPTS versus 55% for standard water heaters, the payback is less than 1.5 years. [calculations].

Furthermore, with these same assumptions, energy savings will be more than 1.5 barrels of oil (equivalent) per family per year!


TPTS Development Company licensed this technology to a major water heater manufacturer in the USA but they did not implement the design and that license has expired. Patent rights, trade secrets and associated intellectual property are available for manufacturing worldwide.


US Patent Number 4,393,663: Two-phase thermosyphon heater (pdf)

An apparatus for transferring heat from a heat source to a heat sink using a vaporizable liquid wherein the vaporizable liquid is heated in an evaporator so that some of the liquid vaporizes to propel the remaining heated liquid to a condenser, where heat is transferred from the heated liquid to the condenser predominantly by forced convection, and wherein the cooled liquid and condensed vapor are returned to the evaporator for reheating, and further wherein a restriction is disposed in the liquid/condensate return path to prevent vapor from the evaporator from flowing to the condenser through the return path.

12 Claims, 4 Drawing Figures

Patent 4393663 at Google Patents (easiest to navigate)

Patent with text and links (from USPTO, archived on this server

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TPTS Development Company
P O Box 7080, Santa Cruz, CA 95061
Tel: +1.831.425.8523

updated 2009 January 26