Barton Evaporation Engine
Encyclopedia
The Barton evaporation engine (BEE) is a heat engine
developed by Sunoba Pty Ltd.
; (2) evaporative cooling at reduced pressure
; and (3) re-compression back to atmospheric pressure
with further evaporation. By this means, the engine produces power
and cooled moist air from water and hot dry air:
With a modest amount of passive solar pre-heating, the engine theoretically is able to produce power in hot arid climates. As well as being a heat engine, the BEE can also be used as an evaporative cooler.
Moreover, the BEE has broadly comparable theoretical efficiency to simple Rankine
steam turbines, without need for high-pressure boiler or condenser. The BEE can function well on industrial waste heat
, particularly the exhaust gas
of open cycle gas turbine
s.
s or condensers as with Rankine cycle engines.
In general, the efficiency of the BEE increases with the inlet temperature and the expansion ratio. A full thermodynamic analysis is available . If the inlet air is sourced from an Open-Cycle Gas Turbine exhaust at 500 degrees Celsius, the theoretical work output is approximately 150 kJ per kg of dry air throughput.
The thermodynamic cycle
s for the BEE and the Brayton gas engine can be combined in an engine consisting of a single device which would have remarkably high efficiency.
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...
developed by Sunoba Pty Ltd.
Principle
The principle of the BEE is based on: (1) adiabatic expansion of unsaturated airRelative humidity
Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...
; (2) evaporative cooling at reduced pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
; and (3) re-compression back to atmospheric pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...
with further evaporation. By this means, the engine produces power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...
and cooled moist air from water and hot dry air:
- hot dry air + water → power + cooled moist air
With a modest amount of passive solar pre-heating, the engine theoretically is able to produce power in hot arid climates. As well as being a heat engine, the BEE can also be used as an evaporative cooler.
Moreover, the BEE has broadly comparable theoretical efficiency to simple Rankine
Rankine cycle
The Rankine cycle is a cycle that converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 90% of all electric power used throughout the world, including virtually all solar thermal, biomass, coal and nuclear power plants. It is...
steam turbines, without need for high-pressure boiler or condenser. The BEE can function well on industrial waste heat
Waste heat
Waste heat sometimes called Secondary heat or Low-grade heat refers to heat produced by machines, electrical equipment and industrial processes for which no useful application is found. Energy is often produced by a heat engine, running on a source of high-temperature heat...
, particularly the exhaust gas
Exhaust gas
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline/petrol, diesel fuel, fuel oil or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack or propelling nozzle.It often disperses...
of open cycle gas turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....
s.
Performance
It is claimed that under suitable weather conditions, and assuming evaporation to saturation at constant volume in the low-pressure section and no further evaporation, a BEE engine would convert approximately 4-5% of energy collected at 30-40C above ambient into electrical or mechanical power (further evaporation during the re-compression step (3) would more than double this estimate). Whilst this efficiency is not high, the inputs will be inexpensive since the requisite pre-heating can be accomplished by passive solar methods, and hot air is both the heat transfer medium and the working gas. The engine does not require heat exchangerHeat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
s or condensers as with Rankine cycle engines.
In general, the efficiency of the BEE increases with the inlet temperature and the expansion ratio. A full thermodynamic analysis is available . If the inlet air is sourced from an Open-Cycle Gas Turbine exhaust at 500 degrees Celsius, the theoretical work output is approximately 150 kJ per kg of dry air throughput.
The thermodynamic cycle
Thermodynamic cycle
A thermodynamic cycle consists of a series of thermodynamic processes transferring heat and work, while varying pressure, temperature, and other state variables, eventually returning a system to its initial state...
s for the BEE and the Brayton gas engine can be combined in an engine consisting of a single device which would have remarkably high efficiency.