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Compact vapor generation system based on a linear concentrating solar collector for polygeneration.

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Heat transport and supply, district heating
Heat pump
Cooling technologies
Solar/Thermal energy
Solar/Thermal energy
Investigation activities
Tertiary education


A Spanish university has developed a device for compact vapor generation that allows to perform two basic functions of absorption machines. First, it directly generates refrigerant vapor without a heat carrying circuit, using solar thermal energy. Second, it separates vapor from solution, reducing costs and improving the efficiency of the device. The university is currently looking for industrial partners or end-users to sign financial, technical cooperation or joint-venture agreements.



A Spanish university has developed a device for the generation of compact vapor, more efficient and economical than conventional absorption machines.
Absorption machines are thermal machines that pump heat from a source to a sink at a higher temperature. They can work like refrigerating machines, where the heat is removed from the exterior at a lower temperature, or like heat pumps, where the heat is discharged into the exterior at the higher of the two temperatures. The heat from the cold source (from the environment, i.e., atmospheric air, water or soil) is generally gratuitous. Unlike conventional mechanical compression heat pumps, which consume work to produce heat pumping, absorption machines consume heat at a moderate temperature. Efficiently, the residual heat can be recovered or used as renewable heat, such as geothermal heat or solar heat obtained by solar thermal collectors. These machines have been around for over a century but they are not used as much as mechanical compression machines due to their higher cost, weight and volume. However, they do not destroy the ozone layer or contribute to the greenhouse effect as they use natural fluids.
Today, parabolic collectors are used to heat a fluid in a thermodynamic cycle for the production of work in solar thermal power plants. By means of a reflective surface, normally parabolic or Fresnel type with a horizontal axis, solar radiation is concentrated along a straight and horizontal receiver tube located at the optical focus of the collector. A coaxial outer glass tube surrounds the receiver tube, generating a vacuum (much lower pressure than atmospheric pressure) between them, in order to minimize heat losses. For the same purpose, the outer portion of the receiver tube is coated with optically selective layers, which allows increasing overall solar radiation absorptivity while minimizing the overall emissivity at operating temperatures. The ensemble, or just the reflective surface, rotates to follow the sun.
The invented device allows to perform simultaneously two of the basic internal functions of absorption machines, i.e., generating refrigerant vapor directly and separating the vapor from the solution. This is achieved in a compact and efficient manner in a single element (collector tube), so it does not require heat carrying circuits or the use of heat carrying fluids, which provides savings in terms of tubes, pumps, heat exchangers and power consumption, in addition to not consuming a heat carrying fluid. The system forces the internal working fluid of the machine to go through the interior of the receiver tube of the solar collector.

The system is coupled to a hybrid cycle absorption machine, conceived as an integral device that makes the user a “prosumer”, i.e., a consumer that alternately produces heat energy, cold energy and electricity without consuming primer energy, and in the event that the collected solar energy is insufficient, it allows consuming electricity in order to increase it until the demand can be met. The invention consists of the configuration for the direct production of vapor in an upward flow, separated from a solution which slides freely in the form of a film, falling into the receiver tube of a tilted collector. The receiver tube can be commercially available and adapted to the function or it can be custom-designed.
It's valid for activating single-effect, multi-effect, half-effect absorption machines or generator absorber heat exchanger machines, as well as for those based on thermodynamic cycles using a solution from which a vapor is obtained and used for energy-related purposes (heat, cold or power production) or chemistry-related purposes (producing product, purification, detoxification, among others), whether continuous or intermittent.
The university is looking for industrial partner to develop and market the technology or energy provider to test it under financial, technical cooperation or joint-venture agreement.

Advantages & innovations

Cooperation plus value: 
Innovative aspects: - The solar collector forms a compact ensemble with a multi-functional absorption machine. - It simultaneously performs two basic functions: generating refrigerant vapor and separating the vapor from the solution. - It eliminates the need for heat carrying fluid, such as water-glycol or thermal oil. - It does not use heat carrying circuits. - It uses biphasic flow that is stratified and moved by gravity. Advantages: - It eliminates the heat carrying fluid and its cost, together with the associated environmental and efficiency problems. - Less complex installation and maintenance. - Lower costs. - No risk of leakages (closed circuit). - It eliminates the problem with freezing because the solution does not freeze as easily as water does. - Smaller device size and weight (typical limitation of absorption machines). - Since the machine is located next to the solar field, it does not take up any surface area of an indoor machine room. - Integrated with other innovations, it makes the user a “prosumer”, i.e., collecting energy both for its own consumption (consumer) and for external use (producer).

Stage of development

Cooperation stage dev stage: 
Under development/lab tested

Partner sought

Cooperation area: 
The research group is seeking industrial partners for the development and commercialization of the technology and/or users of the technology for testing the technology in a demonstration pilot plant. The specific area of activity of the partner would be engineering consulting firms in case of industrial partners or energy providers/producers in order to test the technology in the pilot plant. In the case of engineering partners, the tasks to be performed would include consultant impact studies, detailed design of pilot plant and/or viability studies. In the case of producers or providers, the tasks would include viability studies/impact/reduction of emission and primary energy, as well as monitoring of the plant. The type of partnership agreement considered includes financial, technical cooperation or joint-venture agreements.


Conceptual diagram of the final target device.