An organic Rankine cycle (ORC) machine is similar to a conventional steam cycle energy conversion system, but uses an organic fluid such as refrigerants and hydrocarbons instead of water. In recent years, research was intensified on this device as it is being progressively adopted as premier technology to convert low-temperature heat resources into power. Available heat resources are: solar energy, geothermal energy, biomass products, surface seawater, and waste heat from various thermal processes. This paper presents existing applications and analyzes their maturity. Binary geothermal and binary biomass CHP are already mature. Provided the interest to recover waste heat rejected by thermal devices and industrial processes continue to grow, and favorable legislative conditions are adopted, waste heat recovery organic Rankine cycle systems in the near future will experience a rapid growth. Solar modular power plants are being intensely investigated at smaller scale for cogeneration applications in buildings but larger plants are also expected in tropical or Sahel regions with constant and low solar radiation intensity. OTEC power plants operating mainly on offshore installations at very low temperature have been advertised as total resource systems and interest on this technology is growing in large isolated islands.

Low­grade heat conversion into power using organic Rankine cycles - A review of various applications

Thermal energy storage for low and medium temperature applications using phase change materials – a review

An overview of thermal energy storage systems

Phase change materials (PCM) for cooling applications in buildings: A review

A review of performance enhancement of PCM based latent heat storage system within the context of materials, thermal stability and compatibility

A state-of-the-art review is presented of the different technologies that are available to deliver refrigeration from solar energy. The review covers solar electric, solar thermal and some new emerging technologies. The solar thermal systems include thermo-mechanical, absorption, adsorption and desiccant solutions. A comparison is made between the different solutions both from the point of view of energy efficiency and economic feasibility. Solar electric and thermo-mechanical systems appear to be more expensive than thermal sorption systems. Absorption and adsorption are comparable in terms of performance but adsorption chillers are more expensive and bulkier than absorption chillers. The total cost of a single-effect LiBr–water absorption system is estimated to be the lowest.

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Solar refrigeration options – a state-of-the-art review

Thermal performance of a multiple PCM thermal storage unit for free cooling

Thermodynamic and physical property data equations for ammonia-lithium nitrate and ammonia-sodium thiocyanate solutions

Exergoeconomic and environmental analyses of CO 2 /NH 3 cascade refrigeration systems equipped with different types of flash tank intercoolers

Horizontal smooth and microfinned copper tubes with an approximate diameter of 9 mm were successively flattened in order to determine changes in flow field characteristics as a round tube is altered into a flattened tube profile. Refrigerants R134a and R410A were investigated over a mass flux range from 75 to 400 kg m−2 s−1 and a quality range from approximately 10–80%. For a given refrigerant mass flow rate, the results show that a significant reduction in refrigerant charge is possible. Pressure drop results show increases of pressure drop at a given mass flux and quality as a tube profile is flattened. Heat transfer results indicate enhancement of the condensation heat transfer coefficient as a tube is flattened. Flattened tubes with an 18° helix angle displayed the highest heat transfer coefficients. Smooth tubes and axial microfin tubes displayed similar levels of heat transfer enhancement. Heat transfer enhancement is dependent on the mass flux, quality and tube profile.

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C.A. Infante Ferreira

Papers

Solar refrigeration options – a state-of-the-art review

Thermal performance of a multiple PCM thermal storage unit for free cooling

Thermodynamic and physical property data equations for ammonia-lithium nitrate and ammonia-sodium thiocyanate solutions

Exergoeconomic and environmental analyses of CO 2 /NH 3 cascade refrigeration systems equipped with different types of flash tank intercoolers

Refrigerant charge, pressure drop, and condensation heat transfer in flattened tubes