Transformation Of Solar Energy Research Articles

(Invited) Development of Hybrid Structured Materials for Electrocatalytic, Bioelectrocatalytic and Photoelectrochemical Reduction of Carbon Dioxide

There has been growing interest in the electrochemical reduction of carbon dioxide, a potent greenhouse gas and a contributor to global climate change. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. To produce highly efficient and selective electrocatalysts, the transition-metal-based molecular materials are often considered. It is believed that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. To optimize the hydrogenation-type electrocatalytic approach, we have proposed to utilize nanostructured metallic centers (e.g. Pd, Pt or Ru) in a form of highly dispersed and reactive nanoparticles generated within supramolecular network of distinct nitrogen, sulfur or oxygen-coordination complexes. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the reduction current densities. Among important issues are the mutual completion between hydrogen evolution and carbon dioxide reduction and specific interactions between coordinating centers and metallic sites. We have also explored the ability of biofilms to form hydro-gel-type aggregates of microorganisms attached to various surfaces including those of carbon electrode materials. Biofilms are able to transfer electrons to and from electrodes, and they can act in a manner analogous to redox or conducting polymer films on electrodes. Here we have explored a biofilm formed by a strain of Yersinia enterocolitica as active bioelectrocatalytic support; it is characterized by long-term stability over wide ranges of pH (4-10) and temperatures (0-40°C). Upon incorporation of various noble metal nanostructures and/or conducting polymer ultra-thin films, a highly reactive and selective system toward CO2-reduction is obtained. Another possibility to enhance electroreduction of carbon dioxide is to explore direct transformation of solar energy to chemical energy using transition metal oxide semiconductor materials. We show here that, by intentional and controlled combination of metal oxide semiconductors, we have been able to drive effectively photoelectrochemical reduction of carbon dioxide. The combination of titanium (IV) oxide and copper (I) oxide has been explored toward the reduction of CO2 before and after illumination. Application of the hybrid system composed of both oxides has resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol, as demonstrated upon identification of final products using conventional and mass-spectrometry-assisted gas chromatography. A role of TiO2 is not only stabilizing: the oxide is also expected to prevent the recombination of charge carriers. Bacterial-biofilm-enhanced photoelectrochemical interfaces for improved reduction of carbon dioxide will also be considered.

Anatase nanoparticles boundaries resulting from titanium tetrachloride hydrolysis

An important factor that governs solar energy transformation into electrical or chemical energy, when using nanoparticles-based devices, is the spatial location of traps limiting electron transport. Evidences have been presented indicating that the electron diffusion is strongly influenced by nanoparticle boundaries, whose characteristics depend on the particles preparation. In the present work we have studied the role of hydrated excess proton structures in the formation of anatase nanoparticles boundaries in samples prepared by TiCl4 hydrolysis at low temperature and strong acidic conditions. The samples, constituted by anatase nanocrystals but, mainly, by amorphous titania, are studied by 1H-MAS NMR, FT-IR and HRTEM. The results indicate that hydrated excess proton species, generated by solvation of bridging hydroxyls protons of highly defective anatase and/or amorphous titania chains, favor the chains bonding to anatase nanoparticles and/or their condensation at the nanoparticles surface. The chains’ bonding facilitates the anatase particles aggregation producing oriented self-assemblings. The preparation conditions determine a strong condensation of amorphous titania chains and it should favor anatase transformation into rutile.

Streptomycin affects the growth and photochemical activity of the alga Chlorella vulgaris

Antibiotics are increasingly being used in human and veterinary medicine, as well as pest control in agriculture. Recently, their emergence in the aquatic environment has become a global concern. The aim of this study was to evaluate the effect of streptomycin on growth and photosynthetic activity of Chlorella vulgaris after 72h exposure. We found that growth, photosynthetic activity and the content of the D1 protein of photosystem II decreased. Analysis of chlorophyll a fluorescence emission shows a reduction in the energy transfer between the antenna complex and reaction center. Also the activity of the oxygen evolution complex and electron flow between QA and QB were significantly reduced; in contrast, we found an increase in the reduction rate of the acceptor side of photosystem I. The foregoing can be attributed to the inhibition of the synthesis of the D1 protein and perhaps other coded chloroplast proteins that are part of the electron transport chain which are essential for the transformation of solar energy in the photosystems. We conclude that micromolar concentrations of streptomycin can affect growth and photosynthetic activity of Chlorella vulgaris. The accumulation of antibiotics in the environment can become an ecological problem for primary producers in the aquatic environment.

Algal application in horticulture: Novel approaches to wards sustainable agriculture

Sustainable agriculture aims at enhancing agricultural production by adopting environmental friendly technology. Algaeare diverse group of unique organism possessing myriad of potentials. They are photosynthetic microbes inhabiting plethora of habitats. Algae are pioneers of the biological transformation of solar energy and nutrients from the waste to the biomass of algae, which can undergo anaerobic fermentation giving methane (approximately 60%) and of Carbon dioxide (about 40%), which in turn can be returned to cultivation of algae as a source of carbon. They have been exploited in agriculture since decades as biofertilizers, soil stablisers and plant growth promoters. Algae production could be more ecofriendly and efficient by closing production cycles, where agricultural wastes and animal wastes are used as a medium for the growth of algae. The biomass generated by virtue of remediation of waste water or utilization of nutrients not consumed by animals can be exploited for biofuels and nutraceuticals. The use of molecular techniques can also enhanced our capacity to understand and manage the algae-crop interaction and this will lead to new products with improved effectiveness and efficiency. Genetic enhancement of algal strains with improved effectiveness may involve addition of one or more traits associated with plant growth promotion. Algal biofertilizers can provide a suitable support to agriculture by reducing use of chemical fertilizers, and ‘organic farming ’can become a reality in the future by exploring the unique potential of algae.

Towards the Capabilities of Rocket Engines with Solar Heating of Working Fluid

The purpose of this research is to show the potentiality of the rocket with solar heating of working fluid. The study describes design of the heater with tungsten pipes, ensuring full-range application of focusing radiation (95 %) under the hydrogen heating to 2900 К; gives an examples of optimization of rocket engine thrust by the flight time with predetermined fuel weight and specific weight of engine with mirror and payload; illustrates design of the engine and mirrors providing the conjugation between the thrust vector and solar radiation vector; demonstrates design of power-supply source with high-efficient solar energy transformation into electric one and compares various types of the rockets.

Development of Nanostructured Hybrid Materials for Electrocatalytic and Photoelectrocatalytic Reduction of Carbon Dioxide

There has been growing interest in the electrochemical reduction of carbon dioxide (CO2), a potent greenhouse gas and a contributor to global climate change, and its conversion into useful carbon-based fuels or chemicals. Numerous homogeneous and heterogeneous catalytic systems have been proposed to induce the CO2 reduction and, depending on the reaction conditions various products that include carbon monoxide, oxalate, formate, carboxylic acids, formaldehyde, acetone or methanol, in addition to various hydrocarbons at different ratios. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. To produce highly efficient and selective electrocatalysts, the transition-metal-based molecular materials are often considered. It is believed that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. Because reduction of CO2 can effectively occur by hydrogenation, to optimize the conventional electrocatalytic approach, we propose such a model catalytic system as nanostructured metallic palladium capable of absorbing reactive hydrogen in addition to the ability to adsorb monoatomic hydrogen at the interface. Under such conditions, the two-electron reduction of CO2 typically to CO is favored. To produce highly dispersed and reactive nanoparticles, we generate them by electrodeposition from N-coordination complexes of palladium(II). The resulting metallic Pd nanoparticles, rather than Pd cationic species, are stabilized and activated by nitrogen coordination centers from the macromolecular matrix. In the present research, we demonstrate that stabilization and activation of highly dispersed nanostructured metallic Pd centers with a supramolecular architecture of “privileged ligands” results in the electrocatalytic enhancement of the CO2 reduction. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities. Among important issues are specific interactions between nitrogen coordinating centers and metallic palladium sites at the electrocatalytic interface. Another possibility to enhance electroreduction of carbon dioxide is to explore direct transformation of solar energy to chemical energy using transition metal oxide semiconductor materials. We show here that, by intentional and controlled combination of metal oxide semiconductors, we have been able to drive effectively photoelectrochemical reduction of carbon dioxide. The combination of titanium (IV) oxide (TiO2) and copper (I) oxide (Cu2O) has been explored toward the reduction of carbon (IV) oxide (CO2) before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH), as demonstrated upon identification of final products using conventional and mass-spectrometry assisted gas chromatography. On mechanistic grounds, the role of TiO2 seems to be not only stabilizing: the oxide is also expected to prevent the recombination of charge carriers.

Study of the optical-energy parameters of planar-type radiation receivers in the structure of photoelectrical modules with parabolic-cylinder concentrators

New photoelectrical modules are considered, including photoreceivers and concentrators for efficient transformation of solar energy into thermal and electric energy. The mathematical simulation is performed to create an algorithm for calculating the thermal–photoelectrical module structure with specified energy parameters using geometric optics laws, as well as the laws of heat and mass exchange.

Cobalt Phosphate Group Modified Hematite Nanorod Array As Photoanode for Efficient Solar Water Splitting

Hydrogen production by photoelectrochemical water splitting based on modified nanostructure hematite is investigated for transformation and store of solar energy. Herein, nanorod hematite arrays were prepared by adjusted-hydrothermal method with a diameter of 30 nm. Phosphate group and cobalt ions were deposited of the surface of hematite by chemical immersion process to improve its photoelectrochemical performance and speed up the oxygen revolution reaction in water splitting. The CoPi-modified α-Fe2O3 nanorod arrays (NAs) showed a greatly enhanced electrochemical and photoelectrochemical property with a photocurrent density 270 μA/cm2 at 1.23V (vs. RHE) for FeCoPi-4 compared with 20 μA/cm2 for untreated α-Fe2O3 NAs. The effect of phosphate groups and cobalt ions on the α-Fe2O3 NAs were both investigated. The Co(Ⅱ) ion is connected closely with the α-Fe2O3 surface through phosphate groups by XPS detection. The phosphate enhances the transport of electron from the α-Fe2O3 to Co ion. The high performance domanstrated in photoelectrochemical test indicates that CoPi-modified α-Fe2O3 NAs is a potential photoelectrocatalyst for water splitting. Figure 1

Photoelectrochemical Reduction of Carbon Dioxide to Methanol at Hybrid System Composed of Titanium(IV) and Copper(I) Oxides

Due to gradual decline of energy resources, there has been growing interest in new energy systems that include direct transformation of solar energy to chemical energy using oxide semiconductor materials. Furthermore, carbon dioxide (CO2), as the primary greenhouse gas also emitted through human activities, could be converted using sunlight to organic compounds. The approach permits simultaneous generation of alternative fuels and environmental remediation of carbon emissions from the continued use of conventional fuels. The aim of this work has been to develop hybrid materials by utilizing combination of metal oxide semiconductors thus capable of effective photoelectrochemical reduction of carbon dioxide. The combination of titanium (IV) oxide (TiO2) and copper (I) oxide (Cu2O) has been explored toward the reduction of carbon (IV) oxide (CO2) before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. In particular, fabrication of the hybrid system (heterojunction photocathode) of TiO2 and Cu2O (on the conducting glass) has required first the cathodic electrodeposition copper (I) oxide. The latter step has been followed by sputtering n-type titanium (IV) oxide. The spectral responses of the Cu2O/TiO2­ electrode is comparable to that of simple Cu2O, and the photoresponse is enhanced at relatively short wavelengths. It is reasonable to expect that the light absorbed by the inner Cu2O film produces energetic electron (e-) – hole (h+) pairs. The excited electrons are driven through the conduction band to the external TiO2/electrolyte interface. The role of TiO2 is not stabilizing; the oxide is also expected to prevent the recombination of charge carriers (e- - h+ pairs). By using gas chromatography with the flame ionization detector, it was confirmed that methanol predominates as a final product.

Blacking FTO by strongly cathodic polarization with enhanced photocurrent

Transparent fluorine-doped tin oxide (TFTO) coating on quartz glass is widely used as substrate in photoelectrochemistry for solar energy transformation, sensing and so on. We observed that the TFTO could become blackish by strongly cathodic polarization. Characterization of the black FTO (BFTO) by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy revealed that part of SnO2 on the TFTO was reduced into metal Sn nanoparticles during the cathodic polarization. The BFTO greatly increased solar absorption and enhanced photocurrent responses in comparison with TFTO. It might be necessary to take caution in photoelectrochemical measurements while the FTO is strongly cathodically polarized.

ChemInform Abstract: Transformation and Storage of Solar Energy: Photochemistry and ‐catalysis for Future Energy Supply

AbstractReview: 39 refs.

Photoinduced electron transfer pathways in hydrogen-evolving reduced graphene oxide-boosted hybrid nano-bio catalyst.

Photocatalytic production of clean hydrogen fuels using water and sunlight has attracted remarkable attention due to the increasing global energy demand. Natural and synthetic dyes can be utilized to sensitize semiconductors for solar energy transformation using visible light. In this study, reduced graphene oxide (rGO) and a membrane protein bacteriorhodopsin (bR) were employed as building modules to harness visible light by a Pt/TiO2 nanocatalyst. Introduction of the rGO boosts the nano-bio catalyst performance that results in hydrogen production rates of approximately 11.24 mmol of H2 (μmol protein)(-1) h(-1). Photoelectrochemical measurements show a 9-fold increase in photocurrent density when TiO2 electrodes were modified with rGO and bR. Electron paramagnetic resonance and transient absorption spectroscopy demonstrate an interfacial charge transfer from the photoexcited rGO to the semiconductor under visible light.

Solar energy capture and transformation in the sea

Solar energy ultimately drives all biogeochemical cycles and sustains planetary habitability. All life forms and processes on Earth, including human economic and social systems, exist within a complex network of energy flow. In the sea, microorganisms comprise most of the genetic and metabolic diversity, and are responsible for a majority of the system energy flow including solar energy capture, transformation, and dissipation. All of these processes involve conversion of low quality forms of energy into a smaller fraction of higher quality energy plus degraded heat, in accordance with the basic laws of thermodynamics. Energy flow is at the core of ecosystem analysis (Odum 1968). Sunlight is the most abundant form of energy for marine microorganisms, and biophysical/biochemical mechanisms for solar energy capture have evolved by natural selection during eons of Earth’s history (Brown and Ulgiati 2004; Nealson and Rye 2003). Marine ecosystems, especially the expansive subtropical gyres, have an enormous capacity for solar energy capture and transformation. Ecologists often use the term “carbon and energy flow” to describe solar energy capture, organic matter transformation, and heat dissipation through the food web via the coupled processes of photosynthesis and respiration. A number of different methods have been used to track the flow of carbon and associated bioelements (e.g., nitrogen, phosphorus, oxygen, and sulfur), but energy flow is rarely if ever measured in field studies. An untested assumption is that matter and energy flow are inextricably and quantitatively linked in space and time in the open sea. Howard T. Odum, largely in collaboration with his brother Eugene P. Odum, pioneered the discipline of systems ecology. He observed and studied a variety of aquatic ecosystems and was the first to characterize them as networks of energy circuits (e.g., Silver Springs, Florida; Odum 1956). Odum later developed an explicit energy circuit language and set of symbols that could be used to represent interactive energy capture, transformation, and dissipation in both natural and manmade systems (Odum 1983a). While some scientists have criticized “Odum’s conjectures” and his energy-centric approach to the study of ecosystems (e.g., Mansson and McGlade 1993), the debate centers on the formidable obstacles to a comprehensive, quantitative analysis and understanding of ecological energy flow rather than a challenge to its fundamental importance in ecosystem analysis. In a pioneering essay on the relationship of energy flow to evolution, Alfred Lotka concluded that natural selection will operate to preserve and expand those species “possessing superior energy-capturing and directing devices” (Lotka 1922). Consequently, he reasoned, as long as there is a residue of untapped available energy, “the total organic mass of the system, the rate of circulation of mass through the system, and the total energy flux” will be maximized. This reasoning has since become known as the maximum power principle (Odum and Pinkerton 1955; Odum 1983b), and has led to vigorous debate over the validity and implications of what some have termed the fourth law of thermodynamics (see Sciubba 2011 for a recent assessment). The Earth is an energetically open system where solar energy input is balanced by radiative heat loss. There are numerous connections among the hydrosphere, lithosphere, and atmosphere such that materials and energy can be easily exchanged. In a thought-provoking commentary, On certain unifying principles in ecology, Ramon Margalef concluded that the energy required to maintain an ecosystem is inversely proportional to Domain Editor-in-Chief Jody W. Deming, University of Washington

Transformation of solar wind energy into the energy of magnetospheric processes

When the solar wind flows round the magnetosphere, its flow structure and interplanetary magnetic field lines are affected. This indicates the appearance of an electric current system in near-Earth space. the magnetized solar wind plasma moving at the solar wind velocity in the coordinate system of near-earth bow shock induces an electric field in this system. When crossing the bow shock front at the nose point, the tangential magnetic field component increases nearly four times, and the magnetic field energy density—15 times.

Research Advances in the Synthesis of Nanocarbon-Based Photocatalysts and Their Applications for Photocatalytic Conversion of Carbon Dioxide to Hydrocarbon Fuels

Hydrocarbon fuels are the most important sources of energy in modern society because of their natural abundance, stability, and high energy density. However, the emissions of carbon dioxide from them and the associated global warming effect impose worldwide pressure on the use of sustainable solar energy and carbon dioxide transformation and sequestration. Photocatalytic conversion of CO2 to fuels using semiconductors is proposed as an effective solution. More recently, nanocarbons, such as carbon nanotube, graphene oxide, and graphene, possessing high thermal conductivity, high theoretical specific surface area, unique carrier mobility, low-dimensional structure, and sp2-hybridized carbon configuration, have shown promotion to photocatalysis. It has been proven that nanocarbon/semiconductor hybrids can be a competitive material compared to traditional metal oxides for CO2 reduction. This review summarizes the recent research advances in the synthesis of nanocarbon hybrid photocatalysts and their applications in photocatalytic reduction of CO2 to hydrocarbons. The roles of nanocarbons in extending light absorption, increasing separation of carriers, band gap engineering, and preferred CO2 adsorption in manipulating activity/selectivity are discussed. The studies in this topic will facilitate the design of advanced functional materials for energy innovation via solar energy use.

Environmental Performance of Thermosyphonic Domestic Solar Hot Water Systems under Different Climatic Conditions: A Case Study for Greece

Undoubtedly, sun is the cleanest energy source. Specific systems are needed however for the collection and transformation of solar energy and the manufacturing processes of such systems, as well as the production of the raw materials required, are associated with impacts to the environment. As a result, the life cycle environmental impact of solar systems depends on the type and the size of the systems. System characteristics and also the climate of the installation area, affect the substituted conventional energy (solar coverage). In this paper, the net environmental gain of flat plate thermosyphonic solar systems for domestic use is determined, accounting for the household size (different collector sizes) and the installation area (different solar coverage and transportation distance) for the major cities of Greece. Calculations are based on the “Eco-Indicator ‘99” methodology and database and it is proved that substituting electricity with solar energy is always environmentally beneficial for systems installed in all major cities of Greece.

Improving the Electrical Parameters of a Photovoltaic Panel by Means of an Induced or Forced Air Stream

The main priority in photovoltaic (PV) panels is the production of electricity. The transformation of solar energy into electricity depends on the operating temperature in such a way that the performance increases with the decreasing temperatures. In the existing literature, different cooling techniques can be found. The purpose of most of them is to use air or water as thermal energy carriers. This work is focused on the use of air as a working fluid whose movement is either induced by natural convection or forced by means of a fan. The aim of this study is to characterise the electrical behaviour of the solar panels in order to improve the design of photovoltaic installations placed in roof applications ensuring low operating temperatures which will correct and reverse the effects produced on efficiency by high temperature. To do this, a test installation has been constructed at the Universidad Politécnica de Cartagena in Spain. In this paper, the results of the tests carried out on two identical solar panels are included. One of them has been modified and mounted on different channels through which air flows. The different studies conducted show the effects of the air channel cross-section, the air velocity, and the panel temperature on the electrical parameters of the solar panels, such as the voltage, current, power, and performance. The results conclude that the air space between the photovoltaic panels and a steel roof must be high enough to allow the panel to be cooled and consequently to achieve higher efficiency.

Hydrothermal Synthesis and Activity of NiS-PdS/CdS Catalysts for Photocatalytic Hydrogen Evolution under Visible Light Irradiation

To improve the solar energy transformation efficiency, it is necessary to study the efficiency of photocatalysts under visible light irradiation. In this study, the composite photocatalyst NiS-PdS/CdS has been developed using a hydrothermal method from the raw materials cadmium sulfide, palladium chloride, nickel acetate and thiourea. The characteristics of NiS-PdS/CdS were studied by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. In addition, the photocatalytic activities for water splitting were tested using lactic acid as the sacrificial reagent. The results showed that NiS and PdS dispersed well on the surface of CdS. The activity of NiS-PdS/CdS was much higher than that of CdS under visible light irradiation. When the loading amount of NiS and PdS reached 1.5% and 0.41% (w), respectively, NiS-PdS/ CdS showed the highest activity. The H2 evolution rate increased up to 6556 μmolh - 1 , which was six times higher than that of unloaded CdS and nearly two times higher than that of NiS/CdS. The apparent quantum yield was 47.5% (λ =420 nm). The co-catalysts NiS and PdS prompted the transfer of photogenerated electrons and holes, respectively. Compared with single-loading, co-loading the two co-catalysts could transfer and separate charge carriers more efficiently, resulting in enhancement of the activity for

The impact of vegetation cover on temperature and humidity properties in the reclaimed area of a brown coal dump

Vegetation cover of the landscape plays an important role in the transformation of solar energy and the formation of microclimate in the landscape. A study carried out in the Velká podkrušnohorská brown coal dump (Czech Republic) focused on the impact of the structure and functions of landscape cover on temperature and humidity properties in nine localities with various states of vegetation cover. The development of temperature and relative humidity measured in various levels (temperature and relative humidity at 2 m and at canopy level; temperature on soil surface and at the depth of 0.1 m below soil surface) were assessed for the period of 1 July 2010–14 July 2010 and an evaluation of the Landsat 5 TM satellite data, collected on 10 July 2010, was carried out. Temperature development varied between the individual localities mostly at soil surface and in the ground; however, air temperatures and humidity were very similar at a height of 2 m. Extreme values of temperatures were measured on surfaces lacking vegetation cover or covered with sparse vegetation, in particular. On the basis of satellite data analysis, we determined the differences between the amounts of vegetation, temperatures and humidity values depending on the type of landscape cover and the stage of reclamation. The study results proved the significant impact of vegetation on the transformation of falling solarenergy and the formation of microclimate, and thus the importance of fast regeneration of functional vegetation cover in the surfaces newly forming in former brown coal mines.

Experimental investigation of a solid/gas thermochemical storage process for solar air-conditioning

This paper focuses on the experimental performances of a solar air-conditioning pilot plant for housing, which is running in PROMES laboratory (Perpignan-Odeillo, France) since 2006. This pilot of daily cooling capacity of 20 kWh consists of a solid/gas thermochemical sorption process which is powered at 60–70 °C by 20 m2 of flat plate solar collectors. The thermochemical sorption process is based on the coupling of a liquid/gas phase change of a refrigerant (NH3) and a reversible chemical reaction between a reactive solid (BaCl2) and this refrigerant. Its functioning mode is intrinsically discontinuous and cyclic. It is relevant for the storage or transformation of solar energy. An analysis of 2-years experimental working of the prototype leads to an averaged yearly efficiency of solar collectors and a process COP ranging respectively from 40 to 50% and 30–40%. This prototype enables thus a daily cooling productivity at 4 °C of about 0.8–1.2 kWh of cold per m2 of flate plate solar collector and leads to a global solar COP ranging from 15 to 23%.