To assess the suitability of solar collector systems in which polymeric materials are used versus those in which more traditional materials are used, a case study was undertaken. In this case study a solar heating system with polymeric solar collectors was compared with two equivalent but more traditional solar heating systems: one with flat plate solar collectors and one with evacuated tube solar collectors. To make the comparison, a total cost accounting approach was adopted. The life cycle assessment (LCA) results clearly indicated that the polymeric solar collector system is the best as regards climatic and environmental performance when they are expressed in terms of the IPPC 100 a indicator and the Ecoindicator99, H/A indicator, respectively. In terms of climatic and environmental costs per amount of solar heat collected, the differences between the three kinds of collector systems were small when compared with existing energy prices. With the present tax rates, it seems unlikely that the differences in environmental and climatic costs will have any significant influence on which system is the most favoured, from a total cost point of view. In the choice between a renewable heat source and a heat source based on the use of a fossil fuel, the conclusion was that for climatic performance to be an important economic factor, the tax or trade rate of carbon dioxide emissions must be increased significantly, given the initial EU carbon dioxide emission trade rate. The rate would need to be at least of the same order of magnitude as the general carbon dioxide emission tax rate used in Sweden. If environmental costs took into account not only the greenhouse effect but also other mechanisms for damaging the environment as, for example, the environmental impact factor Ecoindicator99 does, the viability of solar heating versus that of a natural gas heating system would be much higher.
To assess suitability ofsolar collector systems with polymeric materials versus those with moretraditional materials such as metals a case study was undertaken within theframework of Task 39 of the IEA Solar Heating and Cooling Programme. In thisstudy one solar heating system with polymeric solar collectors were comparedwith two equivalent but more traditional solar heating systems, one with flatplate collectors and one with evacuated tube solar collectors. Life Cycle Assessment(LCA) results obtained clearly indicated that the polymeric solar collectorsystem is the most favourable as regards climatic and environmentalperformance. In terms of climatic and environmental costs per solar heat collected,the differences between the three kinds of collector systems, however, aresmall when compared with existing energy prices. In the choice between arenewable heat source and a heat source based on the use of a fossil fuel,which was also analysed in the present study, the conclusion was that forclimatic performance to be an important economic factor, the rate of carbondioxide emission must be considerably increased above the level given by thepresent EU carbon dioxide emission trade rate. The rate would be at least ofthe same order of magnitude as the general carbon dioxide emission tax rateemployed in
Sweden.An alternative to an increase in the EU carbon dioxide emission trade ratewould be to introduce a tax system based on environmental cost, making use ofe.g. Ecoindicator99, to include also other impacts on the environment not justthe greenhouse effect.
Présentation des résultats d'essai d'un accumulateur de chaleur latente utilisant l'hexahydrate de chlorure de calcium. Evaluation des performances thermiques mesurées à l'aide d'un modèle de transfert de chaleur quasi stationnaire
The invention relates to a method and apparatus for storing heat in a heat-of-fusion storage medium, e.g. a salt hydrate, and the heat exchange and mixing in conjunction with the taking of heat from the storage medium. In a closed system including a vapor chamber (5) and a chamber for a solid/liquid phase, the storage medium (2, 4) is brought into direct contact with a substance, i.e., a heat transfer medium (3) having the capacity of taking up heat from the storage medium by being vaporized. The vapor travels to the vapor chamber (5), and when heat is removed from the vapor, the vapor is caused to condense and the condensate returns to the storage medium. The substance has insignificant solubility in the storage medium and a density which is higher, or equal to the density of the storage medium in its liquid phase. Suitable combinations of storage medium and substance include calcium chloride hexahydrate and trifluorotrichloroethane or Clauber's salt and octafluorocyclobutane.
The complex constants for the Cu(II)-chloride complexes CuCl+ and CuCl2 have been determined spectrophotometrically at 25°C and in 1 M HClO4. The evaluation procedure employed was a regression analysis for the simultaneous determination of complex constants and absorption spectra and yielded K1 = 2.3 ± 0.4 and K2 = 0.72 ± 0.09. There is a strong overlap between the 2 absorption spectra (λmax = 250 nm in both cases, ε1=530, , ε2 = 1620) which made it particularly necessary to arrange the numerical analysis in such a way that the spectral differences were fully exploited.
An extended Mie theory has been used to interpret the green colour change observed in the photochemical disproportionation of CuCl. Comparison of calculated and experimental spectra leads to the following conclusions: (i) the green colour arises from colloidal metallic copper in CuCl present in low concentrations (<5 vol %); (ii) the colloid consists of particles with an average diameter of about 3 nm in diameter and probably oblate in shape with an axis ratio of about 0.6; (iii) under the conditions of the present experiment the spectrum of the green species stayed constant, i.e. continued exposure has primarily the effect of increasing the number of copper particles without affecting their size and shape.
The performance of a solar collector system for high temperature heat delivery based on a photochromic reaction is discussed. The system consists of a non-focusing collector and a reactor integrated into a flow system. In the collector, kept close to ambient temperature, the chemical potential of the photochromic system is increased through an endothermic photochemical reaction and is used to drive the reverse thermal reaction taking place in the reactor at a high temperature. No separation of the photoproducts is involved. Accordingly, the highest temperature at which heat can be delivered from the reactor is determined by the maximum attainable photostationary state in the collector and not, as in a conventional flat-plate collector, by heat-loss from the collector to the surroundings. Accordingly, the highest temperature at which heat can be delivered from the reactor is determined by the maximum attainable photostationary state in the collector and not, as in a conventional flat-plate collector, by heat-loss from the collector to the surroundings. The functioning of the device is exemplified by calculations for a model system utilizing the photodissociation of gaseous nitrosylchloride. The results show that it should be possible to build a system which, on a clear day, delivers about 100 W heat at temperature above 200°C for each m2 collector area. A tenfold reduction in the radiation flux density of the incident light will only slightly reduce output efficiency.
The photochromic properties of the system CuCl(s)---H2O(l) in relation to the composition of the aqueous solution were studied using diffuse reflectance spectroscopy. The photochemical disproportionation of Cu+ into Cu2+ and Cu0 proved to be essentially independent of pH, ionic strength and the concentrations of Cu2+ and Cl− in the solution. The reverse reaction, i.e. thermal fading, takes place in two steps, one initial exponential step followed by a second step of zero order, i.e. of constant reaction rate. For both steps the reaction rate is independent of the concentration of metallic copper. The rate of the initial step is proportional to the product of the Cu2+ and Cl− concentrations of the solution. The rate of the second step is independent of the Cu2+ concentration and proportional to the Cl− concentration. The results are consistent with the following mechanism for the bleaching reaction: (I) diffusion of Cu2+---Cl− complexes to reaction sites on the surface; (II) fast chemical reaction between Cu2+---Cl− and Cu0 at the reaction sites yielding CuCl; (III) desorption of the product CuCl by complex formation with Cl− ions.
Method when heating a building with solar collectors comprising also a heat pump and energy storage using phase change materials. The invention is charaterized in that the energy storage system comprises to two containers, one placed indoors, where the phase change material has a melting point between 19 and 30 degrees Celsius, and a second container located outdoors and buried in the ground, where the phase change material has a conversion temperature which corresponds to or is lower than the mean temperature of the ground surrounding the container.