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[en] The effect of the payback time on the spectacular diffusion of solar hot water systems (SHWS) in Greece was investigated in this work. The time pattern of the diffusion of flat plate solar collectors since its first appearance in 1974 shows that the diffusion rate grew exponentially at first, with the annual sales figure reaching 185,000 m2 in the mid-80s. A rapid decline of the growth rate, down to the present annual sales level followed. By the year 2000, more than 2,000,000 m2 of collectors had been installed. The economic behaviour of the main type of users (households and hotels) was found to have undergone two stages: in one of them, 1978-2002, the change of sales is in agreement with a change in economic feasibility, measured by payback time, while in the other, the early growth stage, 1974-1977, the demand grew despite a negative economic trend, obviously because of non-economic factors. The role of tax deduction, which is the most influential incentive, has been rather instrumental in the growth period 1978-1989, but lost its significance thereafter. This incentive has been withdrawn since the beginning of 1993
[en] This article sets out the basic principles of ground coupled heat pumps with buried plastic pipes circulating antifreeze which absorbs heat from the soil and releases the heat on return to a building and passage through a compressor. The design of residential and commercial heat pumps, the operation of a compressor, and promising technology developments are reviewed. Brief details of a ground source heat pump installation in Louisiana are given
[en] A brief description is given of the physico-chemical parameters characterized a hot water geothermal reservoir and of its exploitation by means of single or coupled (doublet) wells. The technical aspects of geothermal heat to the users is then discussed, beginning with corrosion of materials caused by seven main agents: oxygen, hydrogen sulphide, carbon dioxide, ammonia, hydrogen, sulphates and chlorides. A brief mention is made of scaling due to calcium carbonate, silica and calcium sulphates. The basic components of a geothermal plant for non-electric uses are then discussed: production pumps, surface pipelines, heat exchangers, heat pumps and reinjection pumps. The advantages and disadvantages of the different equipment and materials used in the geothermal sector are also presented. A list is also given of the criteria used in the energy and economic balance of a geothermal operation. (author). 24 refs, 13 figs, 2 tabs
[en] Solar hot water technology was made great strides in the past two decades. Every home, commercial building, and industrial facility requires hot water. DOE has helped to develop reliable and durable solar hot water systems. For industrial applications, the growth potential lies in large-scale systems, using flat-plate and trough-type collectors. Flat-plate collectors are commonly used in residential hot water systems and can be integrated into the architectural design of the building
[en] The speed at which many energy efficient technologies have been adopted has been very slow and the reasons why this is the case are often not well understood. An important area for New Zealand is domestic hot water which typically accounts for one-third of a household's electricity usage. We use in-depth interviews to examine the decision processes of six householders who were replacing existing hot water systems or building new homes. We also interviewed different trades people and professionals advising those households. Seven themes emerge from the interviews which demonstrate huge inertia to change. Using methods from decision sciences we also construct an information processing model describing the possible steps in the adoption decision. This model emphasises the complexity and difficulty a householder currently faces if they wish to pursue an alternative system for heating hot water. - Highlights: ► The decision process regarding the adoption of hot water systems is essentially the same regardless of context. ► Householders get no real support from suppliers and others who might appropriately advise on energy efficient systems. ► Available information on energy efficient options is seen as confusing, irrelevant and partial. ► Huge inertia exists preventing people moving away from simple and convenient technologies represented by the status quo.
[en] Highlights: ► Develop a prototype of a solar domestic hot water system using a gravity assisted heat pipe. ► Investigate of the energy behavior of the heat pipe. ► Different fill charges have been experimentally tested. ► Investigate the influence of the liquid fill charge on the thermal performance. ► Predict the maximum performance. - Abstract: This paper deals with an experimental investigation of the effect of the working fluid inventory on the performance of the gravity assisted solar heat pipe. Measurements of solar flux and the temperature in different positions over the heat pipe have permitted us to evaluate the performance of the system for different working conditions. Results prove that the optimum performance is observed when the 2/3 of evaporator volume is filled with methanol.
[en] Flat-plate solar collector is the most popular type of collector for hot water system to replace gas or electric heater. Solar thermal energy source is clean and infinite to replace fossil fuel source that is declining and harmful to the environment. However, current solar technology is still expensive, low in efficiency and takes up a lot of space. One effective way to increase the efficiency is by applying high conductivity fluid as nanofluid. This paper analyzes the potential of size reduction of solar collector when MWCNT nanofluid is used as absorbing medium. The analysis is based on different mass flow rate, nanoparticles mass fraction, and presence of surfactant in the fluid. For the same output temperature, it can be observed that the collector's size can be reduced up to 37% of its original size when applying MWCNT nanofluid as the working fluid and thus can reduce the overall cost of the system.
[en] An overview of the technical, economic and legal aspects of thermal water resources in Bulgaria is made. There is 137 sources of thermal waters in the country with a total flowrate of 3865 l/s and average temperature 44.5oC. Some recommendations to various governmental bodies concerning thorough investigation, assessment and effective utilization of thermal waters as energy source are presented. 1 tab