A photovoltaic system (PV system) is an environmental friendly power generation system. However, PV system’s installation ratio in Japan is still small. For its smooth increase, a questionnaire survey and a conjoint analysis have been done for understanding consumer’s willingness. The survey was done by mail to inhabitants in 22 prefectures considering irradiance climate categories, because there are varieties of installation ratio between prefectures. From the survey, 61% are interested in the photovoltaic systems. Major reasons were “saving utility cost”, “mitigating global warming”, and “backup for emergency”. Rest of the answers corresponding to 39% is not interested. A major reason was “expensive installation cost”. On the other hand, possible investment for the photovoltaic systems was that 5% chose 2,000,000 yen, 19 % chose 1,000,000 yen, and 35% chose 500,000 yen. 39 % chose “I do not invest”. Then, an analysis on choice probability has been done. Comparing three initial costs of PV systems with same cost pay-back time, highest choice probability was the lowest initial cost. That is, lower price of PV systems will be preferred even they are same cost pay-back time. In addition, “willingness to pay” was evaluated by the conjoint analysis. The willingness to pay for 10,000 yen utility-cost-saving was approximately 50,000 yen. This means that cost pay-back time is 5 years. Moreover, cost pay-back times of the irradiance climate categories were calculated. They were 4.6 to 5.2 years, in which no clear differences or relations with the climate categories were obtained.

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The ways of using solar energy for human being are to use solar cells for direct solar ray, or to warm up object by using radiant heat of the sun. However, most of the solar energy which is showered upon the earth is used for the heat-reserve in seawater and the earth. There seems not to have existed in the past that the ways of thinking to utilize heat energy near the normal temperature as the effective work, exergy, which was directly stored up in the earth.
This paper presents a new energy source, which is got from room temperature heat source. There exist a new heat cycle that creates exergy from room temperature materials. This is composed of a unique heat cycle of CO₂ gas as a heat medium. The mechanism is shown through exergy analysis as to the heat cycle which creates valid work. Proper systems are discussed on generation of electricity, and warm or cold heat, using this cycle.

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This paper describes experiments and analyses of sheet covered snow mounds for the purpose of cold storage. First, we conducted an experiment on melting characteristics of an open cast snow mound and environment of a storage dome inside the mound, and confirmed snow (initial value: 360,000 m³) left until late November. The temperature inside the storage dome and the heat flow from the ground resulted 0-0.5°C and around 1.5 W/m², respectively. Second, we conducted experiments on melting characteristics of a waterproof/solar shading sheet, and on the ice storage by direct burying in the snow mound. Melting length until mid-September was around 9-11 m and stored ice maintained the initial condition. Furthermore, experiments and analyses on thermal insulation characteristics of an air film insulation sheet and the enhanced insulation sheet were carried out. The high insulation performance of the sheets was verified.

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This paper describes the effectiveness of residential condensing boiler and load following gas engine (GE) combined heat and power (CHP) systems in cold regions for energy conservation. Filed measurements of GE-CHP were carried out. From the feature that the exhaust heat is only used for space heating, GE-CHP does not operate when space heating is not required. However, when space heating is applied, both power and heating load become rather high, making the introducing effects of GE-CHP high. Operating results of the filed measurements clarified that high effects can be obtained throughout a year.

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It is quite common now to exploit the waste heat from heat engines and other energy conversion devices, in keeping with the need to make more efficient use of energy. However, it is impossible to ensure that a sufficient quantity of waste heat will be available at the time when it is needed. Therefore, it is necessary to identify a method of temperature control that maintains the object to be heated within the appropriate temperature range, and this must be provided by a control system independent of the source of the waste heat. A method of controlling heat transfer to control temperature during waste heat recovery has been conceived that employs bubbling to force convection currents, and was confirmed in an experiment with a model that employed water as the heat transfer medium. It was first confirmed that the heat transfer coefficient varied according to the bubbling; it was then demonstrated that it was possible to control temperature by activating and deactivating bubbling. This was shown by employing a simple air pump designed for aquariums. This technique shows promise for use in small-scale bioreactors and other devices.

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