The Stirling engine has been expected to be a "dream engine" able to enhance power-generation efficiency close to that of Carnot cycle for 200 years，but yet to prevail for practical use. In 2015，Professor Jürgen Kleinwächter published the low-temperature Stirling engine Sunpulse500 (with heat-source temperature of 200℃ and 25℃，on the high- and low-temperature side，respectively，and with power-generation efficiency of 12%) after many years of research.

  We have developed a new low-temperature Stirling engine (detailed design level) with reference to the Sunpulse 500，incorporating the latest advanced technologies such as low friction-coefficient materials and highly heat-insulating materials. Power-generation output of 308 W and efficiency of 11.4% should be achieved with heat-source temperature of 95℃ and 5℃，on the high and low temperature side，respectively，in our estimation.

  Excellent in power-generation efficiency while lowering energy loss and device，operation，and heat-source costs，the Low-temperature Stirling engine should use a heat source with low exergy and a low-grade heat source，to reduce power-generation cost with price competitiveness against other power generation equipment and power generation methods.

  We have realized Solar hot water Thermal Energy Conversion (STEC), which has safety, stability, load followability, expandability, and low cost of power generation, besides environmental protection.

  To be universal and inexhaustible, STEC uses solar heat as a heat source. Lowering the heat collection temperature to 95℃, we suppress energy loss and equipment costs in light collection, working medium transportation, and heat storage, securing power generation stability (24 hours / day and 365 days / year). Low-temperature Stirling engines whose possibility was examined in a separate report, enable STEC to improve the efficiency and reduce the cost of power generation.

  Utilization not only of solar heat but also of low-grade waste or geothermal heat as a heat source, can mitigate heat pollution and heat islands, and realize the self-sufficient power, energy supply necessary to household, company, region, national unit at low cost, to contribute to the world's environment, livelihood, society and cultural foundation in the world.

Using an overlapping generations model under monopolistic competition, we consider the existence of involuntary unemployment due to insufficient demand and examine the possibility of achieving full employment through fiscal policy. The main conclusions are as follows: In order to achieve full employment by expanding fiscal spending in a situation where involuntary unemployment exists, it is necessary to run a budget deficit and create government debt. After that, a balanced budget will be required to maintain full employment. Therefore, there is no need to redeem the initial government debt. Similarly, when full employment is achieved by cutting taxes, the direct increase in consumption resulting from the tax cut should be financed by the government debt, and there is no need to redeem it. Not redeeming government bonds means that they will either be non-maturity bonds or that the central bank will buy them.