In the present work was made the analysis of state of the art of development of solid-state vacuum tunnel diodes (VTDs) for cooling devices as well as for power generators. Quantum-mechanical calculations of cooling power, maximum temperature difference and efficiency for VTDs operating in cooling mode, and maximum electric power and efficiency in dependence on width of a vacuum gap and temperature difference on electrodes for VTDs operating in power generation mode had been made. It is shown that VTDs can be used in cooling devices with efficiency of up to 100% and in high efficiency power generators working from various heat sources in temperature range of 300-600 degC. Different technologies including nanotechnologies of the manufacturing of VTDs with gaps in nm-range and electrodes made from metals, semiconductors and thermoelectric materials were discussed. Also there were formulated the directions of scientific researches for creation of large area VTDs for cooling devices and power generators