The paper provides an overview of space energy in three main directions:
1) Space energy is imported to Earth, contributing to global economy
2) Space energy is exploited on site to foster further development (e.g energy on Mars to power bases)
3) Space energy comes from a lunar body near the main site
The paper states that space energy could supplement Earth energy and provide for future space exploration. The interest in space energy has gone up drastically in the past years, with the directions still garnering different amounts of research. Space solar energy is well researched with SSPS (space solar power station) plans in preliminary and basic stages for several countries. The problems with SSPS are its huge launch cost and ground station cost, moreover a limited lifetime due to hostile environment. Japan has been quite successful, having achieved 1.8 kW beamed to 50 metres in 2015 by JAXA and 10KW beamed 500 metres in 2015 by Mitsubishi. China, however, aims to have a megawatt-level solar power plant in place by 2030. Russia's Roscosmos is also working on a 100kW prototype.
The second direction is interesting for space exploration – for example the exploration of Mars. Fuels are heavy, taking up a lot of weight and resulting in high velocity needs. Solar energy, geothermal energy and wind provide opportunities for energy on-site, removing the need to bring it in from Earth. Geothermal energy is particularly interesting, as due to its relatively low temperatures (ca 30-50C), it can be successfully used both for heating and for cooling, providing good energy sources for buildings, greenhouses and electricity production.
As for lunar, solar seems to be perfect – there is no atmosphere, no wind, no rain, no clouds, thus constant perfect sunshine.