I do not believe the heat pump comparison is a good one.
The Kender Energy technology is more similar to the steam turbine. Where water is heated in a boiler by the use of coal or natural gas. It changes to steam which travels through a conduit and spins a turbine to generate electricity. A steam system is an open system with loss due to required venting to maintain a given pressure at all times. If you have ever driven by a coal or gas fired power plant steam clouds are what you see comming from the cones.
Like I stated in an earlier post the Kender system is closed with no loss to atmosphere. The solar panel provides the heat source to change the temperature of the helium and cause it to circulate in a closed loop and spin the compressor and turbine.