The numbers in the article suggest the stirling engine needs 1kW of energy input. There is no need to use expensive photovoltaic panels. 1kW is about 1 square m

The numbers in the article suggest the stirling engine needs 1kW of energy input. There is no need to use expensive photovoltaic panels. 1kW is about 1 square meter of mirrors in a solar concentrator on a sunny day at many latitudes. Solar concentrators and stirling engines pair nicely, though there may be issues at that small scale. Nothing more mirrors won't fix though.