I couldn't help thinking about EROEI for solar panels and Stirling engine, at least to come up with a back-of-an-envelope calculation.

Given that any transformation of matter involves energy and all energy would incur a cost, the price of a product would be a good proxy for the embedded energy, the accumulated energy needed to make that product, its components and transformations. So in the following, I will try to come up with a simple metric that allows comparing energy production devices.

In the UK, one can expect to harvest approximately 30W/m^2 on average using a 15% efficient solar panel. Every square meter would yield approximately 250kWh per annum or about 5,000kWh over a 20 year life span, per square meter. Also in the UK, I would pay approximately $200/m^2 for a monocrystalline solar panel. If the panel was produced in China at an electricity price of 10c/kWh, the equivalent energy expenditure would amount to 2,000kWh/m^2. Not accounting for labour and other bits and bobs, the net energy would still be 3,000kWh over 20 years or an EROEI of 5/2.

In comparison, a Sterling engine would not only need a generator, possibly a DC generator, but also an inverter to get AC, the question would be: can one build a contraption consisting of a Stirling motor, generator and closed loop heat circulation system to capture 1m^2 of sunlight at an equivalent energy expenditure, i.e. 2,000kWh/m^2 or $200/m^2? Possibly. Would it run for 20 years given that there are many moving parts that need lubrication? Possibly.

Perhaps one message in @B.'s post was that not all energy does have to be in the form of electricity. Some may be needed in low temperature heat. Then a legitimate question would be: why go through the complex system of solar panels, inverter and heat pumps if the same could be achieved with much simpler "steam-punk" means? Perhaps we'll get there.