Energy "concept" for old farmhouse

Heat pumps in combination with underfloor heating are efficient heating systems - Since you have plenty of space and presumably no rocky ground, I recommend you look into the ice storage heating system. It only pays off with higher energy demand - which you have due to the large and old buildings. The principle is simple and maximally environmentally friendly: The energy is stored in a concrete tank with water installed in the ground and extracted there by a heat pump through pipes with refrigerant. The trick is the use of the crystallization energy released when water freezes. The soil supplies the water tank with heat energy through its constant temperature and "heats" the water back up against the energy extraction.
Why?
From my point of view, this system offers the advantages of constant geothermal heat without affecting the temperature conditions of the microorganisms deep underground, which are so important for good soil and water. At the same time, the heat pump can be set very effectively (constant conditions) and does not suffer from the winter efficiency loss of systems that extract energy from the ambient air.
Disadvantage: Still relatively few installed systems on the market, "I don’t know it - I won’t build it" mentality of many installers and consultants.

What do you understand by greater energy demand? So rather not for a modern single-family house? Because I haven't really read anything in that direction yet.

Gas+photovoltaics+air conditioning which is also a heat pump. And also controlled residential ventilation with heat recovery. Although we need a high peak performance because of the pool. Otherwise, we would have taken a hybrid system gas+fuel cell.