Electric cars, photovoltaics, heat pumps – these are topics that, in the broadly understood utility of consciousness, operate on a daily basis. Everyone has an opinion on them, including breakfast TV presenters and politicians. On two topics I will not stand out, but on heat pumps that I have the right and competence. Fortunately, one principle of physics that requires cutting short the polemic.
Heat pumps (PC) are actually a very good source of inexpensive heat and are mainly used in the context of underfloor heating, most often in small houses. However, it is a solution with great potential on a much larger scale – on the scale of district heating networks. We are talking about PC with a capacity of 1 or 2, or even 15 MW. What technology should be used is not entirely determined by personal preferences.
The list of issues defining technology is extremely short, because it contains two questions.
Question 1: What are the characteristics of the lower and upper heat sources?
For relatively low upstream temperatures (say below 75°C) we can consider all three of the most popular technologies: F-gas, R744 and NH3. For higher temperatures, we are talking rather only about R744 and NH3, with the note that CO2 – to be profitable – will require low return temperatures, below 25 ° C.
Question 2: What is the required power?
F-gases are great at low to medium power. In my career, I encountered one reasonable, small (5kW), to medium-sized – around 2 or 3 MW. Devices that will actually support urban networks will usually be only ammonia.
PCs offered by MAN break out with a big bang from the above. The manufacturer provides extraordinary advanced CO2 devices that can operate at high return temperatures, can give heat at temperatures up to 150°C and exist in powers up to 80MW! you don’t believe? Type in the search engine.