Heat pump capacity profile

Heat pump capacity varies from its nominal capacity as a function of source and sink temperature. It would be good to be able to generate this profile with atlite.

Detailed Description

The nominal is based on 7/35C (from what I can see). There's probably an ISO standard for it. I previously implemented it in a project based on a manufacturer's product sheets, but I expect there is a simple expression linking source/sink temp with capacity out there.

Context

Capacity costs in a model are linked to nominal capacities. If that capacity can vary then it should be reflected so that the model is "forced" to invest in more if it wants to meet a certain demand. It's particularly important because capacity deviates most when demand is highest (i.e. coldest days).

Possible Implementation

Same as coefficient_of_performance, i.e., (source='air', sink_T=55.0, c0=None, c1=None, c2=None, **params). I expect there will be some coefficients one can define if we do find a general expression.

Start by reviewing the existing coefficient_of_performance entry point and the referenced heat_pump_characteristics.csv implementation. Determine how a source/sink-temperature capacity profile should fit the proposed API, then define completion around generating capacity that varies from nominal capacity across those temperatures.