Sindhu Kanya Nalini Ramakrishna Electrical engineering

 Sindhu Kanya Nalini Ramakrishna is a PhD student in the research group Electrical machines and power electronics, division Electric power engineering.

Discussion leader is professo rLennars Söder, Kth

Examiner is professor Torbjörn Thiringer, Chalmers

Abstract:

Flexibility is needed for strengthening a renewable generation dominated power system. To tackle this
challenge, the current work deals with the quantification of flexibility from heating systems in Swedish
single family houses equipped with heat pumps. The main contributions of this work are (1) Modelling
of space heating systems equipped with heat pumps. (2) Modelling of space and water heating systems
equipped with heat pumps having enhanced vapour injection technology. (3) Quantification of flexibility
in terms of power and electric energy reduction at outdoor ambient temperatures varying between -
10◦C and 10◦C. (4) Quantification of electricity consumption as a function of time during flexibility
and recovery period which serves as a valuable information for power balancing. (5) Quantification
of performance comparison between a fixed and a variable speed heat pump. Also, the performance
difference of a physics-based model of a variable speed heat pump with empirical models is quantified.
(6) Demonstration of the importance of slow recovery in energy savings compared to rapid recovery
after the flexibility period. (7) Demonstration of utilising flexibility from heat pumps in limiting the
frequency nadir, during an outage of a major power installation in the modified Nordic-32 system, with
a high share of renewable power integration.
A flexibility potential ranging between 2.1 GW and 0.5 GW is found, for outdoor ambient temperatures ranging between -10◦C and 10◦C respectively, for a power-system with a dimensioning fault of 1.45 GW. Estimations of electric energy reduction are between 5.4 GWh and 3.2
GWh, when the indoor and water temperatures are reduced from 20◦C and 55◦C, to 18◦C and
50◦C respectively over 17.25 hours, considering 24 hours recovery period. During these conditions, the period with no electricity consumption varies between 0.85 hours and 2 hours. Furthermore, in the modified Nordic-32 bus system, during the loss of a major generation corresponding to 12% of the load, the frequency nadir reaches below 48 Hz. By utilizing house heating flexibility corresponding to 5.9% of the load, limits the frequency nadir to above 48.8 Hz