ENERGY BALANCE ANALYSIS IN A RESIDENTIAL RENEWABLE ENERGY COMMUNITY IN STOCKHOLM : A MATLAB-Based Simulation of Photovoltaic, Battery Storage, and CHP Integration for Local Self-Sufficiency

This thesis evaluates how rooftop photovoltaic systems, battery energy storage and a small renewable fuel combined heat and power unit are able improve factors such as adequacy, cost, and emissions for a Swedish residential Renewable Energy Community. A time-series simulation for Stockholm models three configurations which are PV only, PV with a 200 kWh lithium-ion battery, as well as a PV with the same battery plus a 100 kWₑ CHP operated on HVO. Hourly PV production is taken from PVGIS for a multi-apartment building in Skarpnäck, and the electricity demand is represented by a synthetic 600 MWh/year load profile for 150 dwellings. Annual indicators and representative January, July, and October profiles are used in order to assess self-consumption, self-sufficiency, grid interaction, operating cost, and CO₂ outcomes, with rule-based, price-aware dispatch, and a sensitivity analysis on CHP and storage sizing and HVO price. PV alone shows strong seasonal and intra-day mismatch with self-consumption being 60.3 %, self-sufficiency 17.9 %, exports 70.8 MWh, and imports 492.4 MWh. Adding the battery shifts part of the midday surplus into the evening, lifting self-consumption to 73.6% and self-sufficiency to 20.9 %, while the exports fall to 47.2 MWh and imports to 474.9 MWh, with about 294 full-cycle equivalents per year. Introducing CHP changes the system most materially. Annual CHP generation reaches 417.8 MWhₑ and raises self-sufficiency to 90.5 % while imports drop to 57.1 MWh. CHP also delivers 633 MWhₜₕ of useful heat, covering 30.1 % of an assumed 2.1 GWh thermal demand. Annual operating cost is about 1.33 MSEK for PV only, 1.20 MSEK for PV plus battery, and 3.64 MSEK for PV + battery + CHP when fuel and maintenance costs and annualised CHP investment are included. Grid-related CO₂ is low in Sweden (9.4, 9.0, and 1.1 t for the three cases), while CHP tailpipe emissions are around 357.8 t, under certified life-cycle accounting for renewable diesel this burden would be substantially reduced. Sensitivity results show diminishing returns to storage size, a strong dependence of CHP economics on HVO price and heat credit, and limited effect of electricity price assumptions on autonomy. The findings imply that Swedish RECs need hybrid architectures. PV with battery is the cost-efficient baseline that improves day-to-day operation and reduces peak imports, while adding a modest CHP provides winter adequacy and near autonomy when supported by sustainable fuel pathways and favourable policy for heat valorisation.