Efficiency study: Low voltage DC usage in a commercial building - A benefit analysis of two different 380V DC solutions in a commercial building

Examensarbete för masterexamen
Master Thesis
Electric power engineering (MPEPO), MSc
Behrendt, Martin
The purpose with this thesis is to answer what value a commercial building 380V DC solution holds, in regards to energy and financial savings, in comparison to an equivalent AC system. Energy savings are investigated in the distribution system and in the load conversion steps. This work is purely an efficiency study, no regards has been taken to system reliability or safety aspects. Two different 380V DC solutions has been evaluated, one referred to as the DC solution and the other one as the optimized DC solution, where the latter use loads which are optimized for DC usage, with no unnecessary power electronics. Efficiencies are studied for distribution system, photovoltaic system and chosen loads such as data center, lighting, ventilation fans and receptacles (process energy). Load profiles are created and scaled with efficiencies corresponding to each system, AC, DC and optimized DC. The AC system is used as a reference system and the difference in required energy between the systems are simulated on an hourly basis. This is done for thee difference load points, 20%, 50% and 80% of maximum load and for weekdays, Saturdays and Sundays, resulting in nine different cases per system evaluated. This resulted in, for the DC solution, energy savings ranging between -29 450 kWh/year (-0.8%) to 109 119 kWh/year (3.2%), resulting in yearly financial savings of €-1 458 to €5 401. For the optimized DC solution, energy savings ranges between 164 234 kWh/year (4.4%) to 276 352 kWh/year (8.2%), resulting in yearly financial savings of €8 130 to €13 680. The DC solution were found non-feasible, the shortest payback-time were found to be 34 years, thus longer than the expected equipment life-time. The optimized DC solution payback-time were found to range between 14 and 23 years, with an even load distribution between the three load points the payback-time was found to be 17 years. Thus, even in worst case, the optimized DC solution is still feasible, with an overall system efficiency gain of 4.4% and yearly financial savings of €8 130.
Elkraftteknik , Electric power engineering
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