Energy efficient heating-cooling-power systems for office buildings

As a result of economic and political requirements, renewable energy investments are supported with various incentives all over the world, while fossil fuel systems are restricted by regulations. This article aims to make conventional heating, cooling and power systems more efficient or to develop an alternative system based on renewable energy by modelling an office building. For this reason, three different system designs compatible with office building identity are constructed as different scenarios on a computational setting. These scenarios are determined as classical heating-cooling system, combined cooling-heating-power system and zero energy building. Energy and life-cycle cost analyses of the test building, which serves as a public facility in the climate conditions of Bursa – Turkey, are conducted separately for each scenario, and 3 different sub-scenarios were generated under the renewable energy scenario. As a result of the analysis performed by using Hourly Analysis Program (HAP), the building's cooling design load was found to be 742.7 kW, and the heating design load was found to be 439.8 kW. The ground source heat pump calculation was performed by taking U-type vertical borehole as basis, which gave the resulting figures of necessary borehole length, 20,371 m for cooling and 9,137 m for heating. After vertical borehole calculations, the average amount of heat discharged into the borehole was determined as -44,3 W/m, and the average amount of heat drawn from the borehole was determined as 34 W/m. Annual energy generation of the photovoltaic plant was determined as 607.639 kWh, a value that was projected by a plant installation with polycrystalline silicon photovoltaic panel with a total surface area of 2.787 m2. The photovoltaic panel installed power of for this plant was calculated as 463 kWp. Lifecycle cost analyses were performed by using P1-P2 method and according to the calculations, the payback period for the extra investment cost is 37 months for the combined cooling-heating-power plant, whereas it is 94 months for the improved zero energy building design. Similarly, the payback period for the full investment cost is determined as 58 months for the combined cooling-heating-power plant, and 127 months for the improved zero energy building design. As a result, a hybrid zero energy building (air source condenser + ground source heat pump, hava kaynaklı soğutucu, photovoltaic power plant) is proposed as the best design option for the office building identity.