Abstract
Applications of renewable electricity in cities are mostly limited to photovoltaics, and they need other renewable sources, batteries, and the grid to guarantee reliability. This paper proposes a hybrid system, combining biomass and photovoltaics, to supply electricity to educational buildings. This system is reliable and provides at least 50% of electricity based on renewable sources. Buildings with small (<500 kW) installed power based on renewables, mainly biomass, are usually expensive. Besides, in urban areas, photovoltaic capacity is limited due to roof availability. This paper analyzes different configurations, meeting these constraints to obtain an economically feasible solution based on photovoltaic-biomass modelling of small size hybrid systems. The technology used for biomass energy valorization is a fluidized bed gasification power plant, which has been modelled with real data obtained from experimental tests and previous research projects. Thereby, real costs and electric efficiency are included in the model. The techno-economic feasibility analysis using HOMER software with metered real load curves from an educational building has been modelled. The results of the model show that hybrid renewable systems are very feasible in the scenario of 50% of electricity contribution, however, higher contribution (>70%) implies high electricity costs.
Highlights
The world energy scenario and implemented policies over the last 30 years show an important increase in energy efficiency and contribution of renewable sources, but they can only partially alleviate or soften the continuous increase in energy demand due to unstoppable population growth and necessary development of rural areas [1]
Significant carbon emission reductions can be achieved with different renewables, but fossil fuels, like natural gas, usually provide the dispatchable power capacity for reliable electricity generation [6]
It must be taken into account that wind power’s intermittency makes that fossil gas-fired generation systems work at partial load and reduced efficiency most of the time to follow load request [1,7]
Summary
The world energy scenario and implemented policies over the last 30 years show an important increase in energy efficiency and contribution of renewable sources, but they can only partially alleviate or soften the continuous increase in energy demand due to unstoppable population growth and necessary development of rural areas [1]. It must be taken into account that wind power’s intermittency (and it could be extended to photovoltaics and other intermittent sources) makes that fossil gas-fired generation systems work at partial load (when wind production is temporally high) and reduced efficiency most of the time to follow load request [1,7] It is desirable, thinking towards a massive deployment of renewables, that these systems minimize the need for conventional generation power plants. The simplest HRES could combine photovoltaic and diesel systems, providing high reliability due to the availability of a diesel system that provides the needed electricity when the solar system cannot cover the electricity demand (lack of solar radiation, failure in the system, etc.) This kind of HRES presents environmental and economic drawbacks due to the emissions coming from the use of fossil fuels and the cost to supply the diesel. This paper presents an exhaustive feasibility analysis of the implementation of an HRES on a higher education building (university), performed using a complete year of energy demand measurements of an existing building, real costs and efficiency of small biomass gasification power plants, and HOMER software for an economic/technical feasibility simulation
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