Good Literature Review About Hybrid Renewable Energy System For Zero Energy Building (Zeb)
Hybrid Renewable Energy System for Zero Energy Building
A zero energy building (ZEB) has been defined as a building whose energy needs have been greatly reduced by improving its energy efficiency gains and that its extra energy requirements are met by renewable energy technologies. The concept of renewable hybrid energy systems and zero energy buildings are inseparable because the first objective of a ZEB design is to optimize energy efficiency then use renewable energy available on site (Torcellini et al, 2006; Li, Yang, and Lam, 2013). Interest in ZEB has being growing due to the need to reduce energy costs and also to minimize environmental consequences arising from the use of fossil fuels as energy sources. Renewable energy sources have also found wide acceptance for buildings in remote off-grid locations. Documented evidence suggest commercial and residential buildings energy use in the US account for approximately 40% of primary energy and 70% of the electricity consumed. Renewable energy technologies that can be exploited include solar energy, wind energy, biomass, geothermal, and biogas.
Research shows that buildings account for a large percentage of global energy consumption and consequently carbon emissions. The idea of formulating sustainable strategies in the context of energy consumption often involve measures to increase energy efficiency in buildings and increase the utilization of clean energy systems. The ultimate design strategy of a building that is ZEB compliant results in high efficiency leading to minimum energy consumption and subsequently minimum carbon emissions and the use of renewable energy technologies to complement the extra balance of energy required. Researchers interested in finding solutions usually breaks down the energy loads of a building into specific units for ease of study and simulation. For example, majority of energy consumed in buildings has been found to be heating and cooling. Other areas that involve use of energy involve equipment such as escalators, lighting, and other machines. Design of effective energy efficiency measures requires a study of the three major aspects of a building: building services systems, building envelope, and internal conditions. Building envelopes include a consideration of building’s features such as window glazing, day lighting, thermal mass, thermal insulation, reflective or green roofing. Indoor conditions include study of indoor design conditions as well as internal heat loads, which can be due to lighting, equipment or appliances. Building services systems include heating, ventilation, and air conditioning systems (HVAC systems); electrical services including lighting; and heavy machines such as escalators and lift services (Li, Yang, and Lam, 2013).
The building services systems, building envelope, and internal conditions of a building are studied in detail with an objective of incorporating element of energy efficiency. For example, the analysis might recommend a replacement of energy consuming incandescent light bulbs be replaced with more energy efficient LED light bulbs or if the building loses a lot of energy in winter, the idea might be to insulate it to improve its thermal performance. Even after all this has been done, it is very likely that the building still requires some energy to power equipment like lifts, escalators, energy efficient bulbs etc. however, due to energy efficiency, the final energy required might be very small compared with the initial energy requirements prior to assessment. That extra energy required can be obtained from various sources. However, since the overall objective is to save money and conserve environment, the next best alternative is to choose renewable systems. Where more than one source of renewable energy system is available onsite, the idea is usually to exploit all of them by tapping and using them in a hybrid system. However, in some situations, one type of system such as solar power might be available relying on photovoltaic as the sole energy might preset some challenges. A study conducted by Scognamiglio and Røstvik (2012) content that photovoltaic power is not good for ZEBs as the sole energy source due to their intermittent nature.
Technological advancements in aspects of design, optimization, operation and control has made it possible to integrate two or more renewable energy systems (such as wind and solar) to obtain a renewable hybrid energy system configuration (Bajpai and Dash, 2012). The results have been development of new, innovative, clean, and efficient energy systems that compliment other efforts made in the designs of ZEBs. Prasda, Reddy, and Saibabu (2011) studied the possibility of incorporating renewable hybrid energy sources in ZEBs. Their objective was to understand the environmental and economic benefits of integrating renewable energy system in ZEBs. Their study involved collection and analysis of data about energy requirements. From the results, they suggested ways of ensuring how ZEBs can be achieved with incorporation of renewable hybrid energy systems. In their study, they considered a photovoltaic-wind hybrid system for ZEBs. The hybrid system architecture was composed of a PV array, a wind turbine, a generator, storage battery, inverter, rectifier, and dispatch strategy cycle charging. An existing building was chosen and simulations were performed based on the collected and analyzed data of energy the building’s energy requirements. The results of the simulations of the old building was then compared with the simulations of a modified building with the demonstration of how such a solar-wind hybrid system could effectively feed the modified building’s load. A HOMER software was used in the simulations. The results of the simulations suggest renewable hybrid systems are feasible for integration in Zero Energy Buildings. Their findings also suggested that besides offering solution for ZEBs, the hybrid system also has economic and environmental benefits.
In an attempt to find a solution for a typical zero energy building, Lu and Wang (2014) came up with an optimal design for renewable hybrid energy systems. They chose Hong Kong Zero Carbon building with its meteorological data of 1987 as their reference point for their study. They were able to generate the annual cooling load profile of the building with the use of a TRNSYS building model. Among the building’s data collected used as a basis for load profile included aspects of lighting schedule, occupancy schedule, equipment energy consumption, electricity energy demand, air conditioning, and energy generation values. In order to simulate the energy systems of the building, they had to first develop simplified models of renewable energy systems and air-conditioning systems using a Matlab software. The building’s annual load profile was taken as the input. Among the variables they optimized were wind turbine, solar photovoltaic, and bio-diesel generator that were going to form the renewable hybrid system for the building. The values of solar, wind and bio-diesel were just trial values varied accordingly to simulate the anticipated circumstances and a possibility of generating the best combination possible that factors in elements of economics, environment, and the overall concept of ZEB. Finally, the results of the performance of the building with varied combination of the renewable energy system sizes was used to perform comparative analysis and system evaluations.
Bajpai, P. and Dash, V. (2012). Hybrid renewable energy systems for power generation in stand-alone applications: A review. Renewable and Sustainable Energy Reviews, 16(5), pp.2926-2939.
Lia, D.H.W., Yang, L., Lam, J.C. (2013). Zero energy buildings and sustainable development implications – A review. Energy, 54, 1-10.
Lu, Y., Wang, S. (2014). Optimal Design of Renewable Energy Systems in Low/Zero Energy Buildings. International High Performance Buildings Conference. Paper 129. Retrieved from: http://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1128&context=ihpbc
Prasad, S.G., Reddy, V.K., & Saibabu, C.H. (2011). Integration of renewable energy sources in Zero energy buildings with economic and environmental aspects by using HOMER. International Journal of Advanced Engineering Sciences and Technologies, 9(2), 212-217.
Scognamiglio, A., & Røstvik, H.N. (2012). Photovoltaics and zero energy buildings: a new opportunity and challenge for design. Progress in Photovoltaics: Research and Applications conference. Frankfurt: John Wiley & Sons.
Torcellini, P., Pless, S., Deru, M. & Crawley, D. (2006). Zero Energy Buildings: A Critical Look at the Definition. Pacific Grove, CA: NREL.