Design and control of mixed-mode cooling and ventilation in low-energy residential buildings
Charalampos Angelopoulos, 1st year PhD student at Loughborough University
Introduction
In most of the developed or developing countries, the residential sector accounts for a significant percentage of the total energy demand in the building sector. Residential buildings in India account for almost 22% of the total electricity consumption and the projections indicate that the figure will continue to rise by 8% annually (Kumar, 2011). In recent years, mechanical ventilation and air conditioning have penetrated in the market not only in the developed but also in the developing countries. Due to the sustained economic growth in the developing countries, more people can nowadays afford mechanical systems to maintain indoor thermal comfort (Kumar, 2011). This has a negative impact on the total energy consumption as well as on the CO2 emissions.
Researchers and engineers are challenged to reduce the energy consumption in buildings without compromising indoor air quality (IAQ) or the thermal comfort of occupants. The effective cooling of residential buildings in predominantly warm climates requires urgent attention by designers. Natural ventilation strategies cannot always maintain thermally comfortable internal environments due to extreme weather conditions, and relying solely on mechanical cooling technologies will result in higher energy consumption. Hence, space cooling of residential buildings should be carefully designed to utilize the use of natural ventilation strategies. For additional cooling supply, low energy cooling technologies should be used. By combining both natural and mechanical cooling, known as mixed-mode systems, it is possible to reduce the energy consumption while still providing comfortable internal conditions (Brager & Baker, 2009). The difference between conventional cooling and mixed-mode systems is that the latter is a sophisticated system that can be automatically controlled to switch from natural to mechanical mode. Several studies have demonstrated the positive impact of a mixed mode system in reducing building energy consumption (Zhai, et al., 2011) whilst providing good IAQ (Emmerich, 2006). However, limited work has evaluated the performance of different control algorithms in mixed-mode systems for hot climates, such as in India, with respect to energy consumption, IAQ and indoor thermal conditions in residential buildings.
The purpose of this research is to develop a sophisticated control algorithm that will take into account regional climate conditions and the building characteristics to define the optimal cooling and ventilation strategies for a given range of conditions. Hence, it would be feasible to switch from natural to mechanical mode without compromising the IAQ and indoor thermal comfort and by ensuring the minimum energy consumption.
The aim of this research is to examine and develop flexible control algorithms for mixed-mode residential buildings in India in order to deliver comfortable indoor conditions with the minimum energy demand.
The main research questions that this research attempts to address are:
- Which natural ventilation and mechanical cooling strategies could be suitable for mixed-mode residential buildings in India?
- Which control strategies should be employed at mixed-mode buildings, in order to meet thermal comfort expectations for the Indian climate zones?
- Can more sophisticated control algorithms for mixed-mode buildings reduce the energy demand without compromising the indoor air quality for a representative apartment block in India?
To investigate these research questions, different simulation tools will be used to develop the flexible control algorithms (Modelica), to examine the energy saving potentials (Dynamic Thermal Modelling) and the IAQ (Computational Fluid Dynamics).
The outcomes of this research will bridge the gap in knowledge regarding the appropriate control of mixed-mode systems in residential buildings with respect to the energy consumption and IAQ and provide guidelines for their implementation